incular-core 0.1.1

//! Small renderer-neutral geometry and paint values.

use std::ops::{Add, Sub};

use palette::{FromColor, Hsl, Hsv, LinSrgba, Srgba, WithAlpha};

pub use kurbo::Affine;
use kurbo::{Point, Vec2};

#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub struct Size {
    pub width: f32,
    pub height: f32,
}

impl Size {
    pub const ZERO: Self = Self {
        width: 0.0,
        height: 0.0,
    };

    #[must_use]
    pub fn new(width: f32, height: f32) -> Self {
        assert!(
            width.is_finite() && height.is_finite() && width >= 0.0 && height >= 0.0,
            "sizes must be finite and non-negative"
        );
        Self { width, height }
    }
}

#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub struct Offset {
    pub x: f32,
    pub y: f32,
}

impl Offset {
    pub const ZERO: Self = Self { x: 0.0, y: 0.0 };

    #[must_use]
    pub const fn new(x: f32, y: f32) -> Self {
        Self { x, y }
    }

    /// Replaces non-finite components with zero.
    #[must_use]
    pub fn finite_or_zero(self) -> Self {
        Self::new(finite_or_zero(self.x), finite_or_zero(self.y))
    }
}

/// Replaces NaN and infinities with zero so untrusted geometry cannot poison
/// layout or rendering.
#[inline]
#[must_use]
pub fn finite_or_zero(value: f32) -> f32 {
    if value.is_finite() { value } else { 0.0 }
}

/// [`finite_or_zero`] clamped to be non-negative, for extents, insets and radii.
#[inline]
#[must_use]
pub fn finite_non_negative(value: f32) -> f32 {
    finite_or_zero(value).max(0.0)
}

impl Add for Offset {
    type Output = Self;

    fn add(self, rhs: Self) -> Self {
        Self::new(self.x + rhs.x, self.y + rhs.y)
    }
}

impl Sub for Offset {
    type Output = Self;

    fn sub(self, rhs: Self) -> Self {
        Self::new(self.x - rhs.x, self.y - rhs.y)
    }
}

#[derive(Clone, Copy, Debug, Default, PartialEq)]
pub struct Rect {
    pub origin: Offset,
    pub size: Size,
}

impl Rect {
    #[must_use]
    pub fn from_origin_size(origin: Offset, size: Size) -> Self {
        Self { origin, size }
    }

    #[must_use]
    pub fn contains(self, point: Offset) -> bool {
        point.x >= self.origin.x
            && point.x <= self.origin.x + self.size.width
            && point.y >= self.origin.y
            && point.y <= self.origin.y + self.size.height
    }

    #[must_use]
    pub fn intersects(self, other: Self) -> bool {
        self.origin.x < other.origin.x + other.size.width
            && other.origin.x < self.origin.x + self.size.width
            && self.origin.y < other.origin.y + other.size.height
            && other.origin.y < self.origin.y + self.size.height
    }

    #[must_use]
    pub fn intersection(self, other: Self) -> Option<Self> {
        let left = self.origin.x.max(other.origin.x);
        let top = self.origin.y.max(other.origin.y);
        let right = (self.origin.x + self.size.width).min(other.origin.x + other.size.width);
        let bottom = (self.origin.y + self.size.height).min(other.origin.y + other.size.height);
        (right >= left && bottom >= top).then(|| {
            Self::from_origin_size(
                Offset::new(left, top),
                Size::new(right - left, bottom - top),
            )
        })
    }
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct Color {
    pub red: u8,
    pub green: u8,
    pub blue: u8,
    pub alpha: u8,
}

impl Color {
    pub const TRANSPARENT: Self = Self::rgba(0, 0, 0, 0);
    pub const WHITE: Self = Self::rgba(255, 255, 255, 255);
    pub const BLACK: Self = Self::rgba(0, 0, 0, 255);

    #[must_use]
    pub const fn rgba(red: u8, green: u8, blue: u8, alpha: u8) -> Self {
        Self {
            red,
            green,
            blue,
            alpha,
        }
    }

