#version 330 core
in vec2 vUV;
out float FragColor;

uniform sampler2D gDepth;
uniform sampler2D gNormal;
uniform sampler2D texNoise;

uniform vec3 samples[64];
uniform mat4 proj;
uniform mat4 invProj;
uniform float radius;
uniform float bias;
uniform float noiseScale;

uniform int kernelSize;
uniform float power;

vec3 getViewPos(vec2 uv)
{
    float depth = texture(gDepth, uv).r;
    if (depth == 1.0) return vec3(0.0);
    float z = depth * 2.0 - 1.0;
    vec4 clip = vec4(uv * 2.0 - 1.0, z, 1.0);
    vec4 viewPos = invProj * clip;
    viewPos /= viewPos.w;
    return viewPos.xyz;
}

void main()
{
    vec3 fragPos = getViewPos(vUV);
    if (fragPos == vec3(0.0))
    {
        FragColor = 1.0;
        return;
    }

    vec3 normal = texture(gNormal, vUV).rgb;
    normal = normalize(normal * 2.0 - 1.0);

    vec3 randomVec = normalize(texture(texNoise, vUV * noiseScale).xyz * 2.0 - 1.0);

    
    vec3 tangent = normalize(randomVec - normal * dot(randomVec, normal));
    vec3 bitangent = cross(normal, tangent);
    mat3 TBN = mat3(tangent, bitangent, normal);

    float occlusion = 0.0;
    for (int i = 0; i < kernelSize; ++i)
    {
        vec3 sample = TBN * samples[i];
        sample = fragPos + sample * radius;

        
        vec4 offset = proj * vec4(sample, 1.0);
        offset.xyz /= offset.w;
        vec2 sampleUV = offset.xy * 0.5 + 0.5;

        if (sampleUV.x < 0.0 || sampleUV.x > 1.0 || sampleUV.y < 0.0 || sampleUV.y > 1.0)
            continue;

        vec3 samplePos = getViewPos(sampleUV);
        if (samplePos == vec3(0.0))
            continue;

        float rangeCheck = smoothstep(0.0, 1.0, radius / abs(fragPos.z - samplePos.z));
        float diff = samplePos.z - sample.z;
        if (diff > bias)
            occlusion += rangeCheck;
    }

    occlusion = 1.0 - (occlusion / float(kernelSize));
    occlusion = pow(occlusion, power);
    FragColor = occlusion;
}