max / makeover

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1	//! Shared theme loading + intent resolution for TOML-based theme files.
2	//!
3	//! Used by GoingsOn, Balanced Breakfast (Tauri apps), audiofiles (egui), and the
4	//! MNW web server. Themes are authored by intent ("human design"): colors are
5	//! declared by role (surface / content / action / status / line / category), not
6	//! by hue. This crate is the single place that resolves an authored theme into a
7	//! full set of intent tokens — including the derived interactive states
8	//! (hover/active/selection/row-stripe/contrast) that each app used to recompute
9	//! itself — and emits them as CSS variables or RGB tuples.
10	//!
11	//! Theme file shape:
12	//! ```text
13	//! [meta]
14	//! name = "Nord"
15	//! variant = "dark" # or "light"
16	//!
17	//! [surface] # container backgrounds by role/elevation
18	//! page = "#2e3440"; raised = "#3b4252"; sunken = "#434c5e"; overlay = "#3b4252"
19	//!
20	//! [content] # the ink. Its emphasis steps are derived, not authored:
21	//! primary = "#d8dee9" # `content-secondary` and `content-muted` are tonal
22	//! # steps of this toward `surface.page`. See `Emphasis`.
23	//!
24	//! [action] # interactive / brand color
25	//! primary = "#81a1c1"
26	//!
27	//! [status] # state semantics
28	//! danger = "#bf616a"; success = "#a3be8c"; warning = "#ebcb8b"; info = "#88c0d0"
29	//!
30	//! [line]
31	//! border = "#4c566a"
32	//!
33	//! [category] # distinct decorative colors for tags/badges/charts
34	//! one = "#bf616a"; two = "#a3be8c"; three = "#81a1c1"
35	//! four = "#ebcb8b"; five = "#b48ead"; six = "#88c0d0"
36	//! ```
37
38	// Color-space math: single-letter channel names (r/g/b/l/m/s) and the published
39	// high-precision OKLab/sRGB matrix constants are the domain vocabulary here.
40	#![allow(clippy::many_single_char_names, clippy::unreadable_literal)]
41
42	use serde::Serialize;
43	use std::collections::{BTreeMap, HashMap};
44	use std::path::{Path, PathBuf};
45
46	/// The color sections an authored theme may declare.
47	pub const COLOR_SECTIONS: &[&str] = &["surface", "content", "action", "status", "line", "category"];
48
49	/// Theme metadata parsed from the `[meta]` section.
50	#[derive(Debug, Clone, Serialize)]
51	#[serde(rename_all = "camelCase")]
52	pub struct ThemeMeta {
53	pub id: String,
54	pub name: String,
55	pub variant: String,
56	pub is_custom: bool,
57	}
58
59	/// A loaded theme: metadata plus the authored colors, flattened to dotted keys
60	/// (e.g. `"surface.page"`, `"status.danger"`, `"category.one"`).
61	#[derive(Debug, Serialize)]
62	#[serde(rename_all = "camelCase")]
63	pub struct ThemeColors {
64	pub meta: ThemeMeta,
65	pub colors: HashMap<String, String>,
66	}
67
68	// ============================================================================
69	// Color math — perceptual (OKLab) derivations + WCAG contrast.
70	//
71	// Interactive states (hover/active/selection/surfaces) are derived in OKLab so
72	// equal steps look equal across every theme's hues (Ottosson 2020; the modern
73	// CIELAB). Text-on-color is picked by the WCAG 2.x contrast ratio, not a naive
74	// luminance threshold, so the choice actually meets AA where achievable.
75	// This is the single source of truth shared by every product.
76	// ============================================================================
77
78	/// An sRGB color. Hex round-trips losslessly.
79	#[derive(Clone, Copy, Debug, PartialEq, Eq)]
80	pub struct Rgb {
81	pub r: u8,
82	pub g: u8,
83	pub b: u8,
84	}
85
86	impl Rgb {
87	/// Parse `#rgb` or `#rrggbb` (case-insensitive). Returns `None` otherwise.
88	pub fn from_hex(s: &str) -> Option<Rgb> {
89	let h = s.strip_prefix('#')?;
90	let (r, g, b) = match h.len() {
91	6 => (
92	u8::from_str_radix(&h[0..2], 16).ok()?,
93	u8::from_str_radix(&h[2..4], 16).ok()?,
94	u8::from_str_radix(&h[4..6], 16).ok()?,
95	),
96	3 => {
97	let d = \|c: &str\| u8::from_str_radix(c, 16).ok().map(\|v\| v * 17);
98	(d(&h[0..1])?, d(&h[1..2])?, d(&h[2..3])?)
99	}
100	_ => return None,
101	};
102	Some(Rgb { r, g, b })
103	}
104
105	/// Lowercase `#rrggbb`.
106	pub fn to_hex(self) -> String {
107	format!("#{:02x}{:02x}{:02x}", self.r, self.g, self.b)
108	}
109
110	pub fn tuple(self) -> (u8, u8, u8) {
111	(self.r, self.g, self.b)
112	}
113	}
114
115	/// A color in OKLab (perceptually uniform): `l` lightness in [0,1], `a`/`b` opponent axes.
116	#[derive(Clone, Copy, Debug)]
117	pub struct Oklab {
118	pub l: f32,
119	pub a: f32,
120	pub b: f32,
121	}
122
123	fn srgb_to_linear(c: u8) -> f32 {
124	let c = c as f32 / 255.0;
125	if c <= 0.04045 {
126	c / 12.92
127	} else {
128	((c + 0.055) / 1.055).powf(2.4)
129	}
130	}
131
132	fn linear_to_srgb(c: f32) -> u8 {
133	let c = c.clamp(0.0, 1.0);
134	let v = if c <= 0.0031308 {
135	c * 12.92
136	} else {
137	1.055 * c.powf(1.0 / 2.4) - 0.055
138	};
139	(v * 255.0).round().clamp(0.0, 255.0) as u8
140	}
141
142	impl Rgb {
143	/// Convert to OKLab (Ottosson's sRGB matrices).
144	///
145	/// The matrix coefficients are quoted at their published precision so they
146	/// can be diffed against the reference. `f32` rounds them at compile time;
147	/// truncating the literals would only make them harder to check.
148	#[allow(clippy::excessive_precision)]
149	pub fn to_oklab(self) -> Oklab {
150	let (r, g, b) = (
151	srgb_to_linear(self.r),
152	srgb_to_linear(self.g),
153	srgb_to_linear(self.b),
154	);
155	let l = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b;
156	let m = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b;
157	let s = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b;
158	let (l_, m_, s_) = (l.cbrt(), m.cbrt(), s.cbrt());
159	Oklab {
160	l: 0.2104542553 * l_ + 0.7936177850 * m_ - 0.0040720468 * s_,
161	a: 1.9779984951 * l_ - 2.4285922050 * m_ + 0.4505937099 * s_,
162	b: 0.0259040371 * l_ + 0.7827717662 * m_ - 0.8086757660 * s_,
163	}
164	}
165
166	/// Convert from OKLab back to the nearest in-gamut sRGB.
167	///
168	/// Published precision, as in [`Rgb::to_oklab`].
169	#[allow(clippy::excessive_precision)]
170	pub fn from_oklab(c: Oklab) -> Rgb {
171	let l_ = c.l + 0.3963377774 * c.a + 0.2158037573 * c.b;
172	let m_ = c.l - 0.1055613458 * c.a - 0.0638541728 * c.b;
173	let s_ = c.l - 0.0894841775 * c.a - 1.2914855480 * c.b;
174	let (l, m, s) = (l_ * l_ * l_, m_ * m_ * m_, s_ * s_ * s_);
175	Rgb {
176	r: linear_to_srgb(4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s),
177	g: linear_to_srgb(-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s),
178	b: linear_to_srgb(-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s),
179	}
180	}
181	}
182
183	/// WCAG 2.x relative luminance of an sRGB color.
184	fn rel_luminance(c: Rgb) -> f32 {
185	0.2126 * srgb_to_linear(c.r) + 0.7152 * srgb_to_linear(c.g) + 0.0722 * srgb_to_linear(c.b)
186	}
187
188	/// WCAG 2.x contrast ratio between two colors, in [1, 21].
189	pub fn wcag_contrast(a: Rgb, b: Rgb) -> f32 {
190	let (la, lb) = (rel_luminance(a), rel_luminance(b));
191	let (hi, lo) = if la >= lb { (la, lb) } else { (lb, la) };
192	(hi + 0.05) / (lo + 0.05)
193	}
194
195	/// Pick black or white for legible text on `bg`, by the higher WCAG contrast
196	/// ratio (so the choice meets AA wherever the background allows it).
197	pub fn readable_on(bg: Rgb) -> Rgb {
198	let white = Rgb {
199	r: 255,
200	g: 255,
201	b: 255,
202	};
203	let black = Rgb { r: 0, g: 0, b: 0 };
204	if wcag_contrast(white, bg) >= wcag_contrast(black, bg) {
205	white
206	} else {
207	black
208	}
209	}
210
211	/// Shift OKLab lightness by `delta` (perceptually uniform). Positive lightens.
212	pub fn lighten(c: Rgb, delta: f32) -> Rgb {
213	let mut lab = c.to_oklab();
214	lab.l = (lab.l + delta).clamp(0.0, 1.0);
215	Rgb::from_oklab(lab)
216	}
217
218	/// Shift OKLab lightness down by `delta` (perceptually uniform).
219	pub fn darken(c: Rgb, delta: f32) -> Rgb {
220	lighten(c, -delta)
221	}
222
223	/// Interpolate between `a` and `b` by `t` in [0,1] in OKLab (perceptual blend).
224	pub fn mix(a: Rgb, b: Rgb, t: f32) -> Rgb {
225	let (x, y) = (a.to_oklab(), b.to_oklab());
226	Rgb::from_oklab(Oklab {
227	l: x.l + (y.l - x.l) * t,
228	a: x.a + (y.a - x.a) * t,
229	b: x.b + (y.b - x.b) * t,
230	})
231	}
232
233	// ============================================================================
234	// Tonal steps
235	// ============================================================================
236
237	/// How far a tonal step sits from the token it is a step of.
238	///
239	/// The named ratios. [`tonal`] is the same operation with the number written
240	/// out, and this is the small set of steps the vocabulary has agreed on, so a
241	/// consumer asking for "the muted form of this" names it rather than picking a
242	/// number and disagreeing with the next consumer to pick one.
243	///
244	/// The rule these encode, stated as the three-tone convention:
245	///
246	/// \| step \| what it means \|
247	/// \|------\|---------------\|
248	/// \| [`Full`](Self::Full) \| active, emphasised, the thing itself \|
249	/// \| [`Secondary`](Self::Secondary) \| inactive but usable: a control that still answers \|
250	/// \| [`Muted`](Self::Muted) \| inert: disabled, or not a control at all \|
251	#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
252	pub enum Emphasis {
253	/// The token unchanged.
254	Full,
255	/// One step back. Still legible as content, not competing with `Full`.
256	Secondary,
257	/// Two steps back. Present, and saying it is not the point.
258	Muted,
259	}
260
261	impl Emphasis {
262	/// The fraction of the way to the ground this step travels.
263	///
264	/// Both numbers are the shipped corpus' own, not invented: across the 31
265	/// bundled themes, hand-authored `content.secondary` sat at a median 0.115
266	/// of the way from `content.primary` to `surface.page`, and `content.muted`
267	/// at 0.424. So the derivation reproduces what theme authors converged on
268	/// by eye, and the themes that move are the ones that were off the cluster.
269	#[must_use]
270	pub const fn ratio(self) -> f32 {
271	match self {
272	Self::Full => 0.0,
273	Self::Secondary => 0.12,
274	Self::Muted => 0.42,
275	}
276	}
277
278	/// The suffix a derived token takes, or `None` for the token itself.
279	///
280	/// `content` + [`Muted`](Self::Muted) is `content-muted`, which is the
281	/// naming every consumer already spells by hand. Grouping a family this way
282	/// is what makes `danger-muted` or `action-secondary` nameable without a
283	/// second table saying what they mean.
284	#[must_use]
285	pub const fn suffix(self) -> Option<&'static str> {
286	match self {
287	Self::Full => None,
288	Self::Secondary => Some("-secondary"),
289	Self::Muted => Some("-muted"),
290	}
291	}
292
293	/// The derived token key for `token` at this step.
294	#[must_use]
295	pub fn token(self, token: &str) -> String {
296	match self.suffix() {
297	Some(suffix) => format!("{token}{suffix}"),
298	None => token.to_string(),
299	}
300	}
301	}
302
303	/// A tonal step of `base`, `ratio` of the way toward the `ground` it is read
304	/// against.
305	///
306	/// The numerical form of [`Emphasis`], for a consumer that wants a step the
307	/// named set does not have. `ratio` is clamped to [0,1]: past 1 the step is no
308	/// longer a step of `base` but a colour beyond the ground, which is a different
309	/// operation wearing this one's name.
310	///
311	/// # Toward the ground, not toward grey
312	///
313	/// A tonal step is a reduction in contrast against what it is read on, so it
314	/// interpolates toward the surface rather than desaturating or lightening. That
315	/// is why it takes two colours: lightening is wrong on a light theme and
316	/// darkening is wrong on a dark one, and mixing toward the ground is correct on
317	/// both without asking which theme this is. It is also why the ground is a
318	/// parameter rather than assumed — text in a well is read against the well.
319	///
320	/// # It composes
321	///
322	/// Two steps toward the same ground are one step toward that ground, since
323	/// OKLab interpolation is linear: `tonal(tonal(c, g, a), g, b)` is
324	/// `tonal(c, g, a + b - a*b)`. So a family can be derived recursively — the
325	/// muted form of a secondary is a well-defined colour and not a compounding
326	/// error — and re-deriving a token that was already derived is stable rather
327	/// than a slow slide into the background.
328	#[must_use]
329	pub fn tonal(base: Rgb, ground: Rgb, ratio: f32) -> Rgb {
330	mix(base, ground, ratio.clamp(0.0, 1.0))
331	}
332
333	/// A named tonal step of `base` against the `ground` it is read on.
334	///
335	/// [`tonal`] with [`Emphasis::ratio`], and the form to reach for: the two
336	/// spellings of "muted" a pair of consumers pick independently are the drift
337	/// this replaces.
338	#[must_use]
339	pub fn emphasized(base: Rgb, ground: Rgb, emphasis: Emphasis) -> Rgb {
340	tonal(base, ground, emphasis.ratio())
341	}
342
343	// ============================================================================
344	// Low-color terminals
345	// ============================================================================
346
347	/// The 16 colors an ANSI terminal addresses by index, in the PC/VGA
348	/// arrangement the Linux console and most emulators start from.
349	///
350	/// 0-7 are the normal colors and 8-15 the bright ones. Index 7 is a light gray
351	/// rather than white, which is the entry a themed surface usually lands on, and
352	/// index 15 is the true white.
353	///
354	/// Emulators let the user repaint all sixteen, so this is the standard
355	/// arrangement rather than a promise about any one terminal. The Linux console
356	/// keeps it, which is the case that matters: a console app cannot fall back to
357	/// 24-bit color there.
