punktfunk/crates/pf-console-ui/src/library.rs

//! The console library's model and math — everything about the coverflow that isn't
//! Skia: the shared binary↔overlay state (games, phase, incoming art bytes), the
//! spring-driven motion and cursor arithmetic (ported verbatim from the GTK launcher,
//! tests included), and the geometry constants. Rendering lives in `skia_overlay`.

use std::collections::VecDeque;
use std::sync::{Arc, Mutex};

// --- Geometry (the GTK launcher's constants — Apple coverflow parity) --------------------

/// Poster geometry: 2:3 covers, sized so the focused poster + detail panel + hint bar
/// fit a Deck's 1280×800 with air. Scaled uniformly for other window sizes.
pub const POSTER_W: f64 = 220.0;
pub const POSTER_H: f64 = 330.0;
/// Center of the focused card to the center of its first neighbor.
pub const FOCUS_GAP: f64 = 230.0;
/// Center-to-center distance between successive SIDE cards — much tighter than their
/// projected width, so the side stacks overlap like the classic coverflow shelf.
pub const SIDE_SPACING: f64 = 104.0;
/// Cards farther than this from the eased position aren't drawn at all.
pub const VISIBLE_RANGE: f64 = 5.5;
/// Neighbors recede to this scale…
pub const RECEDE_SCALE: f64 = 0.24;
/// …and swing this many degrees about their own vertical axis under perspective, side
/// cards facing the corridor (their inner edge recedes behind the focus).
pub const ROTATE_DEG: f64 = 38.0;
/// Perspective depth for the tilt, px (CSS `perspective()` semantics).
pub const PERSPECTIVE: f64 = 800.0;
/// The darkening veil's max opacity (side cards stay opaque — they overlap).
pub const RECEDE_DIM: f64 = 0.30;
/// Boundary recoil: a refused move deflects the strip this many px against the push.
pub const BUMP_PX: f64 = 16.0;
/// L1/R1 jump distance.
pub const JUMP: i32 = 5;

// The motion is spring-driven (semi-implicit Euler), not eased — velocity carries across
// retargets, so holding a direction glides and a release settles like a detent.
/// Cursor chase: ζ ≈ 0.85 — settles in ~0.3 s with a whisker of overshoot.
pub const SPRING_K: f64 = 200.0;
pub const SPRING_C: f64 = 24.0;
/// Boundary recoil: stiffer and more underdamped (ζ ≈ 0.55) — one visible wobble.
pub const BUMP_K: f64 = 600.0;
pub const BUMP_C: f64 = 27.0;

/// One semi-implicit-Euler step of a damped spring toward `target`.
fn spring_step(pos: f64, vel: f64, target: f64, k: f64, c: f64, dt: f64) -> (f64, f64) {
    let vel = vel + (k * (target - pos) - c * vel) * dt;
    (pos + vel * dt, vel)
}

/// Advance a damped spring by a whole frame, integrating in ≤ 8 ms substeps — a stalled
/// frame stays far inside the integrator's stability bound, so the motion feels
/// identical at any frame rate.
pub fn spring_advance(
    mut pos: f64,
    mut vel: f64,
    target: f64,
    k: f64,
    c: f64,
    dt: f64,
) -> (f64, f64) {
    let n = (dt / 0.008).ceil().max(1.0) as usize;
    let h = dt / n as f64;
    for _ in 0..n {
        (pos, vel) = spring_step(pos, vel, target, k, c, h);
    }
    (pos, vel)
}

/// Pure cursor arithmetic for a move/jump: `clamp` lands jumps on the ends, a plain
/// step refuses to leave them.
#[derive(Debug, PartialEq, Eq)]
pub enum StepResult {
    Moved(i32),
    Boundary,
}

pub fn step_cursor(cursor: i32, len: usize, delta: i32, clamp: bool) -> StepResult {
    if len == 0 {
        return StepResult::Boundary;
    }
    let max = len as i32 - 1;
    let target = if clamp {
        (cursor + delta).clamp(0, max)
    } else {
        cursor + delta
    };
    if target == cursor || target < 0 || target > max {
        StepResult::Boundary
    } else {
        StepResult::Moved(target)
    }
}

// --- 4×4 matrix (row-major) — the coverflow card transform ------------------------------

/// `T(cx,cy) · P(depth) · Ry(angle) · S(s) · T(-w/2,-h/2)`: card-local (0..w, 0..h) →
/// screen, rotated about the card's own vertical center axis under perspective — the
/// GSK transform chain from the GTK launcher, as one row-major matrix for
/// `Canvas::concat_44`.
#[allow(clippy::too_many_arguments)]
pub fn card_matrix(
    cx: f64,
    cy: f64,
    angle_deg: f64,
    scale: f64,
    w: f64,
    h: f64,
    depth: f64,
) -> [f32; 16] {
    let t1 = translate(cx, cy);
    let p = perspective(depth);
    let r = rotate_y(angle_deg.to_radians());
    let s = scale_xy(scale);
    let t2 = translate(-w / 2.0, -h / 2.0);
    let m = mat_mul(&mat_mul(&mat_mul(&mat_mul(&t1, &p), &r), &s), &t2);
    core::array::from_fn(|i| m[i] as f32)
}

fn translate(x: f64, y: f64) -> [f64; 16] {
    let mut m = identity();
    m[3] = x;
    m[7] = y;
    m
}

