// OSCILLOSCOPE RIBBON — the raw waveform drawn as a lit ribbon across the
// frame, with two older copies of the SAME window trailing behind it.
//
// This is the `audio_wave(t)` demo. `t` runs 0..1 across the stored window
// (about 1.4 s); 1 is the newest sample. Sliding the read window is how a
// scope "scrolls" here — the trail copies read the same texture at an
// offset instead of keeping a history buffer of their own.
{
    name: "Oscilloscope Ribbon"
    engine: "screen"
    seed: 21

    speed: 1.0
    beat_pulse: 0.45
    beat_rate: 1.0
    bar_beats: 4
    glow: 1.1

    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "AMP", bind: "p0", default: 0.5},
        {name: "SPAN", bind: "p1", default: 0.5},
        {name: "TRAIL", bind: "p2", default: 0.5}
    ]

    color_bg: #x02060a
    color_a: #x44ffc8
    color_b: #x3aa0ff
    color_c: #xffffff

    stages: [
        {kind: "bloom", threshold: 0.4, strength: 1.3, levels: 3}
    ]

    shader: draw.DrawVjFxScreen {
        // Trace height at screen x for a window ending `lag` back.
        trace: fn(x: float, lag: float, amp: float) -> float {
            // SPAN squeezes the read window: a short span is a slow, fat
            // wave; a long one packs seconds of audio into the frame.
            let span = 0.10 + 0.85 * clamp(self.user.y, 0.0, 1.0)
            let t = clamp(1.0 - lag - span * (1.0 - clamp(x, 0.0, 1.0)), 0.0, 1.0)
            let w = self.audio_wave(t)
            // IDLE: silence is a flat zero, so add a small travelling sine
            // that the real signal instantly swamps.
            let idle = 0.055 * sin(x * 24.0 - self.time_beat.x * 3.1)
                * (1.0 + self.time_beat.w)
            return 0.5 - (w * amp + idle) * 0.5
        }

        fx_color: fn(uv: vec2, content: vec4, cmix: float) -> vec4 {
            let amp = 0.5 + 1.4 * clamp(self.user.x, 0.0, 1.0)
            let trail = clamp(self.user.z, 0.0, 1.0)

            let y0 = self.trace(uv.x, 0.0, amp)
            let y1 = self.trace(uv.x, 0.02 + 0.10 * trail, amp)
            let y2 = self.trace(uv.x, 0.05 + 0.24 * trail, amp)

            // A line is a distance field: thin core, wide glow.
            let d0 = abs(uv.y - y0)
            let d1 = abs(uv.y - y1)
            let d2 = abs(uv.y - y2)
            let core = exp(0.0 - d0 * 460.0)
            let glow = exp(0.0 - d0 * 55.0)
            let g1 = exp(0.0 - d1 * 70.0) * 0.42
            let g2 = exp(0.0 - d2 * 90.0) * 0.22

            // The RIBBON: fill between the live trace and the oldest trail
            // copy, so the scope reads as a band and not three hairlines.
            let lo = min(y0, y2)
            let hi = max(y0, y2)
            let band = smoothstep(0.0, 0.004, uv.y - lo)
                * smoothstep(0.0, 0.004, hi - uv.y) * 0.22

            let tint = self.col_a.xyz.mix(self.col_b.xyz, clamp(uv.x, 0.0, 1.0))
            let mut rgb = self.col_bg.xyz
            // Graticule: a faint scope grid so the frame is never empty.
            let grid = smoothstep(0.985, 1.0, max(
                abs(sin(uv.x * 25.1327)),
                abs(sin(uv.y * 25.1327))
            ))
            rgb = rgb + self.col_b.xyz * (grid * 0.05)
            rgb = rgb + tint * (band + g1 + g2 + glow * 0.35)
            rgb = rgb + self.col_c.xyz * (core * 0.9)
            return vec4(rgb * self.fog.y, 1.0)
        }
    }
}