use crate::Tone;

// Names this module's prose links to, resolved for rustdoc.
#[allow(unused_imports)]
use crate::{Choice, Notice, Readiness};

/// How much of a set is done.
///
/// Nine sites across the two webview apps drew a bar and nothing here named
/// one, so every described screen concatenated the two numbers into its
/// heading text instead: "Subtasks 3/7", "Time Tracking 45m tracked / 30m est,
/// over". Every fact survives that and the reading does not, which is the same
/// loss `RowPart::Tokens` closed when a toned status badge became prose.
///
/// # Why a pair and not a percentage
///
/// Both numbers, not the percentage the apps compute from them. The percentage
/// was the obvious shape and it had already been tried: goingson's
/// `Task::time_progress` divides, rounds, and then clamps to 100, which throws
/// away the one case the bar exists to show — 45 minutes tracked against a
/// 30-minute estimate. It carries a separate `is_over_estimate` boolean beside
/// it to recover the fact the clamp dropped. A pair keeps the over-run without a
/// companion flag, and [`percent`](Meter::percent) is still one call away for a
/// renderer that wants it.
///
/// The pair is also what the apps already have at every site. All seven
/// determinate bars write the ratio into the accessible layer and never the
/// percentage: `title="3/7 subtasks"`, `aria-label="3 of 7 subtasks completed"`,
/// a milestone's own `3/7` span. Given 43 nothing can recover "3 of 7", so a
/// percentage member would have made [`label`](Meter::label) mandatory at every
/// call site, which is the concatenated text this member removes, moved one
/// layer down.
///
/// # What this is not
///
/// The progress of an *operation*. Two of the nine sites are that — goingson's
/// focus timer, Balanced Breakfast's feed fetch — and they get nothing here, on
/// purpose. Both are imperative controllers over a live handle, driven by a tick
/// or an event stream, and a description is built once and dropped. Holding one
/// would mean growing a way to update a description between renders, which is a
/// different feature. [`Readiness::Pending`] and a [`Notice::Toast`] carry the
/// honest part.
///
/// The two cases are distinguishable in the markup rather than by taste: every
/// determinate bar in both apps carries a tone, and neither operation bar
/// carries one. Two codebases drew that line the same way without coordinating.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Meter<'a> {
    /// How much is done. May exceed [`total`](Self::total), and that is the
    /// case worth drawing.
    pub done: u32,
    /// How much there is to do. Zero means there is no set, not that the set is
    /// complete.
    pub total: u32,
    /// What the proportion means right now.
    ///
    /// Carried rather than derived, because no renderer can work it out. The
    /// same 90% is [`Tone::Success`] on a subtask rollup and [`Tone::Danger`] on
    /// a time estimate, and goingson picks between them from `is_over_estimate`,
    /// a fact about the data and not about the number.
    pub tone: Tone,
    /// What is being counted, if the bar says so: "subtasks", "tasks".
    ///
    /// The noun, not the ratio. A renderer builds "3 of 7 subtasks" from this
    /// and the two numbers; handing it the assembled string would put the
    /// sentence order in the description, where a terminal at one line and a
    /// tooltip want different ones.
    pub label: Option<&'a str>,
}

impl<'a> Meter<'a> {
    /// A proportion with no tone and no label.
    #[must_use]
    pub const fn new(done: u32, total: u32) -> Self {
        Self {
            done,
            total,
            tone: Tone::Neutral,
            label: None,
        }
    }

    /// What the proportion means.
    #[must_use]
    pub const fn tone(mut self, tone: Tone) -> Self {
        self.tone = tone;
        self
    }

    /// What is being counted.
    #[must_use]
    pub const fn label(mut self, label: &'a str) -> Self {
        self.label = Some(label);
        self
    }

    /// How full the bar is, 0 to 100, clamped.
    ///
    /// For drawing, which is the only thing a clamped number is good for. Ask
    /// [`overflowing`](Self::overflowing) before reporting it as a fact, or this
    /// is `time_progress`'s bug again with the clamp moved.
    ///
    /// An empty set reads as 0. Nothing is done, because there is nothing to do
    /// and no bar to fill; the apps guard on the count before drawing at all.
    #[must_use]
    pub const fn percent(&self) -> u8 {
        if self.total == 0 {
            return 0;
        }
        let scaled = (self.done as u64 * 100) / self.total as u64;
        if scaled > 100 { 100 } else { scaled as u8 }
    }