    /// Converts the compact encoded sRGBA8 value to straight, linear-sRGB
    /// components. Palette owns the CPU transfer function; WGSL retains its
    /// equivalent explicit shader-side math at the GPU boundary.
    #[must_use]
    pub fn to_linear_rgba(self) -> [f32; 4] {
        let linear = Srgba::new(
            self.red as f32 / 255.0,
            self.green as f32 / 255.0,
            self.blue as f32 / 255.0,
            self.alpha as f32 / 255.0,
        )
        .into_linear();
        [
            linear.color.red,
            linear.color.green,
            linear.color.blue,
            linear.alpha,
        ]
    }

    /// Converts straight linear-sRGB components into compact encoded sRGBA8.
    /// Non-finite and out-of-range components are sanitized to `0.0..=1.0`.
    /// Palette owns the transfer function in both directions so CPU color-space
    /// boundaries cannot drift from [`Self::to_linear_rgba`].
    #[must_use]
    pub fn from_linear_rgba([red, green, blue, alpha]: [f32; 4]) -> Self {
        let encoded = Srgba::<u8>::from_linear(LinSrgba::new(
            unit(red),
            unit(green),
            unit(blue),
            unit(alpha),
        ));
        Self::rgba(
            encoded.color.red,
            encoded.color.green,
            encoded.color.blue,
            encoded.alpha,
        )
    }

    /// Converts this sRGB color to the HSL representation used by style and
    /// theme code. Hue is expressed in degrees and alpha in `0.0..=1.0`.
    #[must_use]
    pub fn to_hsl(self) -> HslColor {
        HslColor::from_color(self)
    }

    /// Converts this sRGB color to HSV. Hue is expressed in degrees and alpha
    /// in `0.0..=1.0`.
    #[must_use]
    pub fn to_hsv(self) -> HsvColor {
        HsvColor::from_color(self)
    }
}

/// Hue, saturation, lightness, and opacity in an sRGB color space.
///
/// Hue is normalized to `0.0..360.0`; saturation, lightness, and alpha are
/// normalized to `0.0..=1.0`. Constructors accept non-finite values but
/// sanitize them, keeping configuration values safe to use in rendering.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct HslColor {
    pub hue: f32,
    pub saturation: f32,
    pub lightness: f32,
    pub alpha: f32,
}

impl HslColor {
    #[must_use]
    pub fn new(hue: f32, saturation: f32, lightness: f32, alpha: f32) -> Self {
        Self {
            hue: normalize_hue(hue),
            saturation: unit(saturation),
            lightness: unit(lightness),
            alpha: unit(alpha),
        }
    }

    #[must_use]
    pub fn from_color(color: Color) -> Self {
        let source = palette_color(color);
        let hsl = Hsl::from_color(source.color);
        Self::new(
            hsl.hue.into_degrees(),
            hsl.saturation,
            hsl.lightness,
            source.alpha,
        )
    }

    #[must_use]
    pub fn to_color(self) -> Color {
        let hsl = Hsl::new_srgb(
            normalize_hue(self.hue),
            unit(self.saturation),
            unit(self.lightness),
        );
        color_from_palette(Srgba::from_color(hsl).with_alpha(unit(self.alpha)))
    }
}

/// Hue, saturation, value, and opacity in an sRGB color space.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct HsvColor {
    pub hue: f32,
    pub saturation: f32,
    pub value: f32,
    pub alpha: f32,
}

impl HsvColor {
    #[must_use]
    pub fn new(hue: f32, saturation: f32, value: f32, alpha: f32) -> Self {
        Self {
            hue: normalize_hue(hue),
            saturation: unit(saturation),
            value: unit(value),
            alpha: unit(alpha),
        }
    }

    #[must_use]
    pub fn from_color(color: Color) -> Self {
        let source = palette_color(color);
        let hsv = Hsv::from_color(source.color);
        Self::new(
            hsv.hue.into_degrees(),
            hsv.saturation,
            hsv.value,
            source.alpha,
        )
    }

    #[must_use]
    pub fn to_color(self) -> Color {
        let hsv = Hsv::new_srgb(
            normalize_hue(self.hue),
            unit(self.saturation),
            unit(self.value),
        );
        color_from_palette(Srgba::from_color(hsv).with_alpha(unit(self.alpha)))
    }
}

fn unit(value: f32) -> f32 {
    if value.is_finite() {
        value.clamp(0.0, 1.0)
    } else {
        0.0
    }
}

fn normalize_hue(hue: f32) -> f32 {
    if hue.is_finite() {
        hue.rem_euclid(360.0)
    } else {
        0.0
    }
}

fn palette_color(color: Color) -> Srgba {
    Srgba::new(
        color.red as f32 / 255.0,
        color.green as f32 / 255.0,
        color.blue as f32 / 255.0,
        color.alpha as f32 / 255.0,
    )
}

fn color_from_palette(color: Srgba) -> Color {
    let byte = |value: f32| (unit(value) * 255.0).round() as u8;
    Color::rgba(
        byte(color.color.red),
        byte(color.color.green),
        byte(color.color.blue),
        byte(color.alpha),
    )
}