358	pub const ANSI_16: [Rgb; 16] = [
359	Rgb {
360	r: 0x00,
361	g: 0x00,
362	b: 0x00,
363	},
364	Rgb {
365	r: 0xaa,
366	g: 0x00,
367	b: 0x00,
368	},
369	Rgb {
370	r: 0x00,
371	g: 0xaa,
372	b: 0x00,
373	},
374	Rgb {
375	r: 0xaa,
376	g: 0x55,
377	b: 0x00,
378	},
379	Rgb {
380	r: 0x00,
381	g: 0x00,
382	b: 0xaa,
383	},
384	Rgb {
385	r: 0xaa,
386	g: 0x00,
387	b: 0xaa,
388	},
389	Rgb {
390	r: 0x00,
391	g: 0xaa,
392	b: 0xaa,
393	},
394	Rgb {
395	r: 0xaa,
396	g: 0xaa,
397	b: 0xaa,
398	},
399	Rgb {
400	r: 0x55,
401	g: 0x55,
402	b: 0x55,
403	},
404	Rgb {
405	r: 0xff,
406	g: 0x55,
407	b: 0x55,
408	},
409	Rgb {
410	r: 0x55,
411	g: 0xff,
412	b: 0x55,
413	},
414	Rgb {
415	r: 0xff,
416	g: 0xff,
417	b: 0x55,
418	},
419	Rgb {
420	r: 0x55,
421	g: 0x55,
422	b: 0xff,
423	},
424	Rgb {
425	r: 0xff,
426	g: 0x55,
427	b: 0xff,
428	},
429	Rgb {
430	r: 0x55,
431	g: 0xff,
432	b: 0xff,
433	},
434	Rgb {
435	r: 0xff,
436	g: 0xff,
437	b: 0xff,
438	},
439	];
440
441	/// The 256 colors an xterm-compatible terminal addresses by index, so that
442	/// entry `i` is what the terminal paints for `38;5;i`.
443	///
444	/// Three regions, and they are not equally trustworthy. 0-15 are the [`ANSI_16`]
445	/// system colors, which every emulator lets the user repaint. 16-231 are a
446	/// 6x6x6 RGB cube and 232-255 a 24-step gray ramp, and those 240 are fixed.
447	///
448	/// So a color whose whole job is to be told apart from another should quantize
449	/// against [`ANSI_240`] rather than against this table: a match landing in the
450	/// low sixteen is a match against a color the user may have moved.
451	pub const ANSI_256: [Rgb; 256] = build_ansi_256();
452
453	/// The fixed region of [`ANSI_256`]: the 6x6x6 cube and the gray ramp, without
454	/// the sixteen repaintable system colors.
455	///
456	/// Quantizing against this returns an index into this slice; add
457	/// [`ANSI_240_OFFSET`] to get the index the terminal wants.
458	pub const ANSI_240: &[Rgb] = ANSI_256.split_at(16).1;
459
460	/// What to add to an [`ANSI_240`] index to get an [`ANSI_256`] one.
461	pub const ANSI_240_OFFSET: usize = 16;
462
463	/// The twelve chromatic ANSI slots, as the intents that paint them.
464	///
465	/// Indexed 1-6 and 9-14. The hues do not depend on whether the theme is light
466	/// or dark, since red is the theme's danger tone either way, which is exactly
467	/// why the four achromatic slots are not in this table.
468	///
469	/// Lifted from Alloy's `skelgen` on 2026-07-31, which had folded three
470	/// disagreeing hand-maintained copies into one and is the reason the
471	/// arrangement is trusted. It moved here so a program that paints its own
472	/// palette at runtime, rather than reading a generated config, resolves the
473	/// same slots. Slot 14 was the one the copies disagreed on and is
474	/// `category.six`, which both the Linux console table and the retired
475	/// `vtrgb.py` had.
476	const CHROMATIC: [(usize, &str); 12] = [
477	(1, "status.danger"),
478	(2, "status.success"),
479	(3, "status.warning"),
480	(4, "status.info"),
481	(5, "category.five"),
482	(6, "category.six"),
483	(9, "action.primary"), // bright red, the theme's warm accent
484	(10, "status.success"),
485	(11, "status.warning"),
486	(12, "status.info"),
487	(13, "category.five"),
488	(14, "category.six"),
489	];
490
491	/// The four achromatic slots, 0, 7, 8 and 15, which invert with the theme.
492	///
493	/// These are the slots a naive table gets wrong. ANSI 0 is "black" and 7 is
494	/// "white", but what a terminal wants there is the darkest tone and *the
495	/// lightest tone*, and which intent that is flips with the theme's polarity. A
496	/// light theme's darkest tone is its ink; a dark theme's is its deepest
497	/// surface. Pinning slot 0 to `content.primary` reads correctly on a light
498	/// theme and hands a dark one a pale cream as "black".
499	///
500	/// Slot 7 is a surface and not a text tone, because it is what a program with
501	/// no way to name anything else draws its container on: a greeter's login card
502	/// is a light card on the darker field slot 0 paints.
503	///
504	/// Anything that is not `dark`, including `high-contrast`, follows the light
505	/// anchors.
506	fn achromatic_slot(index: usize, variant: &str) -> Option<&'static str> {
507	let dark = variant == "dark";
508	Some(match (index, dark) {
509	(0, false) => "content.primary", // darkest text tone
510	(0, true) => "surface.sunken", // darkest surface
511	(7, false) => "surface.raised", // the login card
512	(7, true) => "content.secondary", // a readable light tone
513	(8, _) => "content.muted", // muted chrome, either way
514	(15, false) => "surface.overlay", // lightest surface
515	(15, true) => "content.primary", // lightest text tone
516	_ => return None,
517	})
518	}
519
520	/// The authored intent painting ANSI slot `index` under a theme of `variant`,
521	/// as a dotted key into [`ThemeColors::colors`].
522	///
523	/// `None` for an index outside 0-15. Every slot in range resolves, so a caller
524	/// that has the intent can fill all sixteen.
525	///
526	/// This is what makes a bare console, a terminal emulator and a generated
527	/// config agree on what red means. They disagreed for as long as each kept its
528	/// own table.
529	#[must_use]
530	pub fn ansi_intent(index: usize, variant: &str) -> Option<&'static str> {
531	achromatic_slot(index, variant).or_else(\|\| {
532	CHROMATIC
533	.iter()
534	.find(\|(slot, _)\| *slot == index)
535	.map(\|(_, intent)\| *intent)
536	})
537	}
538
539	const fn build_ansi_256() -> [Rgb; 256] {
540	let mut table = [Rgb { r: 0, g: 0, b: 0 }; 256];
541
542	let mut i = 0;
543	while i < 16 {
544	table[i] = ANSI_16[i];
545	i += 1;
546	}
547
548	// The cube's six levels are not evenly spaced. The step from black to the
549	// first is more than twice any later one, which is xterm's arrangement
550	// rather than a choice available here, and it is why the darkest tones a
551	// theme can reach on 256 colors come from the gray ramp instead.
552	const LEVELS: [u8; 6] = [0, 95, 135, 175, 215, 255];
553	let mut r = 0;
554	while r < 6 {
555	let mut g = 0;
556	while g < 6 {
557	let mut b = 0;
558	while b < 6 {
559	table[16 + 36 * r + 6 * g + b] = Rgb {
560	r: LEVELS[r],
561	g: LEVELS[g],
562	b: LEVELS[b],
563	};
564	b += 1;
565	}
566	g += 1;
567	}
568	r += 1;
569	}
570
571	// 8 to 238 in steps of 10. Neither end is black or white; both of those are
572	// in the cube, so the ramp is 24 steps of gray between them rather than 24
573	// steps of the whole range.
574	let mut k = 0;
575	while k < 24 {
576	let v = 8 + 10 * k as u8;
577	table[232 + k as usize] = Rgb { r: v, g: v, b: v };
578	k += 1;
579	}
580
581	table
582	}
583
584	/// The contrast ratio two colors must clear to read as separate areas.
585	///
586	/// WCAG 2.x asks 3:1 of user interface components and graphics, which is what
587	/// a border, a rule, or a focus ring is. Text wants more, and a caller drawing
588	/// text can ask for more by checking [`wcag_contrast`] itself.
589	pub const DISTINCT: f32 = 3.0;
590
591	/// Perceptual distance between two colors, for choosing the closest of a set.
592	fn oklab_distance(a: Rgb, b: Rgb) -> f32 {
593	let (x, y) = (a.to_oklab(), b.to_oklab());
594	((x.l - y.l).powi(2) + (x.a - y.a).powi(2) + (x.b - y.b).powi(2)).sqrt()
595	}
596
597	/// Index of the entry in `palette` that looks most like `c`.
598	///
599	/// OKLab distance rather than distance in sRGB, for the same reason [`mix`]
600	/// interpolates there: sRGB's numbers are not spaced the way seeing is, so a
601	/// nearest match computed in it picks visibly wrong entries in the mid tones.
602	///
603	/// # Panics
604	///
605	/// If `palette` is empty.
606	pub fn quantize(c: Rgb, palette: &[Rgb]) -> usize {
607	assert!(!palette.is_empty(), "a palette needs at least one color");
608	let mut best = 0;
609	let mut best_distance = f32::INFINITY;
610	for (index, entry) in palette.iter().enumerate() {
611	let distance = oklab_distance(c, *entry);
612	if distance < best_distance {
613	best = index;
614	best_distance = distance;
615	}
616	}
617	best
618	}
619
620	/// Index of the entry in `palette` closest to `fg` that still reads against
621	/// `bg`.
622	///
623	/// [`quantize`] answers about one color at a time, and two colors that differ
624	/// can quantize to the same entry: a themed page and a border drawn on it are
625	/// often a few steps apart in a 24-bit theme and land together on a 16-color
626	/// terminal, leaving one flat area where there was a frame. Alloy's console
627	/// showed exactly this, and it is not a contrived pairing: a light page and the
628	/// mid-tone border derived from it both land on index 7.
629	///
630	/// So the background is quantized first, because what the border must be
631	/// distinguished from is the entry the terminal will actually paint, not the
632	/// color the theme asked for. Then the nearest entry to `fg` clearing
633	/// [`DISTINCT`] against it wins. When nothing clears it, the entry that gets
634	/// furthest does: at that point the palette cannot honor the design, and the
635	/// most legible approximation beats the closest invisible one.
636	///
637	/// Only for colors whose whole job is to be told apart from their background.
638	/// Applied to every token it would push a deliberately quiet one until it
639	/// shouted.
640	///
641	/// # Panics
642	///
643	/// If `palette` is empty.
644	pub fn quantize_against(fg: Rgb, bg: Rgb, palette: &[Rgb]) -> usize {
645	assert!(!palette.is_empty(), "a palette needs at least one color");
646	let shown = palette[quantize(bg, palette)];
647
648	let mut order: Vec<usize> = (0..palette.len()).collect();
649	order.sort_by(\|a, b\| {
650	oklab_distance(fg, palette[a]).total_cmp(&oklab_distance(fg, palette[b]))
651	});
652
653	order
654	.iter()
655	.copied()
656	.find(\|index\| wcag_contrast(palette[*index], shown) >= DISTINCT)
657	.unwrap_or_else(\|\| {
658	order
659	.iter()
660	.copied()
661	.max_by(\|a, b\| {
662	wcag_contrast(palette[a], shown).total_cmp(&wcag_contrast(palette[b], shown))
663	})
664	.expect("the palette is not empty")
665	})
666	}
667
668	// ============================================================================
669	// Intent resolution
670	// ============================================================================
671
672	/// Base intents: (TOML dotted source key, canonical token key). The token key
673	/// is the CSS-var stem (`--{token}`) and the `rgb()` lookup key.
674	///
675	/// Read straight from the loaded theme, which is not quite the same as read
676	/// from the file: `content.secondary` and `content.muted` are tonal steps of
677	/// `content.primary` and are filled in at load by [`derive_tonal_steps`], so
678	/// they arrive here already computed and take this path like any other.
679	pub const BASE_INTENTS: &[(&str, &str)] = &[
680	("surface.page", "surface-page"),
681	("surface.raised", "surface-raised"),
682	("surface.sunken", "surface-sunken"),
683	("surface.overlay", "surface-overlay"),
684	("content.primary", "content"),
685	("content.secondary", "content-secondary"),
686	("content.muted", "content-muted"),
687	("action.primary", "action"),
688	("status.danger", "danger"),
689	("status.success", "success"),
690	("status.warning", "warning"),
691	("status.info", "info"),
692	("line.border", "border"),
693	("category.one", "category-one"),
694	("category.two", "category-two"),
695	("category.three", "category-three"),
696	("category.four", "category-four"),
697	("category.five", "category-five"),
698	("category.six", "category-six"),
699	];
700
701	/// A fully resolved intent layer: every token key → concrete `#rrggbb`.
702	/// Includes both authored base intents and the computed derived intents.
703	#[derive(Debug, Clone, Serialize)]
704	#[serde(rename_all = "camelCase")]
705	pub struct SemanticTokens {
706	pub meta: ThemeMeta,
707	/// token-key → resolved hex. Stable, deterministic ordering.
708	pub intents: BTreeMap<String, String>,
709	}
710
711	impl SemanticTokens {
712	/// Resolved hex for a token key, if present.
713	pub fn hex(&self, key: &str) -> Option<&str> {
714	self.intents.get(key).map(String::as_str)
715	}
716
717	/// Resolved RGB tuple for a token key (for egui / native consumers).
718	///
719	/// `None` for a translucent token. Two intents are emitted as `rgba(...)`
720	/// rather than hex, `overlay` and `elevation`, and dropping the alpha would
721	/// hand a native consumer an opaque near-black where it asked for a scrim.
722	/// Those want [`rgba`](Self::rgba).
723	pub fn rgb(&self, key: &str) -> Option<(u8, u8, u8)> {
724	self.intents
725	.get(key)
726	.and_then(\|h\| Rgb::from_hex(h))
727	.map(Rgb::tuple)
728	}
729
730	/// Resolved RGBA tuple for a token key, alpha as 0-255.
731	///
732	/// Reads both spellings, so a caller that does not care whether an intent
733	/// happens to be translucent can use this for everything: an opaque token
734	/// comes back at 255.
735	///
736	/// It exists because a CSS consumer can take `rgba(...)` as a string
737	/// straight out of [`hex`](Self::hex) and a native one cannot. Without it
738	/// the two translucent intents are reachable from a stylesheet and from
739	/// nowhere else, which is the coupling deriving in the crate was meant to
740	/// avoid.
741	pub fn rgba(&self, key: &str) -> Option<(u8, u8, u8, u8)> {
742	let value = self.intents.get(key)?;
743	if let Some(rgb) = Rgb::from_hex(value) {
744	let (r, g, b) = rgb.tuple();
745	return Some((r, g, b, 255));
746	}
747	let inner = value.strip_prefix("rgba(")?.strip_suffix(')')?;
748	let mut parts = inner.split(',').map(str::trim);
749	let r = parts.next()?.parse().ok()?;
750	let g = parts.next()?.parse().ok()?;
751	let b = parts.next()?.parse().ok()?;
752	let alpha: f32 = parts.next()?.parse().ok()?;
753	if parts.next().is_some() \|\| !(0.0..=1.0).contains(&alpha) {
754	return None;
755	}
756	Some((r, g, b, (alpha * 255.0).round() as u8))
757	}
758	}
759
760	/// Resolve an authored theme into the full intent token set.
761	///
762	/// 1. Copy each present base intent from the authored colors.
763	/// 2. Compute the derived interactive states from the base intents, using the
764	/// same math the apps used to apply individually (so output is identical).
765	///
766	/// Each derived token is emitted only when its source intents exist, mirroring
767	/// the skip-missing behavior of the rest of the crate.