fn perspective(d: f64) -> [f64; 16] {
    let mut m = identity();
    m[14] = -1.0 / d; // row 3, col 2 — w' = 1 − z/d (CSS convention)
    m
}

fn rotate_y(rad: f64) -> [f64; 16] {
    let (s, c) = rad.sin_cos();
    let mut m = identity();
    m[0] = c;
    m[2] = s;
    m[8] = -s;
    m[10] = c;
    m
}

fn scale_xy(s: f64) -> [f64; 16] {
    let mut m = identity();
    m[0] = s;
    m[5] = s;
    m
}

fn identity() -> [f64; 16] {
    let mut m = [0.0; 16];
    m[0] = 1.0;
    m[5] = 1.0;
    m[10] = 1.0;
    m[15] = 1.0;
    m
}

fn mat_mul(a: &[f64; 16], b: &[f64; 16]) -> [f64; 16] {
    let mut out = [0.0; 16];
    for r in 0..4 {
        for c in 0..4 {
            out[r * 4 + c] = (0..4).map(|k| a[r * 4 + k] * b[k * 4 + c]).sum();
        }
    }
    out
}

// --- Mesh-gradient background (the Swift `GamepadScreenBackground` MeshGradient, ported) --

/// The 16 mesh colours, row-major 4×4 (sRGB) — a verbatim port of the Swift client's
/// `meshColors`: dark-violet corners sink the frame, the edges carry mid-tone violets, and
/// the four interior points hold the bright brand family (warm pools left, cool right).
pub const MESH_COLORS: [(f64, f64, f64); 16] = [
    (0.075, 0.060, 0.160),
    (0.34, 0.27, 0.72),
    (0.30, 0.26, 0.74),
    (0.075, 0.060, 0.160),
    (0.42, 0.20, 0.54),
    (0.49, 0.39, 0.95),
    (0.28, 0.31, 0.84),
    (0.16, 0.26, 0.64),
    (0.45, 0.23, 0.60),
    (0.53, 0.31, 0.75),
    (0.35, 0.35, 0.91),
    (0.19, 0.28, 0.70),
    (0.075, 0.060, 0.160),
    (0.22, 0.18, 0.54),
    (0.24, 0.20, 0.58),
    (0.075, 0.060, 0.160),
];

/// The four interior control points that wander; the 12 boundary points stay pinned to the
/// frame (a drifting edge point would shrink the field and expose the black behind it). Each
/// row is `(base_ux, base_uy, amplitude, speed_x, speed_y, phase)` in unit UV / rad·s⁻¹ —
/// the exact `wob()` parameters from the Swift `meshPoints(at:)`. Their live displacement
/// `(amp·sin(t·sx+ph), amp·cos(t·sy+ph·1.3))` drives a domain warp, so the bright colour
/// pools follow the points as they breathe (periods ~90–130 s, out of phase so it never loops).
pub const MESH_INTERIOR: [(f64, f64, f64, f64, f64, f64); 4] = [
    (0.333, 0.333, 0.11, 0.049, 0.063, 0.4),
    (0.667, 0.333, 0.10, 0.055, 0.052, 2.1),
    (0.333, 0.667, 0.10, 0.058, 0.049, 3.6),
    (0.667, 0.667, 0.12, 0.047, 0.061, 5.0),
];

// --- Background palettes -------------------------------------------------------------------

/// One background colour family for the gamepad UI's living backdrop.
///
/// A palette is a short ordered ramp of [`Palette::stops`] — several DISTINCT hues, not one hue
/// at several brightnesses. The 4×4 mesh samples that ramp diagonally with a per-cell offset
/// ([`CELL_RAMP`]), so neighbouring cells land on different parts of it and the colours pool and
/// swirl the way a real gradient poster does; the interior points' existing domain warp then
/// drifts those pools around. An earlier version rotated ONE field's hue per palette, which is
/// why every non-default palette read as flat and monotone.
///
/// A palette also owns the UI it sits under: [`Palette::accent`] is the focus wash / selected
/// pill / switch colour, and [`Palette::light`] flips the ink (see [`crate::theme::Ink`]) so a
/// pale field gets dark text instead of white. The Apple and Android clients carry the same
/// table under the same ids, so one `ui_palette` value is one look everywhere.
pub struct Palette {
    /// The stored `ui_palette` value (see `trust::Settings::ui_palette`).
    pub id: &'static str,
    /// What the settings row shows.
    pub name: &'static str,
    /// The colour ramp, dark end first. `None` = use [`MESH_COLORS`] verbatim (the brand
    /// default, kept bit-identical to what every install already sees).
    pub stops: Option<&'static [(f64, f64, f64)]>,
    /// The field's ground — what the corners settle onto and what the calm mix lifts toward.
    pub ground: (f64, f64, f64),
    /// The UI accent: focus wash, selected tab pill, switch track, caret.
    pub accent: (f64, f64, f64),
    /// A pale field: the UI flips to dark ink and the legibility scrims go white.
    pub light: bool,
}

/// Where each of the 16 mesh cells samples the ramp. The base is the diagonal
/// `0.5·(x + y)` — top-left is the ramp's dark end, bottom-right its bright one, like both
/// reference gradients — and the per-cell nudges break the banding that a pure diagonal would
/// give, so hues pool instead of striping.
#[rustfmt::skip]
const CELL_RAMP: [f64; 16] = [
     0.10, -0.06,  0.04, -0.12,
    -0.08,  0.14, -0.10,  0.06,
     0.06, -0.12,  0.16, -0.04,
    -0.10,  0.08, -0.06,  0.12,
];