/// A retained two-dimensional affine transform.
///
/// Incular keeps its ordinary layout geometry in `f32`; Kurbo is the single
/// authority for affine composition, inversion, and geometric bounds. The
/// conversion happens only at this boundary, so applications do not need to
/// adopt a second basic point/rectangle vocabulary for normal widget code.
#[derive(Clone, Copy, Debug, PartialEq)]
pub struct Transform(Affine);

impl Default for Transform {
    fn default() -> Self {
        Self::IDENTITY
    }
}

impl Transform {
    pub const IDENTITY: Self = Self(Affine::IDENTITY);

    #[must_use]
    pub fn translation(offset: Offset) -> Self {
        Self(Affine::translate(Vec2::new(
            f64::from(offset.x),
            f64::from(offset.y),
        )))
    }

    #[must_use]
    pub const fn scale(scale: f32) -> Self {
        Self(Affine::scale(scale as f64))
    }

    #[must_use]
    pub const fn scale_non_uniform(x: f32, y: f32) -> Self {
        Self(Affine::scale_non_uniform(x as f64, y as f64))
    }

    /// Rotates clockwise in Incular's y-down coordinate system.
    #[must_use]
    pub fn rotation(radians: f32) -> Self {
        Self(Affine::rotate(f64::from(radians)))
    }

    #[must_use]
    pub const fn skew(x: f32, y: f32) -> Self {
        Self(Affine::skew(x as f64, y as f64))
    }

    /// The affine `[a, b, c, d, e, f]` mapping `(x, y)` to
    /// `(a·x + c·y + e, b·x + d·y + f)`: a 2D `Matrix4` given by the first
    /// two entries of its first, second and fourth columns.
    #[must_use]
    pub const fn from_coefficients(coefficients: [f64; 6]) -> Self {
        Self(Affine::new(coefficients))
    }

    #[must_use]
    pub const fn from_kurbo(affine: Affine) -> Self {
        Self(affine)
    }

    #[must_use]
    pub const fn to_kurbo(self) -> Affine {
        self.0
    }

    /// Applies `other` first, then this transform.
    #[must_use]
    pub fn then(self, other: Self) -> Self {
        Self(self.0 * other.0)
    }

    #[must_use]
    pub fn inverse(self) -> Option<Self> {
        let inverse = self.0.inverse();
        inverse.is_finite().then_some(Self(inverse))
    }

    #[must_use]
    pub fn inverse_translation(self) -> Self {
        self.inverse().unwrap_or(Self::IDENTITY)
    }

    #[must_use]
    pub fn translation_offset(self) -> Offset {
        let coefficients = self.0.as_coeffs();
        Offset::new(coefficients[4] as f32, coefficients[5] as f32)
    }

    #[must_use]
    pub fn is_translation(self) -> bool {
        let [a, b, c, d, _, _] = self.0.as_coeffs();
        a == 1. && b == 0. && c == 0. && d == 1.
    }

    /// Conservative bound on the linear part's operator norm: no unit
    /// vector stretches more than this. It is the Frobenius norm, which
    /// dominates the operator norm, rounded up to a representable value
    /// so the bound never underestimates through float conversion.
    /// Unlike largest-column norms it also covers shear, where diagonal
    /// directions stretch more than either basis vector.
    ///
    /// Degenerate zero maps report `0.0`. Non-finite inputs report
    /// infinity, consistent with [`Self::inverse`] failing on them:
    /// downstream geometry is culled rather than measured.
    #[must_use]
    pub fn magnification_bound(self) -> f32 {
        let [a, b, c, d, _, _] = self.0.as_coeffs();
        let bound = a.hypot(b).hypot(c.hypot(d));
        if !bound.is_finite() {
            f32::INFINITY
        } else if bound == 0.0 {
            // All-zero linear part stretches nothing exactly; rounding up
            // a true zero would only whitelist nothing.
            0.0
        } else {
            (bound as f32).next_up()
        }
    }

