#version 330

in vec4 position_in_viewspace;
in vec3 normal_in_viewspace;
in vec2 tex_coord;

out vec4 color;

uniform sampler2D diffuse_map;
uniform sampler2D tree_normal;
uniform vec4 diffuse = vec4(0,0,0,1);

uniform struct SLight {
        vec3 position_in_viewspace;
        float radius;
        vec3 material_color_diffuse;
        vec3 material_color_specular;
        vec3 material_color_ambient;
} light[64];
uniform int light_count;

float compute_blinn_term(in vec3 N, in vec3 L, in vec3 V, in float NdotL, in float shininess)
{
        vec3 H = normalize(L + V);
        float term = dot(N,H);
        term = max(clamp(term, 0.0, 1.0), 0.0);
        term = pow(term, shininess);
        return term;
}

vec3 color_from_light(in int light_index, in vec3 N, in vec3 V, in vec3 diffuse)
{
        vec3 L = (light[light_index].position_in_viewspace - position_in_viewspace.xyz);
        vec3 L_rad = L / light[light_index].radius;
        float light_attenuation = max(0, 1.0 - dot(L_rad,L_rad));
        vec3 light_diffuse = light[light_index].material_color_diffuse;
        vec3 light_specular = light[light_index].material_color_specular;
        vec3 light_ambient = light[light_index].material_color_ambient;

        float NdotL = max(dot(N,L), 0.0);
        float shininess = 0.75;
        float term = compute_blinn_term(N, L, V, NdotL, shininess);

        //Uncomment to debug light attenuation
        //return vec4(1,1,1,1) * light_attenuation;

        return vec3(
                (diffuse * NdotL * light_diffuse * light_attenuation) +
                (diffuse * term * light_specular * light_attenuation) +
                (diffuse * light_ambient * 0.5)
        );
}

void main() {

    vec3 N = normalize(normal_in_viewspace);
    //vec3 N = normalize(texture(tree_normal, tex_coord).rgb * 1.0 - vec3(1.0));
    vec3 V = normalize(-position_in_viewspace.xyz);


vec4 texel = diffuse * texture(diffuse_map, tex_coord);
if(texel.a < 0.5){
    discard;
}
color = texel;

    for(int i = 0; i < light_count; i++)
    {
        color += vec4(color_from_light(i, N, V, diffuse.rgb * vec3(0.05)),1);
    }
    if(color == vec4(0,0,0,1)) {
        color = diffuse;
    }

    const float LOG2 = 1.442695;
    float fog_density = 0.0045;
    vec4 fog_color = vec4(0.431372,0.458823,0.486274, 0.5);
    float z = gl_FragCoord.z / gl_FragCoord.w;
    float fog_factor = exp2( -fog_density*fog_density * z*z * LOG2 );
    fog_factor = clamp(fog_factor, 0.0, 1.0);

    color = mix(fog_color, color, fog_factor);

}