makeover 5.4.0

//! Intent resolution

use crate::{
    DISTINCT, Rgb, Rgba, STEP_FLOOR, ThemeColors, ThemeMeta, darken, lighten, mix, readable_on,
    wcag_contrast,
};
use serde::Serialize;
use std::collections::BTreeMap;

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

/// Declares [`Token`]: each variant with its CSS stem, and the list of all of
/// them. One table, so a stem cannot be spelled two ways.
macro_rules! tokens {
    ($($(#[$doc:meta])* $variant:ident => $stem:literal,)*) => {
        /// One resolved intent, by name.
        ///
        /// The CSS stem ([`as_str`](Self::as_str)) is the custom property a
        /// stylesheet reads, `--{stem}`, and the spelling a stored or
        /// serialised token uses. Ordered by that stem, so a
        /// [`SemanticTokens`] emits in the same order whichever way it is read.
        #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
        #[non_exhaustive]
        pub enum Token {
            $($(#[$doc])* $variant,)*
        }

        impl Token {
            /// Every token, in declaration order.
            pub const ALL: &'static [Token] = &[$(Token::$variant,)*];

            /// The CSS stem: `--{stem}` in a stylesheet.
            pub const fn as_str(self) -> &'static str {
                match self {
                    $(Token::$variant => $stem,)*
                }
            }
        }
    };
}

tokens! {
    /// The page ground.
    SurfacePage => "surface-page",
    /// A surface raised off the page.
    SurfaceRaised => "surface-raised",
    /// A surface sunk into the page.
    SurfaceSunken => "surface-sunken",
    /// A surface floating over the page.
    SurfaceOverlay => "surface-overlay",
    /// The ink.
    Content => "content",
    /// The ink, one tonal step back.
    ContentSecondary => "content-secondary",
    /// The ink, two tonal steps back.
    ContentMuted => "content-muted",
    /// The interactive colour.
    Action => "action",
    Danger => "danger",
    Success => "success",
    Warning => "warning",
    Info => "info",
    Border => "border",
    CategoryOne => "category-one",
    CategoryTwo => "category-two",
    CategoryThree => "category-three",
    CategoryFour => "category-four",
    CategoryFive => "category-five",
    CategorySix => "category-six",
    /// [`Action`](Self::Action) under a pointer.
    ActionHover => "action-hover",
    /// Text that reads on [`Action`](Self::Action).
    ContentOnAction => "content-on-action",
    /// The keyboard focus ring.
    FocusRing => "focus-ring",
    /// The modal scrim. Translucent.
    Overlay => "overlay",
    /// The cast a floating surface throws on the page. Translucent.
    Elevation => "elevation",
    /// A bevel's lit edge.
    BevelLight => "bevel-light",
    /// A bevel's shadowed edge.
    BevelDark => "bevel-dark",
    /// An inset well in a raised surface.
    SurfaceWell => "surface-well",
    InfoSurface => "info-surface",
    SuccessSurface => "success-surface",
    WarningSurface => "warning-surface",
    DangerSurface => "danger-surface",
    InfoSurfaceHover => "info-surface-hover",
    SuccessSurfaceHover => "success-surface-hover",
    WarningSurfaceHover => "warning-surface-hover",
    DangerSurfaceHover => "danger-surface-hover",
    /// A table row under a pointer.
    RowHover => "row-hover",
    /// The hairline between table rows.
    RowRule => "row-rule",
    /// The row a keyboard cursor is on.
    RowSelected => "row-selected",
    /// A plain surface under a pointer.
    HoverSurface => "hover-surface",
    /// The emphatic border tier.
    BorderStrong => "border-strong",
    /// [`Danger`](Self::Danger) as text: its hue, at the lightness that reads
    /// on every text ground and on its own toned surface.
    DangerText => "danger-text",
    /// [`Success`](Self::Success) as text, as [`DangerText`](Self::DangerText).
    SuccessText => "success-text",
    /// [`Warning`](Self::Warning) as text, as [`DangerText`](Self::DangerText).
    WarningText => "warning-text",
    /// [`Info`](Self::Info) as text, as [`DangerText`](Self::DangerText).
    InfoText => "info-text",
    /// [`CategoryOne`](Self::CategoryOne) as text, on every text ground.
    CategoryOneText => "category-one-text",
    /// [`CategoryTwo`](Self::CategoryTwo) as text.
    CategoryTwoText => "category-two-text",
    /// [`CategoryThree`](Self::CategoryThree) as text.
    CategoryThreeText => "category-three-text",
    /// [`CategoryFour`](Self::CategoryFour) as text.
    CategoryFourText => "category-four-text",
    /// [`CategoryFive`](Self::CategoryFive) as text.
    CategoryFiveText => "category-five-text",
    /// [`CategorySix`](Self::CategorySix) as text.
    CategorySixText => "category-six-text",
    /// A language keyword in highlighted code.
    SyntaxKeyword => "syntax-keyword",
    /// A string literal in highlighted code.
    SyntaxString => "syntax-string",
    /// A comment in highlighted code: the muted ink, held to the text floor.
    SyntaxComment => "syntax-comment",
    /// A numeric or named constant in highlighted code.
    SyntaxConstant => "syntax-constant",
    /// A type, function or other named entity in highlighted code.
    SyntaxEntity => "syntax-entity",
    /// A variable in highlighted code.
    SyntaxVariable => "syntax-variable",
    /// A library or built-in name in highlighted code.
    SyntaxSupport => "syntax-support",
}

impl Token {
    /// The token with this CSS stem, or `None`.
    pub fn parse(stem: &str) -> Option<Self> {
        Self::ALL
            .iter()
            .copied()
            .find(|token| token.as_str() == stem)
    }
}

impl Ord for Token {
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        self.as_str().cmp(other.as_str())
    }
}

impl PartialOrd for Token {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

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

impl Serialize for Token {
    fn serialize<S: serde::Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
        serializer.serialize_str(self.as_str())
    }
}