768	pub fn resolve(theme: &ThemeColors) -> SemanticTokens {
769	let mut intents: BTreeMap<String, String> = BTreeMap::new();
770
771	// 1. Base intents (authored). Copy only values that parse as a hex color and
772	// re-emit them in canonical `#rrggbb` form, so an authored value can never
773	// carry arbitrary bytes into the emitted CSS (the resolved tokens are inlined
774	// raw into a `<style>` block by the web server). A malformed value is skipped,
775	// mirroring the skip-missing behavior for absent intents.
776	for (src, token) in BASE_INTENTS {
777	if let Some(rgb) = theme.colors.get(*src).and_then(\|v\| Rgb::from_hex(v)) {
778	intents.insert((*token).to_string(), rgb.to_hex());
779	}
780	}
781
782	// Helper: parse an already-resolved token to Rgb.
783	let get = \|m: &BTreeMap<String, String>, k: &str\| m.get(k).and_then(\|h\| Rgb::from_hex(h));
784
785	// 2. Derived intents — perceptual (OKLab) steps + WCAG-picked text.
786	// Lightness deltas are in OKLab L units; mix ratios interpolate in OKLab.
787	let mut derived: Vec<(String, Rgb)> = Vec::new();
788	if let Some(action) = get(&intents, "action") {
789	derived.push(("action-hover".into(), lighten(action, 0.05)));
790	derived.push(("content-on-action".into(), readable_on(action)));
791	// The focus ring is the action colour itself, not a tint of it: a ring
792	// is a statement that the keyboard is here, and a faded one reads as a
793	// disabled control rather than an emphatic one.
794	//
795	// One ring, not one per primitive. Where the ring sits is a depth
796	// question and not a per-component choice: a well takes it inside its
797	// own edge and a raised surface takes it outside. That is one decision
798	// with two renderings rather than one decision per component, which is
799	// how the three apps ended up with three rings. This token is the one
800	// shared artifact; which thing wears it, and how it is drawn, is each
801	// renderer's own (see `makeover_layout`'s crate header, "reach, focus
802	// and the focus ring").
803	derived.push(("focus-ring".into(), action));
804	}
805	if let Some(page) = get(&intents, "surface-page") {
806	// Modal scrim: a near-black tone carrying a faint hint of the theme's
807	// hue, at 50% alpha. Anchored very dark (OKLab L=0.08) so it dims the
808	// page on light and dark themes. Emitted as rgba (not a flat hex), so
809	// it is inserted directly rather than through the hex loop below.
810	let mut o = page.to_oklab();
811	o.l = 0.08;
812	let s = Rgb::from_oklab(o);
813	intents.insert(
814	"overlay".into(),
815	format!("rgba({}, {}, {}, 0.5)", s.r, s.g, s.b),
816	);
817
818	// What a surface that FLOATS OVER the page is cast onto it with.
819	//
820	// The one intent here about a surface's relationship to the page rather
821	// than about the surface itself, which is why it is derived from `page`
822	// and not from `surface-raised`. A shadow is not the thing, it is the
823	// absence of light on what is behind the thing.
824	//
825	// SCOPE, and it is the whole point of this intent existing rather than
826	// a general "shadow": a surface that overlays the page takes this, a
827	// surface IN the page takes a bevel. Menus, toasts, popovers and
828	// dropdowns overlay. A card, a plate and a framed image do not, and
829	// reaching for this on one of those is how a pre-Platinum look survives
830	// a conversion wearing a token's name. `.raised` is the answer there.
831	//
832	// Same anchor as the scrim above and for the same reason: a tone read
833	// off the theme's hue but pinned very dark, so it reads as absence of
834	// light on a light theme and on a dark one alike. A shadow tinted to a
835	// dark theme's own lightness would not be a shadow.
836	//
837	// The alpha is the only number here that is a look decision rather than
838	// a derivation. 0.18 sits between the two literal scales it replaces:
839	// the MNW server's --shadow-2 (0.10) reads as nothing under a menu, and
840	// its --shadow-3 (0.15) was measured invisible at plate size. Geometry
841	// stays with the consumer, the way bevel thickness does.
842	intents.insert(
843	"elevation".into(),
844	format!("rgba({}, {}, {}, 0.18)", s.r, s.g, s.b),
845	);
846	}
847	if let Some(raised) = get(&intents, "surface-raised") {
848	// The two edges of a bevel: a raised control is lit from the top left,
849	// so its top and left edges take `bevel-light` and its bottom and right
850	// edges `bevel-dark`. Inverting the pair gives a pressed state and an
851	// inset well, which is what makes the idiom cheap for a consumer.
852	//
853	// Derived here rather than composed per-app because the two webviews
854	// could do it in `color-mix()` and audiofiles, which is egui, could not.
855	// Geometry (thickness, radius, which side gets which) stays app-side.
856	//
857	// The deltas are asymmetric because the eye is: an equal step down reads
858	// as a smaller change than the same step up, so the shadow is cut deeper
859	// than the highlight is raised.
860	//
861	// A face already at the top of the ramp cannot hold a highlight — the
862	// lightening clamps and the control bevels on two sides without ever
863	// resolving as lit. That is a property of the theme, not of this
864	// derivation; `bevel_edges_are_distinct_from_their_face` names the
865	// shipped themes it currently bites.
866	derived.push(("bevel-light".into(), lighten(raised, 0.14)));
867	derived.push(("bevel-dark".into(), darken(raised, 0.18)));
868
869	// An inset well: the content surface inside a raised container, so a
870	// list reads as content in a container rather than as bands on a panel.
871	// `surface-sunken` cannot serve, because a theme is free to author it
872	// darker than raised (goingson does) and a well has to go the other way.
873	//
874	// Which way is "the other way" depends on the theme, and this is the one
875	// derivation here that inverts. A well is lighter than its face on a
876	// light theme and darker on a dark one, where the bevel pair sidesteps
877	// the question by emitting both directions at once.
878	//
879	// Read the direction off `content` rather than off `Variant`. A theme
880	// whose text is dark is a theme whose surfaces are light, whatever its
881	// `variant` field claims, so this resolves correctly even when that
882	// field is wrong and it keeps the branch on measured color rather than
883	// on metadata.
884	//
885	// Deltas are asymmetric for the same reason the bevel's are, and smaller
886	// than the bevel's because a well is an area rather than an edge. The
887	// step up is the specimen's, measured: #D9DDF4 to #F3F5FD is 0.069.
888	//
889	// A face at the top of its ramp cannot hold a lighter well, the same
890	// clamp `bevel-light` hits; `well_is_visible_against_its_face` names the
891	// shipped themes where it bites.
892	if let Some(content) = get(&intents, "content") {
893	let content_is_darker = content.to_oklab().l < raised.to_oklab().l;
894	let well = if content_is_darker {
895	lighten(raised, 0.07)
896	} else {
897	darken(raised, 0.09)
898	};
899	derived.push(("surface-well".into(), well));
900	}
901	}
902	if let Some(sunken) = get(&intents, "surface-sunken") {
903	derived.push(("hover-surface".into(), sunken));
904	}
905	if let Some(border) = get(&intents, "border") {
906	derived.push(("border-strong".into(), darken(border, 0.05)));
907	}
908
909	for (token, rgb) in derived {
910	intents.insert(token, rgb.to_hex());
911	}
912
913	SemanticTokens {
914	meta: theme.meta.clone(),
915	intents,
916	}
917	}
918
919	/// Emit the resolved intent layer as CSS declarations (no selector), one
920	/// ` --token: #hex;` line each, in deterministic (BTreeMap) order.
921	pub fn intent_css_declarations(tokens: &SemanticTokens) -> String {
922	let mut out = String::new();
923	for (token, hex) in &tokens.intents {
924	out.push_str(" --");
925	out.push_str(token);
926	out.push_str(": ");
927	out.push_str(hex);
928	out.push_str(";\n");
929	}
930	out
931	}
932
933	/// Emit the resolved intent layer as a `:root { … }` block — the single TOML →
934	/// CSS mapping every web surface injects.
935	pub fn intent_css_vars(tokens: &SemanticTokens) -> String {
936	format!(":root {{\n{}}}\n", intent_css_declarations(tokens))
937	}
938
939	// ============================================================================
940	// Loading / parsing
941	// ============================================================================
942
943	/// Validate a theme ID contains only safe characters (alphanumeric, hyphens, underscores).
944	pub fn validate_theme_id(id: &str) -> Result<(), String> {
945	if !id
946	.chars()
947	.all(\|c\| c.is_alphanumeric() \|\| c == '-' \|\| c == '_')
948	{
949	return Err(format!("Invalid theme ID: {id}"));
950	}
951	Ok(())
952	}
953
954	/// Parse the `[meta]` section into `ThemeMeta`.
955	///
956	/// Falls back to the file ID as the name and `"dark"` as the variant.
957	pub fn parse_meta(id: &str, table: &toml::Table, is_custom: bool) -> ThemeMeta {
958	let meta = table.get("meta").and_then(\|m\| m.as_table());
959	let name = meta
960	.and_then(\|m\| m.get("name"))
961	.and_then(\|v\| v.as_str())
962	.unwrap_or(id)
963	.to_string();
964	let variant = meta
965	.and_then(\|m\| m.get("variant"))
966	.and_then(\|v\| v.as_str())
967	.unwrap_or("dark")
968	.to_string();
969
970	ThemeMeta {
971	id: id.to_string(),
972	name,
973	variant,
974	is_custom,
975	}
976	}
977
978	// ============================================================================
979	// Choosing a theme.
980	//
981	// The file half of this crate was always shared; the selection half was not,
982	// and four apps re-rolled it four ways. GoingsOn stores a "system" sentinel in
983	// localStorage, Balanced Breakfast treats an absent value as follow-the-system
984	// and hardcodes two theme ids as its light/dark pair, audiofiles keeps the id
985	// in a synced SQLite table, and the Alloy console parses COLORFGBG. They also
986	// disagreed about what a variant string means: this crate defaults a missing
987	// one to "dark" while alloy_tui parsed an unrecognized one as light.
988	//
989	// What cannot be shared is the store — localStorage, a synced config table and
990	// a TOML file are genuinely different places. What can be shared, and is here,
991	// is the meaning: one vocabulary for variants, one encoding for "what did the
992	// user choose", and one rule for turning that into an id that exists.
993	// ============================================================================
994
995	/// A theme's kind, as declared by `meta.variant`.
996	///
997	/// Three, not two: one shipped theme is `high-contrast`, and an app that
998	/// matched on light-or-dark alone would quietly file it under the wrong one.
999	#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize)]
1000	#[serde(rename_all = "kebab-case")]
1001	pub enum Variant {
1002	Light,
1003	Dark,
1004	HighContrast,
1005	}
1006
1007	impl Variant {
1008	/// The spelling used in a theme file and in [`ThemeMeta::variant`].
1009	#[must_use]
1010	pub const fn as_str(self) -> &'static str {
1011	match self {
1012	Variant::Light => "light",
1013	Variant::Dark => "dark",
1014	Variant::HighContrast => "high-contrast",
1015	}
1016	}
1017
1018	/// Read a variant string, or `None` if it names none of them.
1019	#[must_use]
1020	pub fn parse(raw: &str) -> Option<Self> {
1021	match raw {
1022	"light" => Some(Variant::Light),
1023	"dark" => Some(Variant::Dark),
1024	"high-contrast" => Some(Variant::HighContrast),
1025	_ => None,
1026	}
1027	}
1028	}
1029
1030	impl std::fmt::Display for Variant {
1031	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
1032	f.write_str(self.as_str())
1033	}
1034	}
1035
1036	/// Anything unrecognized reads as dark, which is what [`parse_meta`] already
1037	/// does with a missing one. Consumers that guessed light for an unknown string
1038	/// were disagreeing with the crate that produced it.
1039	impl From<&str> for Variant {
1040	fn from(raw: &str) -> Self {
1041	Variant::parse(raw).unwrap_or(Variant::Dark)
1042	}
1043	}
1044
1045	impl ThemeMeta {
1046	/// This theme's variant as a value rather than a string.
1047	#[must_use]
1048	pub fn kind(&self) -> Variant {
1049	Variant::from(self.variant.as_str())
1050	}
1051	}
1052
1053	/// The spelling of "follow whatever the system is doing", in every store.
1054	pub const FOLLOW: &str = "system";
1055
1056	/// What the user chose, as opposed to what is being rendered.
1057	///
1058	/// The distinction is the whole point: `Follow` is a standing instruction that
1059	/// resolves differently as the ambient mode changes, and a `Fixed` id is an
1060	/// answer that does not. An app that stored only the rendered id could not tell
1061	/// the two apart the next time the system flipped to dark.
1062	#[derive(Debug, Clone, PartialEq, Eq, Default)]
1063	pub enum ThemeSelection {
1064	/// Track the ambient light/dark mode.
1065	#[default]
1066	Follow,
1067	/// Always this theme.
1068	Fixed(String),
1069	}
1070
1071	impl ThemeSelection {
1072	/// Read a stored selection. An empty or absent value is [`Follow`], which
1073	/// is what an app with nothing saved yet should do.
1074	///
1075	/// [`Follow`]: ThemeSelection::Follow
1076	#[must_use]
1077	pub fn parse(raw: Option<&str>) -> Self {
1078	match raw.map(str::trim) {
1079	None \| Some("" \| FOLLOW) => ThemeSelection::Follow,
1080	Some(id) => ThemeSelection::Fixed(id.to_string()),
1081	}
1082	}
1083
1084	/// The string to persist, whatever the store is.
1085	#[must_use]
1086	pub fn as_str(&self) -> &str {
1087	match self {
1088	ThemeSelection::Follow => FOLLOW,
1089	ThemeSelection::Fixed(id) => id,
1090	}
1091	}
1092
1093	/// Turn a selection into a theme id that exists.
1094	///
1095	/// `ambient` is the light/dark mode the app learned however it can: a
1096	/// `prefers-color-scheme` media query, an OS appearance API, `COLORFGBG`
1097	/// from a terminal. `available` is what [`list_themes_from_dirs`] found.
1098	///
1099	/// A `Fixed` id that is no longer on disk falls through to the same path as
1100	/// `Follow` rather than being returned anyway. Themes are deletable in
1101	/// three of the four apps, and handing back an id that will fail to load
1102	/// only moves the error somewhere less helpful.
1103	///
1104	/// The fallback chain is: the app's own default for the ambient mode if it
1105	/// is installed, then any installed theme of that variant, then the app's
1106	/// default regardless. The last step means this always returns something,
1107	/// and an app with no theme directory at all gets the id it ships with and
1108	/// the load error it would have had anyway.
1109	#[must_use]
1110	pub fn resolve(
1111	&self,
1112	ambient: Variant,
1113	defaults: &ThemeDefaults,
1114	available: &[ThemeMeta],
1115	) -> String {
1116	let installed = \|id: &str\| available.iter().any(\|meta\| meta.id == id);
1117
1118	if let ThemeSelection::Fixed(id) = self
1119	&& installed(id)
1120	{
1121	return id.clone();
1122	}
1123
1124	let preferred = defaults.for_variant(ambient);
1125	if installed(preferred) {
1126	return preferred.to_string();
1127	}
1128	available
1129	.iter()
1130	.find(\|meta\| meta.kind() == ambient)
1131	.map_or_else(\|\| preferred.to_string(), \|meta\| meta.id.clone())
1132	}
1133	}
1134
1135	impl std::fmt::Display for ThemeSelection {
1136	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
1137	f.write_str(self.as_str())
1138	}
1139	}
1140
1141	/// The themes an app falls back to, one per ambient mode.
