//! Shared theme loading + intent resolution for TOML-based theme files.
//!
//! Used by GoingsOn, Balanced Breakfast (Tauri apps), audiofiles (egui), and the
//! MNW web server. Themes are authored by **intent** ("human design"): colors are
//! declared by role (surface / content / action / status / line / category), not
//! by hue. This crate is the single place that resolves an authored theme into a
//! full set of intent tokens — including the derived interactive states
//! (hover/active/selection/row-stripe/contrast) that each app used to recompute
//! itself — and emits them as CSS variables or RGB tuples.
//!
//! Theme file shape:
//! ```text
//! [meta]
//! name = "Nord"
//! variant = "dark"          # or "light"
//!
//! [surface]                 # container backgrounds by role/elevation
//! page = "#2e3440"; raised = "#3b4252"; sunken = "#434c5e"; overlay = "#3b4252"
//!
//! [content]                 # text/ink by emphasis
//! primary = "#d8dee9"; secondary = "#e5e9f0"; muted = "#616e88"
//!
//! [action]                  # interactive / brand color
//! primary = "#81a1c1"
//!
//! [status]                  # state semantics
//! danger = "#bf616a"; success = "#a3be8c"; warning = "#ebcb8b"; info = "#88c0d0"
//!
//! [line]
//! border = "#4c566a"
//!
//! [category]                # distinct decorative colors for tags/badges/charts
//! one = "#bf616a"; two = "#a3be8c"; three = "#81a1c1"
//! four = "#ebcb8b"; five = "#b48ead"; six = "#88c0d0"
//! ```

// Color-space math: single-letter channel names (r/g/b/l/m/s) and the published
// high-precision OKLab/sRGB matrix constants are the domain vocabulary here.
#![allow(clippy::many_single_char_names, clippy::unreadable_literal)]

use serde::Serialize;
use std::collections::{BTreeMap, HashMap};
use std::path::{Path, PathBuf};

/// The color sections an authored theme may declare.
pub const COLOR_SECTIONS: &[&str] = &["surface", "content", "action", "status", "line", "category"];

/// Theme metadata parsed from the `[meta]` section.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct ThemeMeta {
    pub id: String,
    pub name: String,
    pub variant: String,
    pub is_custom: bool,
}

/// A loaded theme: metadata plus the authored colors, flattened to dotted keys
/// (e.g. `"surface.page"`, `"status.danger"`, `"category.one"`).
#[derive(Debug, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct ThemeColors {
    pub meta: ThemeMeta,
    pub colors: HashMap<String, String>,
}

// ============================================================================
// Color math — perceptual (OKLab) derivations + WCAG contrast.
//
// Interactive states (hover/active/selection/surfaces) are derived in OKLab so
// equal steps look equal across every theme's hues (Ottosson 2020; the modern
// CIELAB). Text-on-color is picked by the WCAG 2.x contrast ratio, not a naive
// luminance threshold, so the choice actually meets AA where achievable.
// This is the single source of truth shared by every product.
// ============================================================================

/// An sRGB color. Hex round-trips losslessly.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Rgb {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}

impl Rgb {
    /// Parse `#rgb` or `#rrggbb` (case-insensitive). Returns `None` otherwise.
    pub fn from_hex(s: &str) -> Option<Rgb> {
        let h = s.strip_prefix('#')?;
        let (r, g, b) = match h.len() {
            6 => (
                u8::from_str_radix(&h[0..2], 16).ok()?,
                u8::from_str_radix(&h[2..4], 16).ok()?,
                u8::from_str_radix(&h[4..6], 16).ok()?,
            ),
            3 => {
                let d = |c: &str| u8::from_str_radix(c, 16).ok().map(|v| v * 17);
                (d(&h[0..1])?, d(&h[1..2])?, d(&h[2..3])?)
            }
            _ => return None,
        };
        Some(Rgb { r, g, b })
    }

    /// Lowercase `#rrggbb`.
    pub fn to_hex(self) -> String {
        format!("#{:02x}{:02x}{:02x}", self.r, self.g, self.b)
    }

    pub fn tuple(self) -> (u8, u8, u8) {
        (self.r, self.g, self.b)
    }
}

/// A color in OKLab (perceptually uniform): `l` lightness in [0,1], `a`/`b` opponent axes.
#[derive(Clone, Copy, Debug)]
pub struct Oklab {
    pub l: f32,
    pub a: f32,
    pub b: f32,
}

fn srgb_to_linear(c: u8) -> f32 {
    let c = c as f32 / 255.0;
    if c <= 0.04045 {
        c / 12.92
    } else {
        ((c + 0.055) / 1.055).powf(2.4)
    }
}

fn linear_to_srgb(c: f32) -> u8 {
    let c = c.clamp(0.0, 1.0);
    let v = if c <= 0.0031308 {
        c * 12.92
    } else {
        1.055 * c.powf(1.0 / 2.4) - 0.055
    };
    (v * 255.0).round().clamp(0.0, 255.0) as u8
}

impl Rgb {
    /// Convert to OKLab (Ottosson's sRGB matrices).
    ///
    /// The matrix coefficients are quoted at their published precision so they
    /// can be diffed against the reference. `f32` rounds them at compile time;
    /// truncating the literals would only make them harder to check.
    #[allow(clippy::excessive_precision)]
    pub fn to_oklab(self) -> Oklab {
        let (r, g, b) = (
            srgb_to_linear(self.r),
            srgb_to_linear(self.g),
            srgb_to_linear(self.b),
        );
        let l = 0.4122214708 * r + 0.5363325363 * g + 0.0514459929 * b;
        let m = 0.2119034982 * r + 0.6806995451 * g + 0.1073969566 * b;
        let s = 0.0883024619 * r + 0.2817188376 * g + 0.6299787005 * b;
        let (l_, m_, s_) = (l.cbrt(), m.cbrt(), s.cbrt());
        Oklab {
            l: 0.2104542553 * l_ + 0.7936177850 * m_ - 0.0040720468 * s_,
            a: 1.9779984951 * l_ - 2.4285922050 * m_ + 0.4505937099 * s_,
            b: 0.0259040371 * l_ + 0.7827717662 * m_ - 0.8086757660 * s_,
        }
    }

    /// Convert from OKLab back to the nearest in-gamut sRGB.
    ///
    /// Published precision, as in [`Rgb::to_oklab`].
    #[allow(clippy::excessive_precision)]
    pub fn from_oklab(c: Oklab) -> Rgb {
        let l_ = c.l + 0.3963377774 * c.a + 0.2158037573 * c.b;
        let m_ = c.l - 0.1055613458 * c.a - 0.0638541728 * c.b;
        let s_ = c.l - 0.0894841775 * c.a - 1.2914855480 * c.b;
        let (l, m, s) = (l_ * l_ * l_, m_ * m_ * m_, s_ * s_ * s_);
        Rgb {
            r: linear_to_srgb(4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s),
            g: linear_to_srgb(-1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s),
            b: linear_to_srgb(-0.0041960863 * l - 0.7034186147 * m + 1.7076147010 * s),
        }
    }
}

/// WCAG 2.x relative luminance of an sRGB color.
fn rel_luminance(c: Rgb) -> f32 {
    0.2126 * srgb_to_linear(c.r) + 0.7152 * srgb_to_linear(c.g) + 0.0722 * srgb_to_linear(c.b)
}

/// WCAG 2.x contrast ratio between two colors, in [1, 21].
pub fn wcag_contrast(a: Rgb, b: Rgb) -> f32 {
    let (la, lb) = (rel_luminance(a), rel_luminance(b));
    let (hi, lo) = if la >= lb { (la, lb) } else { (lb, la) };
    (hi + 0.05) / (lo + 0.05)
}

/// Pick black or white for legible text on `bg`, by the higher WCAG contrast
/// ratio (so the choice meets AA wherever the background allows it).
pub fn readable_on(bg: Rgb) -> Rgb {
    let white = Rgb {
        r: 255,
        g: 255,
        b: 255,
    };
    let black = Rgb { r: 0, g: 0, b: 0 };
    if wcag_contrast(white, bg) >= wcag_contrast(black, bg) {
        white
    } else {
        black
    }
}

/// Shift OKLab lightness by `delta` (perceptually uniform). Positive lightens.
pub fn lighten(c: Rgb, delta: f32) -> Rgb {
    let mut lab = c.to_oklab();
    lab.l = (lab.l + delta).clamp(0.0, 1.0);
    Rgb::from_oklab(lab)
}

/// Shift OKLab lightness down by `delta` (perceptually uniform).
pub fn darken(c: Rgb, delta: f32) -> Rgb {
    lighten(c, -delta)
}