/// The twelve shipped palettes: the brand default, five more dark fields, then six pale ones.
/// Cycling order runs dark → light, so stepping the row walks the whole range in one direction.
/// Adding one here adds it to every console settings screen; the Apple and Android tables must
/// gain the same entry to keep the `ui_palette` key portable.
#[rustfmt::skip]
pub const PALETTES: [Palette; 12] = [
    // --- dark fields (white ink) ---
    Palette {
        id: "violet", name: "Violet", stops: None,
        ground: (0.075, 0.060, 0.160), accent: (0.525, 0.471, 0.961), light: false,
    },
    Palette {
        // Deep indigo climbing through violet into a hot magenta.
        id: "nebula", name: "Nebula",
        stops: Some(&[
            (0.07, 0.05, 0.20), (0.26, 0.14, 0.54), (0.52, 0.20, 0.72),
            (0.82, 0.26, 0.62), (0.98, 0.46, 0.68),
        ]),
        ground: (0.055, 0.040, 0.135), accent: (0.95, 0.42, 0.72), light: false,
    },
    Palette {
        // Ink-blue water: teal → cerulean → a violet undertow.
        id: "abyss", name: "Abyss",
        stops: Some(&[
            (0.02, 0.10, 0.17), (0.04, 0.28, 0.42), (0.07, 0.46, 0.63),
            (0.16, 0.38, 0.78), (0.26, 0.22, 0.58),
        ]),
        ground: (0.018, 0.070, 0.130), accent: (0.26, 0.76, 0.92), light: false,
    },
    Palette {
        // Banked coals: plum embers → crimson → burnt orange → gold.
        id: "ember", name: "Ember",
        stops: Some(&[
            (0.16, 0.03, 0.10), (0.45, 0.06, 0.12), (0.72, 0.18, 0.06),
            (0.90, 0.42, 0.08), (0.95, 0.68, 0.18),
        ]),
        ground: (0.090, 0.035, 0.040), accent: (0.98, 0.62, 0.26), light: false,
    },
    Palette {
        // Forest floor into moss and a lime break.
        id: "moss", name: "Moss",
        stops: Some(&[
            (0.03, 0.11, 0.09), (0.06, 0.27, 0.20), (0.09, 0.45, 0.31),
            (0.28, 0.61, 0.28), (0.58, 0.77, 0.31),
        ]),
        ground: (0.025, 0.085, 0.070), accent: (0.48, 0.86, 0.46), light: false,
    },
    Palette {
        // Neutral, but never flat: barely-there saturation that still travels from a cool
        // charcoal to a warm stone, so even the restrained option has somewhere to go.
        id: "graphite", name: "Graphite",
        stops: Some(&[
            (0.06, 0.07, 0.11), (0.15, 0.18, 0.25), (0.30, 0.31, 0.35),
            (0.45, 0.42, 0.38), (0.60, 0.56, 0.49),
        ]),
        ground: (0.055, 0.055, 0.070), accent: (0.78, 0.80, 0.86), light: false,
    },
    // --- pale fields (dark ink) ---
    Palette {
        // The holographic foil: rose → lilac → periwinkle → aqua, with a white bloom.
        id: "holo", name: "Holo",
        stops: Some(&[
            (0.99, 0.72, 0.90), (0.80, 0.60, 0.98), (0.58, 0.62, 0.99),
            (0.55, 0.86, 0.98), (0.94, 0.98, 1.00),
        ]),
        ground: (0.96, 0.92, 0.99), accent: (0.42, 0.28, 0.86), light: true,
    },
    Palette {
        // The poster sunset: periwinkle → magenta → scarlet → tangerine → gold.
        id: "sunset", name: "Sunset",
        stops: Some(&[
            (0.55, 0.45, 0.92), (0.86, 0.31, 0.66), (0.97, 0.26, 0.34),
            (0.99, 0.51, 0.18), (1.00, 0.80, 0.22),
        ]),
        ground: (0.98, 0.74, 0.34), accent: (0.64, 0.13, 0.44), light: true,
    },
    Palette {
        // Peach into blush and lilac — the softest of the set.
        id: "bloom", name: "Bloom",
        stops: Some(&[
            (1.00, 0.86, 0.72), (0.99, 0.73, 0.79), (0.95, 0.65, 0.89),
            (0.82, 0.68, 0.96), (0.73, 0.79, 0.99),
        ]),
        ground: (0.99, 0.90, 0.89), accent: (0.72, 0.24, 0.55), light: true,
    },
    Palette {
        // First light: pale gold → coral → lilac.
        id: "dawn", name: "Dawn",
        stops: Some(&[
            (1.00, 0.92, 0.70), (1.00, 0.80, 0.62), (0.99, 0.66, 0.62),
            (0.90, 0.62, 0.78), (0.77, 0.69, 0.95),
        ]),
        ground: (1.00, 0.93, 0.82), accent: (0.82, 0.33, 0.28), light: true,
    },
    Palette {
        // Sea glass: mint → aqua → a pale sky.
        id: "mint", name: "Mint",
        stops: Some(&[
            (0.82, 0.98, 0.90), (0.62, 0.94, 0.88), (0.55, 0.88, 0.95),
            (0.63, 0.82, 0.99), (0.82, 0.87, 1.00),
        ]),
        ground: (0.90, 0.98, 0.96), accent: (0.04, 0.42, 0.40), light: true,
    },
    Palette {
        // Near-white, but iridescent rather than flat — rose, sky, mint and cream in turn.
        id: "opal", name: "Opal",
        stops: Some(&[
            (0.98, 0.92, 0.96), (0.87, 0.93, 0.99), (0.91, 0.99, 0.95),
            (0.99, 0.96, 0.88), (0.94, 0.90, 0.99),
        ]),
        ground: (0.97, 0.96, 0.99), accent: (0.36, 0.32, 0.44), light: true,
    },
];