1142	///
1143	/// App-specific on purpose: which theme is "the app's own" is the app's
1144	/// identity, not this crate's business. What is shared is everything around it.
1145	#[derive(Debug, Clone)]
1146	pub struct ThemeDefaults {
1147	light: String,
1148	dark: String,
1149	high_contrast: Option<String>,
1150	}
1151
1152	impl ThemeDefaults {
1153	pub fn new(light: impl Into<String>, dark: impl Into<String>) -> Self {
1154	Self {
1155	light: light.into(),
1156	dark: dark.into(),
1157	high_contrast: None,
1158	}
1159	}
1160
1161	/// Name a theme for a high-contrast ambient mode. Without one, that mode
1162	/// falls back to the dark default, which is the safer of the two to read.
1163	#[must_use]
1164	pub fn high_contrast(mut self, id: impl Into<String>) -> Self {
1165	self.high_contrast = Some(id.into());
1166	self
1167	}
1168
1169	#[must_use]
1170	pub fn for_variant(&self, variant: Variant) -> &str {
1171	match variant {
1172	Variant::Light => &self.light,
1173	Variant::Dark => &self.dark,
1174	Variant::HighContrast => self.high_contrast.as_ref().unwrap_or(&self.dark),
1175	}
1176	}
1177	}
1178
1179	// ============================================================================
1180	// Where themes are looked for.
1181	//
1182	// Four apps built this vector by hand, two of them byte-for-byte identically,
1183	// and one of them built it backwards: the Alloy console pushed the user's own
1184	// directory first, under a comment saying "highest precedence first", when both
1185	// consumers of the vector resolve last wins. A user's custom theme lost to
1186	// the packaged one of the same id.
1187	//
1188	// Hence a builder that names the tiers rather than a function taking a vector.
1189	// The precedence is stated once, here, and a caller cannot express it backwards
1190	// because the order is not theirs to choose.
1191	// ============================================================================
1192
1193	/// Builds the search path [`load_theme`] and [`list_themes_from_dirs`] take.
1194	///
1195	/// Tiers are added in whatever order is convenient and always end up in
1196	/// precedence order: the user's own themes win, then whatever the system
1197	/// ships, then whatever the app bundles.
1198	///
1199	/// A directory that does not exist is dropped rather than carried, so callers
1200	/// can offer every tier they might have without checking each one.
1201	#[derive(Debug, Default, Clone)]
1202	pub struct ThemeDirs {
1203	bundled: Vec<PathBuf>,
1204	system: Vec<PathBuf>,
1205	custom: Option<PathBuf>,
1206	}
1207
1208	impl ThemeDirs {
1209	#[must_use]
1210	pub fn new() -> Self {
1211	Self::default()
1212	}
1213
1214	/// Themes the app ships with. Lowest precedence.
1215	///
1216	/// Takes more than one because a Tauri app has two: the bundled resource
1217	/// directory in production, and the tree `build.rs` materialized for a
1218	/// `cargo run` that has no resource directory at all.
1219	#[must_use]
1220	pub fn bundled(mut self, dir: Option<PathBuf>) -> Self {
1221	self.bundled.extend(dir);
1222	self
1223	}
1224
1225	/// Themes the machine ships, from an image or a package. Overrides bundled.
1226	#[must_use]
1227	pub fn system(mut self, dir: Option<PathBuf>) -> Self {
1228	self.system.extend(dir);
1229	self
1230	}
1231
1232	/// The user's own themes. Highest precedence, and the only tier flagged
1233	/// custom, which is what makes them exportable and deletable.
1234	#[must_use]
1235	pub fn custom(mut self, dir: Option<PathBuf>) -> Self {
1236	self.custom = dir;
1237	self
1238	}
1239
1240	/// The search path, lowest precedence first.
1241	#[must_use]
1242	pub fn build(self) -> Vec<(PathBuf, bool)> {
1243	let mut dirs = Vec::new();
1244	for dir in self.bundled.into_iter().chain(self.system) {
1245	if dir.is_dir() {
1246	dirs.push((dir, false));
1247	}
1248	}
1249	if let Some(dir) = self.custom
1250	&& dir.is_dir()
1251	{
1252	dirs.push((dir, true));
1253	}
1254	dirs
1255	}
1256	}
1257
1258	/// Extract the intent color sections into a flat `HashMap` with dotted keys
1259	/// like `"surface.page"`, `"status.danger"`, `"category.one"`.
1260	///
1261	/// The tonal steps of `content.primary` are filled in here rather than read, by
1262	/// [`derive_tonal_steps`]. Anything a theme authored under those keys is
1263	/// replaced.
1264	pub fn extract_colors(table: &toml::Table) -> HashMap<String, String> {
1265	let mut colors = HashMap::new();
1266	for section in COLOR_SECTIONS {
1267	if let Some(sect) = table.get(*section).and_then(\|s\| s.as_table()) {
1268	for (key, val) in sect {
1269	if let Some(color) = val.as_str() {
1270	colors.insert(format!("{section}.{key}"), color.to_string());
1271	}
1272	}
1273	}
1274	}
1275	derive_tonal_steps(&mut colors);
1276	colors
1277	}
1278
1279	/// Fill in the tonal steps of `content.primary`, overwriting whatever the theme
1280	/// authored under those keys.
1281	///
1282	/// # Why they are not authored
1283	///
1284	/// `content.secondary` and `content.muted` are not independent colours. They are
1285	/// the ink, one step and two steps back, and a theme that names them separately
1286	/// is stating three times something it stated once — which is how three of the
1287	/// bundled themes came to author a `secondary` lighter than their own
1288	/// `primary` (nord, solarized-dark) or identical to it (dracula), inverting the
1289	/// emphasis ramp the whole vocabulary rests on. Deriving them makes
1290	/// `content` > `content-secondary` > `content-muted` true by construction in
1291	/// every theme, including one a user writes.
1292	///
1293	/// Applied at load rather than in [`resolve`] so that there is one answer: the
1294	/// resolved token layer, the ANSI table ([`ansi_intent`] reads authored keys),
1295	/// and every consumer holding a [`ThemeColors`] all see the same value. A
1296	/// derivation visible from only one of those is how a terminal and a webview
1297	/// come to disagree about what muted means.
1298	///
1299	/// Both keys need `content.primary` and `surface.page` to exist and parse. When
1300	/// either is missing the step is skipped and anything authored is left where it
1301	/// is, mirroring the skip-missing behaviour of the rest of the crate — a
1302	/// half-written theme keeps whatever it has rather than losing it.
1303	pub fn derive_tonal_steps<S: std::hash::BuildHasher>(colors: &mut HashMap<String, String, S>) {
1304	let ink = colors.get("content.primary").and_then(\|v\| Rgb::from_hex(v));
1305	let page = colors.get("surface.page").and_then(\|v\| Rgb::from_hex(v));
1306	let (Some(ink), Some(page)) = (ink, page) else {
1307	return;
1308	};
1309	for (key, step) in [
1310	("content.secondary", Emphasis::Secondary),
1311	("content.muted", Emphasis::Muted),
1312	] {
1313	colors.insert(key.to_string(), emphasized(ink, page, step).to_hex());
1314	}
1315	}
1316
1317	/// Scan directories for `.toml` theme files and return metadata for each.
1318	///
1319	/// Directories are checked in order; later entries override earlier ones by ID.
1320	/// Each entry in `dirs` is `(path, is_custom)`.
1321	pub fn list_themes_from_dirs(dirs: &[(PathBuf, bool)]) -> Vec<ThemeMeta> {
1322	let mut seen: HashMap<String, ThemeMeta> = HashMap::new();
1323
1324	for (dir, is_custom) in dirs {
1325	let Ok(entries) = std::fs::read_dir(dir) else {
1326	continue;
1327	};
1328
1329	for entry in entries {
1330	let Ok(entry) = entry else {
1331	continue;
1332	};
1333	let path = entry.path();
1334	if path.extension().and_then(\|e\| e.to_str()) != Some("toml") {
1335	continue;
1336	}
1337
1338	let id = path
1339	.file_stem()
1340	.and_then(\|s\| s.to_str())
1341	.unwrap_or_default()
1342	.to_string();
1343
1344	let Ok(content) = std::fs::read_to_string(&path) else {
1345	continue;
1346	};
1347	let table: toml::Table = match content.parse() {
1348	Ok(t) => t,
1349	Err(_) => continue,
1350	};
1351
1352	seen.insert(id.clone(), parse_meta(&id, &table, *is_custom));
1353	}
1354	}
1355
1356	let mut themes: Vec<ThemeMeta> = seen.into_values().collect();
1357	themes.sort_by(\|a, b\| a.name.cmp(&b.name));
1358	themes
1359	}
1360
1361	/// Find a theme file by ID in the given directories.
1362	///
1363	/// Checks directories in reverse order so the highest-priority directory wins.
1364	/// Returns `(path, is_custom)` or `None` if not found.
1365	pub fn find_theme_path(dirs: &[(PathBuf, bool)], id: &str) -> Option<(PathBuf, bool)> {
1366	let filename = format!("{id}.toml");
1367
1368	for (dir, is_custom) in dirs.iter().rev() {
1369	let path = dir.join(&filename);
1370	if path.is_file() {
1371	return Some((path, *is_custom));
1372	}
1373	}
1374
1375	None
1376	}
1377
1378	/// Parse a complete theme (metadata + colors) from raw TOML content, with no
1379	/// filesystem access. For callers that embed themes at compile time.
1380	pub fn parse_theme_str(id: &str, content: &str, is_custom: bool) -> Result<ThemeColors, String> {
1381	validate_theme_id(id)?;
1382	let table: toml::Table = content
1383	.parse()
1384	.map_err(\|e\| format!("Failed to parse theme '{id}': {e}"))?;
1385	let meta = parse_meta(id, &table, is_custom);
1386	let colors = extract_colors(&table);
1387	Ok(ThemeColors { meta, colors })
1388	}
1389
1390	/// Load a complete theme (metadata + colors) by ID from the given directories.
1391	pub fn load_theme(dirs: &[(PathBuf, bool)], id: &str) -> Result<ThemeColors, String> {
1392	validate_theme_id(id)?;
1393
1394	let (path, is_custom) =
1395	find_theme_path(dirs, id).ok_or_else(\|\| format!("Theme '{id}' not found"))?;
1396
1397	let content = std::fs::read_to_string(&path)
1398	.map_err(\|e\| format!("Failed to read {}: {}", path.display(), e))?;
1399
1400	let table: toml::Table = content
1401	.parse()
1402	.map_err(\|e\| format!("Failed to parse {}: {}", path.display(), e))?;
1403
1404	let meta = parse_meta(id, &table, is_custom);
1405	let colors = extract_colors(&table);
1406
1407	Ok(ThemeColors { meta, colors })
1408	}
1409
1410	/// Load a theme and resolve it to the full intent token set in one step.
1411	pub fn load_semantic(dirs: &[(PathBuf, bool)], id: &str) -> Result<SemanticTokens, String> {
1412	Ok(resolve(&load_theme(dirs, id)?))
1413	}
1414
1415	/// Import a theme TOML file into the custom themes directory.
1416	///
1417	/// Validates that the file is parseable TOML with at least one intent color
1418	/// section, then copies it to `custom_dir/{id}.toml`. Returns the theme metadata.
1419	pub fn import_theme(source_path: &Path, custom_dir: &Path) -> Result<ThemeMeta, String> {
1420	let content = std::fs::read_to_string(source_path)
1421	.map_err(\|e\| format!("Failed to read {}: {}", source_path.display(), e))?;
1422
1423	let table: toml::Table = content.parse().map_err(\|e\| format!("Invalid TOML: {e}"))?;
1424
1425	let has_colors = COLOR_SECTIONS
1426	.iter()
1427	.any(\|s\| table.get(*s).and_then(\|v\| v.as_table()).is_some());
1428	if !has_colors {
1429	return Err(format!(
1430	"Theme file must have at least one color section ({})",
1431	COLOR_SECTIONS.join(", ")
1432	));
1433	}
1434
1435	let id = source_path
1436	.file_stem()
1437	.and_then(\|s\| s.to_str())
1438	.ok_or("Invalid file name")?
1439	.to_string();
1440	validate_theme_id(&id)?;
1441
1442	std::fs::create_dir_all(custom_dir)
1443	.map_err(\|e\| format!("Failed to create {}: {}", custom_dir.display(), e))?;
1444
1445	let dest = custom_dir.join(format!("{id}.toml"));
1446	std::fs::copy(source_path, &dest).map_err(\|e\| format!("Failed to copy theme: {e}"))?;
1447
1448	Ok(parse_meta(&id, &table, true))
1449	}
1450
1451	/// Delete a custom theme by ID.
1452	///
1453	/// Only operates on `custom_dir` — bundled themes are not deletable through
1454	/// this entry point.
1455	pub fn delete_theme(custom_dir: &Path, id: &str) -> Result<(), String> {
1456	validate_theme_id(id)?;
1457
1458	let path = custom_dir.join(format!("{id}.toml"));
1459	if !path.is_file() {
1460	return Err(format!("Custom theme '{id}' not found"));
1461	}
1462
1463	std::fs::remove_file(&path).map_err(\|e\| format!("Failed to delete {}: {}", path.display(), e))
1464	}
1465
1466	/// A four-color preview for theme thumbnails: the representative swatch from
1467	/// each of the principal roles.
1468	#[derive(Debug, Clone, Serialize)]
1469	#[serde(rename_all = "camelCase")]
1470	pub struct ThemePreview {
1471	pub meta: ThemeMeta,
1472	/// Page background (`surface.page`).
1473	pub background: Option<String>,
1474	/// Body text (`content.primary`).
1475	pub foreground: Option<String>,
1476	/// Brand/interactive color (`action.primary`).
1477	pub accent: Option<String>,
1478	/// Divider/outline color (`line.border`).
1479	pub border: Option<String>,
1480	}
1481
1482	fn color_at(table: &toml::Table, section: &str, key: &str) -> Option<String> {
1483	table
1484	.get(section)
1485	.and_then(\|s\| s.as_table())
1486	.and_then(\|s\| s.get(key))
1487	.and_then(\|v\| v.as_str())
1488	.map(std::string::ToString::to_string)
1489	}
1490
1491	/// Load just the preview swatches for a theme — for UI thumbnails.
1492	pub fn load_theme_preview(dirs: &[(PathBuf, bool)], id: &str) -> Result<ThemePreview, String> {
1493	validate_theme_id(id)?;
1494
1495	let (path, is_custom) =
1496	find_theme_path(dirs, id).ok_or_else(\|\| format!("Theme '{id}' not found"))?;
1497
1498	let content = std::fs::read_to_string(&path)
1499	.map_err(\|e\| format!("Failed to read {}: {}", path.display(), e))?;
1500
1501	let table: toml::Table = content
1502	.parse()
1503	.map_err(\|e\| format!("Failed to parse {}: {}", path.display(), e))?;
1504
1505	Ok(ThemePreview {
1506	meta: parse_meta(id, &table, is_custom),
1507	background: color_at(&table, "surface", "page"),
1508	foreground: color_at(&table, "content", "primary"),
1509	accent: color_at(&table, "action", "primary"),
1510	border: color_at(&table, "line", "border"),
1511	})
1512	}
1513
1514	/// Export a theme to a user-chosen path.