/// The look ratios the derivations use, one place.
///
/// Lightness deltas are OKLab L units and mix ratios interpolate in OKLab.
/// These are look decisions, measured against specimens rather than derived,
/// which is why each is named and documented rather than written inline.
pub mod ratio {
    /// How much lighter [`Token::ActionHover`](super::Token::ActionHover) is than the action.
    pub const ACTION_HOVER: f32 = 0.05;
    /// OKLab L the scrim and the elevation cast are pinned to: dark enough to
    /// read as absence of light on a light theme and a dark one alike.
    pub const SHADOW_L: f32 = 0.08;
    /// The scrim's opacity.
    pub const SCRIM_ALPHA: f32 = 0.5;
    /// The elevation cast's opacity. Between the two literal shadow scales it
    /// replaced: 0.10 read as nothing under a menu, 0.15 was invisible at
    /// plate size.
    pub const ELEVATION_ALPHA: f32 = 0.18;
    /// How far a bevel's lit edge is raised off its face.
    pub const BEVEL_LIGHT: f32 = 0.14;
    /// How far a bevel's shadowed edge is cut below its face. Deeper than the
    /// highlight, because an equal step down reads as a smaller change.
    pub const BEVEL_DARK: f32 = 0.18;
    /// A well's step toward lighter, on a theme whose text is darker than its
    /// face. The specimen's, measured: #D9DDF4 to #F3F5FD.
    pub const WELL_LIGHTER: f32 = 0.07;
    /// A well's step toward darker, on a theme whose text is lighter.
    pub const WELL_DARKER: f32 = 0.09;
    /// How far a toned surface's lightness steps from its ground toward the
    /// tone.
    pub const TONE_SURFACE: f32 = 0.12;
    /// The OKLab chroma a toned surface carries, in the tone's own hue: enough
    /// to read as the tone on any ground, or the tone's own if it has less.
    pub const TONE_CHROMA: f32 = 0.05;
    /// The ink mixed into a table row under a pointer.
    pub const ROW_HOVER: f32 = 0.09;
    /// The ink mixed into the hairline between table rows.
    pub const ROW_RULE: f32 = 0.26;
    /// The ink mixed into the cursor row: a neutral-ramp step, not the accent,
    /// which is reserved for the primary action. The marker, not this fill, is
    /// what tells the cursor row apart from the hover step.
    pub const ROW_SELECTED: f32 = 0.18;
    /// How far [`Token::BorderStrong`](super::Token::BorderStrong) steps away from the page.
    pub const BORDER_STRONG: f32 = 0.05;
}

/// Base intents: the TOML dotted source key each is read from, and its token.
///
/// Read straight from the loaded theme, which is not quite the same as read
/// from the file: `content.secondary` and `content.muted` are tonal steps of
/// `content.primary` and are filled in at load by [`derive_tonal_steps`], so
/// they arrive here already computed and take this path like any other.
pub const BASE_INTENTS: &[(&str, Token)] = &[
    ("surface.page", Token::SurfacePage),
    ("surface.raised", Token::SurfaceRaised),
    ("surface.sunken", Token::SurfaceSunken),
    ("surface.overlay", Token::SurfaceOverlay),
    ("content.primary", Token::Content),
    ("content.secondary", Token::ContentSecondary),
    ("content.muted", Token::ContentMuted),
    ("action.primary", Token::Action),
    ("status.danger", Token::Danger),
    ("status.success", Token::Success),
    ("status.warning", Token::Warning),
    ("status.info", Token::Info),
    ("line.border", Token::Border),
    ("category.one", Token::CategoryOne),
    ("category.two", Token::CategoryTwo),
    ("category.three", Token::CategoryThree),
    ("category.four", Token::CategoryFour),
    ("category.five", Token::CategoryFive),
    ("category.six", Token::CategorySix),
];

/// The four status tones, each with its resting and hovered surface.
const TONES: [(Token, Token, Token); 4] = [
    (Token::Info, Token::InfoSurface, Token::InfoSurfaceHover),
    (
        Token::Success,
        Token::SuccessSurface,
        Token::SuccessSurfaceHover,
    ),
    (
        Token::Warning,
        Token::WarningSurface,
        Token::WarningSurfaceHover,
    ),
    (
        Token::Danger,
        Token::DangerSurface,
        Token::DangerSurfaceHover,
    ),
];

/// A floor [`lift_to_floors`] could not clear, with how far it got.
///
/// Lifting converges for every palette a shipped theme carries, but an
/// imported palette owes the depth model nothing and can land an ink on
/// grounds that split it or exhaust the ramp, so an ink can stay under its
/// floor no matter how it is moved. Resolution records those rather than
/// shipping them silent.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct UnmetFloor {
    /// The ink that missed.
    pub token: Token,
    /// The floor it was owed.
    pub floor: f32,
    /// The best contrast it reached against its grounds.
    pub achieved: f32,
}

/// A fully resolved intent layer: every token present, as a colour.
/// Includes both authored base intents and the computed derived intents.
#[derive(Debug, Clone, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct SemanticTokens {
    pub meta: ThemeMeta,
    /// Every token this theme resolved, in stem order.
    pub intents: BTreeMap<Token, Rgba>,
    /// Floors that could not be cleared, empty for every shipped theme.
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub unmet_floors: Vec<UnmetFloor>,
}

impl SemanticTokens {
    /// The resolved colour, alpha included.
    pub fn get(&self, token: Token) -> Option<Rgba> {
        self.intents.get(&token).copied()
    }

    /// The resolved colour, if it is opaque.
    ///
    /// `None` for a translucent token as for a missing one: `overlay` and
    /// `elevation` dropped to opaque would hand a native consumer a
    /// near-black where it asked for a scrim. Those want [`get`](Self::get)
    /// or [`rgba`](Self::rgba).
    pub fn color(&self, token: Token) -> Option<Rgb> {
        self.get(token).and_then(Rgba::opaque_rgb)
    }

    /// `#rrggbb` for an opaque token. `None` for a translucent one, as
    /// [`color`](Self::color).
    pub fn hex(&self, token: Token) -> Option<String> {
        self.color(token).map(Rgb::to_hex)
    }

    /// The CSS value a stylesheet gets: `#rrggbb`, or `rgba(...)` for a
    /// translucent token.
    pub fn css(&self, token: Token) -> Option<String> {
        self.get(token).map(Rgba::css)
    }

    /// `(r, g, b)` for an opaque token.
    pub fn rgb(&self, token: Token) -> Option<(u8, u8, u8)> {
        self.color(token).map(Rgb::tuple)
    }

    /// `(r, g, b, a)` with the alpha as 0-255, for any token. An opaque one
    /// comes back at 255, so a caller need not know which kind it asked for.
    pub fn rgba(&self, token: Token) -> Option<(u8, u8, u8, u8)> {
        self.get(token).map(Rgba::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, so every
///    consumer gets identical output.
///
/// 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 base: BTreeMap<Token, Rgba> = BTreeMap::new();

    // 1. Base intents (authored). Only values that parse as a hex colour are
    // kept, so an authored value can never carry arbitrary bytes into the
    // emitted CSS (the resolved tokens are inlined into a `<style>` block by
    // the web server). A malformed value is skipped, like an absent one.
    for (src, token) in BASE_INTENTS {
        if let Some(rgb) = theme.colors.get(*src).and_then(|v| Rgb::from_hex(v)) {
            base.insert(*token, Rgba::opaque(rgb));
        }
    }

    let (intents, unmet_floors) = lift_to_floors(base);

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

/// A surface on `ground` that reads as `tone`: lightness stepped `step` of the
/// way toward the tone, hue the tone's, chroma `chroma` or the tone's own if it
/// has less.
///
/// Not a [`mix`]: a mix carries the ground's own tint, which cancels a tone
/// opposite it in hue, so a yellow on a lavender ground came out grey.
fn toned(ground: Rgb, tone: Rgb, step: f32, chroma: f32) -> Rgb {
    let (g, t) = (ground.to_oklab(), tone.to_oklab());
    let own = t.a.hypot(t.b);
    let scale = if own > chroma { chroma / own } else { 1.0 };
    Rgb::from_oklab(crate::Oklab {
        l: g.l + (t.l - g.l) * step,
        a: t.a * scale,
        b: t.b * scale,
    })
}

