// -*- mode: c -*-

struct Material {
  vec3 ambient;
  sampler2D ambientMap;
  bool useAmbientMap;
  vec3 diffuse;
  sampler2D diffuseMap;
  bool useDiffuseMap;
  vec3 specular;
  sampler2D specularMap;
  bool useSpecularMap;
  float shininess;
  sampler2D bumpMap;
  bool useBumpMap;
};

struct DirectionalLight {
  vec3 direction;
  vec3 ambient;
  vec3 diffuse;
  vec3 specular;
};

#ifdef GLSL120
varying vec3 fragNorm;
varying vec2 fragTex;
#else
in vec3 fragNorm;
in vec2 fragTex;
#endif

#ifdef GLSL330
out vec4 fragColor;
#endif

uniform Material material;
uniform DirectionalLight directionalLight;

void main() {
  vec3 baseAmbientColor;
  vec3 baseDiffuseColor;
  vec3 baseSpecularColor;
  if(material.useAmbientMap) {
#ifdef GLSL330
    baseAmbientColor = texture(material.ambientMap, fragTex).xyz;
#else
    baseAmbientColor = texture2D(material.ambientMap, fragTex).xyz;
#endif
  } else {
    baseAmbientColor = vec3(1.0, 1.0, 1.0);
  }
  if(material.useDiffuseMap) {
    // discard transparent fragments.
#ifdef GLSL330
    vec4 color = texture(material.diffuseMap, fragTex);
#else
    vec4 color = texture2D(material.diffuseMap, fragTex);
#endif
    if(color.a == 0.0) { discard; }
    baseDiffuseColor = color.xyz;
  } else {
    baseDiffuseColor = vec3(1.0, 1.0, 1.0);
  }
  if(material.useSpecularMap) {
#ifdef GLSL330
    baseSpecularColor = texture(material.specularMap, fragTex).xyz;
#else
    baseSpecularColor = texture2D(material.specularMap, fragTex).xyz;
#endif
  } else {
    baseSpecularColor = vec3(1.0, 1.0, 1.0);
  }
  vec3 ambientColor = material.ambient * baseAmbientColor * baseDiffuseColor;
  vec3 lightDir = normalize(-directionalLight.direction);
  float diffuseFactor = max(dot(lightDir, fragNorm), 0.0);
  vec3 diffuseColor = diffuseFactor * baseDiffuseColor * material.diffuse;
  vec3 reflectDir = reflect(-lightDir, fragNorm);
  float specularFactor = 0;
  if(material.shininess > 0) {
    specularFactor = pow(max(dot(lightDir, reflectDir), 0.0), material.shininess);
  }
  vec3 specularColor = specularFactor * baseSpecularColor * material.specular;
#ifdef GLSL330
  fragColor = vec4(ambientColor + diffuseColor + specularColor, 1.0);
#else
  gl_FragColor = vec4(ambientColor + diffuseColor + specularColor, 1.0);
#endif
}