1515	pub fn export_theme(dirs: &[(PathBuf, bool)], id: &str, dest_path: &Path) -> Result<(), String> {
1516	validate_theme_id(id)?;
1517
1518	let (source, _) = find_theme_path(dirs, id).ok_or_else(\|\| format!("Theme '{id}' not found"))?;
1519
1520	std::fs::copy(&source, dest_path).map_err(\|e\| format!("Failed to export theme: {e}"))?;
1521
1522	Ok(())
1523	}
1524
1525	/// The themes this crate ships, embedded at compile time.
1526	///
1527	/// `include_dir` is an implementation detail: the public API hands back plain
1528	/// `(id, toml_source)` pairs, so how the data is embedded can change without
1529	/// a breaking release.
1530	static EMBEDDED: include_dir::Dir<'static> =
1531	include_dir::include_dir!("$CARGO_MANIFEST_DIR/themes");
1532
1533	/// The themes this crate ships, as `(id, toml_source)` pairs.
1534	///
1535	/// This is the path-free way to reach the bundled set, for consumers that
1536	/// cannot rely on a directory existing at runtime: a crate pulled from
1537	/// crates.io lives in a registry checkout whose location is not knowable at
1538	/// compile time, so `include_dir!` and asset-bundling globs in the depending
1539	/// crate have nothing stable to point at. Embedding here and re-exporting the
1540	/// contents gives them one source of truth without a path.
1541	///
1542	/// Ordering follows the embedded directory and is not guaranteed; collect and
1543	/// sort by id where a stable order matters (a theme picker, say).
1544	pub fn embedded_themes() -> impl Iterator<Item = (&'static str, &'static str)> {
1545	EMBEDDED.files().filter_map(\|file\| {
1546	let path = file.path();
1547	if path.extension().and_then(\|e\| e.to_str()) != Some("toml") {
1548	return None;
1549	}
1550	let id = path.file_stem()?.to_str()?;
1551	Some((id, file.contents_utf8()?))
1552	})
1553	}
1554
1555	/// The theme directory this crate ships, for use as a build-from-source
1556	/// fallback.
1557	///
1558	/// Resolves against `makeover`'s own manifest directory, fixed at compile
1559	/// time, so it works from a path dependency and from a cargo git checkout
1560	/// alike. Installed systems should put their packaged theme directory ahead
1561	/// of this in the search path; this is the entry that keeps `cargo run` in a
1562	/// fresh clone from coming up with no themes at all.
1563	///
1564	/// Returns `None` when the directory is absent — a cargo cache that has been
1565	/// cleaned, or a vendored copy that dropped the data — so callers degrade to
1566	/// their remaining search path rather than failing.
1567	pub fn bundled_themes_dir() -> Option<PathBuf> {
1568	let themes = Path::new(env!("CARGO_MANIFEST_DIR")).join("themes");
1569	if themes.is_dir() { Some(themes) } else { None }
1570	}
1571
1572	#[cfg(test)]
1573	mod tests {
1574	use super::*;
1575	use std::fs;
1576
1577	// ---- id validation ----
1578
1579	#[test]
1580	fn validate_theme_id_alphanumeric() {
1581	assert!(validate_theme_id("darkmode").is_ok());
1582	assert!(validate_theme_id("Theme123").is_ok());
1583	}
1584
1585	#[test]
1586	fn validate_theme_id_hyphens_underscores() {
1587	assert!(validate_theme_id("dark-mode").is_ok());
1588	assert!(validate_theme_id("my_theme_v2").is_ok());
1589	}
1590
1591	#[test]
1592	fn validate_theme_id_rejects_path_traversal() {
1593	assert!(validate_theme_id("../etc/passwd").is_err());
1594	assert!(validate_theme_id("foo/bar").is_err());
1595	assert!(validate_theme_id("theme.toml").is_err());
1596	}
1597
1598	// ---- low-color terminals ----
1599
1600	#[test]
1601	fn the_ansi_palette_is_sixteen_distinct_colors() {
1602	let mut seen: Vec<(u8, u8, u8)> = ANSI_16.iter().map(\|c\| c.tuple()).collect();
1603	seen.sort_unstable();
1604	seen.dedup();
1605	assert_eq!(seen.len(), 16);
1606	}
1607
1608	// ---- the intent-to-slot table ----
1609
1610	// Sixteen slots, every one of them answered. A caller filling a terminal
1611	// palette has no fallback for a hole: the slot would keep whatever the
1612	// emulator started with, and one raw ANSI colour in a themed table is more
1613	// obviously wrong than all sixteen would be.
1614	#[test]
1615	fn every_ansi_slot_names_an_intent_on_either_polarity() {
1616	for variant in ["light", "dark", "high-contrast"] {
1617	for index in 0..16 {
1618	assert!(
1619	ansi_intent(index, variant).is_some(),
1620	"slot {index} unanswered on {variant}"
1621	);
1622	}
1623	assert_eq!(ansi_intent(16, variant), None);
1624	}
1625	}
1626
1627	// The property the four achromatic slots exist to hold: 0 is the darkest
1628	// tone the theme offers and 15 the lightest, in either polarity. A table
1629	// that pins slot 0 to `content.primary` passes this on a light theme and
1630	// inverts on a dark one, which is the bug the polarity split fixes.
1631	#[test]
1632	fn ansi_zero_is_darker_than_ansi_fifteen_on_either_polarity() {
1633	for id in ["akari-dawn", "akari-night"] {
1634	let theme = bundled(id);
1635	let slot = \|i: usize\| -> Rgb {
1636	let key = ansi_intent(i, &theme.meta.variant).expect("in range");
1637	Rgb::from_hex(theme.colors.get(key).expect("theme carries it")).expect("valid hex")
1638	};
1639	assert!(
1640	rel_luminance(slot(0)) < rel_luminance(slot(15)),
1641	"{id}: ANSI 0 {} should be darker than ANSI 15 {}",
1642	slot(0).to_hex(),
1643	slot(15).to_hex(),
1644	);
1645	}
1646	}
1647
1648	// The pair a greeter draws with: its container on 7, its text on 0. If
1649	// those collapse the login screen is one flat block, and slot 7 being a
1650	// surface rather than a text tone is what keeps them apart.
1651	#[test]
1652	fn the_container_slot_and_the_text_slot_stay_legible() {
1653	for id in ["akari-dawn", "akari-night"] {
1654	let theme = bundled(id);
1655	let slot = \|i: usize\| -> Rgb {
1656	let key = ansi_intent(i, &theme.meta.variant).expect("in range");
1657	Rgb::from_hex(theme.colors.get(key).expect("theme carries it")).expect("valid hex")
1658	};
1659	let contrast = wcag_contrast(slot(0), slot(7));
1660	assert!(contrast >= 4.5, "{id}: ANSI 0 on ANSI 7 is {contrast:.2}:1");
1661	}
1662	}
1663
1664	// The hues do not move with polarity. Red is the theme's danger tone on a
1665	// light theme and on a dark one, which is why only four slots are in the
1666	// polarity table at all.
1667	#[test]
1668	fn the_chromatic_slots_do_not_vary_with_polarity() {
1669	for index in [1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 13, 14] {
1670	assert_eq!(
1671	ansi_intent(index, "light"),
1672	ansi_intent(index, "dark"),
1673	"slot {index} moved with polarity"
1674	);
1675	}
1676	}
1677
1678	fn bundled(id: &str) -> ThemeColors {
1679	let dir = bundled_themes_dir().expect("makeover ships its themes");
1680	load_theme(&[(dir, false)], id).expect("the akari pair ships")
1681	}
1682
1683	#[test]
1684	fn quantize_picks_the_obvious_entry() {
1685	let black = Rgb { r: 0, g: 0, b: 0 };
1686	let white = Rgb {
1687	r: 255,
1688	g: 255,
1689	b: 255,
1690	};
1691	assert_eq!(quantize(black, &ANSI_16), 0);
1692	assert_eq!(quantize(white, &ANSI_16), 15);
1693	}
1694
1695	// Nearest-entry quantization is per-color, so two colors a theme keeps
1696	// apart can arrive as one. These two are both closest to the palette's
1697	// light gray, and a border drawn in one on a page painted the other is not
1698	// drawn at all.
1699	#[test]
1700	fn two_colors_can_quantize_to_one_entry() {
1701	let page = Rgb::from_hex("#a8a8a8").unwrap();
1702	let border = Rgb::from_hex("#b4b4b4").unwrap();
1703
1704	assert_eq!(quantize(page, &ANSI_16), quantize(border, &ANSI_16));
1705	assert_ne!(
1706	quantize_against(border, page, &ANSI_16),
1707	quantize(page, &ANSI_16)
1708	);
1709	}
1710
1711	#[test]
1712	fn quantize_against_keeps_the_border_off_the_page() {
1713	let page = Rgb::from_hex("#e4ded6").unwrap();
1714	let border = Rgb::from_hex("#7f786d").unwrap();
1715
1716	let shown_page = ANSI_16[quantize(page, &ANSI_16)];
1717	let shown_border = ANSI_16[quantize_against(border, page, &ANSI_16)];
1718
1719	assert!(
1720	wcag_contrast(shown_border, shown_page) >= DISTINCT,
1721	"border {} on page {} is {:.2}:1",
1722	shown_border.to_hex(),
1723	shown_page.to_hex(),
1724	wcag_contrast(shown_border, shown_page)
1725	);
1726	}
1727
1728	// A color that already reads against its background is left where it is,
1729	// so this can be applied without redesigning what already worked.
1730	#[test]
1731	fn quantize_against_leaves_a_readable_color_alone() {
1732	let page = Rgb::from_hex("#e4ded6").unwrap();
1733	let text = Rgb::from_hex("#1a1816").unwrap();
1734
1735	assert_eq!(
1736	quantize_against(text, page, &ANSI_16),
1737	quantize(text, &ANSI_16)
1738	);
1739	}
1740
1741	// With nothing in the palette to satisfy the request, the most legible
1742	// entry is the answer. Returning the nearest one would return the
1743	// background itself, which is the failure this function exists to avoid.
1744	#[test]
1745	fn an_impossible_palette_gets_the_most_legible_entry() {
1746	let page = Rgb::from_hex("#ffffff").unwrap();
1747	let border = Rgb::from_hex("#fefefe").unwrap();
1748	let palette = [
1749	Rgb::from_hex("#ffffff").unwrap(),
1750	Rgb::from_hex("#fdfdfd").unwrap(),
1751	];
1752
1753	let chosen = palette[quantize_against(border, page, &palette)];
1754	assert_eq!(chosen.to_hex(), "#fdfdfd");
1755	}
1756
1757	// ---- meta ----
1758
1759	#[test]
1760	fn parse_meta_with_name_and_variant() {
1761	let table: toml::Table = "[meta]\nname = \"Nord\"\nvariant = \"light\"\n"
1762	.parse()
1763	.unwrap();
1764	let meta = parse_meta("nord", &table, false);
1765	assert_eq!(meta.id, "nord");
1766	assert_eq!(meta.name, "Nord");
1767	assert_eq!(meta.variant, "light");
1768	assert!(!meta.is_custom);
1769	}
1770
1771	#[test]
1772	fn parse_meta_defaults_to_id_and_dark() {
1773	let table: toml::Table = "".parse().unwrap();
1774	let meta = parse_meta("fallback", &table, true);
1775	assert_eq!(meta.name, "fallback");
1776	assert_eq!(meta.variant, "dark");
1777	assert!(meta.is_custom);
1778	}
1779
1780	// ---- color math (formulas must match the apps they came from) ----
1781
1782	#[test]
1783	fn rgb_hex_roundtrip() {
1784	assert_eq!(
1785	Rgb::from_hex("#6196FF").unwrap(),
1786	Rgb {
1787	r: 0x61,
1788	g: 0x96,
1789	b: 0xff
1790	}
1791	);
1792	assert_eq!(
1793	Rgb::from_hex("#abc").unwrap(),
1794	Rgb {
1795	r: 0xaa,
1796	g: 0xbb,
1797	b: 0xcc
1798	}
1799	);
1800	assert_eq!(
1801	Rgb {
1802	r: 0x61,
1803	g: 0x96,
1804	b: 0xff
1805	}
1806	.to_hex(),
1807	"#6196ff"
1808	);
1809	assert!(Rgb::from_hex("not-a-color").is_none());
1810	}
1811
1812	#[test]
1813	fn oklab_roundtrips_within_tolerance() {
1814	for hex in ["#6196ff", "#2e3440", "#ffffff", "#000000", "#c0392b"] {
1815	let c = Rgb::from_hex(hex).unwrap();
1816	let back = Rgb::from_oklab(c.to_oklab());
1817	// Gamut round-trip is near-exact (±1 per channel from rounding).
1818	assert!((c.r as i16 - back.r as i16).abs() <= 1, "{hex} r");
1819	assert!((c.g as i16 - back.g as i16).abs() <= 1, "{hex} g");
1820	assert!((c.b as i16 - back.b as i16).abs() <= 1, "{hex} b");
1821	}
1822	}
1823
1824	#[test]
1825	fn wcag_contrast_known_pairs() {
1826	let white = Rgb {
1827	r: 255,
1828	g: 255,
1829	b: 255,
1830	};
1831	let black = Rgb { r: 0, g: 0, b: 0 };
1832	assert!((wcag_contrast(white, black) - 21.0).abs() < 0.01);
1833	assert!((wcag_contrast(white, white) - 1.0).abs() < 0.01);
1834	}
1835
1836	#[test]
1837	fn readable_on_picks_by_wcag() {
1838	assert_eq!(
1839	readable_on(Rgb {
1840	r: 255,
1841	g: 255,
1842	b: 255
1843	}),
1844	Rgb { r: 0, g: 0, b: 0 }
1845	);
1846	assert_eq!(
1847	readable_on(Rgb { r: 0, g: 0, b: 0 }),
1848	Rgb {
1849	r: 255,
1850	g: 255,
1851	b: 255
1852	}
1853	);
1854	// A light blue action -> black text reads better.
1855	let action = Rgb::from_hex("#6196ff").unwrap();
1856	assert_eq!(readable_on(action), Rgb { r: 0, g: 0, b: 0 });
1857	}
1858
1859	#[test]
1860	fn lighten_darken_move_oklab_lightness() {
1861	let c = Rgb::from_hex("#6196ff").unwrap();
1862	let l0 = c.to_oklab().l;
1863	assert!(lighten(c, 0.05).to_oklab().l > l0);
1864	assert!(darken(c, 0.05).to_oklab().l < l0);
1865	}
1866
1867	#[test]
1868	fn mix_endpoints_and_midpoint() {
1869	let a = Rgb::from_hex("#000000").unwrap();
1870	let b = Rgb::from_hex("#6196ff").unwrap();
1871	assert_eq!(mix(a, b, 0.0), a);
1872	assert_eq!(mix(a, b, 1.0), b);
1873	// Midpoint sits between the endpoints in OKLab lightness.