/// The palette stored under `id`, falling back to the brand default — an unknown name is a
/// palette a newer client shipped, not a reason to draw nothing.
pub fn palette(id: &str) -> &'static Palette {
    PALETTES.iter().find(|p| p.id == id).unwrap_or(&PALETTES[0])
}

/// Sample an ordered colour ramp at `t` ∈ [0, 1] (linear between neighbouring stops). Ported
/// verbatim to Swift and Kotlin — keep the three copies in step or a palette drifts between
/// clients.
pub fn ramp(stops: &[(f64, f64, f64)], t: f64) -> (f64, f64, f64) {
    match stops.len() {
        0 => (0.0, 0.0, 0.0),
        1 => stops[0],
        n => {
            let x = t.clamp(0.0, 1.0) * (n - 1) as f64;
            let i = (x.floor() as usize).min(n - 2);
            let f = x - i as f64;
            let (a, b) = (stops[i], stops[i + 1]);
            (
                a.0 + (b.0 - a.0) * f,
                a.1 + (b.1 - a.1) * f,
                a.2 + (b.2 - a.2) * f,
            )
        }
    }
}

impl Palette {
    /// The 16 mesh colours for this palette: the ramp sampled per cell (see [`CELL_RAMP`]), or
    /// [`MESH_COLORS`] verbatim for the brand default.
    pub fn mesh_colors(&self) -> [(f64, f64, f64); 16] {
        let Some(stops) = self.stops else {
            return MESH_COLORS;
        };
        core::array::from_fn(|i| {
            let (x, y) = ((i % 4) as f64 / 3.0, (i / 4) as f64 / 3.0);
            ramp(stops, 0.5 * (x + y) + CELL_RAMP[i])
        })
    }

    /// Four drifting blob colours, for the clients that approximate the mesh with a blob field
    /// (Android). Spread across the ramp so the field still shows several hues at once.
    pub fn blob_colors(&self) -> [(f64, f64, f64); 4] {
        let stops = self.stops.unwrap_or(&VIOLET_BLOBS);
        core::array::from_fn(|i| ramp(stops, 0.15 + 0.25 * i as f64))
    }
}

/// The brand default's blob ramp — the four colours the pre-palette Android/legacy-Apple field
/// used, kept so `violet` is unchanged there too.
const VIOLET_BLOBS: [(f64, f64, f64); 5] = [
    (0.53, 0.47, 0.96),
    (0.24, 0.20, 0.72),
    (0.62, 0.30, 0.80),
    (0.22, 0.38, 0.86),
    (0.53, 0.47, 0.96),
];