/// Interpolate between `a` and `b` by `t` in [0,1] in OKLab (perceptual blend).
pub fn mix(a: Rgb, b: Rgb, t: f32) -> Rgb {
    let (x, y) = (a.to_oklab(), b.to_oklab());
    Rgb::from_oklab(Oklab {
        l: x.l + (y.l - x.l) * t,
        a: x.a + (y.a - x.a) * t,
        b: x.b + (y.b - x.b) * t,
    })
}

// ============================================================================
// Low-color terminals
// ============================================================================

/// The 16 colors an ANSI terminal addresses by index, in the PC/VGA
/// arrangement the Linux console and most emulators start from.
///
/// 0-7 are the normal colors and 8-15 the bright ones. Index 7 is a light gray
/// rather than white, which is the entry a themed surface usually lands on, and
/// index 15 is the true white.
///
/// Emulators let the user repaint all sixteen, so this is the standard
/// arrangement rather than a promise about any one terminal. The Linux console
/// keeps it, which is the case that matters: a console app cannot fall back to
/// 24-bit color there.
pub const ANSI_16: [Rgb; 16] = [
    Rgb {
        r: 0x00,
        g: 0x00,
        b: 0x00,
    },
    Rgb {
        r: 0xaa,
        g: 0x00,
        b: 0x00,
    },
    Rgb {
        r: 0x00,
        g: 0xaa,
        b: 0x00,
    },
    Rgb {
        r: 0xaa,
        g: 0x55,
        b: 0x00,
    },
    Rgb {
        r: 0x00,
        g: 0x00,
        b: 0xaa,
    },
    Rgb {
        r: 0xaa,
        g: 0x00,
        b: 0xaa,
    },
    Rgb {
        r: 0x00,
        g: 0xaa,
        b: 0xaa,
    },
    Rgb {
        r: 0xaa,
        g: 0xaa,
        b: 0xaa,
    },
    Rgb {
        r: 0x55,
        g: 0x55,
        b: 0x55,
    },
    Rgb {
        r: 0xff,
        g: 0x55,
        b: 0x55,
    },
    Rgb {
        r: 0x55,
        g: 0xff,
        b: 0x55,
    },
    Rgb {
        r: 0xff,
        g: 0xff,
        b: 0x55,
    },
    Rgb {
        r: 0x55,
        g: 0x55,
        b: 0xff,
    },
    Rgb {
        r: 0xff,
        g: 0x55,
        b: 0xff,
    },
    Rgb {
        r: 0x55,
        g: 0xff,
        b: 0xff,
    },
    Rgb {
        r: 0xff,
        g: 0xff,
        b: 0xff,
    },
];

/// The contrast ratio two colors must clear to read as separate areas.
///
/// WCAG 2.x asks 3:1 of user interface components and graphics, which is what
/// a border, a rule, or a focus ring is. Text wants more, and a caller drawing
/// text can ask for more by checking [`wcag_contrast`] itself.
pub const DISTINCT: f32 = 3.0;

/// Perceptual distance between two colors, for choosing the closest of a set.
fn oklab_distance(a: Rgb, b: Rgb) -> f32 {
    let (x, y) = (a.to_oklab(), b.to_oklab());
    ((x.l - y.l).powi(2) + (x.a - y.a).powi(2) + (x.b - y.b).powi(2)).sqrt()
}

/// Index of the entry in `palette` that looks most like `c`.
///
/// OKLab distance rather than distance in sRGB, for the same reason [`mix`]
/// interpolates there: sRGB's numbers are not spaced the way seeing is, so a
/// nearest match computed in it picks visibly wrong entries in the mid tones.
///
/// # Panics
///
/// If `palette` is empty.
pub fn quantize(c: Rgb, palette: &[Rgb]) -> usize {
    assert!(!palette.is_empty(), "a palette needs at least one color");
    let mut best = 0;
    let mut best_distance = f32::INFINITY;
    for (index, entry) in palette.iter().enumerate() {
        let distance = oklab_distance(c, *entry);
        if distance < best_distance {
            best = index;
            best_distance = distance;
        }
    }
    best
}

/// Index of the entry in `palette` closest to `fg` that still reads against
/// `bg`.
///
/// [`quantize`] answers about one color at a time, and two colors that differ
/// can quantize to the same entry: a themed page and a border drawn on it are
/// often a few steps apart in a 24-bit theme and land together on a 16-color
/// terminal, leaving one flat area where there was a frame. Alloy's console
/// showed exactly this, and it is not a contrived pairing: a light page and the
/// mid-tone border derived from it both land on index 7.
///
/// So the background is quantized first, because what the border must be
/// distinguished from is the entry the terminal will actually paint, not the
/// color the theme asked for. Then the nearest entry to `fg` clearing
/// [`DISTINCT`] against it wins. When nothing clears it, the entry that gets
/// furthest does: at that point the palette cannot honor the design, and the
/// most legible approximation beats the closest invisible one.
///
/// Only for colors whose whole job is to be told apart from their background.
/// Applied to every token it would push a deliberately quiet one until it
/// shouted.
///
/// # Panics
///
/// If `palette` is empty.
pub fn quantize_against(fg: Rgb, bg: Rgb, palette: &[Rgb]) -> usize {
    assert!(!palette.is_empty(), "a palette needs at least one color");
    let shown = palette[quantize(bg, palette)];

    let mut order: Vec<usize> = (0..palette.len()).collect();
    order.sort_by(|a, b| {
        oklab_distance(fg, palette[*a]).total_cmp(&oklab_distance(fg, palette[*b]))
    });

    order
        .iter()
        .copied()
        .find(|index| wcag_contrast(palette[*index], shown) >= DISTINCT)
        .unwrap_or_else(|| {
            order
                .iter()
                .copied()
                .max_by(|a, b| {
                    wcag_contrast(palette[*a], shown).total_cmp(&wcag_contrast(palette[*b], shown))
                })
                .expect("the palette is not empty")
        })
}

// ============================================================================
// Intent resolution
// ============================================================================

/// Authored base intents: (TOML dotted source key, canonical token key).
/// These are read straight from the theme; the token key is the CSS-var stem
/// (`--{token}`) and the `rgb()` lookup key.
pub const BASE_INTENTS: &[(&str, &str)] = &[
    ("surface.page", "surface-page"),
    ("surface.raised", "surface-raised"),
    ("surface.sunken", "surface-sunken"),
    ("surface.overlay", "surface-overlay"),
    ("content.primary", "content"),
    ("content.secondary", "content-secondary"),
    ("content.muted", "content-muted"),
    ("action.primary", "action"),
    ("status.danger", "danger"),
    ("status.success", "success"),
    ("status.warning", "warning"),
    ("status.info", "info"),
    ("line.border", "border"),
    ("category.one", "category-one"),
    ("category.two", "category-two"),
    ("category.three", "category-three"),
    ("category.four", "category-four"),
    ("category.five", "category-five"),
    ("category.six", "category-six"),
];

/// A fully resolved intent layer: every token key → concrete `#rrggbb`.
/// Includes both authored base intents and the computed derived intents.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct SemanticTokens {
    pub meta: ThemeMeta,
    /// token-key → resolved hex. Stable, deterministic ordering.
    pub intents: BTreeMap<String, String>,
}

impl SemanticTokens {
    /// Resolved hex for a token key, if present.
    pub fn hex(&self, key: &str) -> Option<&str> {
        self.intents.get(key).map(String::as_str)
    }

    /// Resolved RGB tuple for a token key (for egui / native consumers).
    pub fn rgb(&self, key: &str) -> Option<(u8, u8, u8)> {
        self.intents
            .get(key)
            .and_then(|h| Rgb::from_hex(h))
            .map(Rgb::tuple)
    }
}

/// Resolve an authored theme into the full intent token set.
///
/// 1. Copy each present base intent from the authored colors.
/// 2. Compute the derived interactive states from the base intents, using the
///    same math the apps used to apply individually (so output is identical).
///
/// Each derived token is emitted only when its source intents exist, mirroring
/// the skip-missing behavior of the rest of the crate.
pub fn resolve(theme: &ThemeColors) -> SemanticTokens {
    let mut intents: BTreeMap<String, String> = BTreeMap::new();

    // 1. Base intents (authored). Copy only values that parse as a hex color and
    // re-emit them in canonical `#rrggbb` form, so an authored value can never
    // carry arbitrary bytes into the emitted CSS (the resolved tokens are inlined
    // raw into a `<style>` block by the web server). A malformed value is skipped,
    // mirroring the skip-missing behavior for absent intents.
    for (src, token) in BASE_INTENTS {
        if let Some(rgb) = theme.colors.get(*src).and_then(|v| Rgb::from_hex(v)) {
            intents.insert((*token).to_string(), rgb.to_hex());
        }
    }