1874	let mid = mix(a, b, 0.5).to_oklab().l;
1875	assert!(mid > a.to_oklab().l && mid < b.to_oklab().l);
1876	}
1877
1878	// ---- extract + resolve ----
1879
1880	fn nord_toml() -> &'static str {
1881	r##"
1882	[meta]
1883	name = "Nord"
1884	variant = "dark"
1885
1886	[surface]
1887	page = "#2e3440"
1888	raised = "#3b4252"
1889	sunken = "#434c5e"
1890	overlay = "#3b4252"
1891
1892	[content]
1893	primary = "#d8dee9"
1894	secondary = "#e5e9f0"
1895	muted = "#616e88"
1896
1897	[action]
1898	primary = "#81a1c1"
1899
1900	[status]
1901	danger = "#bf616a"
1902	success = "#a3be8c"
1903	warning = "#ebcb8b"
1904	info = "#88c0d0"
1905
1906	[line]
1907	border = "#4c566a"
1908
1909	[category]
1910	one = "#bf616a"
1911	two = "#a3be8c"
1912	three = "#81a1c1"
1913	four = "#ebcb8b"
1914	five = "#b48ead"
1915	six = "#88c0d0"
1916	"##
1917	}
1918
1919	#[test]
1920	fn extract_colors_reads_intent_sections() {
1921	let table: toml::Table = nord_toml().parse().unwrap();
1922	let colors = extract_colors(&table);
1923	assert_eq!(colors.get("surface.page").unwrap(), "#2e3440");
1924	assert_eq!(colors.get("content.primary").unwrap(), "#d8dee9");
1925	assert_eq!(colors.get("action.primary").unwrap(), "#81a1c1");
1926	assert_eq!(colors.get("status.danger").unwrap(), "#bf616a");
1927	assert_eq!(colors.get("line.border").unwrap(), "#4c566a");
1928	assert_eq!(colors.get("category.five").unwrap(), "#b48ead");
1929	assert_eq!(colors.len(), 19);
1930	}
1931
1932	#[test]
1933	fn resolve_base_intents_passthrough() {
1934	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
1935	let t = resolve(&theme);
1936	assert_eq!(t.hex("surface-page"), Some("#2e3440"));
1937	assert_eq!(t.hex("content"), Some("#d8dee9")); // content.primary -> content
1938	// Not a passthrough: a tonal step of the ink, whatever the file said.
1939	assert_eq!(
1940	t.hex("content-muted").unwrap(),
1941	emphasized(
1942	Rgb::from_hex("#d8dee9").unwrap(),
1943	Rgb::from_hex("#2e3440").unwrap(),
1944	Emphasis::Muted
1945	)
1946	.to_hex()
1947	);
1948	assert_eq!(t.hex("action"), Some("#81a1c1"));
1949	assert_eq!(t.hex("danger"), Some("#bf616a"));
1950	assert_eq!(t.hex("border"), Some("#4c566a"));
1951	assert_eq!(t.hex("category-five"), Some("#b48ead"));
1952	}
1953
1954	#[test]
1955	fn a_tonal_step_lands_between_its_base_and_its_ground() {
1956	let ink = Rgb::from_hex("#d8dee9").unwrap();
1957	let page = Rgb::from_hex("#2e3440").unwrap();
1958	for step in [Emphasis::Full, Emphasis::Secondary, Emphasis::Muted] {
1959	let out = emphasized(ink, page, step).to_oklab().l;
1960	assert!(
1961	out <= ink.to_oklab().l && out >= page.to_oklab().l,
1962	"{step:?} left the interval between the ink and the page"
1963	);
1964	}
1965	assert_eq!(emphasized(ink, page, Emphasis::Full).to_hex(), ink.to_hex());
1966	}
1967
1968	#[test]
1969	fn tonal_steps_compose_rather_than_compound() {
1970	// Two steps toward one ground are one step toward it, which is what
1971	// makes deriving a family recursively well-defined. Within a rounding
1972	// step, since each hop lands back in 8-bit sRGB.
1973	let ink = Rgb::from_hex("#d8dee9").unwrap();
1974	let page = Rgb::from_hex("#2e3440").unwrap();
1975	let (a, b) = (0.12f32, 0.42f32);
1976	let twice = tonal(tonal(ink, page, a), page, b);
1977	let once = tonal(ink, page, a + b - a * b);
1978	let (x, y) = (twice.tuple(), once.tuple());
1979	for (l, r) in [(x.0, y.0), (x.1, y.1), (x.2, y.2)] {
1980	assert!(l.abs_diff(r) <= 1, "{twice:?} is not {once:?}");
1981	}
1982	}
1983
1984	#[test]
1985	fn a_ratio_outside_the_interval_is_clamped_rather_than_extrapolated() {
1986	let ink = Rgb::from_hex("#d8dee9").unwrap();
1987	let page = Rgb::from_hex("#2e3440").unwrap();
1988	assert_eq!(tonal(ink, page, -1.0).to_hex(), ink.to_hex());
1989	assert_eq!(tonal(ink, page, 2.0).to_hex(), page.to_hex());
1990	}
1991
1992	#[test]
1993	fn a_derived_token_key_is_the_family_plus_the_step() {
1994	assert_eq!(Emphasis::Muted.token("content"), "content-muted");
1995	assert_eq!(Emphasis::Secondary.token("content"), "content-secondary");
1996	assert_eq!(Emphasis::Full.token("content"), "content");
1997	// The point of the suffix being a property of the step: any family can
1998	// be grouped the same way without a second table saying what it means.
1999	assert_eq!(Emphasis::Muted.token("danger"), "danger-muted");
2000	}
2001
2002	#[test]
2003	fn every_shipped_theme_ramps_one_way() {
2004	// The property authoring the steps separately could not hold: three
2005	// themes had shipped a secondary lighter than their own primary, so a
2006	// renderer reading the emphasis order got the reverse of it.
2007	for (id, toml) in embedded_themes() {
2008	let theme = parse_theme_str(id, toml, false).unwrap();
2009	let t = resolve(&theme);
2010	let page = Rgb::from_hex(t.hex("surface-page").unwrap()).unwrap();
2011	let steps = ["content", "content-secondary", "content-muted"]
2012	.map(\|k\| wcag_contrast(Rgb::from_hex(t.hex(k).unwrap()).unwrap(), page));
2013	assert!(
2014	steps[0] > steps[1] && steps[1] > steps[2],
2015	"{id}: emphasis does not fall monotonically: {steps:?}"
2016	);
2017	}
2018	}
2019
2020	#[test]
2021	fn an_authored_emphasis_step_does_not_survive_loading() {
2022	// `nord_toml` still authors both, because a user's theme file might and
2023	// the answer has to be the same one.
2024	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2025	assert_ne!(theme.colors.get("content.muted").unwrap(), "#616e88");
2026	assert_ne!(theme.colors.get("content.secondary").unwrap(), "#e5e9f0");
2027	}
2028
2029	#[test]
2030	fn a_theme_with_no_page_keeps_what_it_authored() {
2031	// Skip-missing: there is nothing to read the step against, so the step
2032	// is not taken and a half-written theme does not lose a colour.
2033	let mut colors = HashMap::new();
2034	colors.insert("content.primary".to_string(), "#d8dee9".to_string());
2035	colors.insert("content.muted".to_string(), "#616e88".to_string());
2036	derive_tonal_steps(&mut colors);
2037	assert_eq!(colors.get("content.muted").unwrap(), "#616e88");
2038	}
2039
2040	#[test]
2041	fn resolve_derived_intents() {
2042	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2043	let t = resolve(&theme);
2044	let action = Rgb::from_hex("#81a1c1").unwrap();
2045	let page = Rgb::from_hex("#2e3440").unwrap();
2046	let _ = page;
2047	assert_eq!(
2048	t.hex("action-hover").unwrap(),
2049	lighten(action, 0.05).to_hex()
2050	);
2051	assert_eq!(
2052	t.hex("content-on-action").unwrap(),
2053	readable_on(action).to_hex()
2054	);
2055	assert_eq!(t.hex("focus-ring"), Some("#81a1c1"));
2056	assert_eq!(t.hex("hover-surface"), Some("#434c5e")); // = surface.sunken
2057	// Pruned by the usage audit (0 consumers): action-active, the *-surface
2058	// tints, selection, row-stripe. Apps that need them derive inline via
2059	// the shared mix().
2060	assert!(t.hex("action-active").is_none());
2061	assert!(t.hex("danger-surface").is_none());
2062	assert!(t.hex("selection").is_none());
2063	assert!(t.hex("row-stripe").is_none());
2064	}
2065
2066	#[test]
2067	fn resolve_bevel_intents() {
2068	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2069	let t = resolve(&theme);
2070	let raised = Rgb::from_hex("#3b4252").unwrap();
2071	assert_eq!(
2072	t.hex("bevel-light").unwrap(),
2073	lighten(raised, 0.14).to_hex()
2074	);
2075	assert_eq!(t.hex("bevel-dark").unwrap(), darken(raised, 0.18).to_hex());
2076	}
2077
2078	// A bevel is two edges around one face, so both edges have to be visibly off
2079	// that face or the control never resolves as lit. The lightening clamps at
2080	// the top of the ramp, which means a theme authoring a white raised surface
2081	// gets a highlight identical to the surface it is meant to sit on.
2082	//
2083	// The list is asserted rather than merely reported so that changing a theme
2084	// has to come here and say so. Shrinking it is the fix; growing it is a
2085	// regression in the theme, not in this derivation.
2086	#[test]
2087	fn bevel_edges_are_distinct_from_their_face() {
2088	const CANNOT_BEVEL: &[&str] = &["neobrute", "oxocarbon-light"];
2089
2090	let mut degenerate: Vec<String> = Vec::new();
2091	for (id, source) in embedded_themes() {
2092	let theme = parse_theme_str(id, source, false).unwrap();
2093	let t = resolve(&theme);
2094	let Some(raised) = t.hex("surface-raised") else {
2095	continue;
2096	};
2097	let light = t.hex("bevel-light").expect("raised implies bevel-light");
2098	let dark = t.hex("bevel-dark").expect("raised implies bevel-dark");
2099	if light == raised \|\| dark == raised {
2100	degenerate.push(id.to_string());
2101	}
2102	}
2103	degenerate.sort();
2104
2105	assert_eq!(
2106	degenerate, CANNOT_BEVEL,
2107	"themes whose raised surface cannot hold both bevel edges"
2108	);
2109	}
2110
2111	// The well inverts by theme, so assert both directions explicitly rather
2112	// than only the one the light themes happen to take.
2113	#[test]
2114	fn resolve_well_intent_follows_the_content_direction() {
2115	// nord is dark: light text on a dark raised surface, so the well goes
2116	// down and away from the text.
2117	let dark = resolve(&parse_theme_str("nord", nord_toml(), false).unwrap());
2118	let dark_raised = Rgb::from_hex("#3b4252").unwrap();
2119	assert_eq!(
2120	dark.hex("surface-well").unwrap(),
2121	darken(dark_raised, 0.09).to_hex()
2122	);
2123
2124	// The shipped light themes take the other branch.
2125	let goingson = embedded_themes()
2126	.into_iter()
2127	.find(\|(id, _)\| *id == "goingson")
2128	.expect("goingson is embedded")
2129	.1;
2130	let light = resolve(&parse_theme_str("goingson", goingson, false).unwrap());
2131	let light_raised = light
2132	.hex("surface-raised")
2133	.and_then(Rgb::from_hex)
2134	.expect("goingson authors a raised surface");
2135	assert_eq!(
2136	light.hex("surface-well").unwrap(),
2137	lighten(light_raised, 0.07).to_hex()
2138	);
2139	}
2140
2141	// A well is a fill, not an edge, so the only thing that makes it read is
2142	// being a different color from the surface it is cut into.
2143	//
2144	// Same shape and the same asserted-list discipline as
2145	// `bevel_edges_are_distinct_from_their_face`, and it bites the same two
2146	// themes for the same reason: a raised surface already at the top of the
2147	// ramp has nothing lighter to go to.
2148	#[test]
2149	fn well_is_distinct_from_its_face() {
2150	const CANNOT_WELL: &[&str] = &["neobrute", "oxocarbon-light"];
2151
2152	let mut degenerate: Vec<String> = Vec::new();
2153	for (id, source) in embedded_themes() {
2154	let theme = parse_theme_str(id, source, false).unwrap();
2155	let t = resolve(&theme);
2156	let Some(raised) = t.hex("surface-raised") else {
2157	continue;
2158	};
2159	let well = t.hex("surface-well").expect("raised implies surface-well");
2160	if well == raised {
2161	degenerate.push(id.to_string());
2162	}
2163	}
2164	degenerate.sort();
2165
2166	assert_eq!(
2167	degenerate, CANNOT_WELL,
2168	"themes whose raised surface cannot hold a well"
2169	);
2170	}
2171
2172	// Distinct is not the same as visible. A face near the top of the ramp
2173	// clamps partway rather than exactly, which yields a well that differs from
2174	// its face by a hex digit and by nothing the eye can find. `rosepine-dawn`
2175	// authors raised at L=0.987 and gets 0.009 of the 0.07 it asked for.
2176	//
2177	// Worth a separate test from the one above because the fix differs: an
2178	// exactly-degenerate theme needs its raised surface off the ramp end, while
2179	// these need it merely lowered. Both fixes are the theme's, not this
2180	// derivation's, which is why the list is asserted rather than warned about.
2181	#[test]
2182	fn well_is_visible_against_its_face() {
2183	// Below this, the well and its face are the same surface to a reader.
2184	const MIN_DELTA_L: f32 = 0.02;
2185	const CANNOT_HOLD_A_VISIBLE_WELL: &[&str] =
2186	&["neobrute", "oxocarbon-light", "rosepine-dawn"];
2187
2188	let mut invisible: Vec<String> = Vec::new();
2189	for (id, source) in embedded_themes() {
2190	let theme = parse_theme_str(id, source, false).unwrap();
2191	let t = resolve(&theme);
2192	let (Some(raised), Some(well)) = (
2193	t.hex("surface-raised").and_then(Rgb::from_hex),
2194	t.hex("surface-well").and_then(Rgb::from_hex),
2195	) else {
2196	continue;
2197	};
2198	if (well.to_oklab().l - raised.to_oklab().l).abs() < MIN_DELTA_L {
2199	invisible.push(id.to_string());
2200	}
2201	}
2202	invisible.sort();
2203
2204	assert_eq!(
2205	invisible, CANNOT_HOLD_A_VISIBLE_WELL,
2206	"themes whose well is too close to its face to read as one"
2207	);
2208	}
2209
2210	// The three tests above each measure a derived color against the face it was
2211	// derived from, so a theme can pass all of them and still have nothing lift
2212	// off anything: the face itself sits on the page, and that relationship is
2213	// the one a bevel needs in order to read as an object rather than as a
2214	// rectangle with decorated edges. makenot.work passed all three and could
2215	// not hold a bevel, which is what this covers.
2216	//
2217	// The threshold is picked against the ramps already ruled on rather than
2218	// against a round number. makenot.work shipped at 0.024 and was invisible,
2219	// was tried at 0.036 and rejected as marginal on badges and chips, and was
2220	// accepted at 0.058; goingson and audiofiles sit at 0.119 and 0.065. Every
2221	// ramp judged inadequate is below 0.036 and every one judged adequate is
2222	// above 0.058, so the line goes in the gap between them. Note the unit: this
2223	// is oklab L on 0 to 1, not the CIE L* on 0 to 100 that the theme files quote
2224	// in their comments, and the two are not interchangeable.
2225	//
2226	// Most of the list is imported palettes, which were authored for syntax
2227	// highlighting and owe our depth model nothing. Failing here says a theme
2228	// cannot hold a bevel, not that it is wrong. Shrinking the list is the fix;
2229	// growing it is a regression in the theme, not in this derivation.
2230	//
2231	// tokyonight left the list on 2026-08-15, and it is the only entry that could
2232	// leave without a judgment call about someone else's palette. Its page and
2233	// raised were the identical hex, so it had no ramp at all rather than a
2234	// shallow one, and the fix is upstream's own `bg_highlight` (#292e42, 0.079
2235	// above the page) rather than a color we picked. The other nineteen are
2236	// shallow ramps in published palettes, which is a different claim, and they
2237	// stay deferred until every app is migrated and eyeballed.
