uniform sampler2D texture;
uniform int width;
uniform sampler2D lightmap;
uniform vec3 lightColor;

//final step in the lighting algorithm.
//generates the final shadow image from the
//generated occlusion map :-DDDD wow haha
const float cutoff = 0.1f;
const float bias = .5f;
const int intensitylevel = 3;

vec2 roundP(vec2 poop){
    //pixel to pixel divided by 2
    float p2p = 1.0f / width;
    return poop.xy - mod(poop, vec2(p2p)) + vec2(p2p*0.5f);
}

float GetShadowDistanceH(vec2 TexCoord)
{
    float u = TexCoord.x;
    float v = TexCoord.y;

    u = abs(u-0.5f) * 2.0f;
    v = v * 2.0f - 1.0f;
    float v0 = v/u;
    v0 = (v0 + 1.0f) / 2.0f;

    vec2 newCoords = vec2(TexCoord.x,v0);
    //horizontal info was stored in the Red component
    //gl_FragColor = texture2D(lightmap, newCoords);
    //return newCoords.x < 0.5f ? 0 : 1;
    return texture2D(lightmap, roundP(newCoords)).r; // * 0.70588235; //revert mult done in distancing
}

float GetShadowDistanceV(vec2 TexCoord)
{
    float u = TexCoord.y;
    float v = TexCoord.x;

    u = abs(u-0.5f) * 2.0f;
    v = v * 2.0f - 1.0f;
    float v0 = v/u;
    v0 = (v0 + 1.0f) / 2.0f;

    vec2 newCoords = vec2(TexCoord.y, v0);
    //vertical info was stored in the Green component
    //gl_FragColor = texture2D(lightmap, newCoords);
    //return newCoords.x < 0.5f ? 0 : 1;
    return texture2D(lightmap, roundP(newCoords)).g; // * 0.70588235; //revert mult done in distancing
}

void main()
{
    // distance of this pixel from the center
    float dist = length(gl_TexCoord[0].xy - 0.5f);

    //apply pixel bias
    dist -= 1.0f / width * bias;

    //distance stored in the shadow map
    float shadowMapDistance;
    //coords in [-1,1]
    float nY = 2.0f*( gl_TexCoord[0].y - 0.5f);
    float nX = 2.0f*( gl_TexCoord[0].x - 0.5f);

    //for debug
    float red = 1.0f;
    float green = 1.0f;

    //we use these to determine which quadrant we are in
    if      (abs(nY) < abs(nX))
    {
        shadowMapDistance = GetShadowDistanceH(gl_TexCoord[0].xy);
        green = 1.5f; //for debug
    }
    else if (abs(nY) > abs(nX))
    {
        red = 1.5f; //for debug
        shadowMapDistance = GetShadowDistanceV(gl_TexCoord[0].xy);
    }
    else shadowMapDistance = 0.0f;


    //if distance to this pixel is lower than distance from shadowMap,
    //then we are not in shadow
    //float light = dist;
    float light = dist < shadowMapDistance ? 1:0;

    float intensity = 1.0f - dist;
    for(int i = 1; i < intensitylevel; i++){
        intensity = intensity * (1-dist);
    }

    gl_FragColor = vec4(light > 0 ? (lightColor.r * intensity - cutoff) * red       : 0.0f,
                        light > 0 ? (lightColor.g * intensity - cutoff) * green     : 0.0f,
                        light > 0 ? lightColor.b * intensity - cutoff           : 0.0f,
                        1.0f);

    //gl_FragColor = vec4(light, light, light, 1.0f - (dist / 1.4f));
}