/// Every derived token, computed from the base intents.
fn derive(base: &BTreeMap<Token, Rgba>) -> BTreeMap<Token, Rgba> {
    use ratio::{
        ACTION_HOVER, BEVEL_DARK, BEVEL_LIGHT, BORDER_STRONG, ELEVATION_ALPHA, ROW_HOVER, ROW_RULE,
        ROW_SELECTED, SCRIM_ALPHA, SHADOW_L, TONE_CHROMA, TONE_SURFACE, WELL_DARKER, WELL_LIGHTER,
    };

    let mut intents = base.clone();
    let get = |m: &BTreeMap<Token, Rgba>, token: Token| m.get(&token).and_then(|c| c.opaque_rgb());

    // 2. Derived intents: perceptual (OKLab) steps and WCAG-picked text.
    let mut derived: Vec<(Token, Rgba)> = Vec::new();
    let mut put = |token: Token, rgb: Rgb| derived.push((token, Rgba::opaque(rgb)));
    if let Some(action) = get(&intents, Token::Action) {
        put(Token::ActionHover, lighten(action, ACTION_HOVER));
        put(Token::ContentOnAction, readable_on(action));
        // The focus ring is the action colour itself, not a tint of it: a ring
        // is a statement that the keyboard is here, and a faded one reads as a
        // disabled control rather than an emphatic one.
        //
        // One ring, not one per primitive. Where the ring sits is a depth
        // question and not a per-component choice: a well takes it inside its
        // own edge and a raised surface takes it outside. That is one decision
        // with two renderings. This token is the one shared artifact; which
        // thing wears it, and how it is drawn, is each renderer's own (see
        // `makeover_layout`'s crate header, "reach, focus and the focus ring").
        //
        // A ring is a boundary between two areas, so it answers to the 3:1 two
        // areas need against every surface it is drawn on. An accent that misses
        // that keeps its hue and has its lightness moved until it clears.
        let grounds: Vec<Rgb> = [Token::SurfacePage, Token::SurfaceRaised]
            .into_iter()
            .filter_map(|ground| get(&intents, ground))
            .collect();
        put(Token::FocusRing, cleared(action, &grounds, DISTINCT));
    }
    if let Some(page) = get(&intents, Token::SurfacePage) {
        // Modal scrim and elevation cast: one near-black tone carrying a faint
        // hint of the theme's hue, at two weights. Anchored very dark so it
        // dims the page on light and dark themes alike.
        //
        // The cast is what a surface that FLOATS OVER the page throws on it:
        // menus, toasts, popovers and dropdowns. A card, a plate and a framed
        // image are IN the page and take a bevel instead. Geometry stays with
        // the consumer, the way bevel thickness does.
        let mut o = page.to_oklab();
        o.l = SHADOW_L;
        let shadow = Rgb::from_oklab(o);
        intents.insert(Token::Overlay, Rgba::translucent(shadow, SCRIM_ALPHA));
        intents.insert(Token::Elevation, Rgba::translucent(shadow, ELEVATION_ALPHA));
    }
    if let Some(raised) = get(&intents, Token::SurfaceRaised) {
        // The two edges of a bevel: a raised control is lit from the top left,
        // so its top and left edges take `bevel-light` and its bottom and right
        // edges `bevel-dark`. Inverting the pair gives a pressed state and an
        // inset well. Geometry (thickness, radius, which side gets which) stays
        // app-side.
        //
        // A face already at the top of the ramp cannot hold a highlight: the
        // lightening clamps. That is a property of the theme, not of this
        // derivation; `bevel_edges_are_distinct_from_their_face` names the
        // shipped themes it bites.
        put(Token::BevelLight, lighten(raised, BEVEL_LIGHT));
        put(Token::BevelDark, darken(raised, BEVEL_DARK));

        // An inset well: the content surface inside a raised container.
        // `surface-sunken` cannot serve, because a theme is free to author it
        // darker than raised and a well has to go the other way.
        //
        // The direction is read off `content` rather than off `Variant`: a
        // theme whose text is dark is a theme whose surfaces are light, whatever
        // its `variant` field claims. A face with no room in the requested
        // direction takes the other one (see `step_with_room`); `bevel-light`
        // does not, since a highlight darker than its face is a second shadow.
        if let Some(content) = get(&intents, Token::Content) {
            let content_is_darker = content.to_oklab().l < raised.to_oklab().l;
            let well = if content_is_darker {
                step_with_room(raised, WELL_LIGHTER)
            } else {
                step_with_room(raised, -WELL_DARKER)
            };
            put(Token::SurfaceWell, well);

            // A status chip's fill, wiki `table-model`: the raised ground's
            // lightness in the tone's hue, edged in the tone, inked in
            // `content`. The hovered fill is built off the sunken ground the
            // way `hover-surface` is, so a toned control and a plain one travel
            // the same distance under a pointer.
            let sunken = get(&intents, Token::SurfaceSunken);
            for (tone, surface, hover) in TONES {
                if let Some(color) = get(&intents, tone) {
                    put(surface, toned(raised, color, TONE_SURFACE, TONE_CHROMA));
                    if let Some(sunken) = sunken {
                        put(hover, toned(sunken, color, TONE_SURFACE, TONE_CHROMA));
                    }
                }
            }

            // The table model's row tones, wiki `table-model`: the ink mixed
            // into the raised surface a table sits on. Toward `content` rather
            // than darker, for the reason the well reads its direction off
            // `content`. The hairline stays under the 3:1 that separates two
            // areas on purpose, since a row is not a region.
            //
            // No stripe tone. Alternate rows sit on `surface-page`, a step of
            // the theme's own neutral ramp, so the table separates its rows
            // with colours the theme already authored rather than a fourth
            // mix of its ink.
            put(Token::RowHover, mix(raised, content, ROW_HOVER));
            put(Token::RowRule, mix(raised, content, ROW_RULE));

            // The row a keyboard cursor is on, for a host that has one. A step
            // of the neutral ramp, not the accent: accent is reserved for the
            // primary action. A fill and never a foreground, so a failed row
            // stays red under it.
            put(Token::RowSelected, mix(raised, content, ROW_SELECTED));
        }
    }
    if let Some(sunken) = get(&intents, Token::SurfaceSunken) {
        put(Token::HoverSurface, sunken);
    }
    if let Some(border) = get(&intents, Token::Border) {
        // The emphatic border tier: one step further from the page than
        // `border` is, which is not the same as one step darker. Direction is
        // read off `content` against `surface-page`, because a dark theme's
        // ground is at the bottom of the ramp. A theme with no page or no
        // content keeps the darkening, the light-theme answer.
        let away_from_page = match (
            get(&intents, Token::Content),
            get(&intents, Token::SurfacePage),
        ) {
            (Some(content), Some(page)) => content.to_oklab().l > page.to_oklab().l,
            _ => false,
        };
        let strong = if away_from_page {
            lighten(border, BORDER_STRONG)
        } else {
            darken(border, BORDER_STRONG)
        };
        put(Token::BorderStrong, strong);
    }

    intents.extend(derived);
    intents
}

/// `tokens` with every [`TEXT_INKS`] row added: each ink keeps its source's
/// hue and moves its lightness until it reads on every ground in its row.
///
/// Run once on the settled tokens rather than inside [`derive`]: no ground is
/// derived from a text ink, so the fixed point does not need them.
fn with_text_inks(mut tokens: BTreeMap<Token, Rgba>) -> BTreeMap<Token, Rgba> {
    let get = |m: &BTreeMap<Token, Rgba>, token: Token| m.get(&token).and_then(|c| c.opaque_rgb());
    let mut inks: Vec<(Token, Rgba)> = Vec::new();
    for &(ink, source, grounds) in TEXT_INKS {
        let Some(color) = get(&tokens, source) else {
            continue;
        };
        let grounds: Vec<Rgb> = grounds.iter().filter_map(|g| get(&tokens, *g)).collect();
        inks.push((ink, Rgba::opaque(cleared(color, &grounds, TEXT))));
    }
    tokens.extend(inks);
    tokens
}

