// SPDX-FileCopyrightText: 2026 fuddlesworth
// SPDX-License-Identifier: LGPL-2.1-or-later
//
// Fade Color transition — ported from liixini/shaders niri shader
// (https://github.com/liixini/shaders/tree/main/fadecolor). Phased
// fade — visibility ramps from 40% progress onward with smoothstep.
//
// Niri's fadecolor ships symmetric close.glsl/open.glsl — bodies are
// identical apart from `p = niri_clamped_progress` vs
// `p = 1.0 - niri_clamped_progress`, so the open leg is the close
// played in reverse. PlasmaZones already flips iTime on reverse legs
// (1→0 on close, 0→1 on open), so we use the niri OPEN body verbatim
// with `niri_clamped_progress` translated to `clamp(iTime, 0.0, 1.0)`
// and the runtime flip auto-mirrors the visual on close. No
// `iIsReversed` branch required.
//
// niri's `niri_geo_to_tex` is the identity mat3 in PlasmaZones (geometry
// == texture coords here), so the matrix multiply is dropped and
// `texture(uTexture0, uv)` samples directly. `texture2D` (GLSL ES) is
// rewritten to `texture` (GLSL 4.50 core) inline.

#version 450

#include <animation_uniforms.glsl>

// metadata.json declaration order → customParams[0] sub-slots
#define colorPhase customParams[0].x

layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 fragColor;

void main() {
    // ── niri OPEN body (handles both legs via runtime iTime flip) ──
    float p = clamp(iTime, 0.0, 1.0);
    vec2 uv = vTexCoord;

    vec4 win = surfaceColor(uv);

    float reveal = smoothstep(colorPhase, 1.0, p);
    fragColor = win * reveal;
}
