precision highp float;

// Inputs from vertex shader
in vec4 Position;     // Fragment position in camera coordinates
in vec3 Normal;       // Fragment normal in camera coordinates
in vec2 FragTexcoord; // Fragment texture coordinates

#include <lights>
#include <material>
#include <phong_model>

// Final fragment color
out vec4 FragColor;

void main() {

    // Compute final texture color
    vec4 texMixed = vec4(1);
    #if MAT_TEXTURES > 0
        bool firstTex = true;
        if (MatTexVisible(0)) {
            vec4 texColor = texture(MatTexture[0], FragTexcoord * MatTexRepeat(0) + MatTexOffset(0));
            if (firstTex) {
                texMixed = texColor;
                firstTex = false;
            } else {
                texMixed = Blend(texMixed, texColor);
            }
        }
        #if MAT_TEXTURES > 1
            if (MatTexVisible(1)) {
                vec4 texColor = texture(MatTexture[1], FragTexcoord * MatTexRepeat(1) + MatTexOffset(1));
                if (firstTex) {
                    texMixed = texColor;
                    firstTex = false;
                } else {
                    texMixed = Blend(texMixed, texColor);
                }
            }
            #if MAT_TEXTURES > 2
                if (MatTexVisible(2)) {
                    vec4 texColor = texture(MatTexture[2], FragTexcoord * MatTexRepeat(2) + MatTexOffset(2));
                    if (firstTex) {
                        texMixed = texColor;
                        firstTex = false;
                    } else {
                        texMixed = Blend(texMixed, texColor);
                    }
                }
            #endif
        #endif
    #endif

    // Combine material with texture colors
    vec4 matDiffuse = vec4(MatDiffuseColor, MatOpacity) * texMixed;
    vec4 matAmbient = vec4(MatAmbientColor, MatOpacity) * texMixed;

    // Normalize interpolated normal as it may have shrinked
    vec3 fragNormal = normalize(Normal);

    // Calculate the direction vector from the fragment to the camera (origin)
    vec3 camDir = normalize(-Position.xyz);

    // Workaround for gl_FrontFacing
    vec3 fdx = dFdx(Position.xyz);
    vec3 fdy = dFdy(Position.xyz);
    vec3 faceNormal = normalize(cross(fdx,fdy));
    if (dot(fragNormal, faceNormal) < 0.0) { // Back-facing
        fragNormal = -fragNormal;
    }

    // Calculates the Ambient+Diffuse and Specular colors for this fragment using the Phong model.
    vec3 Ambdiff, Spec;
    phongModel(Position, fragNormal, camDir, vec3(matAmbient), vec3(matDiffuse), Ambdiff, Spec);

    // Final fragment color
    FragColor = min(vec4(Ambdiff + Spec, matDiffuse.a), vec4(1.0));
}