/// The mesh gradient as SkSL, palette + motion baked into the source (resolution, time and
/// the calm mix are uniforms). A smooth bicubic blend of the 16 colours — a separable
/// cubic-Bézier basis in x then y, C∞ and edge-to-edge, the fragment-shader analogue of
/// SwiftUI's `MeshGradient(smoothsColors: true)`. The four interior points drive a
/// bounded (weighted-average) domain warp so the bright pools drift; then the whole field
/// gets the ±8°/~5-min hue sway, an elliptical vignette, and the vertical legibility scrim,
/// all matching the Swift `composite(at:)`. Runs on the GPU at full rate.
///
/// `u_tc.y` is the CALM mix, 0 → 1: at 1 the same living field is flattened toward its own
/// corner colour (`u_lift`), which is how the form screens (settings, add-host, pair) stay
/// restful while still drifting — the motion never changes speed, only the contrast, so the
/// crossfade between a launcher screen and a form screen can't make the field jump.
pub fn mesh_sksl(colors: &[(f64, f64, f64); 16]) -> String {
    // Colours as `float3(r, g, b)` literals, indices 0..15 (row-major 4×4).
    let c = |i: usize| {
        let (r, g, b) = colors[i];
        format!("float3({r}, {g}, {b})")
    };
    // The four interior-point domain-warp accumulators. Displacement matches Swift `wob()`:
    // x uses sin(t·sx+ph), y uses cos(t·sy+ph·1.3). SIG sets how far each point's pull
    // reaches; the warp is the weight-normalised average displacement, so |warp| ≤ max|amp|.
    let mut warp = String::new();
    for (bx, by, amp, sx, sy, ph) in MESH_INTERIOR {
        warp.push_str(&format!(
            "    q = uv - float2({bx}, {by});\n\
                 ww = exp(-dot(q, q) / (2.0 * 0.30 * 0.30));\n\
                 d = float2({amp} * sin(tt * {sx} + {ph}), \
                            {amp} * cos(tt * {sy} + {ph} * 1.3));\n\
                 wsum += d * ww; wtot += ww;\n",
        ));
    }
    format!(
        "uniform float2 u_res;\n\
         // x = seconds since the shell started, y = the calm mix (0 launcher, 1 form).\n\
         uniform float2 u_tc;\n\
         // rgb = the palette's corner colour scaled for the calm lift; a is unused (float4\n\
         // so the uniform block stays 16-byte aligned under any packing rule).\n\
         uniform float4 u_lift;\n\
         // rgb = what the vignette and scrims tend toward (black under a dark palette, white\n\
         // under a pale one — darkening a pastel field would strand the dark text on it), and\n\
         // a = how hard. A pale field needs far less: mixing toward white at the dark field's\n\
         // strength bleaches the chroma straight out of the gradient.\n\
         uniform float4 u_scrim;\n\
         \n\
         // Cubic-Bézier basis over four control values — the smooth 4-point blend per axis.\n\
         float bz(float t, float a, float b, float c, float d) {{\n\
         \x20   float u = 1.0 - t;\n\
         \x20   return u*u*u*a + 3.0*u*u*t*b + 3.0*u*t*t*c + t*t*t*d;\n\
         }}\n\
         float3 bz3(float t, float3 a, float3 b, float3 c, float3 d) {{\n\
         \x20   return float3(bz(t, a.r, b.r, c.r, d.r), bz(t, a.g, b.g, c.g, d.g), \
                              bz(t, a.b, b.b, c.b, d.b));\n\
         }}\n\
         // Hue rotation about the grey axis (Rodrigues) — the ±8° warm/cool sway.\n\
         float3 hue(float3 col, float a) {{\n\
         \x20   float3 k = float3(0.5773503);\n\
         \x20   float cs = cos(a); float sn = sin(a);\n\
         \x20   return col*cs + cross(k, col)*sn + k*dot(k, col)*(1.0 - cs);\n\
         }}\n\
         \n\
         half4 main(float2 xy) {{\n\
         \x20   float tt = u_tc.x; float calm = u_tc.y;\n\
         \x20   float2 uv = xy / u_res;\n\
         \x20   // Interior control points wander → bounded domain warp (pools follow them).\n\
         \x20   float2 wsum = float2(0.0); float wtot = 0.0; float2 q; float ww; float2 d;\n\
         {warp}\
         \x20   uv = clamp(uv - wsum / (wtot + 1e-4), 0.0, 1.0);\n\
         \n\
         \x20   // Bicubic blend of the 16 mesh colours: cubic-Bézier in x per row, then in y.\n\
         \x20   float3 r0 = bz3(uv.x, {c0}, {c1}, {c2}, {c3});\n\
         \x20   float3 r1 = bz3(uv.x, {c4}, {c5}, {c6}, {c7});\n\
         \x20   float3 r2 = bz3(uv.x, {c8}, {c9}, {c10}, {c11});\n\
         \x20   float3 r3 = bz3(uv.x, {c12}, {c13}, {c14}, {c15});\n\
         \x20   float3 col = bz3(uv.y, r0, r1, r2, r3);\n\
         \n\
         \x20   col = hue(col, sin(tt * 0.021) * 0.1396263);\n\
         \n\
         \x20   // Calm: flatten the field toward its own corner colour — the pools dim and the\n\
         \x20   // corners lift, so a form screen keeps real colour under its glass rows while\n\
         \x20   // losing the launcher's contrast. Motion is untouched (see the doc comment).\n\
         \x20   col = mix(col, col * 0.60 + u_lift.rgb, calm);\n\
         \n\
         \x20   // Elliptical vignette: clear at r=0.25 → black·0.42 at r=1.15 (aspect-fit ellipse).\n\
         \x20   // Halved under calm: a launcher's cards sit in the pooled centre, but a form\n\
         \x20   // screen's rows run out toward the edges, where crushing to black just eats them.\n\
         \x20   float2 e = (xy / u_res - 0.5) * 2.0;\n\
         \x20   float vig = clamp((length(e) - 0.25) / 0.90, 0.0, 1.0)\n\
         \x20             * mix(0.42, 0.21, calm) * u_scrim.a;\n\
         \x20   col = mix(col, u_scrim.rgb, vig);\n\
         \n\
         \x20   // Vertical legibility scrim: black 0.38/0.06/0.08/0.40 at 0/0.32/0.68/1.\n\
         \x20   float v = xy.y / u_res.y;\n\
         \x20   float s = v < 0.32 ? mix(0.38, 0.06, v / 0.32)\n\
         \x20           : v < 0.68 ? mix(0.06, 0.08, (v - 0.32) / 0.36)\n\
         \x20           : mix(0.08, 0.40, (v - 0.68) / 0.32);\n\
         \x20   col = mix(col, u_scrim.rgb, s * u_scrim.a);\n\
         \n\
         \x20   return half4(half3(col), 1.0);\n\
         }}\n",
        c0 = c(0), c1 = c(1), c2 = c(2), c3 = c(3),
        c4 = c(4), c5 = c(5), c6 = c(6), c7 = c(7),
        c8 = c(8), c9 = c(9), c10 = c(10), c11 = c(11),
        c12 = c(12), c13 = c(13), c14 = c(14), c15 = c(15),
    )
}

// --- The shared binary↔overlay model ------------------------------------------------------