    /// Whether more is done than there was to do.
    ///
    /// The fact [`percent`](Self::percent) destroys, kept reachable so a
    /// renderer can mark the over-run rather than drawing a full bar and
    /// implying it landed exactly.
    #[must_use]
    pub const fn overflowing(&self) -> bool {
        self.done > self.total
    }

    /// Whether there is a set at all.
    ///
    /// A meter over nothing is sayable on purpose, for the same reason a field
    /// with no options is: it is what an app with an unloaded count actually
    /// has, and a renderer that shows an empty bar says so on screen rather than
    /// dividing by zero.
    #[must_use]
    pub const fn is_empty(&self) -> bool {
        self.total == 0
    }
}

/// One figure with a caption: a number and what it counts.
///
/// The dashboard shape. A large value over a small caption, several of them in
/// a strip: a current streak, a completion rate, a total. Four put the value
/// above the caption and one inverts it, which is drift inside the shape
/// rather than a second shape.
///
/// # Why the value is text
///
/// "17", "84%", "12/30", "3d". A figure is whatever the app computed, already
/// formatted, and the formatting is the app's because only it knows whether the
/// number is a percentage, a duration or a ratio. This carries none of the
/// arithmetic [`Meter`] carries, and that is the difference between them: a
/// meter is a proportion a renderer draws, and a figure is a fact a renderer
/// sets in type.
///
/// # Tone is carried, for [`Meter`]'s reason
///
/// Three of the five sites tone the figure by their own means — `red`/`blue` on
/// the weekly review, a `${type}` class on the monthly one, `sync-stat-warn` on
/// sync. So tone is carried at every site that needs it and derived at none, and
/// no renderer can work out that a streak of zero is worth colouring.
///
/// # What is not here
///
/// Whether the figure answers a click. One of the five is a control — sync's
/// "Not Applied: 3" opens the list — and an action is not something this crate
/// can name: nothing here knows what a route is. That belongs beside the figure
/// in whatever layer holds the actions, the same way a row's activation sits
/// beside its parts rather than inside them.
///
/// The arrangement is not here either. Several figures in a strip is a set, and
/// a renderer given them one at a time cannot tell it is looking at one; the
/// layer that holds the tree is where the set gets said.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Figure<'a> {
    /// The number, formatted the way the app means it to read.
    pub value: &'a str,
    /// What it counts. The caption under the value.
    pub caption: &'a str,
    /// How the value has moved, if the app is tracking that.
    ///
    /// Text, for [`value`](Self::value)'s reason: only the app knows whether a
    /// move reads as `+12.5%`, `+3` or `2x`, and a renderer handed a number
    /// would have to guess.
    ///
    /// This is what [`tone`](Self::tone) was for and had no consumer of. The MNW
    /// server has four screens whose stat card is a label, a value and a delta,
    /// and the delta is the toned part: the figure itself is an ordinary fact
    /// and it is the movement that reads as good or bad. Without this the delta
    /// has to be folded into the caption, which loses the tone and reads as a
    /// longer caption rather than as a second, smaller line.
    pub change: Option<&'a str>,
    /// What the figure means right now. [`Tone::Neutral`] is an ordinary fact.
    ///
    /// Applies to [`change`](Self::change) where there is one, since that is the
    /// part that carries the judgement, and to the value where there is not.
    pub tone: Tone,
}

impl<'a> Figure<'a> {
    /// A figure that is an ordinary fact.
    #[must_use]
    pub const fn new(value: &'a str, caption: &'a str) -> Self {
        Self {
            value,
            caption,
            change: None,
            tone: Tone::Neutral,
        }
    }

    /// How the value has moved.
    #[must_use]
    pub const fn change(mut self, change: &'a str) -> Self {
        self.change = Some(change);
        self
    }

    /// What the figure means.
    #[must_use]
    pub const fn tone(mut self, tone: Tone) -> Self {
        self.tone = tone;
        self
    }
}