    // Helper: parse an already-resolved token to Rgb.
    let get = |m: &BTreeMap<String, String>, k: &str| m.get(k).and_then(|h| Rgb::from_hex(h));

    // 2. Derived intents — perceptual (OKLab) steps + WCAG-picked text.
    // Lightness deltas are in OKLab L units; mix ratios interpolate in OKLab.
    let mut derived: Vec<(String, Rgb)> = Vec::new();
    if let Some(action) = get(&intents, "action") {
        derived.push(("action-hover".into(), lighten(action, 0.05)));
        derived.push(("content-on-action".into(), readable_on(action)));
        derived.push(("focus-ring".into(), action));
    }
    if let Some(page) = get(&intents, "surface-page") {
        // Modal scrim: a near-black tone carrying a faint hint of the theme's
        // hue, at 50% alpha. Anchored very dark (OKLab L=0.08) so it dims the
        // page on light *and* dark themes. Emitted as rgba (not a flat hex), so
        // it is inserted directly rather than through the hex loop below.
        let mut o = page.to_oklab();
        o.l = 0.08;
        let s = Rgb::from_oklab(o);
        intents.insert(
            "overlay".into(),
            format!("rgba({}, {}, {}, 0.5)", s.r, s.g, s.b),
        );
    }
    if let Some(sunken) = get(&intents, "surface-sunken") {
        derived.push(("hover-surface".into(), sunken));
    }
    if let Some(border) = get(&intents, "border") {
        derived.push(("border-strong".into(), darken(border, 0.05)));
    }

    for (token, rgb) in derived {
        intents.insert(token, rgb.to_hex());
    }

    SemanticTokens {
        meta: theme.meta.clone(),
        intents,
    }
}

/// Emit the resolved intent layer as CSS declarations (no selector), one
/// `  --token: #hex;` line each, in deterministic (BTreeMap) order.
pub fn intent_css_declarations(tokens: &SemanticTokens) -> String {
    let mut out = String::new();
    for (token, hex) in &tokens.intents {
        out.push_str("  --");
        out.push_str(token);
        out.push_str(": ");
        out.push_str(hex);
        out.push_str(";\n");
    }
    out
}

/// Emit the resolved intent layer as a `:root { … }` block — the single TOML →
/// CSS mapping every web surface injects.
pub fn intent_css_vars(tokens: &SemanticTokens) -> String {
    format!(":root {{\n{}}}\n", intent_css_declarations(tokens))
}

// ============================================================================
// Loading / parsing
// ============================================================================

/// Validate a theme ID contains only safe characters (alphanumeric, hyphens, underscores).
pub fn validate_theme_id(id: &str) -> Result<(), String> {
    if !id
        .chars()
        .all(|c| c.is_alphanumeric() || c == '-' || c == '_')
    {
        return Err(format!("Invalid theme ID: {id}"));
    }
    Ok(())
}

/// Parse the `[meta]` section into `ThemeMeta`.
///
/// Falls back to the file ID as the name and `"dark"` as the variant.
pub fn parse_meta(id: &str, table: &toml::Table, is_custom: bool) -> ThemeMeta {
    let meta = table.get("meta").and_then(|m| m.as_table());
    let name = meta
        .and_then(|m| m.get("name"))
        .and_then(|v| v.as_str())
        .unwrap_or(id)
        .to_string();
    let variant = meta
        .and_then(|m| m.get("variant"))
        .and_then(|v| v.as_str())
        .unwrap_or("dark")
        .to_string();

    ThemeMeta {
        id: id.to_string(),
        name,
        variant,
        is_custom,
    }
}

// ============================================================================
// Choosing a theme.
//
// The file half of this crate was always shared; the *selection* half was not,
// and four apps re-rolled it four ways. GoingsOn stores a "system" sentinel in
// localStorage, Balanced Breakfast treats an absent value as follow-the-system
// and hardcodes two theme ids as its light/dark pair, audiofiles keeps the id
// in a synced SQLite table, and the Alloy console parses COLORFGBG. They also
// disagreed about what a variant string means: this crate defaults a missing
// one to "dark" while alloy_tui parsed an unrecognized one as light.
//
// What cannot be shared is the store — localStorage, a synced config table and
// a TOML file are genuinely different places. What can be shared, and is here,
// is the *meaning*: one vocabulary for variants, one encoding for "what did the
// user choose", and one rule for turning that into an id that exists.
// ============================================================================

/// A theme's kind, as declared by `meta.variant`.
///
/// Three, not two: one shipped theme is `high-contrast`, and an app that
/// matched on light-or-dark alone would quietly file it under the wrong one.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize)]
#[serde(rename_all = "kebab-case")]
pub enum Variant {
    Light,
    Dark,
    HighContrast,
}

impl Variant {
    /// The spelling used in a theme file and in [`ThemeMeta::variant`].
    #[must_use]
    pub const fn as_str(self) -> &'static str {
        match self {
            Variant::Light => "light",
            Variant::Dark => "dark",
            Variant::HighContrast => "high-contrast",
        }
    }

    /// Read a variant string, or `None` if it names none of them.
    #[must_use]
    pub fn parse(raw: &str) -> Option<Self> {
        match raw {
            "light" => Some(Variant::Light),
            "dark" => Some(Variant::Dark),
            "high-contrast" => Some(Variant::HighContrast),
            _ => None,
        }
    }
}

impl std::fmt::Display for Variant {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

/// Anything unrecognized reads as dark, which is what [`parse_meta`] already
/// does with a missing one. Consumers that guessed light for an unknown string
/// were disagreeing with the crate that produced it.
impl From<&str> for Variant {
    fn from(raw: &str) -> Self {
        Variant::parse(raw).unwrap_or(Variant::Dark)
    }
}

impl ThemeMeta {
    /// This theme's variant as a value rather than a string.
    #[must_use]
    pub fn kind(&self) -> Variant {
        Variant::from(self.variant.as_str())
    }
}

/// The spelling of "follow whatever the system is doing", in every store.
pub const FOLLOW: &str = "system";

/// What the user chose, as opposed to what is being rendered.
///
/// The distinction is the whole point: `Follow` is a standing instruction that
/// resolves differently as the ambient mode changes, and a `Fixed` id is an
/// answer that does not. An app that stored only the rendered id could not tell
/// the two apart the next time the system flipped to dark.
#[derive(Debug, Clone, PartialEq, Eq, Default)]
pub enum ThemeSelection {
    /// Track the ambient light/dark mode.
    #[default]
    Follow,
    /// Always this theme.
    Fixed(String),
}

impl ThemeSelection {
    /// Read a stored selection. An empty or absent value is [`Follow`], which
    /// is what an app with nothing saved yet should do.
    ///
    /// [`Follow`]: ThemeSelection::Follow
    #[must_use]
    pub fn parse(raw: Option<&str>) -> Self {
        match raw.map(str::trim) {
            None | Some("" | FOLLOW) => ThemeSelection::Follow,
            Some(id) => ThemeSelection::Fixed(id.to_string()),
        }
    }

    /// The string to persist, whatever the store is.
    #[must_use]
    pub fn as_str(&self) -> &str {
        match self {
            ThemeSelection::Follow => FOLLOW,
            ThemeSelection::Fixed(id) => id,
        }
    }

    /// Turn a selection into a theme id that exists.
    ///
    /// `ambient` is the light/dark mode the app learned however it can: a
    /// `prefers-color-scheme` media query, an OS appearance API, `COLORFGBG`
    /// from a terminal. `available` is what [`list_themes_from_dirs`] found.
    ///
    /// A `Fixed` id that is no longer on disk falls through to the same path as
    /// `Follow` rather than being returned anyway. Themes are deletable in
    /// three of the four apps, and handing back an id that will fail to load
    /// only moves the error somewhere less helpful.
    ///
    /// The fallback chain is: the app's own default for the ambient mode if it
    /// is installed, then any installed theme of that variant, then the app's
    /// default regardless. The last step means this always returns something,
    /// and an app with no theme directory at all gets the id it ships with and
    /// the load error it would have had anyway.
    #[must_use]
    pub fn resolve(
        &self,
        ambient: Variant,
        defaults: &ThemeDefaults,
        available: &[ThemeMeta],
    ) -> String {
        let installed = |id: &str| available.iter().any(|meta| meta.id == id);

        if let ThemeSelection::Fixed(id) = self
            && installed(id)
        {
            return id.clone();
        }

        let preferred = defaults.for_variant(ambient);
        if installed(preferred) {
            return preferred.to_string();
        }
        available
            .iter()
            .find(|meta| meta.kind() == ambient)
            .map_or_else(|| preferred.to_string(), |meta| meta.id.clone())
    }
}

impl std::fmt::Display for ThemeSelection {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.as_str())
    }
}