    #[must_use]
    pub fn transform_point(self, point: Offset) -> Offset {
        let point = self.0 * Point::new(f64::from(point.x), f64::from(point.y));
        Offset::new(point.x as f32, point.y as f32)
    }

    #[must_use]
    pub fn inverse_transform_point(self, point: Offset) -> Option<Offset> {
        self.inverse().map(|inverse| inverse.transform_point(point))
    }

    #[must_use]
    pub fn transform_rect_bbox(self, rect: Rect) -> Rect {
        let rect = kurbo::Rect::new(
            f64::from(rect.origin.x),
            f64::from(rect.origin.y),
            f64::from(rect.origin.x + rect.size.width),
            f64::from(rect.origin.y + rect.size.height),
        );
        let rect = self.0.transform_rect_bbox(rect);
        Rect::from_origin_size(
            Offset::new(rect.x0 as f32, rect.y0 as f32),
            Size::new((rect.x1 - rect.x0) as f32, (rect.y1 - rect.y0) as f32),
        )
    }
}

bitflags::bitflags! {
    /// Multi-dimensional damage invalidation representation across independent retained runtime phases.
    #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash)]
    pub struct Invalidation: u16 {
        /// No invalidation required.
        const NONE = 0;
        /// Subtree widget build / structural reconciliation required.
        const BUILD = 1 << 0;
        /// Layout measurement and positioning recalculation required.
        const LAYOUT = 1 << 1;
        /// Picture display list re-recording required.
        const PAINT = 1 << 2;
        /// Retained compositor layer properties or transforms modified.
        const COMPOSITE = 1 << 3;
        /// Accessibility semantics tree update required.
        const SEMANTICS = 1 << 4;
        /// Hit-test routing / pointer target cache update required.
        const HIT_TEST = 1 << 5;
    }
}

/// Alias for [`Invalidation`] for backwards compatibility.
pub type DirtyFlags = Invalidation;

/// A type that can be linearly interpolated between two values.
pub trait Lerp {
    /// Linearly interpolates between `self` and `other` with parameter `t` in `[0.0, 1.0]`.
    #[must_use]
    fn lerp(&self, other: &Self, t: f32) -> Self;
}

impl Lerp for f32 {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        self + (other - self) * t
    }
}

impl Lerp for f64 {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        self + (other - self) * f64::from(t)
    }
}

impl Lerp for Offset {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        Self {
            x: self.x.lerp(&other.x, t),
            y: self.y.lerp(&other.y, t),
        }
    }
}

impl Lerp for Size {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        Self {
            width: self.width.lerp(&other.width, t).max(0.0),
            height: self.height.lerp(&other.height, t).max(0.0),
        }
    }
}

/// Flutter's `Matrix4Tween.lerp`: both matrices are decomposed into
/// translation, rotation quaternion and scale (vector_math's
/// `Matrix4.decompose`); translation and scale interpolate linearly and the
/// rotation by a normalized quaternion lerp, then the parts recompose. Skew is
/// lost, as in Flutter.
impl Lerp for Transform {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        let t = f64::from(t);
        let (begin_translation, begin_rotation, begin_scale) = decompose(self.0);
        let (end_translation, end_rotation, end_scale) = decompose(other.0);
        let mix = |a: f64, b: f64| a * (1.0 - t) + b * t;
        let translation = [
            mix(begin_translation[0], end_translation[0]),
            mix(begin_translation[1], end_translation[1]),
        ];
        let mut rotation = [0.0; 4];
        for (index, value) in rotation.iter_mut().enumerate() {
            *value = mix(begin_rotation[index], end_rotation[index]);
        }
        let length = rotation
            .iter()
            .map(|value| value * value)
            .sum::<f64>()
            .sqrt();
        if length != 0.0 {
            for value in &mut rotation {
                *value /= length;
            }
        }
        let scale = [
            mix(begin_scale[0], end_scale[0]),
            mix(begin_scale[1], end_scale[1]),
        ];
        Self(compose(translation, rotation, scale))
    }
}

