layout (location = 0) out vec4 oColour;

// OpenGL wiki: Recommends do not use vec3 because of drivers. hence the v4s...
layout (std140) uniform ub_world_lighting
{
   vec4 g_cube_min;
   vec4 g_cube_inv_range;

   vec4 g_water_plane;
   vec4 g_depth_bounds;

   vec4 g_daysky_colour;
   vec4 g_nightsky_colour;
   vec4 g_sunset_colour;
   vec4 g_ambient_colour;
   vec4 g_sunset_ambient;
   vec4 g_sun_colour;
   vec4 g_sun_dir;
   vec4 g_board_0;
   vec4 g_board_1;

   float g_water_fog;
   float g_time;
   float g_realtime;
   float g_shadow_length;
   float g_shadow_spread;

   float g_time_of_day;
   float g_day_phase;
   float g_sunset_phase;

   int g_light_preview;
   int g_shadow_samples;

   int g_debug_indices;
   int g_debug_complexity;
};

uniform sampler2D g_world_depth;
uniform samplerBuffer uLightsArray;
uniform usampler3D uLightsIndex;

#include "light_clearskies.glsl"

float world_depth_sample( vec3 pos )
{
   vec2 depth_coord = (pos.xz - g_depth_bounds.xy) * g_depth_bounds.zw; 
   return texture( g_world_depth, depth_coord ).r;
}

float world_water_depth( vec3 pos )
{
   float ref_depth = g_water_plane.y*g_water_plane.w;
   return world_depth_sample( pos ) - ref_depth;
}

float shadow_sample( vec3 co ){
   float height_sample = world_depth_sample( co );

   float fdelta = height_sample - co.y;
   return clamp( fdelta, 0.2, 0.4 )-0.2;
}

float newlight_compute_sun_shadow( vec3 co, vec3 dir ){
   if( g_shadow_samples == 0 ){
      return 1.0;
   }

   float fspread = g_shadow_spread;
   float flength = g_shadow_length;

   float famt = 0.0;
   famt += shadow_sample(co+(dir+vec3(-0.56,0.55, 0.30)*fspread)*flength*0.1);
   famt += shadow_sample(co+(dir+vec3( 0.80,0.68, 0.34)*fspread)*flength*0.2);
   famt += shadow_sample(co+(dir+vec3( 0.78,0.07,-0.06)*fspread)*flength*0.3);
   famt += shadow_sample(co+(dir+vec3(-0.59,0.07,-0.42)*fspread)*flength*0.4);

   //famt+=shadow_sample(co+(dir+vec3(-0.790,-0.933,-0.875)*fspread)*flength*0.5);
   //famt+=shadow_sample(co+(dir+vec3( 0.807,-0.690, 0.472)*fspread)*flength*0.6);
   //famt+=shadow_sample(co+(dir+vec3( 0.522,-0.379, 0.350)*fspread)*flength*0.7);
   //famt+=shadow_sample(co+(dir+vec3( 0.483, 0.201, 0.306)*fspread)*flength*0.8);

   return 1.0 - famt;
}

float newlight_specular( vec3 wnormal, vec3 dir, vec3 halfview, float exponent )
{
   vec3 specdir = reflect( -dir, wnormal );
   return pow(max(dot( halfview, specdir ), 0.0), exponent);
}

vec3 scene_apply_fog( vec3 vfrag, vec3 colour, float fdist ){
   float dist = pow(fdist*0.0010,0.78);
   return mix( vfrag, colour, min( 1.0, dist ) );
}

vec3 scene_calculate_light( int light_index, 
                            vec3 halfview, vec3 co, vec3 normal )
{
   vec4 light_colour = texelFetch( uLightsArray, light_index+0 );
   vec4 light_co     = texelFetch( uLightsArray, light_index+1 );
   vec4 light_dir    = texelFetch( uLightsArray, light_index+2 );

