#version 330

/*
   Film Noir (1940s-1950s) — picom shader
   Classic Hollywood B&W. High contrast, crushed blacks, silver gelatin.
   Super XX panchromatic stock with low-key lighting aesthetic.
*/

in vec2 texcoord;
uniform sampler2D tex;

// BT.601 — period-appropriate panchromatic film response
const vec3 LUMA_601 = vec3(0.299, 0.587, 0.114);

float hash(vec2 p) {
    vec3 p3 = fract(vec3(p.xyx) * .1031);
    p3 += dot(p3, p3.yzx + 33.33);
    return fract((p3.x + p3.y) * p3.z);
}

float vignette(vec2 uv) {
    vec2 d = uv - 0.5;
    float dist = length(d);
    // Heavy vignette — fast lens wide open, ~1.5 stops corner falloff
    return 1.0 - smoothstep(0.25, 0.9, dist) * 0.35;
}

vec4 window_shader() {
    vec2 texsize = textureSize(tex, 0);
    vec4 pixColor = texture2D(tex, texcoord / texsize, 0);

    // Luminance conversion
    float luma = dot(pixColor.rgb, LUMA_601);

    // High-contrast sigmoid S-curve
    float contrast = 2.8;
    float midpoint = 0.45;
    luma = 1.0 / (1.0 + exp(-contrast * 6.0 * (luma - midpoint)));

    // Additional black crush
    luma = smoothstep(0.02, 0.98, luma);

    // Luminance-dependent film grain
    vec2 screenPos = gl_FragCoord.xy;
    float noise = (hash(screenPos * 0.5) - 0.5) * 2.0;
    // More grain in midtones, less in deep shadows and bright highlights
    float grainMask = 1.0 - abs(luma - 0.45) * 1.8;
    grainMask = clamp(grainMask, 0.2, 1.0);
    luma += noise * 0.06 * grainMask;

    luma = clamp(luma, 0.0, 1.0);

    // Silver gelatin toning — very slight warm shadows, cool highlights
    vec3 warmBlack = vec3(0.02, 0.01, 0.0);
    vec3 coolWhite = vec3(0.97, 0.97, 1.0);
    vec3 color = mix(warmBlack, coolWhite, luma);

    // Vignette
    vec2 normalizedCoord = texcoord / texsize;
    color *= vignette(normalizedCoord);

    return vec4(clamp(color, 0.0, 1.0), 1.0);
}