#include "model_fs.glsl"
#include "light.glsl"
#include "brdf.glsl"
#include "sh_lighting.glsl"
#include "lightmap.glsl"

#ifdef SHADING_PHONG
void main() {
    vec3 n = normalize(v_normal_ws);

    vec4 lit = vec4(1.0, 1.0, 1.0, 1.0);
    // SH lighting
    if (!u_texlit) {
        vec3 result = sh_lighting(n);
        if( (result.x*result.x+result.y*result.y+result.z*result.z) > 0.0 ) lit = vec4(result, 1.0);
    }

    // analytical lights
    lit += vec4(lighting(), 0.0);

    // base
    vec4 diffuse;

    if(u_matcaps) {
        vec2 muv = vec2(view * vec4(v_normal_ws, 0))*0.5+vec2(0.5,0.5); // normal (model space) to view space
        diffuse = texture(u_texture2d, vec2(muv.x, 1.0-muv.y));
    } else if(u_textured) {
        diffuse = texture(u_texture2d, v_texcoord);
    } else {
        diffuse = u_diffuse; // * v_color;
    }

    diffuse *= v_color;

    if (u_texlit) {
        vec4 litsample = texture(u_lightmap, v_texcoord);

        if (u_texmod) {
            diffuse *= litsample;
        } else {
            diffuse += litsample;
        }

        diffuse.rgb += sh_lighting(n);
    }
    
    // lighting mix
    fragcolor = diffuse * lit * shadowing();
    
    // rimlight
    #ifdef RIM
    {
        vec3 n = normalize(mat3(M) * v_normal);  // convert normal to view space
        vec3 p = (M * vec4(v_position,1.0)).xyz; // convert position to view space
        vec3 v = vec3(0,-1,0);
        if (!u_rimambient) {
            v = normalize(u_rimpivot-p);
        }
        float rim = 1.0 - max(dot(v,n), 0.0);
        vec3 col = u_rimcolor*(pow(smoothstep(1.0-u_rimrange.x,u_rimrange.y,rim), u_rimrange.z));
        fragcolor += vec4(col, 0.0);
    }
    #endif
}
#endif
#ifdef SHADING_VERTEXLIT
void main() {
    vec3 n = normalize(v_normal_ws);

    vec4 lit = vec4(1.0, 1.0, 1.0, 1.0);
    // SH lighting
    if (!u_texlit) {
        vec3 result = sh_lighting(n);
        if( (result.x*result.x+result.y*result.y+result.z*result.z) > 0.0 ) lit = vec4(result, 1.0);
    }

    lit += vec4(v_vertcolor, 0.0);

    // base
    vec4 diffuse;

    if(u_matcaps) {
        vec2 muv = vec2(view * vec4(v_normal_ws, 0))*0.5+vec2(0.5,0.5); // normal (model space) to view space
        diffuse = texture(u_texture2d, vec2(muv.x, 1.0-muv.y));
    } else if(u_textured) {
        diffuse = texture(u_texture2d, v_texcoord);
    } else {
        diffuse = u_diffuse; // * v_color;
    }

    // vec4 vertcolor4 = vec4(v_vertcolor, 1.0);
    // if (length(diffuse*v_color) > length(vertcolor4)) {
        diffuse *= v_color;
    // }

    if (u_texlit) {
        vec4 litsample = texture(u_lightmap, v_texcoord);

        if (u_texmod) {
            diffuse *= litsample;
        } else {
            diffuse += litsample;
        }

        diffuse.rgb += sh_lighting(n);
    }
    
    // lighting mix
    fragcolor = diffuse * lit * shadowing();
    
    // rimlight
    #ifdef RIM
    {
        vec3 n = normalize(mat3(M) * v_normal);  // convert normal to view space
        vec3 p = (M * vec4(v_position,1.0)).xyz; // convert position to view space
        vec3 v = vec3(0,-1,0);
        if (!u_rimambient) {
            v = normalize(u_rimpivot-p);
        }
        float rim = 1.0 - max(dot(v,n), 0.0);
        vec3 col = u_rimcolor*(pow(smoothstep(1.0-u_rimrange.x,u_rimrange.y,rim), u_rimrange.z));
        fragcolor += vec4(col, 0.0);
    }
    #endif
}
#endif
#ifdef SHADING_PBR
void main(void)
{
    vec3 baseColor = vec3( 0.5, 0.5, 0.5 );
    float roughness = 1.0;
    float metallic = 0.0;
    float ao = 1.0;
    float alpha = 1.0;

    vec4 baseColor_alpha;
    if ( map_albedo.has_tex )
        baseColor_alpha = sample_colormap( map_albedo, v_texcoord );
    else
        baseColor_alpha = sample_colormap( map_diffuse, v_texcoord );
    baseColor = baseColor_alpha.xyz;
    alpha = baseColor_alpha.w;

    if( map_metallic.has_tex && map_roughness.has_tex ) {
        metallic = sample_colormap( map_metallic, v_texcoord ).x;
        roughness = sample_colormap( map_roughness, v_texcoord ).x;
    }
    else if( map_roughness.has_tex ) {
        //< @r-lyeh, metalness B, roughness G, (@todo: self-shadowing occlusion R; for now, any of R/B are metallic)
        metallic = sample_colormap( map_roughness, v_texcoord ).b;// + sample_colormap( map_roughness, v_texcoord ).r;
        roughness = sample_colormap( map_roughness, v_texcoord ).g;
    }