   vec3 light_delta = light_co.xyz-co;
   float dist2 = dot(light_delta,light_delta);

   light_delta = normalize( light_delta );

   float quadratic = dist2*100.0;
   float attenuation  = 1.0/( 1.0 + quadratic );
         attenuation *= max( dot( light_delta, normal ), 0.0 );

   float falloff = max( 0.0, 1.0-(dist2*light_co.w) );

   if( light_dir.w < 0.999999 ){
      float spot_theta = max( 0.0, dot( light_delta, -light_dir.xyz ) );
      falloff *= max( 0.0, (spot_theta - light_dir.w) / (1.0-light_dir.w) );
   }

   return light_colour.rgb * attenuation * falloff 
            * step( g_day_phase, light_colour.w );
}

vec3 scene_calculate_packed_light_patch( uint packed_index, 
                                         vec3 halfview, vec3 co, vec3 normal )
{
   uint light_count = packed_index & 0x3u;

   vec3 l = vec3(0.0);

   if( light_count >= 1u ){
      int index_0 = int( ((packed_index >>  2u) & 0x3ffu) * 3u );
      int index_1 = int( ((packed_index >> 12u) & 0x3ffu) * 3u );
      int index_2 = int( ((packed_index >> 22u) & 0x3ffu) * 3u );

      l += scene_calculate_light( index_0, halfview, co, normal );

      if( light_count >= 2u ){
         l += scene_calculate_light( index_1, halfview, co, normal );

         if( light_count >= 3u ){
            l += scene_calculate_light( index_2, halfview, co, normal );
         }
      }
   }

   return l;
}

vec3 world_compute_lighting( vec3 diffuse, vec3 normal, vec3 co,
                             float light_mask )
{
   if( g_light_preview == 1 )
      diffuse = vec3(0.75);

   // Lighting
   vec3 halfview = uCamera - co;
   float fdist = length(halfview);
   halfview /= fdist;

   float world_shadow = newlight_compute_sun_shadow( 
               co, g_sun_dir.xyz * (1.0/(max(g_sun_dir.y,0.0)+0.2)) );

   vec3 total_light = clearskies_lighting( 
                           normal, min( light_mask, world_shadow ), halfview );

   vec3 cube_coord = (co - g_cube_min.xyz) * g_cube_inv_range.xyz;
        cube_coord = floor( cube_coord );

   if( g_debug_indices == 1 )
   {
      return rand33(cube_coord);
   }

   if( g_debug_complexity == 1 )
   {
      ivec3 coord = ivec3( cube_coord );
      uvec4 index_sample = texelFetch( uLightsIndex, coord, 0 );

      uint light_count = (index_sample.x & 0x3u) + (index_sample.y & 0x3u);
      return vec3( float(light_count)*(1.0/6.0), 0.0, 0.5 );
   }

   // FIXME: this coord should absolutely must be clamped!
   
   ivec3 coord = ivec3( cube_coord );
   uvec4 index_sample = texelFetch( uLightsIndex, coord, 0 );

   total_light += 
      scene_calculate_packed_light_patch( index_sample.x,
                                          halfview, co, normal ) 
                                          * light_mask;
   total_light += 
      scene_calculate_packed_light_patch( index_sample.y,
                                          halfview, co, normal )
                                          * light_mask;

   // Take a section of the sky function to give us a matching fog colour

   vec3 fog_colour  = clearskies_ambient( -halfview );
   float sun_theta  = dot( -halfview, g_sun_dir.xyz );
   float sun_size   = max( 0.0, sun_theta * 0.5 + 0.5 );
   float sun_shape  = sun_size * max(g_sun_dir.y,0.0) * 0.5;
         
   vec3 sun_colour  = mix( vec3(1.0), g_sunset_colour.rgb, g_sunset_phase*0.5 );
        sun_colour *= sun_shape;

   fog_colour += sun_colour;
   return scene_apply_fog( diffuse * total_light, fog_colour, fdist );
}