/// The themes an app falls back to, one per ambient mode.
///
/// App-specific on purpose: which theme is "the app's own" is the app's
/// identity, not this crate's business. What is shared is everything around it.
#[derive(Debug, Clone)]
pub struct ThemeDefaults {
    light: String,
    dark: String,
    high_contrast: Option<String>,
}

impl ThemeDefaults {
    pub fn new(light: impl Into<String>, dark: impl Into<String>) -> Self {
        Self {
            light: light.into(),
            dark: dark.into(),
            high_contrast: None,
        }
    }

    /// Name a theme for a high-contrast ambient mode. Without one, that mode
    /// falls back to the dark default, which is the safer of the two to read.
    #[must_use]
    pub fn high_contrast(mut self, id: impl Into<String>) -> Self {
        self.high_contrast = Some(id.into());
        self
    }

    #[must_use]
    pub fn for_variant(&self, variant: Variant) -> &str {
        match variant {
            Variant::Light => &self.light,
            Variant::Dark => &self.dark,
            Variant::HighContrast => self.high_contrast.as_ref().unwrap_or(&self.dark),
        }
    }
}

// ============================================================================
// Where themes are looked for.
//
// Four apps built this vector by hand, two of them byte-for-byte identically,
// and one of them built it backwards: the Alloy console pushed the user's own
// directory first, under a comment saying "highest precedence first", when both
// consumers of the vector resolve *last* wins. A user's custom theme lost to
// the packaged one of the same id.
//
// Hence a builder that names the tiers rather than a function taking a vector.
// The precedence is stated once, here, and a caller cannot express it backwards
// because the order is not theirs to choose.
// ============================================================================

/// Builds the search path [`load_theme`] and [`list_themes_from_dirs`] take.
///
/// Tiers are added in whatever order is convenient and always end up in
/// precedence order: the user's own themes win, then whatever the system
/// ships, then whatever the app bundles.
///
/// A directory that does not exist is dropped rather than carried, so callers
/// can offer every tier they might have without checking each one.
#[derive(Debug, Default, Clone)]
pub struct ThemeDirs {
    bundled: Vec<PathBuf>,
    system: Vec<PathBuf>,
    custom: Option<PathBuf>,
}

impl ThemeDirs {
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Themes the app ships with. Lowest precedence.
    ///
    /// Takes more than one because a Tauri app has two: the bundled resource
    /// directory in production, and the tree `build.rs` materialized for a
    /// `cargo run` that has no resource directory at all.
    #[must_use]
    pub fn bundled(mut self, dir: Option<PathBuf>) -> Self {
        self.bundled.extend(dir);
        self
    }

    /// Themes the machine ships, from an image or a package. Overrides bundled.
    #[must_use]
    pub fn system(mut self, dir: Option<PathBuf>) -> Self {
        self.system.extend(dir);
        self
    }

    /// The user's own themes. Highest precedence, and the only tier flagged
    /// custom, which is what makes them exportable and deletable.
    #[must_use]
    pub fn custom(mut self, dir: Option<PathBuf>) -> Self {
        self.custom = dir;
        self
    }

    /// The search path, lowest precedence first.
    #[must_use]
    pub fn build(self) -> Vec<(PathBuf, bool)> {
        let mut dirs = Vec::new();
        for dir in self.bundled.into_iter().chain(self.system) {
            if dir.is_dir() {
                dirs.push((dir, false));
            }
        }
        if let Some(dir) = self.custom
            && dir.is_dir()
        {
            dirs.push((dir, true));
        }
        dirs
    }
}

/// Extract the intent color sections into a flat `HashMap` with dotted keys
/// like `"surface.page"`, `"status.danger"`, `"category.one"`.
pub fn extract_colors(table: &toml::Table) -> HashMap<String, String> {
    let mut colors = HashMap::new();
    for section in COLOR_SECTIONS {
        if let Some(sect) = table.get(*section).and_then(|s| s.as_table()) {
            for (key, val) in sect {
                if let Some(color) = val.as_str() {
                    colors.insert(format!("{section}.{key}"), color.to_string());
                }
            }
        }
    }
    colors
}

/// Scan directories for `.toml` theme files and return metadata for each.
///
/// Directories are checked in order; later entries override earlier ones by ID.
/// Each entry in `dirs` is `(path, is_custom)`.
pub fn list_themes_from_dirs(dirs: &[(PathBuf, bool)]) -> Vec<ThemeMeta> {
    let mut seen: HashMap<String, ThemeMeta> = HashMap::new();

    for (dir, is_custom) in dirs {
        let Ok(entries) = std::fs::read_dir(dir) else {
            continue;
        };

        for entry in entries {
            let Ok(entry) = entry else {
                continue;
            };
            let path = entry.path();
            if path.extension().and_then(|e| e.to_str()) != Some("toml") {
                continue;
            }

            let id = path
                .file_stem()
                .and_then(|s| s.to_str())
                .unwrap_or_default()
                .to_string();

            let Ok(content) = std::fs::read_to_string(&path) else {
                continue;
            };
            let table: toml::Table = match content.parse() {
                Ok(t) => t,
                Err(_) => continue,
            };

            seen.insert(id.clone(), parse_meta(&id, &table, *is_custom));
        }
    }

    let mut themes: Vec<ThemeMeta> = seen.into_values().collect();
    themes.sort_by(|a, b| a.name.cmp(&b.name));
    themes
}

/// Find a theme file by ID in the given directories.
///
/// Checks directories in reverse order so the highest-priority directory wins.
/// Returns `(path, is_custom)` or `None` if not found.
pub fn find_theme_path(dirs: &[(PathBuf, bool)], id: &str) -> Option<(PathBuf, bool)> {
    let filename = format!("{id}.toml");

    for (dir, is_custom) in dirs.iter().rev() {
        let path = dir.join(&filename);
        if path.is_file() {
            return Some((path, *is_custom));
        }
    }

    None
}

/// Parse a complete theme (metadata + colors) from raw TOML content, with no
/// filesystem access. For callers that embed themes at compile time.
pub fn parse_theme_str(id: &str, content: &str, is_custom: bool) -> Result<ThemeColors, String> {
    validate_theme_id(id)?;
    let table: toml::Table = content
        .parse()
        .map_err(|e| format!("Failed to parse theme '{id}': {e}"))?;
    let meta = parse_meta(id, &table, is_custom);
    let colors = extract_colors(&table);
    Ok(ThemeColors { meta, colors })
}

/// Load a complete theme (metadata + colors) by ID from the given directories.
pub fn load_theme(dirs: &[(PathBuf, bool)], id: &str) -> Result<ThemeColors, String> {
    validate_theme_id(id)?;

    let (path, is_custom) =
        find_theme_path(dirs, id).ok_or_else(|| format!("Theme '{id}' not found"))?;

    let content = std::fs::read_to_string(&path)
        .map_err(|e| format!("Failed to read {}: {}", path.display(), e))?;

    let table: toml::Table = content
        .parse()
        .map_err(|e| format!("Failed to parse {}: {}", path.display(), e))?;

    let meta = parse_meta(id, &table, is_custom);
    let colors = extract_colors(&table);

    Ok(ThemeColors { meta, colors })
}

/// Load a theme and resolve it to the full intent token set in one step.
pub fn load_semantic(dirs: &[(PathBuf, bool)], id: &str) -> Result<SemanticTokens, String> {
    Ok(resolve(&load_theme(dirs, id)?))
}

/// Import a theme TOML file into the custom themes directory.
///
/// Validates that the file is parseable TOML with at least one intent color
/// section, then copies it to `custom_dir/{id}.toml`. Returns the theme metadata.
pub fn import_theme(source_path: &Path, custom_dir: &Path) -> Result<ThemeMeta, String> {
    let content = std::fs::read_to_string(source_path)
        .map_err(|e| format!("Failed to read {}: {}", source_path.display(), e))?;

    let table: toml::Table = content.parse().map_err(|e| format!("Invalid TOML: {e}"))?;

    let has_colors = COLOR_SECTIONS
        .iter()
        .any(|s| table.get(*s).and_then(|v| v.as_table()).is_some());
    if !has_colors {
        return Err(format!(
            "Theme file must have at least one color section ({})",
            COLOR_SECTIONS.join(", ")
        ));
    }

    let id = source_path
        .file_stem()
        .and_then(|s| s.to_str())
        .ok_or("Invalid file name")?
        .to_string();
    validate_theme_id(&id)?;

    std::fs::create_dir_all(custom_dir)
        .map_err(|e| format!("Failed to create {}: {}", custom_dir.display(), e))?;

    let dest = custom_dir.join(format!("{id}.toml"));
    std::fs::copy(source_path, &dest).map_err(|e| format!("Failed to copy theme: {e}"))?;

