#version 120
varying vec2 vTexCoord;

uniform vec3 u_lightColor;
uniform sampler2D u_texture;


float drawShadow(){
    vec2 loc;
    vec2 norm = normalize(vTexCoord - vec2(.5,.5)); // Pointing from center to point
    vec4 smp;

    float dst = 0.0;

    // For now draw all casters
    if(texture2D(u_texture, vTexCoord - dst * norm).a > 0)
        return 1.0;

    for(int i = 0; i < 256; i++){
        loc = vTexCoord - dst * norm;

        if (length(loc-vec2(.5,.5)) < 1.0/256.0)
            break;

        smp = texture2D(u_texture, loc);

        if(smp.a > 0){
            return 0.0;
        }

        dst += 1.0/256.0;
    }

    return 1.0;
}


void main() {
    float dist = length(vec2(.5,.5) - vTexCoord.xy);

    float shad = drawShadow();

    float intensity = 1-dist*2.0;

    gl_FragColor = vec4(u_lightColor, 1.0)*vec4(shad*vec3(intensity), shad);
}