/// Something the user can do, and what it costs to say so.
///
/// Beside [`Meter`] and [`Figure`] for the reason those are here: a renderer
/// that is handed the parts has to decide how to say them, and a renderer that
/// is handed a finished string has already had the decision made for it.
///
/// No address. Where a control goes is the app's business and every host
/// follows it differently — an `hx-get`, a protocol URL, a function call — so
/// the description says what the control *is* and the caller keeps what it
/// does. That is the same split [`Choice`] makes.
///
/// No confirmation flag either, and that one is a finding rather than an
/// omission: a question asked *after* a control is pressed belongs to whatever
/// is holding the interaction, and a renderer that drew it would be asking
/// before there was anything to answer.
/// How a picture sits in the box it is given.
///
/// An intent rather than a value, so a renderer picks the expression it has:
/// `object-fit` in a webview, a texture's UV rect in egui, and in a terminal a
/// choice about how many cells the blit gets. Named because MNW already makes
/// the distinction deliberately at 17 sites and makes it three different ways,
/// which is a policy the app decided rather than one a shared crate would be
/// picking by accident.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
#[non_exhaustive]
pub enum Fit {
    /// The picture's own proportions, and the box takes the height they imply.
    ///
    /// The default because it is the only one that shows the whole picture at
    /// its own shape, so a renderer that ignores this enum entirely is still
    /// right about the common case. A screenshot wants this; the shipped MNW
    /// carousel sets no `object-fit` at all, which is this.
    #[default]
    Natural,
    /// Fill the box and crop whatever does not fit.
    ///
    /// For a picture in a slot whose shape the layout fixed: a thumbnail, an
    /// avatar, cover art. 15 of MNW's 17 sites.
    Cover,
    /// Fit inside the box whole, leaving space on two sides.
    ///
    /// The letterbox. For when the whole picture matters more than filling the
    /// space, and the space is not the picture's shape.
    Contain,
}

/// A picture's own pixel dimensions.
///
/// Deliberately not [`makeover_geometry`]'s business. Geometry answers *how
/// much space a thing should get*, which is a scale question with the same
/// answer on every screen. This is the intrinsic size of one asset, which is a
/// fact about that asset and varies per picture.
///
/// [`makeover_geometry`]: https://docs.rs/makeover-geometry
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Extent {
    /// Width in the picture's own pixels.
    pub width: u32,
    /// Height in the picture's own pixels.
    pub height: u32,
}

impl Extent {
    /// A picture's dimensions.
    #[must_use]
    pub const fn new(width: u32, height: u32) -> Self {
        Self { width, height }
    }

    /// Width over height, or `None` if either side is zero.
    ///
    /// The form a renderer actually reserves space with: a box that knows its
    /// proportion holds the right height at any width, which is what a
    /// responsive picture needs and what a fixed pixel height cannot give.
    #[must_use]
    pub fn ratio(self) -> Option<f32> {
        (self.width > 0 && self.height > 0).then(|| self.width as f32 / self.height as f32)
    }
}

/// A run of magnitudes read against one axis.
///
/// [`Meter`] is one proportion; this is a series of them that share a maximum,
/// and the shared maximum is the whole difference. A run of meters draws each
/// bar against its own `total`, so a chart said that way states the axis once
/// per bar and nothing holds the copies together. Here the axis is stated once
/// and a bar carries only where it sits on it.
///
/// # Why the axis and not a percentage per bar
///
/// [`Meter`]'s reason, one layer out. The app that drew MNW's revenue chart
/// computed `revenue / most * 100.0` and put the percentage in the markup, and
/// what reached the reader was a width with no numbers behind it: a bar at 100%
/// because it is the largest and a bar at 100% because the axis is wrong are the
/// same width and are not the same fact. Carrying both integers keeps the fact,
/// and [`Bar::fraction`] is one call away for a renderer that wants the ratio.
///
/// It is also the only shape that survives a compiled template. A residual holds
/// numbers the description HANDS a renderer, never ones a renderer works out
/// from two of them, so a chart drawn from a supplied percentage could be
/// described and could not be compiled. See `quasi_router::stage::number_at`.
///
/// # What is worded here and what is not
///
/// [`Bar::at`] is where the bar sits on the axis and [`label`](Self::label) is
/// what the magnitudes are, which is [`Meter::label`]'s split exactly. What
/// differs is [`Bar::reading`] and [`Bar::note`]: both arrive already worded,
/// because a magnitude's own units are the app's ("$42.10", not 4210) and a
/// count's noun inflects ("1 sale", "3 sales"). A renderer that pluralised
/// would be growing a lexer for one language.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Chart<'a> {
    /// The magnitude the axis runs to. Every bar is read against this.
    ///
    /// Zero means there is no axis, not that every bar is full. A renderer draws
    /// nothing rather than dividing by it; see [`is_empty`](Self::is_empty).
    ///
    /// `usize` because that is what a description counts in -- a pager's offset
    /// and page size are the same -- and because it is the only width
    /// `quasi_router::stage::number_at` has a stand-in for, which is what lets a
    /// chart reach a compiled template at all.
    pub most: usize,
    /// What the magnitudes are: "revenue", "plays".
    ///
    /// The noun, not the unit and not the ratio. The unit is already in each
    /// [`Bar::reading`], where it belongs, because only the app knows it.
    pub label: Option<&'a str>,
    /// What the axis means, where it means anything.
    pub tone: Tone,
}