    Ok(parse_meta(&id, &table, true))
}

/// Delete a custom theme by ID.
///
/// Only operates on `custom_dir` — bundled themes are not deletable through
/// this entry point.
pub fn delete_theme(custom_dir: &Path, id: &str) -> Result<(), String> {
    validate_theme_id(id)?;

    let path = custom_dir.join(format!("{id}.toml"));
    if !path.is_file() {
        return Err(format!("Custom theme '{id}' not found"));
    }

    std::fs::remove_file(&path).map_err(|e| format!("Failed to delete {}: {}", path.display(), e))
}

/// A four-color preview for theme thumbnails: the representative swatch from
/// each of the principal roles.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct ThemePreview {
    pub meta: ThemeMeta,
    /// Page background (`surface.page`).
    pub background: Option<String>,
    /// Body text (`content.primary`).
    pub foreground: Option<String>,
    /// Brand/interactive color (`action.primary`).
    pub accent: Option<String>,
    /// Divider/outline color (`line.border`).
    pub border: Option<String>,
}

fn color_at(table: &toml::Table, section: &str, key: &str) -> Option<String> {
    table
        .get(section)
        .and_then(|s| s.as_table())
        .and_then(|s| s.get(key))
        .and_then(|v| v.as_str())
        .map(std::string::ToString::to_string)
}

/// Load just the preview swatches for a theme — for UI thumbnails.
pub fn load_theme_preview(dirs: &[(PathBuf, bool)], id: &str) -> Result<ThemePreview, String> {
    validate_theme_id(id)?;

    let (path, is_custom) =
        find_theme_path(dirs, id).ok_or_else(|| format!("Theme '{id}' not found"))?;

    let content = std::fs::read_to_string(&path)
        .map_err(|e| format!("Failed to read {}: {}", path.display(), e))?;

    let table: toml::Table = content
        .parse()
        .map_err(|e| format!("Failed to parse {}: {}", path.display(), e))?;

    Ok(ThemePreview {
        meta: parse_meta(id, &table, is_custom),
        background: color_at(&table, "surface", "page"),
        foreground: color_at(&table, "content", "primary"),
        accent: color_at(&table, "action", "primary"),
        border: color_at(&table, "line", "border"),
    })
}

/// Export a theme to a user-chosen path.
pub fn export_theme(dirs: &[(PathBuf, bool)], id: &str, dest_path: &Path) -> Result<(), String> {
    validate_theme_id(id)?;

    let (source, _) = find_theme_path(dirs, id).ok_or_else(|| format!("Theme '{id}' not found"))?;

    std::fs::copy(&source, dest_path).map_err(|e| format!("Failed to export theme: {e}"))?;

    Ok(())
}

/// The themes this crate ships, embedded at compile time.
///
/// `include_dir` is an implementation detail: the public API hands back plain
/// `(id, toml_source)` pairs, so how the data is embedded can change without
/// a breaking release.
static EMBEDDED: include_dir::Dir<'static> =
    include_dir::include_dir!("$CARGO_MANIFEST_DIR/themes");

/// The themes this crate ships, as `(id, toml_source)` pairs.
///
/// This is the path-free way to reach the bundled set, for consumers that
/// cannot rely on a directory existing at runtime: a crate pulled from
/// crates.io lives in a registry checkout whose location is not knowable at
/// compile time, so `include_dir!` and asset-bundling globs in the depending
/// crate have nothing stable to point at. Embedding here and re-exporting the
/// contents gives them one source of truth without a path.
///
/// Ordering follows the embedded directory and is not guaranteed; collect and
/// sort by id where a stable order matters (a theme picker, say).
pub fn embedded_themes() -> impl Iterator<Item = (&'static str, &'static str)> {
    EMBEDDED.files().filter_map(|file| {
        let path = file.path();
        if path.extension().and_then(|e| e.to_str()) != Some("toml") {
            return None;
        }
        let id = path.file_stem()?.to_str()?;
        Some((id, file.contents_utf8()?))
    })
}

/// The theme directory this crate ships, for use as a build-from-source
/// fallback.
///
/// Resolves against `makeover`'s own manifest directory, fixed at compile
/// time, so it works from a path dependency and from a cargo git checkout
/// alike. Installed systems should put their packaged theme directory ahead
/// of this in the search path; this is the entry that keeps `cargo run` in a
/// fresh clone from coming up with no themes at all.
///
/// Returns `None` when the directory is absent — a cargo cache that has been
/// cleaned, or a vendored copy that dropped the data — so callers degrade to
/// their remaining search path rather than failing.
pub fn bundled_themes_dir() -> Option<PathBuf> {
    let themes = Path::new(env!("CARGO_MANIFEST_DIR")).join("themes");
    if themes.is_dir() { Some(themes) } else { None }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::fs;

    // ---- id validation ----

    #[test]
    fn validate_theme_id_alphanumeric() {
        assert!(validate_theme_id("darkmode").is_ok());
        assert!(validate_theme_id("Theme123").is_ok());
    }

    #[test]
    fn validate_theme_id_hyphens_underscores() {
        assert!(validate_theme_id("dark-mode").is_ok());
        assert!(validate_theme_id("my_theme_v2").is_ok());
    }

    #[test]
    fn validate_theme_id_rejects_path_traversal() {
        assert!(validate_theme_id("../etc/passwd").is_err());
        assert!(validate_theme_id("foo/bar").is_err());
        assert!(validate_theme_id("theme.toml").is_err());
    }

    // ---- low-color terminals ----

    #[test]
    fn the_ansi_palette_is_sixteen_distinct_colors() {
        let mut seen: Vec<(u8, u8, u8)> = ANSI_16.iter().map(|c| c.tuple()).collect();
        seen.sort_unstable();
        seen.dedup();
        assert_eq!(seen.len(), 16);
    }

    #[test]
    fn quantize_picks_the_obvious_entry() {
        let black = Rgb { r: 0, g: 0, b: 0 };
        let white = Rgb {
            r: 255,
            g: 255,
            b: 255,
        };
        assert_eq!(quantize(black, &ANSI_16), 0);
        assert_eq!(quantize(white, &ANSI_16), 15);
    }

    // Nearest-entry quantization is per-color, so two colors a theme keeps
    // apart can arrive as one. These two are both closest to the palette's
    // light gray, and a border drawn in one on a page painted the other is not
    // drawn at all.
    #[test]
    fn two_colors_can_quantize_to_one_entry() {
        let page = Rgb::from_hex("#a8a8a8").unwrap();
        let border = Rgb::from_hex("#b4b4b4").unwrap();

        assert_eq!(quantize(page, &ANSI_16), quantize(border, &ANSI_16));
        assert!(quantize_against(border, page, &ANSI_16) != quantize(page, &ANSI_16));
    }

    #[test]
    fn quantize_against_keeps_the_border_off_the_page() {
        let page = Rgb::from_hex("#e4ded6").unwrap();
        let border = Rgb::from_hex("#7f786d").unwrap();

        let shown_page = ANSI_16[quantize(page, &ANSI_16)];
        let shown_border = ANSI_16[quantize_against(border, page, &ANSI_16)];

        assert!(
            wcag_contrast(shown_border, shown_page) >= DISTINCT,
            "border {} on page {} is {:.2}:1",
            shown_border.to_hex(),
            shown_page.to_hex(),
            wcag_contrast(shown_border, shown_page)
        );
    }

    // A color that already reads against its background is left where it is,
    // so this can be applied without redesigning what already worked.
    #[test]
    fn quantize_against_leaves_a_readable_color_alone() {
        let page = Rgb::from_hex("#e4ded6").unwrap();
        let text = Rgb::from_hex("#1a1816").unwrap();

        assert_eq!(
            quantize_against(text, page, &ANSI_16),
            quantize(text, &ANSI_16)
        );
    }

    // With nothing in the palette to satisfy the request, the most legible
    // entry is the answer. Returning the nearest one would return the
    // background itself, which is the failure this function exists to avoid.
    #[test]
    fn an_impossible_palette_gets_the_most_legible_entry() {
        let page = Rgb::from_hex("#ffffff").unwrap();
        let border = Rgb::from_hex("#fefefe").unwrap();
        let palette = [
            Rgb::from_hex("#ffffff").unwrap(),
            Rgb::from_hex("#fdfdfd").unwrap(),
        ];

        let chosen = palette[quantize_against(border, page, &palette)];
        assert_eq!(chosen.to_hex(), "#fdfdfd");
    }

