#version 430 core

struct FaceData {
    uint x;
    uint y;
    uint z;
    uint facing; // 0=+X,1=-X,2=+Y,3=-Y,4=+Z,5=-Z
    uint texture;
};

layout(std430, binding = 0) buffer FaceBuffer {
    FaceData faces[];
};

out vec3 fragColor;

vec3 getVertexOffset(uint facing, uint vertIndex) {
    if (facing == 0u) { // +X
        vec3 offsets[6] = vec3[6](
            vec3(0.5, -0.5, -0.5),
            vec3(0.5,  0.5,  0.5),
            vec3(0.5, -0.5,  0.5),
            vec3(0.5,  0.5,  0.5),
            vec3(0.5, -0.5, -0.5),
            vec3(0.5,  0.5, -0.5)
        );
        return offsets[vertIndex];
    } else if (facing == 1u) { // -X
        vec3 offsets[6] = vec3[6](
            vec3(-0.5, -0.5,  0.5),
            vec3(-0.5,  0.5, -0.5),
            vec3(-0.5, -0.5, -0.5),
            vec3(-0.5,  0.5, -0.5),
            vec3(-0.5, -0.5,  0.5),
            vec3(-0.5,  0.5,  0.5)
        );
        return offsets[vertIndex];
    } else if (facing == 2u) { // +Y (top)
        vec3 offsets[6] = vec3[6](
            vec3(-0.5, 0.5, -0.5),
            vec3( 0.5, 0.5,  0.5),
            vec3( 0.5, 0.5, -0.5),
            vec3( 0.5, 0.5,  0.5),
            vec3(-0.5, 0.5, -0.5),
            vec3(-0.5, 0.5,  0.5)
        );
        return offsets[vertIndex];
    } else if (facing == 3u) { // -Y (bottom)
        vec3 offsets[6] = vec3[6](
            vec3(-0.5, -0.5,  0.5),
            vec3( 0.5, -0.5, -0.5),
            vec3( 0.5, -0.5,  0.5),
            vec3( 0.5, -0.5, -0.5),
            vec3(-0.5, -0.5,  0.5),
            vec3(-0.5, -0.5, -0.5)
        );
        return offsets[vertIndex];
    } else if (facing == 4u) { // +Z (front)
        vec3 offsets[6] = vec3[6](
            vec3(-0.5, -0.5, 0.5),
            vec3( 0.5, -0.5, 0.5),
            vec3( 0.5,  0.5, 0.5),
            vec3( 0.5,  0.5, 0.5),
            vec3(-0.5,  0.5, 0.5),
            vec3(-0.5, -0.5, 0.5)
        );
        return offsets[vertIndex];
    } else if (facing == 5u) { // -Z (back)
        vec3 offsets[6] = vec3[6](
            vec3( 0.5, -0.5, -0.5),
            vec3(-0.5, -0.5, -0.5),
            vec3(-0.5,  0.5, -0.5),
            vec3(-0.5,  0.5, -0.5),
            vec3( 0.5,  0.5, -0.5),
            vec3( 0.5, -0.5, -0.5)
        );
        return offsets[vertIndex];
    }
}

uniform mat4 view;
uniform mat4 projection;

void main()
{
    float[6] lightMult = float[6](
        0.6,
        0.6,
        1.0,
        0.5,
        0.8,
        0.8
    );

    uint faceIndex = gl_VertexID / 6;
    uint vertIndex = gl_VertexID % 6;

    FaceData f = faces[faceIndex];
    vec3 basePos = vec3(f.x, f.y, f.z);
    vec4 worldPos = vec4(basePos + getVertexOffset(f.facing, vertIndex), 1.0);

    
    fragColor = vec3(1.0, 1.0, 1.0) * lightMult[f.facing];

    gl_Position = projection * view * worldPos;
}