impl<'a> Chart<'a> {
    /// An axis running to `most`, untoned and unlabelled.
    #[must_use]
    pub const fn new(most: usize) -> Self {
        Self {
            most,
            label: None,
            tone: Tone::Neutral,
        }
    }

    /// What the magnitudes are.
    #[must_use]
    pub const fn label(mut self, label: &'a str) -> Self {
        self.label = Some(label);
        self
    }

    /// What the axis means.
    #[must_use]
    pub const fn tone(mut self, tone: Tone) -> Self {
        self.tone = tone;
        self
    }

    /// Whether there is an axis to read against.
    ///
    /// [`Meter::is_empty`]'s case: an axis running to zero is what an app with
    /// nothing to chart actually has, and saying so beats dividing by it.
    #[must_use]
    pub const fn is_empty(&self) -> bool {
        self.most == 0
    }
}

/// One magnitude in a [`Chart`], at its place on the axis.
///
/// Carries no axis of its own on purpose: a bar read against a maximum it
/// states itself is a meter, and a run of those is not a chart.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct Bar<'a> {
    /// Where on the axis this sits: "Mar 3", "Week 12".
    ///
    /// The position's own name rather than an index, for the reason a pager's
    /// jump carries its page number: what a chart shows is a window over a
    /// series, and an index into that window is not the point it names.
    pub at: &'a str,
    /// The magnitude, in the chart's units, read against [`Chart::most`].
    pub value: usize,
    /// The magnitude as the app words it: "$42.10".
    ///
    /// Worded rather than derived because the units are the app's. A renderer
    /// handed 4210 cannot know it is money, let alone which money.
    pub reading: Option<&'a str>,
    /// A second fact about this bar, already worded: "3 sales".
    ///
    /// Worded for the reason [`reading`](Self::reading) is, plus one of its own:
    /// a count's noun inflects with the count, and that is language rather than
    /// drawing.
    pub note: Option<&'a str>,
}

impl<'a> Bar<'a> {
    /// A place on the axis, with no magnitude on it yet.
    ///
    /// The magnitude arrives through [`of`](Self::of) rather than as a second
    /// argument, and that is not stylistic: `quasi-declare` stages a
    /// constructor's plain arguments all one way or all the other, so a
    /// constructor taking a place AND a magnitude would have the place standing
    /// in as a number. Split, the place is a value and `of` is a count, which is
    /// the same split a pager's `of` makes and the reason it is spelled the
    /// same.
    #[must_use]
    pub const fn at(at: &'a str) -> Self {
        Self {
            at,
            value: 0,
            reading: None,
            note: None,
        }
    }

    /// How far up the axis this bar reaches.
    #[must_use]
    pub const fn of(mut self, value: usize) -> Self {
        self.value = value;
        self
    }

    /// How the app words this magnitude.
    #[must_use]
    pub const fn reading(mut self, reading: &'a str) -> Self {
        self.reading = Some(reading);
        self
    }

    /// A second fact about the bar, already worded.
    #[must_use]
    pub const fn note(mut self, note: &'a str) -> Self {
        self.note = Some(note);
        self
    }

    /// How far up the axis this bar reaches, 0.0 to 1.0, clamped.
    ///
    /// For drawing, which is what a clamped number is good for, and for the two
    /// renderers that draw in cells and pixels rather than in CSS. An empty axis
    /// reads as 0.0 rather than dividing by zero.
    ///
    /// A bar over [`Chart::most`] clamps, and unlike [`Meter`] that is not a
    /// fact being lost: `most` is the maximum of the bars, so a bar above it is
    /// an axis the app got wrong rather than an over-run worth drawing.
    #[must_use]
    pub fn fraction(&self, chart: &Chart<'_>) -> f32 {
        if chart.most == 0 {
            return 0.0;
        }
        (self.value as f64 / chart.most as f64).min(1.0) as f32
    }
}