    // ---- meta ----

    #[test]
    fn parse_meta_with_name_and_variant() {
        let table: toml::Table = "[meta]\nname = \"Nord\"\nvariant = \"light\"\n"
            .parse()
            .unwrap();
        let meta = parse_meta("nord", &table, false);
        assert_eq!(meta.id, "nord");
        assert_eq!(meta.name, "Nord");
        assert_eq!(meta.variant, "light");
        assert!(!meta.is_custom);
    }

    #[test]
    fn parse_meta_defaults_to_id_and_dark() {
        let table: toml::Table = "".parse().unwrap();
        let meta = parse_meta("fallback", &table, true);
        assert_eq!(meta.name, "fallback");
        assert_eq!(meta.variant, "dark");
        assert!(meta.is_custom);
    }

    // ---- color math (formulas must match the apps they came from) ----

    #[test]
    fn rgb_hex_roundtrip() {
        assert_eq!(
            Rgb::from_hex("#6196FF").unwrap(),
            Rgb {
                r: 0x61,
                g: 0x96,
                b: 0xff
            }
        );
        assert_eq!(
            Rgb::from_hex("#abc").unwrap(),
            Rgb {
                r: 0xaa,
                g: 0xbb,
                b: 0xcc
            }
        );
        assert_eq!(
            Rgb {
                r: 0x61,
                g: 0x96,
                b: 0xff
            }
            .to_hex(),
            "#6196ff"
        );
        assert!(Rgb::from_hex("not-a-color").is_none());
    }

    #[test]
    fn oklab_roundtrips_within_tolerance() {
        for hex in ["#6196ff", "#2e3440", "#ffffff", "#000000", "#c0392b"] {
            let c = Rgb::from_hex(hex).unwrap();
            let back = Rgb::from_oklab(c.to_oklab());
            // Gamut round-trip is near-exact (±1 per channel from rounding).
            assert!((c.r as i16 - back.r as i16).abs() <= 1, "{hex} r");
            assert!((c.g as i16 - back.g as i16).abs() <= 1, "{hex} g");
            assert!((c.b as i16 - back.b as i16).abs() <= 1, "{hex} b");
        }
    }

    #[test]
    fn wcag_contrast_known_pairs() {
        let white = Rgb {
            r: 255,
            g: 255,
            b: 255,
        };
        let black = Rgb { r: 0, g: 0, b: 0 };
        assert!((wcag_contrast(white, black) - 21.0).abs() < 0.01);
        assert!((wcag_contrast(white, white) - 1.0).abs() < 0.01);
    }

    #[test]
    fn readable_on_picks_by_wcag() {
        assert_eq!(
            readable_on(Rgb {
                r: 255,
                g: 255,
                b: 255
            }),
            Rgb { r: 0, g: 0, b: 0 }
        );
        assert_eq!(
            readable_on(Rgb { r: 0, g: 0, b: 0 }),
            Rgb {
                r: 255,
                g: 255,
                b: 255
            }
        );
        // A light blue action -> black text reads better.
        let action = Rgb::from_hex("#6196ff").unwrap();
        assert_eq!(readable_on(action), Rgb { r: 0, g: 0, b: 0 });
    }

    #[test]
    fn lighten_darken_move_oklab_lightness() {
        let c = Rgb::from_hex("#6196ff").unwrap();
        let l0 = c.to_oklab().l;
        assert!(lighten(c, 0.05).to_oklab().l > l0);
        assert!(darken(c, 0.05).to_oklab().l < l0);
    }

    #[test]
    fn mix_endpoints_and_midpoint() {
        let a = Rgb::from_hex("#000000").unwrap();
        let b = Rgb::from_hex("#6196ff").unwrap();
        assert_eq!(mix(a, b, 0.0), a);
        assert_eq!(mix(a, b, 1.0), b);
        // Midpoint sits between the endpoints in OKLab lightness.
        let mid = mix(a, b, 0.5).to_oklab().l;
        assert!(mid > a.to_oklab().l && mid < b.to_oklab().l);
    }

    // ---- extract + resolve ----

    fn nord_toml() -> &'static str {
        r##"
[meta]
name = "Nord"
variant = "dark"

[surface]
page = "#2e3440"
raised = "#3b4252"
sunken = "#434c5e"
overlay = "#3b4252"

[content]
primary = "#d8dee9"
secondary = "#e5e9f0"
muted = "#616e88"

[action]
primary = "#81a1c1"

[status]
danger = "#bf616a"
success = "#a3be8c"
warning = "#ebcb8b"
info = "#88c0d0"

[line]
border = "#4c566a"

[category]
one = "#bf616a"
two = "#a3be8c"
three = "#81a1c1"
four = "#ebcb8b"
five = "#b48ead"
six = "#88c0d0"
"##
    }

    #[test]
    fn extract_colors_reads_intent_sections() {
        let table: toml::Table = nord_toml().parse().unwrap();
        let colors = extract_colors(&table);
        assert_eq!(colors.get("surface.page").unwrap(), "#2e3440");
        assert_eq!(colors.get("content.primary").unwrap(), "#d8dee9");
        assert_eq!(colors.get("action.primary").unwrap(), "#81a1c1");
        assert_eq!(colors.get("status.danger").unwrap(), "#bf616a");
        assert_eq!(colors.get("line.border").unwrap(), "#4c566a");
        assert_eq!(colors.get("category.five").unwrap(), "#b48ead");
        assert_eq!(colors.len(), 19);
    }

    #[test]
    fn resolve_base_intents_passthrough() {
        let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
        let t = resolve(&theme);
        assert_eq!(t.hex("surface-page"), Some("#2e3440"));
        assert_eq!(t.hex("content"), Some("#d8dee9")); // content.primary -> content
        assert_eq!(t.hex("content-muted"), Some("#616e88"));
        assert_eq!(t.hex("action"), Some("#81a1c1"));
        assert_eq!(t.hex("danger"), Some("#bf616a"));
        assert_eq!(t.hex("border"), Some("#4c566a"));
        assert_eq!(t.hex("category-five"), Some("#b48ead"));
    }

    #[test]
    fn resolve_derived_intents() {
        let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
        let t = resolve(&theme);
        let action = Rgb::from_hex("#81a1c1").unwrap();
        let page = Rgb::from_hex("#2e3440").unwrap();
        let _ = page;
        assert_eq!(
            t.hex("action-hover").unwrap(),
            lighten(action, 0.05).to_hex()
        );
        assert_eq!(
            t.hex("content-on-action").unwrap(),
            readable_on(action).to_hex()
        );
        assert_eq!(t.hex("focus-ring"), Some("#81a1c1"));
        assert_eq!(t.hex("hover-surface"), Some("#434c5e")); // = surface.sunken
        // Pruned by the usage audit (0 consumers): action-active, the *-surface
        // tints, selection, row-stripe. Apps that need them derive inline via
        // the shared mix().
        assert!(t.hex("action-active").is_none());
        assert!(t.hex("danger-surface").is_none());
        assert!(t.hex("selection").is_none());
        assert!(t.hex("row-stripe").is_none());
    }

    #[test]
    fn resolve_overlay_is_dark_translucent_scrim() {
        let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
        let t = resolve(&theme);
        let overlay = t.hex("overlay").unwrap();
        assert!(
            overlay.starts_with("rgba("),
            "overlay is translucent: {overlay}"
        );
        assert!(overlay.ends_with(", 0.5)"));
        // The scrim tone is anchored very dark regardless of theme.
        let inner = overlay
            .trim_start_matches("rgba(")
            .trim_end_matches(", 0.5)");
        let parts: Vec<u8> = inner.split(", ").map(|p| p.parse().unwrap()).collect();
        let scrim = Rgb {
            r: parts[0],
            g: parts[1],
            b: parts[2],
        };
        assert!(scrim.to_oklab().l < 0.2, "scrim must be near-black");
    }

    #[test]
    fn resolve_drops_non_hex_base_intent() {
        // A base intent that isn't a hex color must never reach the resolved
        // token set (it would otherwise be inlined verbatim into a <style>
        // block). Skipped like a missing intent; valid siblings survive.
        let theme = parse_theme_str(
            "x",
            "[surface]\npage = \"</style><script>alert(1)</script>\"\n[content]\nprimary = \"#111111\"\n",
            false,
        )
        .unwrap();
        let t = resolve(&theme);
        assert!(
            t.hex("surface-page").is_none(),
            "non-hex base intent leaked"
        );
        assert_eq!(t.hex("content").unwrap(), "#111111");
        // The injected markup appears in no resolved value.
        assert!(!t.intents.values().any(|v| v.contains('<')));
    }

