// SCAN SERMON — the pure-document effect: NO engine geometry at all, the
// whole frame is the fragment function in this file.
//
// This is the pattern to copy when an author wants a look no engine has:
// pick `engine: "screen"`, declare a `shader: draw.DrawVjFxScreen` block,
// and write `fx_color(uv, content, cmix)`. The engine contributes nothing
// but the quad and the clock — every pixel below is doc-authored. The
// stage chain still runs on top, so bloom/feedback/warps compose with it.
//
// The look: a broadcast scan head sweeping down the frame, tearing the
// video into bands that lag behind it, with the beat driving the tear and
// a phosphor rgb-split on the leading edge.
{
    name: "Scan Sermon"
    engine: "screen"
    seed: 5

    input0: "test"

    speed: 1.0
    beat_pulse: 0.6
    beat_rate: 1.0
    bar_beats: 4
    glow: 1.0
    // PERFORMANCE DIALS — each default reproduces the stock look exactly
    // (mid-knob multipliers are 1.0 at 0.5).
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "TEAR", bind: "p0", default: 0.5},
        {name: "BANDS", bind: "p1", default: 0.5},
        {name: "SPLIT", bind: "p2", default: 0.5}
    ]

    color_bg: #x03040a
    color_a: #x30ffd0
    color_b: #xff3a86
    color_c: #xfff0d0

    stages: [
        {kind: "bloom", threshold: 0.55, strength: 1.15, levels: 3}
    ]

    // THE LOOK LIVES HERE. There is no engine shading under this at all:
    // whatever this function returns IS the frame.
    // Inputs: uv = screen uv (0,0 top-left), content = input0 at uv,
    // cmix = the pre-gated content strength (0 without real channel video,
    // so a look can tell the fallback pattern from a live clip).
    // Signals: self.time_beat (time, beat, phase, pulse),
    // self.sig (bar, bpm, energy, dt), self.user (p0..p3),
    // self.col_a/b/c/bg, self.fog (density, glow, content, -).
    shader: draw.DrawVjFxScreen {
        fx_color: fn(uv: vec2, content: vec4, cmix: float) -> vec4 {
            // The scan head: one sweep per bar, wrapping.
            let head = fract(self.sig.x)
            // Horizontal bands; more of them as BANDS opens.
            let bands = 6.0 + 26.0 * clamp(self.user.y, 0.0, 1.0)
            let band = floor(uv.y * bands)
            let band01 = fract(uv.y * bands)
            // Distance BELOW the head, wrapped: a band the head just
            // crossed is hot and displaced, and it settles as it ages.
            let age = fract(uv.y - head + 1.0)
            let hot = pow(1.0 - age, 9.0)
            // Tear: each band slides by its own hash, hardest right after
            // the head passes and on the beat pulse.
            let hash = fract(sin(band * 12.9898 + 3.0) * 43758.5453)
            let drive = (0.30 + 1.7 * clamp(self.user.x, 0.0, 1.0))
                * (0.25 + self.time_beat.w)
            let slide = (hash - 0.5) * hot * drive * 0.35
            let suv = clamp(vec2(fract(uv.x + slide), uv.y), vec2(0.0, 0.0), vec2(1.0, 1.0))
            // Phosphor split: the channels separate along the tear.
            let sp = (0.002 + 0.03 * clamp(self.user.z, 0.0, 1.0)) * (0.2 + hot)
            let r = self.tex0.sample_as_bgra(clamp(suv + vec2(sp, 0.0), vec2(0.0, 0.0), vec2(1.0, 1.0)))
            let g = self.tex0.sample_as_bgra(suv)
            let b = self.tex0.sample_as_bgra(clamp(suv - vec2(sp, 0.0), vec2(0.0, 0.0), vec2(1.0, 1.0)))
            let mut rgb = vec3(r.x, g.y, b.z)
            // Scanline gate inside each band + a dark seam between bands.
            let line = 0.86 + 0.14 * sin(uv.y * 900.0)
            let seam = smoothstep(0.0, 0.06, band01) * smoothstep(0.0, 0.06, 1.0 - band01)
            rgb = rgb * (line * (0.35 + 0.65 * seam))
            // The head itself: a bar of col_a with a col_c core.
            let edge = pow(1.0 - age, 60.0)
            rgb = rgb + self.col_a.xyz * (hot * 0.35) + self.col_c.xyz * (edge * 0.9)
            // A band that has not been scanned yet sits in col_b's dark.
            rgb = rgb.mix(self.col_bg.xyz + self.col_b.xyz * 0.06, (1.0 - hot) * 0.22)
            // Without real content (cmix 0) the fallback pattern is all
            // there is, so lift it a little to keep the frame alive.
            let lift = 1.0 + (1.0 - clamp(cmix, 0.0, 1.0)) * 0.25
            return vec4(rgb * (self.fog.y * lift), 1.0)
        }
    }
}