/// Every ground body-size text is set on.
const TEXT_GROUNDS: &[Token] = &[
    Token::SurfacePage,
    Token::SurfaceRaised,
    Token::SurfaceSunken,
    Token::SurfaceWell,
    Token::SurfaceOverlay,
    Token::RowHover,
    Token::RowSelected,
];

/// The text grounds plus a tone's own surface, which a toned ink is set on
/// inside its chip or row.
macro_rules! toned_grounds {
    ($surface:expr) => {
        &[
            Token::SurfacePage,
            Token::SurfaceRaised,
            Token::SurfaceSunken,
            Token::SurfaceWell,
            Token::SurfaceOverlay,
            Token::RowHover,
            Token::RowSelected,
            $surface,
        ]
    };
}

/// The text grounds plus the added and removed rows of a diff, which carry
/// highlighted code.
const CODE_GROUNDS: &[Token] = &[
    Token::SurfacePage,
    Token::SurfaceRaised,
    Token::SurfaceSunken,
    Token::SurfaceWell,
    Token::SurfaceOverlay,
    Token::RowHover,
    Token::RowSelected,
    Token::SuccessSurface,
    Token::DangerSurface,
];

/// Each derived ink, the colour it is taken from, and the grounds it owes
/// [`TEXT`] on. [`derive`] clears every row and [`unmet_floors`] reports any it
/// could not.
const TEXT_INKS: &[(Token, Token, &[Token])] = &[
    (
        Token::DangerText,
        Token::Danger,
        toned_grounds!(Token::DangerSurface),
    ),
    (
        Token::SuccessText,
        Token::Success,
        toned_grounds!(Token::SuccessSurface),
    ),
    (
        Token::WarningText,
        Token::Warning,
        toned_grounds!(Token::WarningSurface),
    ),
    (
        Token::InfoText,
        Token::Info,
        toned_grounds!(Token::InfoSurface),
    ),
    (Token::CategoryOneText, Token::CategoryOne, TEXT_GROUNDS),
    (Token::CategoryTwoText, Token::CategoryTwo, TEXT_GROUNDS),
    (Token::CategoryThreeText, Token::CategoryThree, TEXT_GROUNDS),
    (Token::CategoryFourText, Token::CategoryFour, TEXT_GROUNDS),
    (Token::CategoryFiveText, Token::CategoryFive, TEXT_GROUNDS),
    (Token::CategorySixText, Token::CategorySix, TEXT_GROUNDS),
    (Token::SyntaxKeyword, Token::CategoryFive, CODE_GROUNDS),
    (Token::SyntaxString, Token::CategoryTwo, CODE_GROUNDS),
    (Token::SyntaxComment, Token::ContentMuted, CODE_GROUNDS),
    (Token::SyntaxConstant, Token::CategoryFour, CODE_GROUNDS),
    (Token::SyntaxEntity, Token::CategoryThree, CODE_GROUNDS),
    (Token::SyntaxVariable, Token::CategoryOne, CODE_GROUNDS),
    (Token::SyntaxSupport, Token::CategorySix, CODE_GROUNDS),
];

/// WCAG AA for normal text.
const TEXT: f32 = 4.5;

/// The muted tier's floor: present and readable, deliberately under body text.
const QUIET_TEXT: f32 = 3.0;

/// Each ink, the grounds it is set on, and the contrast it owes every one.
///
/// Resolution lifts each ink toward these floors along the theme's own ramp,
/// and leaves every ink that already clears exactly as authored. An imported
/// palette was drawn for syntax highlighting and owes the depth model nothing,
/// so its ink can land on grounds that split it or exhaust the ramp; when no
/// lift clears a floor, [`UnmetFloor`] records the shortfall instead of
/// shipping it silent. `tests/contrast_floors.rs` is the independent check,
/// and carries these rows.
const INK_FLOORS: &[(Token, &[Token], f32)] = &[
    (
        Token::Content,
        &[
            Token::SurfacePage,
            Token::SurfaceRaised,
            Token::SurfaceSunken,
            Token::SurfaceWell,
            Token::RowHover,
            Token::RowSelected,
            Token::InfoSurface,
            Token::SuccessSurface,
            Token::WarningSurface,
            Token::DangerSurface,
        ],
        TEXT,
    ),
    (Token::ContentSecondary, TEXT_GROUNDS, TEXT),
    (Token::ContentMuted, TEXT_GROUNDS, QUIET_TEXT),
];

/// How far one lift moves an ink, in OKLab lightness. Finer than 8-bit sRGB
/// resolves on the shortest ramp in the corpus, so no lift overshoots the
/// first value that clears by more than a code point.
const LIFT: f32 = 0.005;

/// The derived tokens, with every ink in [`INK_FLOORS`] clearing its floor.
///
/// A fixed point rather than one pass, because the grounds move with the inks:
/// the row tones are mixed toward `content`, so lifting it changes what it is
/// then measured against. Each round lifts every ink still under its floor one
/// [`LIFT`] and derives again. A theme with nothing under a floor leaves on the
/// first round with its tokens exactly as a single derivation gives them.
///
/// `content-secondary` and `content-muted` are tonal steps of `content`, so
/// they travel toward it, which is along the theme's own ramp. `content` has
/// no ink to travel toward and moves its lightness away from its grounds,
/// stepping in whichever direction raises its worst contrast. A secondary
/// that would come to sit closer to `content` than a tonal step may
/// ([`STEP_FLOOR`]) lifts `content` instead, which widens the room between
/// them.
///
/// The returned [`UnmetFloor`] list is empty whenever every floor cleared. A
/// theme whose ramp exhausted with a floor still under it is reported there
/// rather than shipped silent.
fn lift_to_floors(mut base: BTreeMap<Token, Rgba>) -> (BTreeMap<Token, Rgba>, Vec<UnmetFloor>) {
    // More rounds than the longest lift in the corpus needs: the whole ramp is
    // 1.0 of lightness, crossed at [`LIFT`] a round.
    const ROUNDS: usize = 400;