    #[test]
    fn resolve_skips_derived_when_source_missing() {
        // No [action] => no action-derived tokens.
        let theme = parse_theme_str(
            "x",
            "[surface]\npage = \"#000000\"\n[line]\nborder = \"#222222\"\n",
            false,
        )
        .unwrap();
        let t = resolve(&theme);
        assert!(t.hex("action").is_none());
        assert!(t.hex("action-hover").is_none());
        assert!(t.hex("selection").is_none());
        assert_eq!(
            t.hex("border-strong").unwrap(),
            darken(Rgb::from_hex("#222222").unwrap(), 0.05).to_hex()
        );
    }

    #[test]
    fn rgb_accessor_for_native_consumers() {
        let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
        let t = resolve(&theme);
        assert_eq!(t.rgb("action"), Some((0x81, 0xa1, 0xc1)));
        assert_eq!(t.rgb("nonexistent"), None);
    }

    // ---- css emit ----

    #[test]
    fn intent_css_vars_wraps_root_and_includes_tokens() {
        let theme = parse_theme_str("nord", nord_toml(), false).unwrap();
        let css = intent_css_vars(&resolve(&theme));
        assert!(css.starts_with(":root {\n"));
        assert!(css.contains("  --surface-page: #2e3440;\n"));
        assert!(css.contains("  --danger: #bf616a;\n"));
        assert!(css.contains("  --action-hover: "));
        assert!(css.trim_end().ends_with('}'));
    }

    // ---- loading / fs ----

    #[test]
    fn load_and_resolve_round_trip() {
        let dir = tempfile::tempdir().unwrap();
        fs::write(dir.path().join("nord.toml"), nord_toml()).unwrap();
        let dirs = vec![(dir.path().to_path_buf(), false)];
        let t = load_semantic(&dirs, "nord").unwrap();
        assert_eq!(t.meta.name, "Nord");
        assert_eq!(t.hex("action"), Some("#81a1c1"));
    }

    #[test]
    fn load_theme_rejects_invalid_id() {
        assert!(load_theme(&[], "../evil").is_err());
    }

    fn meta(id: &str, variant: &str) -> ThemeMeta {
        ThemeMeta {
            id: id.to_string(),
            name: id.to_string(),
            variant: variant.to_string(),
            is_custom: false,
        }
    }

    fn defaults() -> ThemeDefaults {
        ThemeDefaults::new("flatwhite", "nord")
    }

    // The three the shipped themes actually declare.
    #[test]
    fn every_shipped_variant_parses() {
        assert_eq!(Variant::parse("light"), Some(Variant::Light));
        assert_eq!(Variant::parse("dark"), Some(Variant::Dark));
        assert_eq!(Variant::parse("high-contrast"), Some(Variant::HighContrast));
        assert_eq!(Variant::parse("sepia"), None);
    }

    // parse_meta already defaults a *missing* variant to dark, so an
    // unrecognized one reading as light would have the crate disagreeing with
    // itself. alloy_tui did exactly that before this existed.
    #[test]
    fn an_unrecognized_variant_reads_the_way_a_missing_one_does() {
        assert_eq!(Variant::from("sepia"), Variant::Dark);
        assert_eq!(Variant::from(""), Variant::Dark);

        let missing: toml::Table = "[meta]\nname = \"X\"\n".parse().unwrap();
        assert_eq!(parse_meta("x", &missing, false).kind(), Variant::Dark);
    }

    #[test]
    fn a_selection_round_trips_through_any_store() {
        for (stored, expect) in [
            (Some("system"), ThemeSelection::Follow),
            (None, ThemeSelection::Follow),
            (Some(""), ThemeSelection::Follow),
            (Some("  "), ThemeSelection::Follow),
            (Some("nord"), ThemeSelection::Fixed("nord".into())),
        ] {
            let parsed = ThemeSelection::parse(stored);
            assert_eq!(parsed, expect, "{stored:?}");
            assert_eq!(
                ThemeSelection::parse(Some(parsed.as_str())),
                expect,
                "what is written reads back as what was meant",
            );
        }
    }

    // Nothing saved is follow-the-system, which is what Balanced Breakfast
    // expressed as an absent value and GoingsOn as a sentinel. Both are now the
    // same thing.
    #[test]
    fn nothing_chosen_yet_is_follow() {
        assert_eq!(ThemeSelection::default(), ThemeSelection::Follow);
    }

    #[test]
    fn a_fixed_selection_wins_when_its_theme_is_installed() {
        let available = [meta("nord", "dark"), meta("flatwhite", "light")];
        let fixed = ThemeSelection::Fixed("nord".into());
        assert_eq!(
            fixed.resolve(Variant::Light, &defaults(), &available),
            "nord",
            "a chosen theme is not overridden by the ambient mode",
        );
    }

    // Themes are deletable in three of the four apps. Handing back an id that
    // will fail to load only moves the error somewhere less helpful.
    #[test]
    fn a_fixed_selection_whose_theme_is_gone_falls_back() {
        let available = [meta("nord", "dark"), meta("flatwhite", "light")];
        let fixed = ThemeSelection::Fixed("deleted".into());
        assert_eq!(
            fixed.resolve(Variant::Light, &defaults(), &available),
            "flatwhite",
        );
    }

    #[test]
    fn follow_picks_the_apps_default_for_the_ambient_mode() {
        let available = [meta("nord", "dark"), meta("flatwhite", "light")];
        let follow = ThemeSelection::Follow;
        assert_eq!(
            follow.resolve(Variant::Dark, &defaults(), &available),
            "nord",
        );
        assert_eq!(
            follow.resolve(Variant::Light, &defaults(), &available),
            "flatwhite",
        );
    }

    // The behaviour Balanced Breakfast could not have: following the system
    // into a theme the user installed, when the app's own default is absent.
    #[test]
    fn follow_uses_any_installed_theme_of_the_right_variant() {
        let available = [meta("solarized-light", "light"), meta("mine", "dark")];
        assert_eq!(
            ThemeSelection::Follow.resolve(Variant::Dark, &defaults(), &available),
            "mine",
            "the app's `nord` is not installed, but a dark theme is",
        );
    }

    // Always returns something: an app with no theme directory gets the id it
    // ships with, and the load error it would have had anyway.
    #[test]
    fn an_empty_catalog_still_names_the_apps_default() {
        assert_eq!(
            ThemeSelection::Follow.resolve(Variant::Dark, &defaults(), &[]),
            "nord",
        );
    }

    #[test]
    fn high_contrast_falls_back_to_dark_unless_named() {
        let plain = defaults();
        assert_eq!(plain.for_variant(Variant::HighContrast), "nord");

        let named = defaults().high_contrast("sharp");
        assert_eq!(named.for_variant(Variant::HighContrast), "sharp");
    }

    // The bug this builder exists to prevent: the Alloy console pushed the
    // user's directory first under a comment reading "highest precedence
    // first", when both consumers of this vector resolve last-wins. A custom
    // theme lost to the packaged one of the same id.
    #[test]
    fn the_users_own_themes_outrank_everything() {
        let root = tempfile::tempdir().unwrap();
        let make = |name: &str| {
            let dir = root.path().join(name);
            std::fs::create_dir_all(&dir).unwrap();
            dir
        };
        let (bundled, system, custom) = (make("bundled"), make("system"), make("custom"));

        let dirs = ThemeDirs::new()
            .custom(Some(custom.clone()))
            .bundled(Some(bundled.clone()))
            .system(Some(system.clone()))
            .build();

        assert_eq!(
            dirs,
            vec![(bundled, false), (system, false), (custom.clone(), true)],
            "lowest precedence first, whatever order the tiers were added in",
        );
        assert!(dirs.last().unwrap().1, "only the user's tier is custom");

        // And the ordering means what the consumers think it means.
        for dir in dirs.iter().map(|(dir, _)| dir) {
            std::fs::write(dir.join("shared.toml"), "[meta]\nname = \"x\"\n").unwrap();
        }
        assert_eq!(
            find_theme_path(&dirs, "shared").unwrap().0,
            custom.join("shared.toml"),
            "the user's copy is the one that loads",
        );
    }