/// vector_math's `Matrix4.decompose` for a 2D affine embedded in a 4x4
/// matrix: translation, an `[x, y, z, w]` quaternion, and the x/y scale.
fn decompose(affine: Affine) -> ([f64; 2], [f64; 4], [f64; 2]) {
    let [a, b, c, d, e, f] = affine.as_coeffs();
    let mut sx = a.hypot(b);
    let sy = c.hypot(d);
    if a * d - b * c < 0.0 {
        sx = -sx;
    }
    // The normalized 3x3 rotation block, `m[row][column]`; the z column and
    // row are the identity's.
    let m = [
        [a / sx, c / sy, 0.0],
        [b / sx, d / sy, 0.0],
        [0.0, 0.0, 1.0],
    ];
    ([e, f], quaternion_from_rotation(m), [sx, sy])
}

/// vector_math's `Quaternion.setFromRotation`.
fn quaternion_from_rotation(m: [[f64; 3]; 3]) -> [f64; 4] {
    let mut q = [0.0; 4];
    let trace = m[0][0] + m[1][1] + m[2][2];
    if trace > 0.0 {
        let mut s = (trace + 1.0).sqrt();
        q[3] = s * 0.5;
        s = 0.5 / s;
        q[0] = (m[2][1] - m[1][2]) * s;
        q[1] = (m[0][2] - m[2][0]) * s;
        q[2] = (m[1][0] - m[0][1]) * s;
    } else {
        let i = if m[0][0] < m[1][1] {
            if m[1][1] < m[2][2] { 2 } else { 1 }
        } else if m[0][0] < m[2][2] {
            2
        } else {
            0
        };
        let j = (i + 1) % 3;
        let k = (i + 2) % 3;
        let mut s = (m[i][i] - m[j][j] - m[k][k] + 1.0).sqrt();
        q[i] = s * 0.5;
        s = 0.5 / s;
        q[3] = (m[k][j] - m[j][k]) * s;
        q[j] = (m[j][i] + m[i][j]) * s;
        q[k] = (m[k][i] + m[i][k]) * s;
    }
    q
}

/// vector_math's `Matrix4.compose`, projected back onto the 2D affine.
fn compose(translation: [f64; 2], rotation: [f64; 4], scale: [f64; 2]) -> Affine {
    let [x, y, z, w] = rotation;
    let (x2, y2, z2) = (x + x, y + y, z + z);
    let (xx, xy) = (x * x2, x * y2);
    let (yy, zz) = (y * y2, z * z2);
    let wz = w * z2;
    Affine::new([
        (1.0 - (yy + zz)) * scale[0],
        (xy + wz) * scale[0],
        (xy - wz) * scale[1],
        (1.0 - (xx + zz)) * scale[1],
        translation[0],
        translation[1],
    ])
}

impl Lerp for Rect {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        Self {
            origin: self.origin.lerp(&other.origin, t),
            size: self.size.lerp(&other.size, t),
        }
    }
}

impl Lerp for Color {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        let t = t.clamp(0.0, 1.0);
        let mix = |a: u8, b: u8| -> u8 {
            (f32::from(a) + (f32::from(b) - f32::from(a)) * t)
                .round()
                .clamp(0.0, 255.0) as u8
        };
        Self::rgba(
            mix(self.red, other.red),
            mix(self.green, other.green),
            mix(self.blue, other.blue),
            mix(self.alpha, other.alpha),
        )
    }
}

impl Lerp for HslColor {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        let t = t.clamp(0.0, 1.0);
        let mix = |a: f32, b: f32| a + (b - a) * t;
        Self::new(
            mix(self.hue, other.hue),
            mix(self.saturation, other.saturation),
            mix(self.lightness, other.lightness),
            mix(self.alpha, other.alpha),
        )
    }
}

impl Lerp for HsvColor {
    fn lerp(&self, other: &Self, t: f32) -> Self {
        let t = t.clamp(0.0, 1.0);
        let mix = |a: f32, b: f32| a + (b - a) * t;
        Self::new(
            mix(self.hue, other.hue),
            mix(self.saturation, other.saturation),
            mix(self.value, other.value),
            mix(self.alpha, other.alpha),
        )
    }
}

/// Identifies the invalidation scope required when a property changes.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum ChangeImpact {
    /// No visual or layout change.
    #[default]
    None,
    /// Requires only compositor layer property / transform update.
    Composite,
    /// Requires painting display list regeneration without layout changes.
    Paint,
    /// Requires layout measurement and positioning recalculation.
    Layout,
    /// Requires rebuilding widget subtree.
    Build,
}