#version 330

in vec2 fragTexCoord;
in vec4 fragColor;
in vec3 fragPosition;
in vec3 fragNormal;

uniform sampler2D texture0;
uniform vec4 sunlightColor;
uniform vec4 skyColor;

uniform vec3 lightDir;

out vec4 finalColor;

void main()
{
    vec4 texelColor = texture(texture0, fragTexCoord);

    vec3 N = normalize(fragNormal);
    vec3 L = normalize(lightDir);

    float ndotl = max(dot(N, L), 0.0);
    float ambient = 0.1;
    float sunfactor = ambient + (1.0 - ambient) * ndotl;

    sunfactor *= 1+min(0, L.y);
    vec3 Lmoon = normalize(-lightDir);
    float ndotlMoon = max(dot(N, Lmoon), 0.0);
    float moonfactor = (ambient + (1.0 - ambient) * ndotlMoon) * 8;
    moonfactor *= max(0, -L.y);

    // In fragColor, 'r' is blocklight R, 'g' is blocklight G, 'b' is blocklight B and 'a' is sunlight
    float sunlight = fragColor.a;
    texelColor.r *= sunlight * sunlightColor.r * (sunfactor+moonfactor) + fragColor.r;
    texelColor.g *= sunlight * sunlightColor.g * (sunfactor+moonfactor) + fragColor.g;
    texelColor.b *= sunlight * sunlightColor.b * (sunfactor+moonfactor) + fragColor.b;
    float highlight = texelColor.a;
    if(highlight < 0.25) highlight = 0;
    float highlight_final = abs(N.y)*highlight * 4;
    vec3 highlightColor = sunlightColor.rgb*highlight_final*sunlight;
    highlightColor.r += fragColor.r*highlight_final;
    highlightColor.g += fragColor.g*highlight_final;
    highlightColor.b += fragColor.b*highlight_final;
    finalColor = texelColor + vec4(highlightColor, min(1.0, highlight_final));
}