    let opaque =
        |m: &BTreeMap<Token, Rgba>, token: Token| m.get(&token).and_then(|c| c.opaque_rgb());
    for _ in 0..ROUNDS {
        let tokens = derive(&base);
        let mut moved = false;
        for &(ink, grounds, floor) in INK_FLOORS {
            let Some(color) = opaque(&tokens, ink) else {
                continue;
            };
            let grounds: Vec<Rgb> = grounds.iter().filter_map(|g| opaque(&tokens, *g)).collect();
            if worst(color, &grounds) >= floor {
                continue;
            }
            let lifted = match (ink, opaque(&tokens, Token::Content)) {
                (Token::Content, _) | (_, None) => away_from(color, &grounds, LIFT),
                (_, Some(content)) => {
                    if wcag_contrast(mix(color, content, 0.05), content) < STEP_FLOOR {
                        // No room left between this step and the ink: move the ink.
                        let ink_grounds: Vec<Rgb> = INK_FLOORS[0]
                            .1
                            .iter()
                            .filter_map(|g| opaque(&tokens, *g))
                            .collect();
                        let content_lifted = away_from(content, &ink_grounds, LIFT);
                        if content_lifted != content {
                            base.insert(Token::Content, Rgba::opaque(content_lifted));
                            moved = true;
                        }
                        continue;
                    }
                    mix(color, content, 0.05)
                }
            };
            if lifted != color {
                base.insert(ink, Rgba::opaque(lifted));
                moved = true;
            }
        }
        if !moved {
            let tokens = with_text_inks(tokens);
            let unmet = unmet_floors(&tokens);
            return (tokens, unmet);
        }
    }
    let tokens = with_text_inks(derive(&base));
    let unmet = unmet_floors(&tokens);
    (tokens, unmet)
}

/// The [`INK_FLOORS`] and [`TEXT_INKS`] entries `tokens` still misses, in
/// table order.
fn unmet_floors(tokens: &BTreeMap<Token, Rgba>) -> Vec<UnmetFloor> {
    let opaque =
        |m: &BTreeMap<Token, Rgba>, token: Token| m.get(&token).and_then(|c| c.opaque_rgb());
    INK_FLOORS
        .iter()
        .copied()
        .chain(
            TEXT_INKS
                .iter()
                .map(|&(ink, _, grounds)| (ink, grounds, TEXT)),
        )
        .filter_map(|(ink, grounds, floor)| {
            let color = opaque(tokens, ink)?;
            let grounds: Vec<Rgb> = grounds.iter().filter_map(|g| opaque(tokens, *g)).collect();
            let achieved = worst(color, &grounds);
            (achieved < floor).then_some(UnmetFloor {
                token: ink,
                floor,
                achieved,
            })
        })
        .collect()
}

/// The lowest contrast `ink` makes against any of `grounds`; infinite for none.
fn worst(ink: Rgb, grounds: &[Rgb]) -> f32 {
    grounds
        .iter()
        .map(|ground| wcag_contrast(ink, *ground))
        .fold(f32::INFINITY, f32::min)
}

/// `color` moved `step` away from the ground it reads worst against.
///
/// The ground the ink fails hardest on is the one that decides the floor, so it
/// is the one to move away from, not the mean of all of them. When the grounds
/// split the ink (half darker, half lighter) the mean sits beside it and the
/// step can run toward the very ground that is failing. When the binding ground
/// is the ink itself, "away" has no direction and the two endpoints are not
/// equal: WCAG's `+0.05` makes the darker direction the higher-ceiling one
/// below a mid-grey, so the tie is settled the same way a text picker settles
/// black against white.
fn away_from(color: Rgb, grounds: &[Rgb], step: f32) -> Rgb {
    let Some(binding) = grounds
        .iter()
        .min_by(|a, b| wcag_contrast(color, **a).total_cmp(&wcag_contrast(color, **b)))
    else {
        return color;
    };
    let darker = match binding.to_oklab().l.partial_cmp(&color.to_oklab().l) {
        Some(std::cmp::Ordering::Greater) => true,
        Some(std::cmp::Ordering::Less) => false,
        // The binding ground is the ink itself: settle black against white.
        _ => readable_on(*binding) == Rgb { r: 0, g: 0, b: 0 },
    };
    if darker {
        darken(color, step)
    } else {
        lighten(color, step)
    }
}

/// `color`, or the nearest lightness of its hue that clears `floor` against
/// every ground. Unchanged when it already does.
///
/// Both directions are walked and the shorter walk that clears is taken. One
/// direction at a time, away from whichever ground binds, cannot settle when
/// the grounds sit on both sides of the ink: each step away from one is a step
/// toward another, and the ink turns back and forth between them. When neither
/// direction clears, the lightness that came closest is kept, and
/// [`unmet_floors`] reports it.
fn cleared(color: Rgb, grounds: &[Rgb], floor: f32) -> Rgb {
    // More steps than crossing the whole ramp takes at [`LIFT`].
    const STEPS: usize = 400;

    if worst(color, grounds) >= floor {
        return color;
    }
    // The walk's end: the first lightness that clears and how many steps it
    // took, or the best one met and `None`.
    let walk = |toward_dark: bool| -> (Rgb, f32, Option<usize>) {
        let mut at = color;
        let mut best = (color, worst(color, grounds));
        for step in 1..=STEPS {
            let next = if toward_dark {
                darken(at, LIFT)
            } else {
                lighten(at, LIFT)
            };
            if next == at {
                break;
            }
            at = next;
            let reached = worst(at, grounds);
            if reached >= floor {
                return (at, reached, Some(step));
            }
            if reached > best.1 {
                best = (at, reached);
            }
        }
        (best.0, best.1, None)
    };
    let (dark, lit) = (walk(true), walk(false));
    match (dark.2, lit.2) {
        (Some(d), Some(l)) => {
            if d <= l {
                dark.0
            } else {
                lit.0
            }
        }
        (Some(_), None) => dark.0,
        (None, Some(_)) => lit.0,
        (None, None) => {
            if dark.1 >= lit.1 {
                dark.0
            } else {
                lit.0
            }
        }
    }
}

/// The smallest OKLab L difference at which two fills read as two surfaces.
///
/// Below it a well and the face it is cut into are the same area to a reader,
/// and a derivation landing this close to the end of the ramp lands on anything
/// else that clamped there.
pub(crate) const MIN_VISIBLE_DELTA_L: f32 = 0.02;

/// Shift `c`'s OKLab lightness by `delta`, or by `-delta` when the requested
/// direction has no room.
///
/// "No room" is landing within [`MIN_VISIBLE_DELTA_L`] of either end of the
/// ramp. For a derivation whose only job is to differ from its base: a step
/// that clamps is indistinguishable from every other step that clamped.
fn step_with_room(c: Rgb, delta: f32) -> Rgb {
    let target = c.to_oklab().l + delta;
    if (MIN_VISIBLE_DELTA_L..=1.0 - MIN_VISIBLE_DELTA_L).contains(&target) {
        lighten(c, delta)
    } else {
        lighten(c, -delta)
    }
}

