//! A theme's tokens and the words apps describe their UI in (see the
//! vision's K-UI note): apps say what a thing is (a primary button, a
//! heading), never its colour or size. Themes are files (`themes/*.toml`
//! on the system image), read strictly (`parse`) and refused unless every
//! pairing text is drawn in has enough contrast (`check`). The display
//! holds the one in use and hands it to every window (`wire`). Pure.

#![no_std]
#![forbid(unsafe_code)]

mod accent;
mod contrast;
mod parse;
pub mod wire;

#[cfg(test)]
mod tests;

pub use accent::with_accent;
pub use contrast::{check, ratio};
pub use parse::{Error, parse};

/// A colour as the theme names it: straight (not premultiplied) RGBA.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Rgba(pub u8, pub u8, pub u8, pub u8);

impl Rgba {
    pub const fn opaque(r: u8, g: u8, b: u8) -> Self {
        Self(r, g, b, 255)
    }

    /// From `0xrrggbb`.
    pub const fn rgb(v: u32) -> Self {
        Self::opaque((v >> 16) as u8, (v >> 8) as u8, v as u8)
    }

    pub const fn to_rgb(self) -> u32 {
        (self.0 as u32) << 16 | (self.1 as u32) << 8 | self.2 as u32
    }
}

/// Steps of the spacing scale.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Spacing {
    None,
    Xs,
    Sm,
    Md,
    Lg,
    Xl,
}

/// Steps of the type scale.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum TextStyle {
    Heading,
    Subheading,
    Body,
    Caption,
    Label,
}

/// What a text is, for its colour.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum TextColour {
    Primary,
    Secondary,
    Accent,
    OnAccent,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ButtonVariant {
    Primary,
    Secondary,
    Ghost,
    Destructive,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Weight {
    Regular,
    SemiBold,
}

/// A theme's name: what Settings lists and a user's choice records.
pub const NAME_BYTES: usize = types::name::BYTES;

#[derive(Clone, Copy, Debug, PartialEq)]
pub struct Theme {
    pub name: [u8; NAME_BYTES],
    pub name_len: usize,
    pub background: Rgba,
    pub surface: Rgba,
    pub surface_raised: Rgba,
    pub accent: Rgba,
    pub on_accent: Rgba,
    pub text_primary: Rgba,
    pub text_secondary: Rgba,
    pub destructive: Rgba,
    pub on_destructive: Rgba,
    pub focus: Rgba,
    /// Soft colours the wallpaper glows with, behind the glass.
    pub orbs: [Rgba; 3],
    pub corner_radius: f32,
    /// The spacing scale's unit, in pixels.
    pub spacing_base: f32,
    /// Milliseconds; zero turns motion off.
    pub duration_fast: u16,
    pub duration_normal: u16,
    pub spring_stiffness: u16,
    pub spring_damping: u16,
    /// Pixels.
    pub blur_radius: u8,
    /// Percent.
    pub panel_opacity: u8,
    pub highlight: u8,
}

pub(crate) const fn name_bytes(s: &[u8]) -> ([u8; NAME_BYTES], usize) {
    let mut out = [0u8; NAME_BYTES];
    let mut i = 0;
    while i < s.len() && i < NAME_BYTES {
        out[i] = s[i];
        i += 1;
    }
    (out, i)
}

impl Theme {
    /// What a window shows before the display has said, and what the
    /// display uses when no theme file loads; `disk/themes/whimsy-dark.toml`
    /// says the same (a test keeps them so).
    pub const WHIMSY_DARK: Theme = Theme {
        name: name_bytes(b"Whimsy Dark").0,
        name_len: name_bytes(b"Whimsy Dark").1,
        background: Rgba::rgb(0x0f0e17),
        surface: Rgba::rgb(0x1a1a2e),
        surface_raised: Rgba::rgb(0x2a2a44),
        accent: Rgba::rgb(0x4fc3f7),
        on_accent: Rgba::rgb(0x0f0e17),
        text_primary: Rgba::rgb(0xe0e0e0),
        text_secondary: Rgba::rgb(0x9e9eb8),
        destructive: Rgba::rgb(0xef5350),
        on_destructive: Rgba::rgb(0x1a0a0a),
        focus: Rgba::rgb(0xffffff),
        orbs: [Rgba::rgb(0x3a1c71), Rgba::rgb(0x0f4c5c), Rgba::rgb(0x5b1a4a)],
        corner_radius: 16.0,
        spacing_base: 4.0,
        duration_fast: 150,
        duration_normal: 280,
        spring_stiffness: 300,
        spring_damping: 30,
        blur_radius: 12,
        panel_opacity: 72,
        highlight: 18,
    };

    pub fn name(&self) -> &[u8] {
        &self.name[..self.name_len]
    }

    pub fn space(&self, s: Spacing) -> f32 {
        self.spacing_base
            * match s {
                Spacing::None => 0.0,
                Spacing::Xs => 1.0,
                Spacing::Sm => 2.0,
                Spacing::Md => 4.0,
                Spacing::Lg => 6.0,
                Spacing::Xl => 8.0,
            }
    }

    /// A text style's size in pixels and its weight.
    pub fn text(&self, s: TextStyle) -> (f32, Weight) {
        match s {
            TextStyle::Heading => (32.0, Weight::SemiBold),
            TextStyle::Subheading => (22.0, Weight::SemiBold),
            TextStyle::Body => (17.0, Weight::Regular),
            TextStyle::Caption => (13.0, Weight::Regular),
            TextStyle::Label => (17.0, Weight::SemiBold),
        }
    }

    pub fn text_colour(&self, c: TextColour) -> Rgba {
        match c {
            TextColour::Primary => self.text_primary,
            TextColour::Secondary => self.text_secondary,
            TextColour::Accent => self.accent,
            TextColour::OnAccent => self.on_accent,
        }
    }

    /// A button's fill (none for a ghost) and its label's colour.
    pub fn button(&self, v: ButtonVariant) -> (Option<Rgba>, Rgba) {
        match v {
            ButtonVariant::Primary => (Some(self.accent), self.on_accent),
            ButtonVariant::Secondary => (Some(self.surface_raised), self.text_primary),
            ButtonVariant::Ghost => (None, self.accent),
            ButtonVariant::Destructive => (Some(self.destructive), self.on_destructive),
        }
    }
}