//! @file DeclarationsImpl.glsl includes implementation of common functions and properties accessors
#if defined(FRAGMENT_SHADER)

#if defined(OCC_DEPTH_PEEL_OIT)
uniform sampler2D occDepthPeelingDepth;
uniform sampler2D occDepthPeelingFrontColor;
int IsFrontPeelLayer = -1;
bool occFragEarlyReturn()
{
  #define THE_DEPTH_CLEAR_VALUE -1e15f
  ivec2  aFragCoord = ivec2 (gl_FragCoord.xy);
  vec2   aLastDepth = texelFetch (occDepthPeelingDepth, aFragCoord, 0).rg;
  occPeelFrontColor = texelFetch (occDepthPeelingFrontColor, aFragCoord, 0);
  occPeelDepth.rg   = vec2 (THE_DEPTH_CLEAR_VALUE); // depth value always increases, so that MAX blend equation can be used
  occPeelBackColor  = vec4 (0.0); // back color is blend after each peeling pass

  float aNearDepth = -aLastDepth.x;
  float aFarDepth  =  aLastDepth.y;
  float aFragDepth = gl_FragCoord.z; // 0 - 1
  if (aFragDepth < aNearDepth || aFragDepth > aFarDepth)
  {
    return true; // skip peeled depth
  }
  else if (aFragDepth > aNearDepth && aFragDepth < aFarDepth)
  {
    // to be rendered at next peeling pass
    occPeelDepth.rg = vec2 (-aFragDepth, aFragDepth);
    return true;
  }

  IsFrontPeelLayer = (gl_FragCoord.z == aNearDepth) ? 1 : 0;
  return false;
}
#else
bool occFragEarlyReturn() { return false; }
#endif

void occSetFragColor (in vec4 theColor)
{
#if defined(OCC_ALPHA_TEST)
  if (theColor.a < occAlphaCutoff) discard;
#endif
#if defined(OCC_WRITE_WEIGHT_OIT_COVERAGE)
  float aWeight     = theColor.a * clamp (1e+2 * pow (1.0 - gl_FragCoord.z * occOitDepthFactor, 3.0), 1e-2, 1e+2);
  occFragCoverage.r = theColor.a * aWeight;
  occFragColor      = vec4 (theColor.rgb * theColor.a * aWeight, theColor.a);
#elif defined(OCC_DEPTH_PEEL_OIT)
  if (IsFrontPeelLayer == 1) // front is blended directly
  {
    vec4 aLastColor = occPeelFrontColor;
    float anAlphaMult = 1.0 - aLastColor.a;
    occPeelFrontColor.rgb = aLastColor.rgb + theColor.rgb * theColor.a * anAlphaMult;
    occPeelFrontColor.a = 1.0 - anAlphaMult * (1.0 - theColor.a);
  }
  else if (IsFrontPeelLayer == 0) // back is blended afterwards
  {
    occPeelBackColor = theColor;
  }
#else
  occFragColor = theColor;
#endif
}
#endif

#if defined(THE_MAX_LIGHTS) && (THE_MAX_LIGHTS > 0)
// arrays of light sources
uniform               vec4 occLightSources[THE_MAX_LIGHTS * 4]; //!< packed light sources parameters
uniform THE_PREC_ENUM int occLightSourcesTypes[THE_MAX_LIGHTS]; //!< packed light sources types
#endif

#if defined(THE_IS_PBR)
vec3 occDiffIBLMap (in vec3 theNormal)
{
  vec3 aSHCoeffs[9];
  for (int i = 0; i < 9; ++i)
  {
    aSHCoeffs[i] = occTexture2D (occDiffIBLMapSHCoeffs, vec2 ((float(i) + 0.5) / 9.0, 0.0)).rgb;
  }
  return aSHCoeffs[0]

       + aSHCoeffs[1] * theNormal.x
	   + aSHCoeffs[2] * theNormal.y
	   + aSHCoeffs[3] * theNormal.z

	   + aSHCoeffs[4] * theNormal.x * theNormal.z
	   + aSHCoeffs[5] * theNormal.y * theNormal.z
	   + aSHCoeffs[6] * theNormal.x * theNormal.y

	   + aSHCoeffs[7] * (3.0 * theNormal.z * theNormal.z - 1.0)
	   + aSHCoeffs[8] * (theNormal.x * theNormal.x - theNormal.y * theNormal.y);
}
#endif

// front and back material properties accessors
#if defined(THE_IS_PBR)
uniform vec4 occPbrMaterial[3 * 2];

#define MIN_ROUGHNESS 0.01
float occRoughness (in float theNormalizedRoughness) { return theNormalizedRoughness * (1.0 - MIN_ROUGHNESS) + MIN_ROUGHNESS; }
vec4  occPBRMaterial_Color(in bool theIsFront)     { return theIsFront ? occPbrMaterial[0]     : occPbrMaterial[3]; }
vec3  occPBRMaterial_Emission(in bool theIsFront)  { return theIsFront ? occPbrMaterial[1].rgb : occPbrMaterial[4].rgb; }
float occPBRMaterial_IOR(in bool theIsFront)       { return theIsFront ? occPbrMaterial[1].w   : occPbrMaterial[4].w; }
float occPBRMaterial_Metallic(in bool theIsFront)  { return theIsFront ? occPbrMaterial[2].b   : occPbrMaterial[5].b; }
float occPBRMaterial_NormalizedRoughness(in bool theIsFront) { return theIsFront ? occPbrMaterial[2].g : occPbrMaterial[5].g; }
#else
uniform vec4 occCommonMaterial[4 * 2];

vec4  occMaterial_Diffuse(in bool theIsFront)   { return theIsFront ? occCommonMaterial[0]     : occCommonMaterial[4]; }
vec3  occMaterial_Emission(in bool theIsFront)  { return theIsFront ? occCommonMaterial[1].rgb : occCommonMaterial[5].rgb; }
vec3  occMaterial_Specular(in bool theIsFront)  { return theIsFront ? occCommonMaterial[2].rgb : occCommonMaterial[6].rgb; }
float occMaterial_Shininess(in bool theIsFront) { return theIsFront ? occCommonMaterial[2].a   : occCommonMaterial[6].a; }
vec3  occMaterial_Ambient(in bool theIsFront)   { return theIsFront ? occCommonMaterial[3].rgb : occCommonMaterial[7].rgb; }
#endif

// 2D texture coordinates transformation
vec2  occTextureTrsf_Translation(void) { return occTexTrsf2d[0].xy; }
vec2  occTextureTrsf_Scale(void)       { return occTexTrsf2d[0].zw; }
float occTextureTrsf_RotationSin(void) { return occTexTrsf2d[1].x; }
float occTextureTrsf_RotationCos(void) { return occTexTrsf2d[1].y; }
//! @endfile DeclarationsImpl.glsl