/// Emit the resolved intent layer as CSS declarations (no selector), one
/// `  --token: value;` line each, in stem order. The only place a token
/// becomes CSS text.
pub fn intent_css_declarations(tokens: &SemanticTokens) -> String {
    use std::fmt::Write as _;

    let mut out = String::new();
    for (token, color) in &tokens.intents {
        let _ = writeln!(out, "  --{token}: {color};");
    }
    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))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::fixture::nord_toml;
    #[allow(unused_imports)]
    use crate::{ThemeDirs, ThemeId, Token};
    use crate::{embedded_themes, parse_theme_str};

    #[test]
    fn away_from_moves_away_from_the_binding_ground_not_the_mean() {
        // A mid-grey ink on one light and several dark grounds. The mean sits
        // below the ink, so the old rule lightened it toward the light ground
        // it already failed. The binding ground is the light one, so it has to
        // darken.
        let color = Rgb::from_hex("#808080").unwrap();
        let grounds = [
            Rgb::from_hex("#ffffff").unwrap(),
            Rgb::from_hex("#202020").unwrap(),
            Rgb::from_hex("#202020").unwrap(),
            Rgb::from_hex("#202020").unwrap(),
        ];
        let moved = away_from(color, &grounds, 0.05);
        assert!(
            moved.to_oklab().l < color.to_oklab().l,
            "moved {moved:?} lighter than {color:?}"
        );
    }

    #[test]
    fn away_from_darkens_when_the_binding_ground_is_the_ink() {
        // Everything one grey: darkening is the only direction that reaches
        // 4.5, since white on #808080 tops out around 3.95:1. The tie has to
        // settle on dark, the way a text picker settles black against white.
        let color = Rgb::from_hex("#808080").unwrap();
        let moved = away_from(color, &[color], 0.05);
        assert!(
            moved.to_oklab().l < color.to_oklab().l,
            "an all-#808080 ink must darken, got {moved:?}"
        );
    }

    #[test]
    fn resolve_base_intents_passthrough() {
        let theme = parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap();
        let t = resolve(&theme);
        assert_eq!(t.hex(Token::SurfacePage).as_deref(), Some("#2e3440"));
        // content.primary -> content, lifted: nord's ink is too close to its
        // grounds to hold a muted step at the quiet floor on its row tones, so
        // resolution moves it away from the page, keeping its hue.
        let authored = Rgb::from_hex("#d8dee9").unwrap().to_oklab();
        let content = t.color(Token::Content).unwrap().to_oklab();
        assert!(content.l > authored.l, "{content:?}");
        // Not a passthrough: a tonal step of the ink toward the page, whatever
        // the file said.
        let page = Rgb::from_hex("#2e3440").unwrap().to_oklab();
        let muted = t.color(Token::ContentMuted).unwrap().to_oklab();
        assert!(page.l < muted.l && muted.l < content.l, "{muted:?}");
        assert_eq!(t.hex(Token::Action).as_deref(), Some("#81a1c1"));
        assert_eq!(t.hex(Token::Danger).as_deref(), Some("#bf616a"));
        assert_eq!(t.hex(Token::Border).as_deref(), Some("#4c566a"));
        assert_eq!(t.hex(Token::CategoryFive).as_deref(), Some("#b48ead"));
    }

    /// A toned surface is the tone's hue on every shipped theme, whatever the
    /// ground's own tint: goingson's yellow warning on its lavender raised
    /// ground is the case a mix turned grey.
    #[test]
    fn a_toned_surface_carries_its_tones_hue() {
        let hue = |c: Rgb| {
            let lab = c.to_oklab();
            (lab.b.atan2(lab.a).to_degrees(), lab.a.hypot(lab.b))
        };
        let mut off = Vec::new();
        for (id, toml) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::from_static(id), toml, false).unwrap();
            let t = resolve(&theme);
            for (tone, surface, _) in TONES {
                let (Some(tone_hex), Some(surface_hex)) = (t.hex(tone), t.hex(surface)) else {
                    continue;
                };
                let (want, own) = hue(Rgb::from_hex(&tone_hex).unwrap());
                if own < 0.02 {
                    continue;
                }
                let (got, chroma) = hue(Rgb::from_hex(&surface_hex).unwrap());
                let apart = ((got - want + 540.0) % 360.0 - 180.0).abs();
                if apart > 20.0 || chroma < 0.02 {
                    off.push(format!(
                        "{id} {surface:?}: {apart:.0} degrees off, chroma {chroma:.3}"
                    ));
                }
            }
        }
        assert!(off.is_empty(), "{off:#?}");
    }

    #[test]
    fn resolve_derived_intents() {
        let theme = parse_theme_str(&ThemeId::from_static("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(Token::ActionHover).unwrap(),
            lighten(action, 0.05).to_hex()
        );
        assert_eq!(
            t.hex(Token::ContentOnAction).unwrap(),
            readable_on(action).to_hex()
        );
        assert_eq!(t.hex(Token::FocusRing).as_deref(), Some("#81a1c1"));
        assert_eq!(t.hex(Token::HoverSurface).as_deref(), Some("#434c5e")); // = surface.sunken
        // The toned pair a pressable tinted surface needs: the resting tint off
        // the raised ground, the hover tint off the sunken one, so a toned
        // control travels the same distance under a pointer as a plain one.
        let raised = Rgb::from_hex("#3b4252").unwrap();
        let sunken = Rgb::from_hex("#434c5e").unwrap();
        let danger = Rgb::from_hex("#bf616a").unwrap();
        assert_eq!(
            t.hex(Token::DangerSurface).unwrap(),
            toned(raised, danger, 0.12, 0.05).to_hex()
        );
        assert_eq!(
            t.hex(Token::DangerSurfaceHover).unwrap(),
            toned(sunken, danger, 0.12, 0.05).to_hex()
        );
        assert_ne!(
            t.hex(Token::DangerSurface),
            t.hex(Token::DangerSurfaceHover)
        );
        // Pruned by the usage audit (0 consumers): action-active and selection.
        // Apps that need them derive inline via the shared mix().
        assert!(Token::parse("action-active").is_none());
        assert!(Token::parse("selection").is_none());
    }

    #[test]
    fn resolve_bevel_intents() {
        let theme = parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap();
        let t = resolve(&theme);
        let raised = Rgb::from_hex("#3b4252").unwrap();
        assert_eq!(
            t.hex(Token::BevelLight).unwrap(),
            lighten(raised, 0.14).to_hex()
        );
        assert_eq!(
            t.hex(Token::BevelDark).unwrap(),
            darken(raised, 0.18).to_hex()
        );
    }

    // A bevel is two edges around one face, so both edges have to be visibly off
    // that face or the control never resolves as lit. The lightening clamps at
    // the top of the ramp, which means a theme authoring a white raised surface
    // gets a highlight identical to the surface it is meant to sit on.
    //
    // The list is asserted rather than merely reported so that changing a theme
    // has to come here and say so. Shrinking it is the fix; growing it is a
    // regression in the theme, not in this derivation.
    #[test]
    fn bevel_edges_are_distinct_from_their_face() {
        const CANNOT_BEVEL: &[&str] = &["neobrute", "oxocarbon-light"];

        let mut degenerate: Vec<String> = Vec::new();
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let Some(raised) = t.hex(Token::SurfaceRaised) else {
                continue;
            };
            let light = t
                .hex(Token::BevelLight)
                .expect("raised implies bevel-light");
            let dark = t.hex(Token::BevelDark).expect("raised implies bevel-dark");
            if light == raised || dark == raised {
                degenerate.push(id.to_string());
            }
        }
        degenerate.sort();

        assert_eq!(
            degenerate, CANNOT_BEVEL,
            "themes whose raised surface cannot hold both bevel edges"
        );
    }

