// -*- mode: C; -*-
// Licence: GPL v2
// Author: Vivian Meazza. 

#version 120

varying vec4  ecPosition;
varying vec3  VNormal;
varying vec3  Normal;
varying vec4  constantColor;
varying vec3  vViewVec;
varying vec3  reflVec;

varying vec4 Diffuse;
varying vec3 lightDir, halfVector;
varying float alpha, fogCoord;

uniform samplerCube Environment;
uniform sampler2D Rainbow;
uniform sampler2D BaseTex;
uniform sampler2D Fresnel;

uniform float refl_correction;
uniform float rainbowiness;
uniform float fresneliness;
uniform float ambient_correction;


void main (void)
{
    if (!gl_FrontFacing) discard;

    vec3 n, halfV;
    float NdotL, NdotHV;
    vec4 color = constantColor;
    vec4 specular = vec4(0.0);
    n = VNormal;
    NdotL = max(0.0, dot(n, lightDir));

    // calculate the specular light
    if (NdotL > 0.0) {
        color += Diffuse * NdotL;
        halfV = normalize(halfVector);
        NdotHV = max(dot(n, halfV), 0.0);
        if (gl_FrontMaterial.shininess > 0.0)
            specular.rgb = (gl_FrontMaterial.specular.rgb
            * gl_LightSource[0].specular.rgb
            * pow(NdotHV, gl_FrontMaterial.shininess));
    }

    color.a = alpha;
    color = clamp(color, 0.0, 1.0);
    vec4 texel = texture2D(BaseTex, gl_TexCoord[0].st);
    vec4 texelcolor = color * texel + specular;

    // calculate the fog factor
    float fogCoord = ecPosition.z;
    const float LOG2 = 1.442695;
    float fogFactor = exp2(-gl_Fog.density * gl_Fog.density * fogCoord * fogCoord * LOG2);
    fogFactor = clamp(fogFactor, 0.0, 1.0);

    if(gl_Fog.density == 1.0)
        fogFactor=1.0;

    vec3 normal = normalize(VNormal);
    vec3 viewVec = normalize(vViewVec);

    // Map a rainbowish color
    float v = dot(viewVec, normal);
    vec4 rainbow = texture2D(Rainbow, vec2(v, 0.0));

    // Map a fresnel effect
    vec4 fresnel = texture2D(Fresnel, vec2(v, 0.0));

    // map the refection of the environment
    vec4 reflection = textureCube(Environment, reflVec);

    // set the reflectivity proportional to shininess with user 
    // input ambient
    float transparency_offset = clamp(refl_correction, -1.0, 1.0);
    float reflFactor = (gl_FrontMaterial.shininess / 128) + transparency_offset;
    reflFactor = clamp(reflFactor, 0.0, 1.0);

    // set adjust ambient ambient
    float ambient_offset = clamp(ambient_correction, -1.0, 1.0);
    vec4 ambient_Correction = mix(gl_LightSource[0].ambient, vec4(1.0, 1.0, 0.9, 1.0), 0.5) 
        * ambient_offset;

    // add fringing fresnel and rainbow effects and modulate by reflection
    vec4 reflcolor = mix(reflection, rainbow, rainbowiness * v);
    vec4 reflfrescolor = mix(reflcolor, fresnel, fresneliness * v);
    vec4 raincolor = vec4(reflfrescolor.rgb, 1.0) * reflFactor;
    vec4 mixedcolor = mix(texel, raincolor, reflFactor);

    // the final reflection
    vec4 reflColor = color * mixedcolor + specular + ambient_Correction ;
    reflColor = clamp(reflColor, 0.0, 1.0);

    gl_FragColor = mix(gl_Fog.color, reflColor, fogFactor);
}