out vec4 fragColor;

uniform sampler2D depthBuffer;
uniform sampler2D colorBuffer;
uniform sampler2D normalBuffer;
uniform usampler2D objectId;

uniform vec2 invertedViewportSize;
uniform mat4 WinMatrix; /* inverse WinMatrix */

uniform vec4 viewvecs[3];
uniform vec4 ssao_params;
uniform vec4 ssao_settings;
uniform vec2 curvature_settings;
uniform sampler2D ssao_jitter;

layout(std140) uniform samples_block
{
  vec4 ssao_samples[500];
};

#define ssao_samples_num ssao_params.x
#define jitter_tilling ssao_params.yz
#define ssao_iteration ssao_params.w

#define ssao_distance ssao_settings.x
#define ssao_factor_cavity ssao_settings.y
#define ssao_factor_edge ssao_settings.z
#define ssao_attenuation ssao_settings.w

vec3 get_view_space_from_depth(in vec2 uvcoords, in float depth)
{
  if (WinMatrix[3][3] == 0.0) {
    /* Perspective */
    float d = 2.0 * depth - 1.0;

    float zview = -WinMatrix[3][2] / (d + WinMatrix[2][2]);

    return zview * (viewvecs[0].xyz + vec3(uvcoords, 0.0) * viewvecs[1].xyz);
  }
  else {
    /* Orthographic */
    vec3 offset = vec3(uvcoords, depth);

    return viewvecs[0].xyz + offset * viewvecs[1].xyz;
  }
}

/* forward declaration */
void ssao_factors(in float depth,
                  in vec3 normal,
                  in vec3 position,
                  in vec2 screenco,
                  out float cavities,
                  out float edges);

void main()
{
  vec2 screenco = vec2(gl_FragCoord.xy) * invertedViewportSize;
  ivec2 texel = ivec2(gl_FragCoord.xy);

  float cavity = 0.0, edges = 0.0, curvature = 0.0;

#ifdef USE_CAVITY
  float depth = texelFetch(depthBuffer, texel, 0).x;
  vec3 position = get_view_space_from_depth(screenco, depth);
  vec3 normal_viewport = workbench_normal_decode(texelFetch(normalBuffer, texel, 0).rg);

  ssao_factors(depth, normal_viewport, position, screenco, cavity, edges);
#endif

#ifdef USE_CURVATURE
  curvature = calculate_curvature(
      objectId, normalBuffer, texel, curvature_settings.x, curvature_settings.y);
#endif

  float final_cavity_factor = clamp((1.0 - cavity) * (1.0 + edges) * (1.0 + curvature), 0.0, 4.0);

  /* Using UNORM render target so compress the range. */
  fragColor = vec4(final_cavity_factor / CAVITY_BUFFER_RANGE);
}