    // The well inverts by theme, so assert both directions explicitly rather
    // than only the one the light themes happen to take.
    #[test]
    fn resolve_well_intent_follows_the_content_direction() {
        // nord is dark: light text on a dark raised surface, so the well goes
        // down and away from the text.
        let dark =
            resolve(&parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap());
        let dark_raised = Rgb::from_hex("#3b4252").unwrap();
        assert_eq!(
            dark.hex(Token::SurfaceWell).unwrap(),
            darken(dark_raised, 0.09).to_hex()
        );

        // The shipped light themes take the other branch.
        let goingson = embedded_themes()
            .into_iter()
            .find(|(id, _)| *id == "goingson")
            .expect("goingson is embedded")
            .1;
        let light =
            resolve(&parse_theme_str(&ThemeId::from_static("goingson"), goingson, false).unwrap());
        let light_raised = light
            .color(Token::SurfaceRaised)
            .expect("goingson authors a raised surface");
        assert_eq!(
            light.hex(Token::SurfaceWell).unwrap(),
            lighten(light_raised, 0.07).to_hex()
        );
    }

    // A well is a fill, not an edge, so the only thing that makes it read is
    // being a different color from the surface it is cut into.
    //
    // Same shape and the same asserted-list discipline as
    // `bevel_edges_are_distinct_from_their_face`. It used to bite the same two
    // themes, whose raised surface sits at the top of the ramp; the well now
    // goes the other way when it has no room, so no bundled theme is exempt.
    #[test]
    fn well_is_distinct_from_its_face() {
        const CANNOT_WELL: &[&str] = &[];

        let mut degenerate: Vec<String> = Vec::new();
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let Some(raised) = t.hex(Token::SurfaceRaised) else {
                continue;
            };
            let well = t
                .hex(Token::SurfaceWell)
                .expect("raised implies surface-well");
            if well == raised {
                degenerate.push(id.to_string());
            }
        }
        degenerate.sort();

        assert_eq!(
            degenerate, CANNOT_WELL,
            "themes whose raised surface cannot hold a well"
        );
    }

    // Distinct is not the same as visible. A face near the top of the ramp
    // clamps partway rather than exactly, which yields a well that differs from
    // its face by a hex digit and by nothing the eye can find. `rosepine-dawn`
    // authors raised at L=0.987 and got 0.009 of the 0.07 it asked for, until
    // a step without room started travelling the other way.
    //
    // Kept separate from the test above because a partial clamp passes that
    // one, and the list stays asserted so a theme that defeats the fallback has
    // to come here and say so.
    #[test]
    fn well_is_visible_against_its_face() {
        const CANNOT_HOLD_A_VISIBLE_WELL: &[&str] = &[];

        let mut invisible: Vec<String> = Vec::new();
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let (Some(raised), Some(well)) =
                (t.color(Token::SurfaceRaised), t.color(Token::SurfaceWell))
            else {
                continue;
            };
            if (well.to_oklab().l - raised.to_oklab().l).abs() < MIN_VISIBLE_DELTA_L {
                invisible.push(id.to_string());
            }
        }
        invisible.sort();

        assert_eq!(
            invisible, CANNOT_HOLD_A_VISIBLE_WELL,
            "themes whose well is too close to its face to read as one"
        );
    }

    // The collision the fallback exists for. A light face near the top of the
    // ramp sends both the well and `bevel-light` into the same clamp, so the
    // well measured against its face alone can pass while being the exact
    // colour of the lit edge drawn around it. Ten of the 31 bundled themes did.
    #[test]
    fn well_is_visible_against_the_highlight() {
        let mut collided: Vec<String> = Vec::new();
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let (Some(well), Some(light)) =
                (t.color(Token::SurfaceWell), t.color(Token::BevelLight))
            else {
                continue;
            };
            if (well.to_oklab().l - light.to_oklab().l).abs() < MIN_VISIBLE_DELTA_L {
                collided.push(id.to_string());
            }
        }
        collided.sort();
        assert!(
            collided.is_empty(),
            "themes whose well reads as the lit edge around it: {collided:?}"
        );
    }

    // The table model's row tones, pinned to the specimen they were measured
    // from: treatment C on akari-dawn, artifact d081c72d.
    #[test]
    fn row_tones_reproduce_the_chosen_table_specimen() {
        let source = embedded_themes()
            .into_iter()
            .find(|(id, _)| *id == "akari-dawn")
            .expect("akari-dawn is embedded")
            .1;
        let t =
            resolve(&parse_theme_str(&ThemeId::from_static("akari-dawn"), source, false).unwrap());
        assert_eq!(
            t.hex(Token::RowHover)
                .map(|h| h.to_ascii_lowercase())
                .as_deref(),
            Some("#dedad5")
        );
        assert_eq!(
            t.hex(Token::RowRule)
                .map(|h| h.to_ascii_lowercase())
                .as_deref(),
            Some("#b0ada9")
        );
    }

    // The fallback's direction, pinned on the theme that found it. akari-dawn
    // authors raised at L=0.966, where the well's step up would land in the
    // clamp, so the well goes down instead.
    #[test]
    fn well_without_room_travels_the_other_way() {
        let source = embedded_themes()
            .into_iter()
            .find(|(id, _)| *id == "akari-dawn")
            .expect("akari-dawn is embedded")
            .1;
        let t =
            resolve(&parse_theme_str(&ThemeId::from_static("akari-dawn"), source, false).unwrap());
        let raised = t
            .color(Token::SurfaceRaised)
            .expect("akari-dawn authors a raised surface");
        assert_eq!(
            t.hex(Token::SurfaceWell).unwrap(),
            darken(raised, 0.07).to_hex()
        );
    }