#[derive(Clone, PartialEq)]
pub enum LibraryPhase {
    Loading,
    Error {
        title: String,
        body: String,
        can_retry: bool,
    },
    Empty,
    /// Games are loaded — the carousel.
    Ready,
}

#[derive(Clone)]
pub struct LibraryGame {
    pub id: String,
    pub title: String,
    pub store: String,
    /// This entry opens the launcher itself (Steam Big Picture, Heroic, Lutris) rather than a
    /// title — design D4. The host's `role` field, already reduced to a boolean by
    /// [`pf_client_core::library::GameEntry::is_launcher`] so the "anything that isn't
    /// `launcher` is a game" rule lives in exactly one place.
    pub launcher: bool,
}

struct Shared {
    phase: LibraryPhase,
    games: Vec<LibraryGame>,
    /// Fetched poster bytes the renderer hasn't decoded yet (id, encoded image).
    art_in: VecDeque<(String, Vec<u8>)>,
    /// Bumped on phase/games changes so the renderer re-syncs its snapshot.
    generation: u64,
}

/// The binary's write handle / the overlay's read handle — fetch threads push into it,
/// the renderer drains per frame. Cheap locks, no rendering data inside.
#[derive(Clone)]
pub struct LibraryShared(Arc<Mutex<Shared>>);

impl Default for LibraryShared {
    fn default() -> Self {
        LibraryShared(Arc::new(Mutex::new(Shared {
            phase: LibraryPhase::Loading,
            games: Vec::new(),
            art_in: VecDeque::new(),
            generation: 0,
        })))
    }
}

impl LibraryShared {
    pub fn set_phase(&self, phase: LibraryPhase) {
        let mut s = self.0.lock().unwrap();
        s.phase = phase;
        s.generation += 1;
    }

    /// Loaded games → the carousel (empty = the empty scene).
    ///
    /// **Launcher entries are moved to the front, keeping the host's title order within each
    /// group.** Grouping here rather than in the renderer means the carousel's cursor arithmetic,
    /// the art pump and every future consumer of this model all inherit the invariant for free —
    /// a launcher tile is never buried in the middle of a 400-title shelf.
    pub fn set_games(&self, games: Vec<LibraryGame>) {
        let mut games = games;
        // `sort_by_key` is stable, so this is a partition that preserves the incoming order.
        games.sort_by_key(|g| !g.launcher);
        let mut s = self.0.lock().unwrap();
        s.phase = if games.is_empty() {
            LibraryPhase::Empty
        } else {
            LibraryPhase::Ready
        };
        s.games = games;
        s.generation += 1;
    }

    pub fn push_art(&self, id: String, bytes: Vec<u8>) {
        self.0.lock().unwrap().art_in.push_back((id, bytes));
    }

    /// Renderer side: the generation stamp (re-snapshot on change).
    pub(crate) fn generation(&self) -> u64 {
        self.0.lock().unwrap().generation
    }

    pub(crate) fn snapshot(&self) -> (LibraryPhase, Vec<LibraryGame>, u64) {
        let s = self.0.lock().unwrap();
        (s.phase.clone(), s.games.clone(), s.generation)
    }

    pub(crate) fn drain_art(&self) -> Vec<(String, Vec<u8>)> {
        self.0.lock().unwrap().art_in.drain(..).collect()
    }
}

/// Store id → display label (the GTK `ui_library` table).
pub fn store_label(store: &str) -> &'static str {
    match store {
        "steam" => "Steam",
        "custom" => "Custom",
        "heroic" => "Heroic",
        "lutris" => "Lutris",
        "epic" => "Epic",
        "gog" => "GOG",
        "xbox" => "Xbox",
        _ => "Game",
    }
}

/// Monogram for the placeholder tile: the first letters of the first two words.
pub fn initials(title: &str) -> String {
    title
        .split_whitespace()
        .take(2)
        .filter_map(|w| w.chars().next())
        .flat_map(char::to_uppercase)
        .collect()
}

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

    /// The GTK launcher's cursor tests, ported with the math.
    #[test]
    fn step_refuses_the_ends() {
        assert_eq!(step_cursor(0, 5, -1, false), StepResult::Boundary);
        assert_eq!(step_cursor(4, 5, 1, false), StepResult::Boundary);
        assert_eq!(step_cursor(2, 5, 1, false), StepResult::Moved(3));
        assert_eq!(step_cursor(0, 0, 1, false), StepResult::Boundary);
    }

    /// Design D4: launcher entries lead the shelf, and the host's title order survives within
    /// each group. The renderer's `launcher_count()` reads the launcher group as the prefix
    /// `0..n`, so an interleaved list would silently mislabel the group heading.
    #[test]
    fn set_games_groups_launchers_first_and_keeps_title_order() {
        let g = |title: &str, launcher: bool| LibraryGame {
            id: format!("steam:{title}"),
            title: title.to_string(),
            store: "steam".into(),
            launcher,
        };
        let shared = LibraryShared::default();
        shared.set_games(vec![
            g("Celeste", false),
            g("Big Picture", true),
            g("Portal 2", false),
            g("Heroic", true),
        ]);
        let (phase, games, _) = shared.snapshot();
        assert!(matches!(phase, LibraryPhase::Ready));
        let titles: Vec<&str> = games.iter().map(|g| g.title.as_str()).collect();
        assert_eq!(titles, ["Big Picture", "Heroic", "Celeste", "Portal 2"]);
        assert_eq!(games.iter().take_while(|g| g.launcher).count(), 2);
    }