2238	#[test]
2239	fn raised_is_distinct_from_page() {
2240	// Below this, a raised surface and the page under it are one surface to
2241	// a reader, whichever direction the theme ramps in.
2242	const MIN_DELTA_L: f32 = 0.05;
2243	const CANNOT_LIFT_OFF_THE_PAGE: &[&str] = &[
2244	"akari-dawn",
2245	"akari-night",
2246	"ayu-light",
2247	"ayu-mirage",
2248	"catppuccin-latte",
2249	"catppuccin-mocha",
2250	"dawnfox",
2251	"dracula",
2252	"everforest",
2253	"flatwhite",
2254	"gruvbox-light",
2255	"neobrute",
2256	"one-dark",
2257	"oxocarbon-dark",
2258	"oxocarbon-light",
2259	"poimandres",
2260	"rosepine",
2261	"rosepine-dawn",
2262	"solarized-dark",
2263	];
2264
2265	let mut flat: Vec<String> = Vec::new();
2266	for (id, source) in embedded_themes() {
2267	let theme = parse_theme_str(id, source, false).unwrap();
2268	let t = resolve(&theme);
2269	let (Some(page), Some(raised)) = (
2270	t.hex("surface-page").and_then(Rgb::from_hex),
2271	t.hex("surface-raised").and_then(Rgb::from_hex),
2272	) else {
2273	continue;
2274	};
2275	if (raised.to_oklab().l - page.to_oklab().l).abs() < MIN_DELTA_L {
2276	flat.push(id.to_string());
2277	}
2278	}
2279	flat.sort();
2280
2281	assert_eq!(
2282	flat, CANNOT_LIFT_OFF_THE_PAGE,
2283	"themes whose raised surface is too close to the page to lift off it"
2284	);
2285	}
2286
2287	// What the bevel pair does on a sixteen-color terminal, measured across the
2288	// shipped set rather than assumed. Two results, both load-bearing for a
2289	// consumer that has to render one there.
2290	//
2291	// Exactly one edge survives, never both. A raised face quantizes onto one of
2292	// the palette's three grays, and the palette is too coarse to hold anything
2293	// between that entry and its neighbour, so whichever edge is pushed toward
2294	// the end of the ramp the face already sits on lands back on the face. Light
2295	// themes and most dark ones keep the shadow and lose the highlight; a face
2296	// that quantizes to black keeps the highlight and loses the shadow.
2297	//
2298	// So a low-color consumer draws the single edge it can render, on the side
2299	// the palette left it, rather than a bevel that resolves on two sides.
2300	//
2301	// And `quantize_against` is the wrong function for this pair, though it is
2302	// the right one for a border. It answers "nearest entry that clears DISTINCT
2303	// against the background", which has no notion of direction, so both edges
2304	// are pushed onto the same contrasting entry and the bevel inverts on one
2305	// side. Plain `quantize` keeps them apart and in the right order.
2306	#[test]
2307	fn a_sixteen_color_terminal_gets_one_bevel_edge_and_not_two() {
2308	for (id, source) in embedded_themes() {
2309	let theme = parse_theme_str(id, source, false).unwrap();
2310	let t = resolve(&theme);
2311	let (Some(face), Some(light), Some(dark)) = (
2312	t.hex("surface-raised").and_then(Rgb::from_hex),
2313	t.hex("bevel-light").and_then(Rgb::from_hex),
2314	t.hex("bevel-dark").and_then(Rgb::from_hex),
2315	) else {
2316	continue;
2317	};
2318
2319	let face_index = quantize(face, &ANSI_16);
2320	let light_survives = quantize(light, &ANSI_16) != face_index;
2321	let dark_survives = quantize(dark, &ANSI_16) != face_index;
2322	assert!(
2323	light_survives != dark_survives,
2324	"{id}: expected exactly one bevel edge to survive 16 colors, \
2325	highlight {light_survives} shadow {dark_survives}"
2326	);
2327
2328	// Direction-blind, so it collapses the pair it is asked to separate.
2329	assert_eq!(
2330	quantize_against(light, face, &ANSI_16),
2331	quantize_against(dark, face, &ANSI_16),
2332	"{id}: quantize_against is expected to be unusable for a bevel pair"
2333	);
2334	}
2335	}
2336
2337	// 256 colors is where the bevel starts working. At 16 every shipped theme
2338	// loses an edge; here all but the five whose raised surface sits at the very
2339	// top of the ramp keep both, and those five fail for the reason they fail in
2340	// truecolor rather than for a palette reason.
2341	//
2342	// Three of them cannot bevel at any depth, so they are the
2343	// `bevel_edges_are_distinct_from_their_face` set. The other two are new here:
2344	// they hold a highlight in 24-bit, but not one wide enough to survive
2345	// rounding onto the cube.
2346	#[test]
2347	fn two_hundred_fifty_six_colors_keep_both_bevel_edges() {
2348	const LOSES_AN_EDGE: &[&str] = &[
2349	"gruvbox-light",
2350	"neobrute",
2351	"oxocarbon-light",
2352	"rosepine-dawn",
2353	];
2354
2355	let mut lost: Vec<String> = Vec::new();
2356	for (id, source) in embedded_themes() {
2357	let theme = parse_theme_str(id, source, false).unwrap();
2358	let t = resolve(&theme);
2359	let (Some(face), Some(light), Some(dark)) = (
2360	t.hex("surface-raised").and_then(Rgb::from_hex),
2361	t.hex("bevel-light").and_then(Rgb::from_hex),
2362	t.hex("bevel-dark").and_then(Rgb::from_hex),
2363	) else {
2364	continue;
2365	};
2366
2367	// Against the fixed region, which is what a consumer should use: a
2368	// match in the low sixteen is a match against a repaintable color.
2369	let f = quantize(face, ANSI_240);
2370	let l = quantize(light, ANSI_240);
2371	let d = quantize(dark, ANSI_240);
2372	if l == f \|\| d == f \|\| l == d {
2373	lost.push(id.to_string());
2374	}
2375	}
2376	lost.sort();
2377
2378	assert_eq!(
2379	lost, LOSES_AN_EDGE,
2380	"themes that cannot hold a two-tone bevel on a 256-color terminal"
2381	);
2382	}
2383
2384	#[test]
2385	fn the_256_table_has_its_three_regions() {
2386	// Index is the escape-sequence index, so the low sixteen must match.
2387	assert_eq!(ANSI_256[..16], ANSI_16);
2388	// The cube's corners, at both ends and one interior level.
2389	assert_eq!(ANSI_256[16].tuple(), (0, 0, 0));
2390	assert_eq!(ANSI_256[231].tuple(), (255, 255, 255));
2391	assert_eq!(ANSI_256[16 + 36 * 2 + 6 * 3 + 4].tuple(), (135, 175, 215));
2392	// The gray ramp runs 8 to 238 and contains neither black nor white.
2393	assert_eq!(ANSI_256[232].tuple(), (8, 8, 8));
2394	assert_eq!(ANSI_256[255].tuple(), (238, 238, 238));
2395	// The fixed region is the table minus the repaintable colors.
2396	assert_eq!(ANSI_240.len(), 240);
2397	assert_eq!(ANSI_240[0], ANSI_256[ANSI_240_OFFSET]);
2398	}
2399
2400	#[test]
2401	fn resolve_overlay_is_dark_translucent_scrim() {
2402	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2403	let t = resolve(&theme);
2404	let overlay = t.hex("overlay").unwrap();
2405	assert!(
2406	overlay.starts_with("rgba("),
2407	"overlay is translucent: {overlay}"
2408	);
2409	assert!(overlay.ends_with(", 0.5)"));
2410	// The scrim tone is anchored very dark regardless of theme.
2411	let inner = overlay
2412	.trim_start_matches("rgba(")
2413	.trim_end_matches(", 0.5)");
2414	let parts: Vec<u8> = inner.split(", ").map(\|p\| p.parse().unwrap()).collect();
2415	let scrim = Rgb {
2416	r: parts[0],
2417	g: parts[1],
2418	b: parts[2],
2419	};
2420	assert!(scrim.to_oklab().l < 0.2, "scrim must be near-black");
2421	}
2422
2423	/// Every shipped theme derives it, on both polarities, and it is always a
2424	/// near-black translucent tone. A shadow tinted to a dark theme's own
2425	/// lightness would not read as one.
2426	#[test]
2427	fn elevation_is_a_near_black_cast_on_every_theme() {
2428	for (id, source) in embedded_themes() {
2429	let theme = parse_theme_str(id, source, false).unwrap();
2430	let t = resolve(&theme);
2431	let Some(elevation) = t.hex("elevation") else {
2432	panic!("{id} derives no elevation");
2433	};
2434	assert!(
2435	elevation.starts_with("rgba(") && elevation.ends_with(", 0.18)"),
2436	"{id}: elevation is translucent: {elevation}"
2437	);
2438	let inner = elevation
2439	.trim_start_matches("rgba(")
2440	.trim_end_matches(", 0.18)");
2441	let parts: Vec<u8> = inner.split(", ").map(\|p\| p.parse().unwrap()).collect();
2442	let cast = Rgb {
2443	r: parts[0],
2444	g: parts[1],
2445	b: parts[2],
2446	};
2447	assert!(
2448	cast.to_oklab().l < 0.2,
2449	"{id}: a cast shadow must be near-black, got {elevation}"
2450	);
2451	}
2452	}
2453
2454	/// The scrim and the cast share an anchor and differ only in weight. Stated
2455	/// as a test because the two are easy to drift apart, and a scrim that
2456	/// stopped matching the shadow under the thing it dims would show.
2457	#[test]
2458	fn elevation_and_the_scrim_are_the_same_tone() {
2459	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2460	let t = resolve(&theme);
2461	let scrim = t.hex("overlay").unwrap();
2462	let cast = t.hex("elevation").unwrap();
2463	assert_eq!(
2464	scrim.trim_end_matches(", 0.5)"),
2465	cast.trim_end_matches(", 0.18)"),
2466	);
2467	}
2468
2469	/// The accessor that makes a translucent intent reachable from something
2470	/// that is not a stylesheet. Both spellings, and an opaque token answers
2471	/// 255 so a caller need not know which kind it asked for.
2472	#[test]
2473	fn rgba_reads_both_spellings() {
2474	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2475	let t = resolve(&theme);
2476
2477	let (_, _, _, opaque) = t.rgba("surface-page").expect("page is a hex token");
2478	assert_eq!(opaque, 255);
2479
2480	let (r, g, b, alpha) = t.rgba("elevation").expect("elevation is translucent");
2481	assert_eq!(alpha, 46, "0.18 of 255");
2482	assert_eq!(t.rgb("elevation"), None, "rgb declines to drop the alpha");
2483
2484	let (sr, sg, sb, scrim) = t.rgba("overlay").expect("overlay is translucent");
2485	assert_eq!((sr, sg, sb), (r, g, b), "one tone, two weights");
2486	assert_eq!(scrim, 128);
2487	}
2488
2489	#[test]
2490	fn resolve_drops_non_hex_base_intent() {
2491	// A base intent that isn't a hex color must never reach the resolved
2492	// token set (it would otherwise be inlined verbatim into a <style>
2493	// block). Skipped like a missing intent; valid siblings survive.
2494	let theme = parse_theme_str(
2495	"x",
2496	"[surface]\npage = \"</style><script>alert(1)</script>\"\n[content]\nprimary = \"#111111\"\n",
2497	false,
2498	)
2499	.unwrap();
2500	let t = resolve(&theme);
2501	assert!(
2502	t.hex("surface-page").is_none(),
2503	"non-hex base intent leaked"
2504	);
2505	assert_eq!(t.hex("content").unwrap(), "#111111");
2506	// The injected markup appears in no resolved value.
2507	assert!(!t.intents.values().any(\|v\| v.contains('<')));
2508	}
2509
2510	#[test]
2511	fn resolve_skips_derived_when_source_missing() {
2512	// No [action] => no action-derived tokens.
2513	let theme = parse_theme_str(
2514	"x",
2515	"[surface]\npage = \"#000000\"\n[line]\nborder = \"#222222\"\n",
2516	false,
2517	)
2518	.unwrap();
2519	let t = resolve(&theme);
2520	assert!(t.hex("action").is_none());
2521	assert!(t.hex("action-hover").is_none());
2522	assert!(t.hex("selection").is_none());
2523	assert_eq!(
2524	t.hex("border-strong").unwrap(),
2525	darken(Rgb::from_hex("#222222").unwrap(), 0.05).to_hex()
2526	);
2527	}
2528
2529	#[test]
2530	fn rgb_accessor_for_native_consumers() {
2531	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2532	let t = resolve(&theme);
2533	assert_eq!(t.rgb("action"), Some((0x81, 0xa1, 0xc1)));
2534	assert_eq!(t.rgb("nonexistent"), None);
2535	}
2536
2537	// ---- css emit ----
2538
2539	#[test]
2540	fn intent_css_vars_wraps_root_and_includes_tokens() {
2541	let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
2542	let css = intent_css_vars(&resolve(&theme));
2543	assert!(css.starts_with(":root {\n"));
2544	assert!(css.contains(" --surface-page: #2e3440;\n"));
2545	assert!(css.contains(" --danger: #bf616a;\n"));
2546	assert!(css.contains(" --action-hover: "));
2547	assert!(css.trim_end().ends_with('}'));
2548	}
2549
2550	// ---- loading / fs ----
2551
2552	#[test]
2553	fn load_and_resolve_round_trip() {
2554	let dir = tempfile::tempdir().unwrap();
2555	fs::write(dir.path().join("nord.toml"), nord_toml()).unwrap();
2556	let dirs = vec![(dir.path().to_path_buf(), false)];
2557	let t = load_semantic(&dirs, "nord").unwrap();
2558	assert_eq!(t.meta.name, "Nord");
2559	assert_eq!(t.hex("action"), Some("#81a1c1"));
2560	}
2561
2562	#[test]
2563	fn load_theme_rejects_invalid_id() {
2564	assert!(load_theme(&[], "../evil").is_err());
2565	}
2566
2567	fn meta(id: &str, variant: &str) -> ThemeMeta {
2568	ThemeMeta {
2569	id: id.to_string(),
2570	name: id.to_string(),
2571	variant: variant.to_string(),
2572	is_custom: false,
2573	}
2574	}
2575
2576	fn defaults() -> ThemeDefaults {
2577	ThemeDefaults::new("flatwhite", "nord")
2578	}
2579
2580	// The three the shipped themes actually declare.
2581	#[test]
2582	fn every_shipped_variant_parses() {
2583	assert_eq!(Variant::parse("light"), Some(Variant::Light));
2584	assert_eq!(Variant::parse("dark"), Some(Variant::Dark));
2585	assert_eq!(Variant::parse("high-contrast"), Some(Variant::HighContrast));
2586	assert_eq!(Variant::parse("sepia"), None);
2587	}
2588
2589	// parse_meta already defaults a missing variant to dark, so an
2590	// unrecognized one reading as light would have the crate disagreeing with
2591	// itself. alloy_tui did exactly that before this existed.