    // The three tests above each measure a derived color against the face it was
    // derived from, so a theme can pass all of them and still have nothing lift
    // off anything: the face itself sits on the page, and that relationship is
    // the one a bevel needs in order to read as an object rather than as a
    // rectangle with decorated edges. makenot.work passed all three and could
    // not hold a bevel, which is what this covers.
    //
    // The threshold is picked against the ramps already ruled on rather than
    // against a round number. makenot.work shipped at 0.024 and was invisible,
    // was tried at 0.036 and rejected as marginal on badges and chips, and was
    // accepted at 0.058; goingson and audiofiles sit at 0.119 and 0.065. Every
    // ramp judged inadequate is below 0.036 and every one judged adequate is
    // above 0.058, so the line goes in the gap between them. Note the unit: this
    // is oklab L on 0 to 1, not the CIE L* on 0 to 100 that the theme files quote
    // in their comments, and the two are not interchangeable.
    //
    // Most of the list is imported palettes, which were authored for syntax
    // highlighting and owe our depth model nothing. Failing here says a theme
    // cannot hold a bevel, not that it is wrong. Shrinking the list is the fix;
    // growing it is a regression in the theme, not in this derivation.
    //
    // An imported palette leaves this list only when the fix is upstream's own,
    // never a color we picked, or the list becomes a record of what we were
    // willing to repaint rather than of what cannot hold a bevel. The remaining
    // entries are shallow ramps in published palettes, deferred until every app
    // is migrated and eyeballed.
    //
    // The akari pair is not an imported palette in that sense and is exempt.
    // Upstream ships no file in this schema, so its surface ramp was ours to
    // choose from the start, and it is the pair every app defaults to: a depth
    // model the default theme cannot render is a broken default, not a palette
    // we are borrowing on someone else's terms.
    #[test]
    fn raised_is_distinct_from_page() {
        // Below this, a raised surface and the page under it are one surface to
        // a reader, whichever direction the theme ramps in.
        const MIN_DELTA_L: f32 = 0.05;
        const CANNOT_LIFT_OFF_THE_PAGE: &[&str] = &[
            "ayu-light",
            "ayu-mirage",
            "catppuccin-latte",
            "catppuccin-mocha",
            "dawnfox",
            "dracula",
            "everforest",
            "flatwhite",
            "gruvbox-light",
            "neobrute",
            "one-dark",
            "oxocarbon-dark",
            "oxocarbon-light",
            "poimandres",
            "rosepine",
            "rosepine-dawn",
            "solarized-dark",
            "solarized-light",
        ];

        let mut flat: Vec<String> = Vec::new();
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let (Some(page), Some(raised)) =
                (t.color(Token::SurfacePage), t.color(Token::SurfaceRaised))
            else {
                continue;
            };
            if (raised.to_oklab().l - page.to_oklab().l).abs() < MIN_DELTA_L {
                flat.push(id.to_string());
            }
        }
        flat.sort();

        assert_eq!(
            flat, CANNOT_LIFT_OFF_THE_PAGE,
            "themes whose raised surface is too close to the page to lift off it"
        );
    }

    #[test]
    fn resolve_overlay_is_dark_translucent_scrim() {
        let theme = parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap();
        let t = resolve(&theme);
        let overlay = t.css(Token::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");
    }

    /// Every shipped theme derives it, on both polarities, and it is always a
    /// near-black translucent tone. A shadow tinted to a dark theme's own
    /// lightness would not read as one.
    #[test]
    fn elevation_is_a_near_black_cast_on_every_theme() {
        for (id, source) in embedded_themes() {
            let theme = parse_theme_str(&ThemeId::new(id).unwrap(), source, false).unwrap();
            let t = resolve(&theme);
            let Some(elevation) = t.css(Token::Elevation) else {
                panic!("{id} derives no elevation");
            };
            assert!(
                elevation.starts_with("rgba(") && elevation.ends_with(", 0.18)"),
                "{id}: elevation is translucent: {elevation}"
            );
            let inner = elevation
                .trim_start_matches("rgba(")
                .trim_end_matches(", 0.18)");
            let parts: Vec<u8> = inner.split(", ").map(|p| p.parse().unwrap()).collect();
            let cast = Rgb {
                r: parts[0],
                g: parts[1],
                b: parts[2],
            };
            assert!(
                cast.to_oklab().l < 0.2,
                "{id}: a cast shadow must be near-black, got {elevation}"
            );
        }
    }

    /// The scrim and the cast share an anchor and differ only in weight. Stated
    /// as a test because the two are easy to drift apart, and a scrim that
    /// stopped matching the shadow under the thing it dims would show.
    #[test]
    fn elevation_and_the_scrim_are_the_same_tone() {
        let theme = parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap();
        let t = resolve(&theme);
        let scrim = t.css(Token::Overlay).unwrap();
        let cast = t.css(Token::Elevation).unwrap();
        assert_eq!(
            scrim.trim_end_matches(", 0.5)"),
            cast.trim_end_matches(", 0.18)"),
        );
    }

    /// The accessor that makes a translucent intent reachable from something
    /// that is not a stylesheet. Both spellings, and an opaque token answers
    /// 255 so a caller need not know which kind it asked for.
    #[test]
    fn rgba_reads_both_spellings() {
        let theme = parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap();
        let t = resolve(&theme);

        let (_, _, _, opaque) = t.rgba(Token::SurfacePage).expect("page is a hex token");
        assert_eq!(opaque, 255);

        let (r, g, b, alpha) = t.rgba(Token::Elevation).expect("elevation is translucent");
        assert_eq!(alpha, 46, "0.18 of 255");
        assert_eq!(
            t.rgb(Token::Elevation),
            None,
            "rgb declines to drop the alpha"
        );

        let (sr, sg, sb, scrim) = t.rgba(Token::Overlay).expect("overlay is translucent");
        assert_eq!((sr, sg, sb), (r, g, b), "one tone, two weights");
        assert_eq!(scrim, 128);
    }

    #[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(&ThemeId::from_static("x"),
            "[surface]\npage = \"</style><script>alert(1)</script>\"\n[content]\nprimary = \"#111111\"\n",
            false,
        )
        .unwrap();
        let t = resolve(&theme);
        assert!(
            t.hex(Token::SurfacePage).is_none(),
            "non-hex base intent leaked"
        );
        assert_eq!(t.hex(Token::Content).unwrap(), "#111111");
        // The injected markup appears in no resolved value.
        assert!(!t.intents.values().any(|v| v.css().contains('<')));
    }

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

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

    // ---- the token vocabulary ----

    #[test]
    fn every_token_has_one_stem_and_reads_back_from_it() {
        let mut stems: Vec<&str> = Token::ALL.iter().map(|t| t.as_str()).collect();
        for token in Token::ALL {
            assert_eq!(Token::parse(token.as_str()), Some(*token));
        }
        let count = stems.len();
        stems.sort_unstable();
        stems.dedup();
        assert_eq!(stems.len(), count, "a stem is spelled twice");
    }

    #[test]
    fn tokens_order_by_stem_so_emission_is_alphabetical() {
        let t =
            resolve(&parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap());
        let order: Vec<&str> = t.intents.keys().map(|k| k.as_str()).collect();
        let mut sorted = order.clone();
        sorted.sort_unstable();
        assert_eq!(order, sorted);
    }

    #[test]
    fn a_full_theme_resolves_every_token() {
        let t =
            resolve(&parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap());
        let missing: Vec<&str> = Token::ALL
            .iter()
            .filter(|token| t.get(**token).is_none())
            .map(|token| token.as_str())
            .collect();
        assert!(missing.is_empty(), "{missing:?}");
    }

    #[test]
    fn serialised_tokens_keep_the_css_spelling() {
        let t =
            resolve(&parse_theme_str(&ThemeId::from_static("nord"), nord_toml(), false).unwrap());
        let text = toml::to_string(&t.intents).unwrap();
        assert!(text.contains("surface-page = \"#2e3440\""), "{text}");
        assert!(text.contains("overlay = \"rgba("), "{text}");
    }

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

    #[test]
    fn intent_css_vars_wraps_root_and_includes_tokens() {
        let theme = parse_theme_str(&ThemeId::from_static("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('}'));
    }
}