    /// A library with no launcher entries is untouched — the whole point of the grouping being
    /// invisible until a plugin actually publishes a launcher tile.
    #[test]
    fn set_games_leaves_a_launcher_less_library_alone() {
        let shared = LibraryShared::default();
        shared.set_games(
            ["Celeste", "Portal 2", "Tunic"]
                .iter()
                .map(|t| LibraryGame {
                    id: format!("steam:{t}"),
                    title: (*t).to_string(),
                    store: "steam".into(),
                    launcher: false,
                })
                .collect(),
        );
        let (_, games, _) = shared.snapshot();
        let titles: Vec<&str> = games.iter().map(|g| g.title.as_str()).collect();
        assert_eq!(titles, ["Celeste", "Portal 2", "Tunic"]);
    }

    #[test]
    fn jump_clamps_onto_the_ends() {
        assert_eq!(step_cursor(1, 5, -JUMP, true), StepResult::Moved(0));
        assert_eq!(step_cursor(3, 5, JUMP, true), StepResult::Moved(4));
        assert_eq!(step_cursor(0, 5, -JUMP, true), StepResult::Boundary);
    }

    /// Springs converge onto the target and stay finite through a stalled frame.
    #[test]
    fn springs_converge() {
        let (mut pos, mut vel) = (0.0, 0.0);
        for _ in 0..120 {
            (pos, vel) = spring_advance(pos, vel, 3.0, SPRING_K, SPRING_C, 1.0 / 60.0);
        }
        assert!((pos - 3.0).abs() < 0.01, "{pos}");
        let (p, v) = spring_advance(0.0, 0.0, 1.0, BUMP_K, BUMP_C, 0.05);
        assert!(
            p.is_finite() && v.is_finite() && p > 0.0 && p < 2.0,
            "{p}/{v}"
        );
    }

    /// The focused card (angle 0, scale 1) maps its center to (cx, cy) exactly.
    #[test]
    fn card_matrix_centers_the_focused_card() {
        let m = card_matrix(640.0, 400.0, 0.0, 1.0, POSTER_W, POSTER_H, PERSPECTIVE);
        // Apply to the card-local center (w/2, h/2, 0, 1).
        let (x, y) = (POSTER_W as f32 / 2.0, POSTER_H as f32 / 2.0);
        let px = m[0] * x + m[1] * y + m[3];
        let py = m[4] * x + m[5] * y + m[7];
        let pw = m[12] * x + m[13] * y + m[15];
        assert!((px / pw - 640.0).abs() < 0.01, "{}", px / pw);
        assert!((py / pw - 400.0).abs() < 0.01, "{}", py / pw);
    }

    /// A right-side card's INNER (left) edge recedes: its projected x compresses toward
    /// the center relative to the flat card — the coverflow corridor.
    #[test]
    fn side_card_inner_edge_recedes() {
        let flat = card_matrix(900.0, 400.0, 0.0, 1.0, POSTER_W, POSTER_H, PERSPECTIVE);
        let tilted = card_matrix(
            900.0,
            400.0,
            -ROTATE_DEG,
            1.0,
            POSTER_W,
            POSTER_H,
            PERSPECTIVE,
        );
        let project = |m: &[f32; 16], x: f32, y: f32| {
            let px = m[0] * x + m[1] * y + m[3];
            let pw = m[12] * x + m[13] * y + m[15];
            px / pw
        };
        // The inner edge is x=0 in card space. Perspective divide: receding (w < 1 side)
        // pushes it AWAY from the vanishing center — the edge reads as farther.
        let flat_left = project(&flat, 0.0, POSTER_H as f32 / 2.0);
        let tilt_left = project(&tilted, 0.0, POSTER_H as f32 / 2.0);
        let flat_right = project(&flat, POSTER_W as f32, POSTER_H as f32 / 2.0);
        let tilt_right = project(&tilted, POSTER_W as f32, POSTER_H as f32 / 2.0);
        // Tilt narrows the card's projected width (it turned away from the viewer).
        assert!((tilt_right - tilt_left) < (flat_right - flat_left) * 0.95);
    }

    #[test]
    fn initials_take_two_words() {
        assert_eq!(initials("Dota 2"), "D2");
        assert_eq!(initials("half-life"), "H");
    }

    /// The generated SkSL parses as far as syntax we control (sanity: balanced braces, all
    /// 16 colours baked in, the five bicubic evals and four interior warp terms present).
    #[test]
    fn mesh_sksl_shape() {
        let src = mesh_sksl(&MESH_COLORS);
        assert!(src.matches("float3(").count() >= 16, "16 colours baked");
        assert_eq!(src.matches("bz3(").count(), 6); // 1 definition + 5 call sites
        assert_eq!(src.matches("wtot +=").count(), 4); // one per interior point
        assert_eq!(src.matches('{').count(), src.matches('}').count());
    }