    #[test]
    fn a_directory_that_does_not_exist_is_dropped() {
        let root = tempfile::tempdir().unwrap();
        let real = root.path().join("real");
        std::fs::create_dir_all(&real).unwrap();

        let dirs = ThemeDirs::new()
            .bundled(Some(root.path().join("nope")))
            .system(None)
            .custom(Some(real.clone()))
            .build();

        assert_eq!(dirs, vec![(real, true)]);
    }

    // A Tauri app has two bundled tiers: the resource dir in production and the
    // tree build.rs materialized for a dev run with no resource dir.
    #[test]
    fn more_than_one_bundled_tier_is_allowed() {
        let root = tempfile::tempdir().unwrap();
        let (first, second) = (root.path().join("a"), root.path().join("b"));
        std::fs::create_dir_all(&first).unwrap();
        std::fs::create_dir_all(&second).unwrap();

        let dirs = ThemeDirs::new()
            .bundled(Some(first.clone()))
            .bundled(Some(second.clone()))
            .build();
        assert_eq!(dirs, vec![(first, false), (second, false)]);
    }

    #[test]
    fn list_themes_from_dirs_finds_toml_files() {
        let dir = tempfile::tempdir().unwrap();
        fs::write(dir.path().join("t.toml"), "[meta]\nname = \"T\"\n").unwrap();
        fs::write(dir.path().join("x.txt"), "ignored").unwrap();
        let dirs = vec![(dir.path().to_path_buf(), false)];
        let themes = list_themes_from_dirs(&dirs);
        assert_eq!(themes.len(), 1);
        assert_eq!(themes[0].id, "t");
    }

    #[test]
    fn find_theme_path_reverse_priority() {
        let d1 = tempfile::tempdir().unwrap();
        let d2 = tempfile::tempdir().unwrap();
        fs::write(d1.path().join("s.toml"), "[meta]\n").unwrap();
        fs::write(d2.path().join("s.toml"), "[meta]\n").unwrap();
        let dirs = vec![
            (d1.path().to_path_buf(), false),
            (d2.path().to_path_buf(), true),
        ];
        let (path, is_custom) = find_theme_path(&dirs, "s").unwrap();
        assert!(is_custom);
        assert_eq!(path, d2.path().join("s.toml"));
    }

    #[test]
    fn import_theme_valid_and_rejects_empty() {
        let src_dir = tempfile::tempdir().unwrap();
        let custom_dir = tempfile::tempdir().unwrap();

        let good = src_dir.path().join("my-theme.toml");
        fs::write(&good, "[surface]\npage = \"#1a1b26\"\n").unwrap();
        let meta = import_theme(&good, custom_dir.path()).unwrap();
        assert_eq!(meta.id, "my-theme");
        assert!(custom_dir.path().join("my-theme.toml").exists());

        let empty = src_dir.path().join("empty.toml");
        fs::write(&empty, "[meta]\nname = \"E\"\n").unwrap();
        assert!(import_theme(&empty, custom_dir.path()).is_err());
    }

    #[test]
    fn import_theme_rejects_invalid_toml() {
        let src_dir = tempfile::tempdir().unwrap();
        let custom_dir = tempfile::tempdir().unwrap();
        let src = src_dir.path().join("bad.toml");
        fs::write(&src, "this is not [valid toml [[[").unwrap();
        assert!(import_theme(&src, custom_dir.path()).is_err());
    }

    #[test]
    fn delete_theme_removes_and_guards() {
        let custom = tempfile::tempdir().unwrap();
        let path = custom.path().join("doomed.toml");
        fs::write(&path, "[surface]\npage = \"#000\"\n").unwrap();
        delete_theme(custom.path(), "doomed").unwrap();
        assert!(!path.exists());
        assert!(delete_theme(custom.path(), "../etc/passwd").is_err());
        assert!(delete_theme(custom.path(), "ghost").is_err());
    }

    #[test]
    fn export_theme_copies_file() {
        let src_dir = tempfile::tempdir().unwrap();
        let dest_dir = tempfile::tempdir().unwrap();
        let content = "[meta]\nname = \"E\"\n[surface]\npage = \"#ffffff\"\n";
        fs::write(src_dir.path().join("e.toml"), content).unwrap();
        let dirs = vec![(src_dir.path().to_path_buf(), false)];
        let dest = dest_dir.path().join("out.toml");
        export_theme(&dirs, "e", &dest).unwrap();
        assert_eq!(fs::read_to_string(&dest).unwrap(), content);
        assert!(export_theme(&dirs, "missing", &dest).is_err());
    }

    #[test]
    fn load_theme_preview_returns_role_swatches() {
        let dir = tempfile::tempdir().unwrap();
        fs::write(dir.path().join("nord.toml"), nord_toml()).unwrap();
        let dirs = vec![(dir.path().to_path_buf(), false)];
        let p = load_theme_preview(&dirs, "nord").unwrap();
        assert_eq!(p.background.as_deref(), Some("#2e3440")); // surface.page
        assert_eq!(p.foreground.as_deref(), Some("#d8dee9")); // content.primary
        assert_eq!(p.accent.as_deref(), Some("#81a1c1")); // action.primary
        assert_eq!(p.border.as_deref(), Some("#4c566a")); // line.border
    }

    #[test]
    fn bundled_themes_dir_resolves_to_shipped_themes() {
        // The crate ships its themes, so this must resolve in-tree and the
        // Akari defaults the console falls back to must be present.
        let dir = bundled_themes_dir().expect("makeover ships a themes/ directory");
        assert!(dir.join("akari-dawn.toml").is_file());
        assert!(dir.join("akari-night.toml").is_file());
    }

    #[test]
    fn every_theme_is_accounted_for_in_third_party_notices() {
        // Attribution is a redistribution obligation, not a nicety: adding a
        // theme without a notice entry silently ships someone's work
        // uncredited. Fail here instead.
        let notices = std::fs::read_to_string(
            Path::new(env!("CARGO_MANIFEST_DIR")).join("THIRD-PARTY-NOTICES.md"),
        )
        .expect("THIRD-PARTY-NOTICES.md must exist");
        let missing: Vec<&str> = embedded_themes()
            .map(|(id, _)| id)
            .filter(|id| !notices.contains(*id))
            .collect();
        assert!(
            missing.is_empty(),
            "themes missing from THIRD-PARTY-NOTICES.md: {missing:?}"
        );
    }

    #[test]
    fn adapted_themes_carry_inline_attribution() {
        // Each adapted file must name its upstream in-file, so the credit
        // survives someone copying a single .toml out of the crate.
        const ORIGINALS: [&str; 5] = [
            "makenotwork",
            "goingson",
            "audiofiles",
            "high-contrast",
            "neobrute",
        ];
        for (id, source) in embedded_themes() {
            if ORIGINALS.contains(&id) {
                continue;
            }
            assert!(
                source.contains("adapted from"),
                "adapted theme `{id}` is missing its inline attribution header"
            );
        }
    }

    #[test]
    fn embedded_themes_match_the_directory() {
        // The embedded copy and themes/ are two views of one source. If they
        // ever disagree, path-based and path-free consumers render different
        // theme sets, which is exactly the drift shipping the data was meant
        // to prevent.
        let dir = bundled_themes_dir().unwrap();
        let mut on_disk: Vec<String> = std::fs::read_dir(&dir)
            .unwrap()
            .filter_map(|e| {
                let path = e.ok()?.path();
                if path.extension()? != "toml" {
                    return None;
                }
                Some(path.file_stem()?.to_str()?.to_string())
            })
            .collect();
        let mut embedded: Vec<String> = embedded_themes().map(|(id, _)| id.to_string()).collect();
        on_disk.sort();
        embedded.sort();
        assert_eq!(embedded, on_disk, "embedded theme set drifted from themes/");
    }

    #[test]
    fn every_embedded_theme_parses() {
        // Guards the path-free consumers (MNW server, the Tauri build steps)
        // the same way every_shipped_theme_loads guards the path-based ones.
        let mut count = 0;
        for (id, source) in embedded_themes() {
            parse_theme_str(id, source, false)
                .unwrap_or_else(|e| panic!("embedded theme `{id}` failed to parse: {e}"));
            count += 1;
        }
        assert!(count >= 30, "expected the full theme set, got {count}");
    }

    #[test]
    fn every_shipped_theme_loads() {
        // Guards the data, not just the loader: a malformed or truncated
        // .toml in themes/ is a shipping bug, and it should fail here rather
        // than at a user's first launch.
        let dir = bundled_themes_dir().unwrap();
        let dirs = vec![(dir.clone(), false)];
        let themes = list_themes_from_dirs(&dirs);
        assert!(
            themes.len() >= 30,
            "expected the full theme set, got {}",
            themes.len()
        );
        for meta in &themes {
            load_theme(&dirs, &meta.id)
                .unwrap_or_else(|e| panic!("shipped theme `{}` failed to load: {e}", meta.id));
        }
    }
}