#version 450

layout(set = 0, binding = 0, std430) readonly buffer V210 {
    uint words[];
};

layout(push_constant) uniform PC {
    uint width;
    uint height;
    uint strideBytes;
    uint winW;
    uint winH;
} pc;

layout(location = 0) out vec4 fragColor;

void main() {
    // Letterbox: fit video into the window, preserving aspect ratio.
    float sx = float(pc.winW) / float(pc.width);
    float sy = float(pc.winH) / float(pc.height);
    float scale = min(sx, sy);
    float dispW = float(pc.width)  * scale;
    float dispH = float(pc.height) * scale;
    float offX = (float(pc.winW) - dispW) * 0.5;
    float offY = (float(pc.winH) - dispH) * 0.5;
    float fbx = gl_FragCoord.x - offX;
    float fby = gl_FragCoord.y - offY;
    if (fbx < 0.0 || fbx >= dispW || fby < 0.0 || fby >= dispH) {
        fragColor = vec4(0.0, 0.0, 0.0, 1.0);
        return;
    }
    // Framebuffer y is bottom-origin; flip to video top-origin.
    uint x = uint(fbx / scale);
    uint y = uint(fby / scale);

    // V210: 6 pixels per group of 4 words; 3 ten-bit components per word
    // (bits 0-9 / 10-19 / 20-29). Stream order: Cb Y Cr Y Cb Y Cr Y ...
    uint group = x / 6u;
    uint sub   = x % 6u;
    uint wordsPerLine = pc.strideBytes / 4u;
    uint base = y * wordsPerLine + group * 4u;

    uint w0 = words[base + 0u];
    uint w1 = words[base + 1u];
    uint w2 = words[base + 2u];
    uint w3 = words[base + 3u];

    uint cb0 = (w0      ) & 0x3FFu;
    uint y0  = (w0 >> 10u) & 0x3FFu;
    uint cr0 = (w0 >> 20u) & 0x3FFu;
    uint y1  = (w1      ) & 0x3FFu;
    uint cb1 = (w1 >> 10u) & 0x3FFu;
    uint y2  = (w1 >> 20u) & 0x3FFu;
    uint cr1 = (w2      ) & 0x3FFu;
    uint y3  = (w2 >> 10u) & 0x3FFu;
    uint cb2 = (w2 >> 20u) & 0x3FFu;
    uint y4  = (w3      ) & 0x3FFu;
    uint cr2 = (w3 >> 10u) & 0x3FFu;
    uint y5  = (w3 >> 20u) & 0x3FFu;

    float Y, Cb, Cr;
    if      (sub == 0u) { Y = float(y0); Cb = float(cb0); Cr = float(cr0); }
    else if (sub == 1u) { Y = float(y1); Cb = float(cb0); Cr = float(cr0); }
    else if (sub == 2u) { Y = float(y2); Cb = float(cb1); Cr = float(cr1); }
    else if (sub == 3u) { Y = float(y3); Cb = float(cb1); Cr = float(cr1); }
    else if (sub == 4u) { Y = float(y4); Cb = float(cb2); Cr = float(cr2); }
    else                { Y = float(y5); Cb = float(cb2); Cr = float(cr2); }

    float yf = (Y  - 64.0)  / 876.0;
    float uf = (Cb - 512.0) / 896.0;
    float vf = (Cr - 512.0) / 896.0;
    float r = yf + 1.5748 * vf;
    float g = yf - 0.1873 * uf - 0.4681 * vf;
    float b = yf + 1.8556 * uf;
    fragColor = vec4(clamp(r, 0.0, 1.0), clamp(g, 0.0, 1.0), clamp(b, 0.0, 1.0), 1.0);
}