2592	#[test]
2593	fn an_unrecognized_variant_reads_the_way_a_missing_one_does() {
2594	assert_eq!(Variant::from("sepia"), Variant::Dark);
2595	assert_eq!(Variant::from(""), Variant::Dark);
2596
2597	let missing: toml::Table = "[meta]\nname = \"X\"\n".parse().unwrap();
2598	assert_eq!(parse_meta("x", &missing, false).kind(), Variant::Dark);
2599	}
2600
2601	#[test]
2602	fn a_selection_round_trips_through_any_store() {
2603	for (stored, expect) in [
2604	(Some("system"), ThemeSelection::Follow),
2605	(None, ThemeSelection::Follow),
2606	(Some(""), ThemeSelection::Follow),
2607	(Some(" "), ThemeSelection::Follow),
2608	(Some("nord"), ThemeSelection::Fixed("nord".into())),
2609	] {
2610	let parsed = ThemeSelection::parse(stored);
2611	assert_eq!(parsed, expect, "{stored:?}");
2612	assert_eq!(
2613	ThemeSelection::parse(Some(parsed.as_str())),
2614	expect,
2615	"what is written reads back as what was meant",
2616	);
2617	}
2618	}
2619
2620	// Nothing saved is follow-the-system, which is what Balanced Breakfast
2621	// expressed as an absent value and GoingsOn as a sentinel. Both are now the
2622	// same thing.
2623	#[test]
2624	fn nothing_chosen_yet_is_follow() {
2625	assert_eq!(ThemeSelection::default(), ThemeSelection::Follow);
2626	}
2627
2628	#[test]
2629	fn a_fixed_selection_wins_when_its_theme_is_installed() {
2630	let available = [meta("nord", "dark"), meta("flatwhite", "light")];
2631	let fixed = ThemeSelection::Fixed("nord".into());
2632	assert_eq!(
2633	fixed.resolve(Variant::Light, &defaults(), &available),
2634	"nord",
2635	"a chosen theme is not overridden by the ambient mode",
2636	);
2637	}
2638
2639	// Themes are deletable in three of the four apps. Handing back an id that
2640	// will fail to load only moves the error somewhere less helpful.
2641	#[test]
2642	fn a_fixed_selection_whose_theme_is_gone_falls_back() {
2643	let available = [meta("nord", "dark"), meta("flatwhite", "light")];
2644	let fixed = ThemeSelection::Fixed("deleted".into());
2645	assert_eq!(
2646	fixed.resolve(Variant::Light, &defaults(), &available),
2647	"flatwhite",
2648	);
2649	}
2650
2651	#[test]
2652	fn follow_picks_the_apps_default_for_the_ambient_mode() {
2653	let available = [meta("nord", "dark"), meta("flatwhite", "light")];
2654	let follow = ThemeSelection::Follow;
2655	assert_eq!(
2656	follow.resolve(Variant::Dark, &defaults(), &available),
2657	"nord",
2658	);
2659	assert_eq!(
2660	follow.resolve(Variant::Light, &defaults(), &available),
2661	"flatwhite",
2662	);
2663	}
2664
2665	// The behaviour Balanced Breakfast could not have: following the system
2666	// into a theme the user installed, when the app's own default is absent.
2667	#[test]
2668	fn follow_uses_any_installed_theme_of_the_right_variant() {
2669	let available = [meta("solarized-light", "light"), meta("mine", "dark")];
2670	assert_eq!(
2671	ThemeSelection::Follow.resolve(Variant::Dark, &defaults(), &available),
2672	"mine",
2673	"the app's `nord` is not installed, but a dark theme is",
2674	);
2675	}
2676
2677	// Always returns something: an app with no theme directory gets the id it
2678	// ships with, and the load error it would have had anyway.
2679	#[test]
2680	fn an_empty_catalog_still_names_the_apps_default() {
2681	assert_eq!(
2682	ThemeSelection::Follow.resolve(Variant::Dark, &defaults(), &[]),
2683	"nord",
2684	);
2685	}
2686
2687	#[test]
2688	fn high_contrast_falls_back_to_dark_unless_named() {
2689	let plain = defaults();
2690	assert_eq!(plain.for_variant(Variant::HighContrast), "nord");
2691
2692	let named = defaults().high_contrast("sharp");
2693	assert_eq!(named.for_variant(Variant::HighContrast), "sharp");
2694	}
2695
2696	// The bug this builder exists to prevent: the Alloy console pushed the
2697	// user's directory first under a comment reading "highest precedence
2698	// first", when both consumers of this vector resolve last-wins. A custom
2699	// theme lost to the packaged one of the same id.
2700	#[test]
2701	fn the_users_own_themes_outrank_everything() {
2702	let root = tempfile::tempdir().unwrap();
2703	let make = \|name: &str\| {
2704	let dir = root.path().join(name);
2705	std::fs::create_dir_all(&dir).unwrap();
2706	dir
2707	};
2708	let (bundled, system, custom) = (make("bundled"), make("system"), make("custom"));
2709
2710	let dirs = ThemeDirs::new()
2711	.custom(Some(custom.clone()))
2712	.bundled(Some(bundled.clone()))
2713	.system(Some(system.clone()))
2714	.build();
2715
2716	assert_eq!(
2717	dirs,
2718	vec![(bundled, false), (system, false), (custom.clone(), true)],
2719	"lowest precedence first, whatever order the tiers were added in",
2720	);
2721	assert!(dirs.last().unwrap().1, "only the user's tier is custom");
2722
2723	// And the ordering means what the consumers think it means.
2724	for dir in dirs.iter().map(\|(dir, _)\| dir) {
2725	std::fs::write(dir.join("shared.toml"), "[meta]\nname = \"x\"\n").unwrap();
2726	}
2727	assert_eq!(
2728	find_theme_path(&dirs, "shared").unwrap().0,
2729	custom.join("shared.toml"),
2730	"the user's copy is the one that loads",
2731	);
2732	}
2733
2734	#[test]
2735	fn a_directory_that_does_not_exist_is_dropped() {
2736	let root = tempfile::tempdir().unwrap();
2737	let real = root.path().join("real");
2738	std::fs::create_dir_all(&real).unwrap();
2739
2740	let dirs = ThemeDirs::new()
2741	.bundled(Some(root.path().join("nope")))
2742	.system(None)
2743	.custom(Some(real.clone()))
2744	.build();
2745
2746	assert_eq!(dirs, vec![(real, true)]);
2747	}
2748
2749	// A Tauri app has two bundled tiers: the resource dir in production and the
2750	// tree build.rs materialized for a dev run with no resource dir.
2751	#[test]
2752	fn more_than_one_bundled_tier_is_allowed() {
2753	let root = tempfile::tempdir().unwrap();
2754	let (first, second) = (root.path().join("a"), root.path().join("b"));
2755	std::fs::create_dir_all(&first).unwrap();
2756	std::fs::create_dir_all(&second).unwrap();
2757
2758	let dirs = ThemeDirs::new()
2759	.bundled(Some(first.clone()))
2760	.bundled(Some(second.clone()))
2761	.build();
2762	assert_eq!(dirs, vec![(first, false), (second, false)]);
2763	}
2764
2765	#[test]
2766	fn list_themes_from_dirs_finds_toml_files() {
2767	let dir = tempfile::tempdir().unwrap();
2768	fs::write(dir.path().join("t.toml"), "[meta]\nname = \"T\"\n").unwrap();
2769	fs::write(dir.path().join("x.txt"), "ignored").unwrap();
2770	let dirs = vec![(dir.path().to_path_buf(), false)];
2771	let themes = list_themes_from_dirs(&dirs);
2772	assert_eq!(themes.len(), 1);
2773	assert_eq!(themes[0].id, "t");
2774	}
2775
2776	#[test]
2777	fn find_theme_path_reverse_priority() {
2778	let d1 = tempfile::tempdir().unwrap();
2779	let d2 = tempfile::tempdir().unwrap();
2780	fs::write(d1.path().join("s.toml"), "[meta]\n").unwrap();
2781	fs::write(d2.path().join("s.toml"), "[meta]\n").unwrap();
2782	let dirs = vec![
2783	(d1.path().to_path_buf(), false),
2784	(d2.path().to_path_buf(), true),
2785	];
2786	let (path, is_custom) = find_theme_path(&dirs, "s").unwrap();
2787	assert!(is_custom);
2788	assert_eq!(path, d2.path().join("s.toml"));
2789	}
2790
2791	#[test]
2792	fn import_theme_valid_and_rejects_empty() {
2793	let src_dir = tempfile::tempdir().unwrap();
2794	let custom_dir = tempfile::tempdir().unwrap();
2795
2796	let good = src_dir.path().join("my-theme.toml");
2797	fs::write(&good, "[surface]\npage = \"#1a1b26\"\n").unwrap();
2798	let meta = import_theme(&good, custom_dir.path()).unwrap();
2799	assert_eq!(meta.id, "my-theme");
2800	assert!(custom_dir.path().join("my-theme.toml").exists());
2801
2802	let empty = src_dir.path().join("empty.toml");
2803	fs::write(&empty, "[meta]\nname = \"E\"\n").unwrap();
2804	assert!(import_theme(&empty, custom_dir.path()).is_err());
2805	}
2806
2807	#[test]
2808	fn import_theme_rejects_invalid_toml() {
2809	let src_dir = tempfile::tempdir().unwrap();
2810	let custom_dir = tempfile::tempdir().unwrap();
2811	let src = src_dir.path().join("bad.toml");
2812	fs::write(&src, "this is not [valid toml [[[").unwrap();
2813	assert!(import_theme(&src, custom_dir.path()).is_err());
2814	}
2815
2816	#[test]
2817	fn delete_theme_removes_and_guards() {
2818	let custom = tempfile::tempdir().unwrap();
2819	let path = custom.path().join("doomed.toml");
2820	fs::write(&path, "[surface]\npage = \"#000\"\n").unwrap();
2821	delete_theme(custom.path(), "doomed").unwrap();
2822	assert!(!path.exists());
2823	assert!(delete_theme(custom.path(), "../etc/passwd").is_err());
2824	assert!(delete_theme(custom.path(), "ghost").is_err());
2825	}
2826
2827	#[test]
2828	fn export_theme_copies_file() {
2829	let src_dir = tempfile::tempdir().unwrap();
2830	let dest_dir = tempfile::tempdir().unwrap();
2831	let content = "[meta]\nname = \"E\"\n[surface]\npage = \"#ffffff\"\n";
2832	fs::write(src_dir.path().join("e.toml"), content).unwrap();
2833	let dirs = vec![(src_dir.path().to_path_buf(), false)];
2834	let dest = dest_dir.path().join("out.toml");
2835	export_theme(&dirs, "e", &dest).unwrap();
2836	assert_eq!(fs::read_to_string(&dest).unwrap(), content);
2837	assert!(export_theme(&dirs, "missing", &dest).is_err());
2838	}
2839
2840	#[test]
2841	fn load_theme_preview_returns_role_swatches() {
2842	let dir = tempfile::tempdir().unwrap();
2843	fs::write(dir.path().join("nord.toml"), nord_toml()).unwrap();
2844	let dirs = vec![(dir.path().to_path_buf(), false)];
2845	let p = load_theme_preview(&dirs, "nord").unwrap();
2846	assert_eq!(p.background.as_deref(), Some("#2e3440")); // surface.page
2847	assert_eq!(p.foreground.as_deref(), Some("#d8dee9")); // content.primary
2848	assert_eq!(p.accent.as_deref(), Some("#81a1c1")); // action.primary
2849	assert_eq!(p.border.as_deref(), Some("#4c566a")); // line.border
2850	}
2851
2852	#[test]
2853	fn bundled_themes_dir_resolves_to_shipped_themes() {
2854	// The crate ships its themes, so this must resolve in-tree and the
2855	// Akari defaults the console falls back to must be present.
2856	let dir = bundled_themes_dir().expect("makeover ships a themes/ directory");
2857	assert!(dir.join("akari-dawn.toml").is_file());
2858	assert!(dir.join("akari-night.toml").is_file());
2859	}
2860
2861	#[test]
2862	fn every_theme_is_accounted_for_in_third_party_notices() {
2863	// Attribution is a redistribution obligation, not a nicety: adding a
2864	// theme without a notice entry silently ships someone's work
2865	// uncredited. Fail here instead.
2866	let notices = std::fs::read_to_string(
2867	Path::new(env!("CARGO_MANIFEST_DIR")).join("THIRD-PARTY-NOTICES.md"),
2868	)
2869	.expect("THIRD-PARTY-NOTICES.md must exist");
2870	let missing: Vec<&str> = embedded_themes()
2871	.map(\|(id, _)\| id)
2872	.filter(\|id\| !notices.contains(*id))
2873	.collect();
2874	assert!(
2875	missing.is_empty(),
2876	"themes missing from THIRD-PARTY-NOTICES.md: {missing:?}"
2877	);
2878	}
2879
2880	#[test]
2881	fn adapted_themes_carry_inline_attribution() {
2882	// Each adapted file must name its upstream in-file, so the credit
2883	// survives someone copying a single .toml out of the crate.
2884	const ORIGINALS: [&str; 5] = [
2885	"makenotwork",
2886	"goingson",
2887	"audiofiles",
2888	"high-contrast",
2889	"neobrute",
2890	];
2891	for (id, source) in embedded_themes() {
2892	if ORIGINALS.contains(&id) {
2893	continue;
2894	}
2895	assert!(
2896	source.contains("adapted from"),
2897	"adapted theme `{id}` is missing its inline attribution header"
2898	);
2899	}
2900	}
2901
2902	#[test]
2903	fn embedded_themes_match_the_directory() {
2904	// The embedded copy and themes/ are two views of one source. If they
2905	// ever disagree, path-based and path-free consumers render different
2906	// theme sets, which is exactly the drift shipping the data was meant
2907	// to prevent.
2908	let dir = bundled_themes_dir().unwrap();
2909	let mut on_disk: Vec<String> = std::fs::read_dir(&dir)
2910	.unwrap()
2911	.filter_map(\|e\| {
2912	let path = e.ok()?.path();
2913	if path.extension()? != "toml" {
2914	return None;
2915	}
2916	Some(path.file_stem()?.to_str()?.to_string())
2917	})
2918	.collect();
2919	let mut embedded: Vec<String> = embedded_themes().map(\|(id, _)\| id.to_string()).collect();
2920	on_disk.sort();
2921	embedded.sort();
2922	assert_eq!(embedded, on_disk, "embedded theme set drifted from themes/");
2923	}
2924
2925	#[test]
2926	fn every_embedded_theme_parses() {
2927	// Guards the path-free consumers (MNW server, the Tauri build steps)
2928	// the same way every_shipped_theme_loads guards the path-based ones.
2929	let mut count = 0;
2930	for (id, source) in embedded_themes() {
2931	parse_theme_str(id, source, false)
2932	.unwrap_or_else(\|e\| panic!("embedded theme `{id}` failed to parse: {e}"));
2933	count += 1;
2934	}
2935	assert!(count >= 30, "expected the full theme set, got {count}");
2936	}
2937
2938	#[test]
2939	fn every_shipped_theme_loads() {
2940	// Guards the data, not just the loader: a malformed or truncated
2941	// .toml in themes/ is a shipping bug, and it should fail here rather
2942	// than at a user's first launch.
2943	let dir = bundled_themes_dir().unwrap();
2944	let dirs = vec![(dir.clone(), false)];
2945	let themes = list_themes_from_dirs(&dirs);
2946	assert!(
2947	themes.len() >= 30,
2948	"expected the full theme set, got {}",
2949	themes.len()
2950	);
2951	for meta in &themes {
2952	load_theme(&dirs, &meta.id)
2953	.unwrap_or_else(\|e\| panic!("shipped theme `{}` failed to load: {e}", meta.id));
2954	}
2955	}
2956	}
2957