    /// The brand default must still be the SHIPPED field, colour for colour. Every install
    /// already sees it, and a palette table that quietly restyled the default would be a
    /// regression dressed as a feature.
    #[test]
    fn violet_is_the_untouched_shipped_field() {
        assert_eq!(PALETTES[0].id, "violet");
        assert!(
            PALETTES[0].stops.is_none(),
            "the default is the explicit grid"
        );
        assert_eq!(palette("violet").mesh_colors(), MESH_COLORS);
        // An unknown name is a newer client's palette, not an error.
        assert_eq!(palette("chartreuse").id, "violet");
        assert_eq!(palette("").id, "violet");
    }

    /// Hue angle in degrees, or `None` for something too grey to have one.
    fn hue(c: (f64, f64, f64)) -> Option<f64> {
        let (r, g, b) = c;
        let max = r.max(g).max(b);
        let min = r.min(g).min(b);
        let d = max - min;
        if d < 0.04 {
            return None;
        }
        let h = if max == r {
            60.0 * (((g - b) / d) % 6.0)
        } else if max == g {
            60.0 * ((b - r) / d + 2.0)
        } else {
            60.0 * ((r - g) / d + 4.0)
        };
        Some((h + 360.0) % 360.0)
    }

    /// A palette must read as SEVERAL hues, not one hue at several brightnesses — that was
    /// exactly the complaint about the hue-rotation model this replaced. Measured as the
    /// widest gap between any two of the 16 mesh colours' hue angles.
    #[test]
    fn every_palette_is_multi_tone() {
        for p in &PALETTES {
            let hues: Vec<f64> = p.mesh_colors().iter().filter_map(|c| hue(*c)).collect();
            assert!(hues.len() >= 8, "{}: too few coloured cells", p.id);
            let spread = hues
                .iter()
                .flat_map(|a| {
                    hues.iter().map(move |b| {
                        let d = (a - b).abs() % 360.0;
                        d.min(360.0 - d)
                    })
                })
                .fold(0.0f64, f64::max);
            // Graphite and Opal are deliberately near-neutral; everything else must carry a
            // real hue journey.
            let floor = if matches!(p.id, "graphite" | "opal") {
                20.0
            } else {
                45.0
            };
            assert!(spread >= floor, "{} spans only {spread:.0}° of hue", p.id);
        }
    }

    /// Ids, order and the light/dark split are the cross-client contract — the Apple and
    /// Android tables must match this exactly.
    #[test]
    fn table_matches_the_other_clients() {
        let ids: Vec<&str> = PALETTES.iter().map(|p| p.id).collect();
        assert_eq!(
            ids,
            [
                "violet", "nebula", "abyss", "ember", "moss", "graphite", "holo", "sunset",
                "bloom", "dawn", "mint", "opal",
            ]
        );
        // Dark fields lead, pale ones follow, so stepping the row walks one direction.
        let first_light = PALETTES
            .iter()
            .position(|p| p.light)
            .expect("some are light");
        assert!(PALETTES[first_light..].iter().all(|p| p.light));
        assert_eq!(first_light, 6);
    }

    /// Every colour a palette produces stays in gamut, and a pale palette really is pale —
    /// its ink flips, so a mislabelled one would put dark text on a dark field.
    #[test]
    fn palettes_are_in_gamut_and_honest_about_lightness() {
        let luma = |c: (f64, f64, f64)| 0.2126 * c.0 + 0.7152 * c.1 + 0.0722 * c.2;
        for p in &PALETTES {
            for c in p.mesh_colors().iter().chain(p.blob_colors().iter()) {
                for v in [c.0, c.1, c.2] {
                    assert!((0.0..=1.0).contains(&v), "{} {c:?}", p.id);
                }
            }
            let mean = p.mesh_colors().iter().map(|c| luma(*c)).sum::<f64>() / 16.0;
            if p.light {
                assert!(mean > 0.5, "{} is flagged light but means {mean:.2}", p.id);
                assert!(luma(p.ground) > 0.6, "{}'s ground is dark", p.id);
            } else {
                assert!(mean < 0.45, "{} is flagged dark but means {mean:.2}", p.id);
                assert!(luma(p.ground) < 0.2, "{}'s ground is light", p.id);
            }
            // The accent tints glass of the OPPOSITE polarity to the field, so it has to be
            // legible there: dark accents on white frost, bright ones on dark glass.
            let a = luma(p.accent);
            if p.light {
                assert!(a < 0.45, "{}'s accent is too pale for white glass", p.id);
            } else {
                assert!(a > 0.25, "{}'s accent is too dark for dark glass", p.id);
            }
        }
    }

    /// The ramp is the shared sampling rule the Swift and Kotlin ports reproduce.
    #[test]
    fn ramp_interpolates_between_stops() {
        let stops = [(0.0, 0.0, 0.0), (1.0, 0.0, 0.0), (1.0, 1.0, 1.0)];
        assert_eq!(ramp(&stops, 0.0), (0.0, 0.0, 0.0));
        assert_eq!(ramp(&stops, 1.0), (1.0, 1.0, 1.0));
        assert_eq!(ramp(&stops, 0.5), (1.0, 0.0, 0.0));
        let q = ramp(&stops, 0.25);
        assert!((q.0 - 0.5).abs() < 1e-9 && q.1 == 0.0);
        // Out of range clamps rather than panicking.
        assert_eq!(ramp(&stops, -3.0), (0.0, 0.0, 0.0));
        assert_eq!(ramp(&stops, 9.0), (1.0, 1.0, 1.0));
        assert_eq!(ramp(&[], 0.5), (0.0, 0.0, 0.0));
    }
}