    if ( map_ao.has_tex )
        ao = sample_colormap( map_ao, v_texcoord ).x;
    else if ( map_ambient.has_tex )
        ao = sample_colormap( map_ambient, v_texcoord ).x;

    vec3 emissive = sample_colormap( map_emissive, v_texcoord ).rgb;

    vec3 normalmap = texture( map_normals_tex, v_texcoord ).xyz * vec3(2.0) - vec3(1.0);
    float normalmap_mip = textureQueryLod( map_normals_tex, v_texcoord ).x;
    float normalmap_length = length(normalmap);
    normalmap /= normalmap_length;

    vec3 normal = v_normal_ws;

    if ( map_normals.has_tex )
    {
        // Mikkelsen's tangent space normal map decoding. See http://mikktspace.com/ for rationale.
        vec3 bi = cross( v_normal_ws, v_tangent );
        vec3 nmap = normalmap.xyz;
        normal = nmap.x * v_tangent + nmap.y * bi + nmap.z * v_normal_ws;
    }

    normal = normalize( normal );

    if( USE_MAP_DEBUGGING && !USE_AMBIENT_DEBUGGING )
    {
        vec3 c = vec3(1., 0., 0.);
        float x = gl_FragCoord.x / resolution.x;
        float y = gl_FragCoord.y / resolution.y;
        if ( y < (7.0/7.0) ) c = vec3(.5) + .5*v_normal_ws;
        if ( y < (6.0/7.0) ) c = vec3(.5) + .5*normalmap;
        if ( y < (5.0/7.0) ) c = vec3(ao);
        if ( y < (4.0/7.0) ) c = vec3(emissive);
        if ( y < (3.0/7.0) ) c = vec3(metallic);
        if ( y < (2.0/7.0) ) c = vec3(roughness);
        if ( y < (1.0/7.0) ) c = baseColor;
        fragcolor = vec4(c, 1.);
        return;
    }

    if (USE_NORMAL_VARIATION_TO_ROUGHNESS)
    {
        // Try to reduce specular aliasing by increasing roughness when minified normal maps have high variation.
        float variation = 1. - pow( normalmap_length, 8. );
        float minification = clamp( normalmap_mip - 2., 0., 1. );
        roughness = mix( roughness, 1.0, variation * minification );
    }

    fragcolor = baseColor_alpha;


    vec3 N = normal;
    vec3 V = normalize( v_to_camera );

    vec3 Lo = vec3(0.);
    vec3 F0 = vec3(0.04);
    F0 = mix( F0, baseColor, metallic );

    bool use_ibl = has_tex_skysphere;
    // use_ibl = false;

    // Add contributions from analytic lights.

    {
        for ( int i = 0; i < u_num_lights; i++ )
        {
            light_t l = u_lights[i];
            vec3 lightDir;
            float attenuation = 1.0;

            if (l.type == LIGHT_DIRECTIONAL) {
                lightDir = normalize(-l.dir);
            } else if (l.type == LIGHT_POINT || l.type == LIGHT_SPOT) {
                vec3 toLight = l.pos - v_position_ws;
                lightDir = normalize(toLight);
                float distance = length(toLight);
                attenuation = 1.0 / (l.constant + l.linear * distance + l.quadratic * (distance * distance));

                if (l.type == LIGHT_SPOT) {
                    float angle = dot(l.dir, -lightDir);
                    if (angle > l.outerCone) {
                        float intensity = (angle-l.outerCone)/(l.innerCone-l.outerCone);
                        attenuation *= clamp(intensity, 0.0, 1.0);
                    } else {
                        attenuation = 0.0;
                    }
                }
            }

            // fast-rejection for faraway vertices
            if (attenuation <= 0.01) {
                continue;
            }

            vec3 radiance = l.diffuse * BOOST_LIGHTING;

            vec3 L = normalize( lightDir );
            vec3 H = normalize( V + L );

            vec3 F = fresnel_schlick( H, V, F0 );
            vec3 kS = F;
            vec3 kD = vec3(1.0) - kS;
            kD *= 1.0 - metallic;

            // Premultiplied alpha applied to the diffuse component only
            kD *= alpha;

            float D = distribution_ggx( N, H, roughness );
            float G = geometry_smith( N, V, L, roughness );

            vec3 num = D * F * G;
            float denom = 4. * max( 0., dot( N, V ) ) * max( 0., dot( N, L ) );

            vec3 specular = kS * (num / max( 0.001, denom ));

            float NdotL = max( 0., dot( N, L ) );

            Lo += ( kD * ( baseColor / PI ) + specular ) * radiance * NdotL * attenuation;
        }
    }

    vec3 ambient = sample_colormap( map_ambient, v_texcoord ).xyz;
    vec3 diffuse_ambient;
    vec3 specular_ambient;

    if ( use_ibl )
    {
        // Image based lighting.
        // Based on https://learnopengl.com/PBR/IBL/Diffuse-irradiance

        vec3 irradiance = vec3(0.);

        if ( USE_BRUTEFORCE_IRRADIANCE )
        {
            irradiance = sample_irradiance_slow( normal, v_tangent );
        }
        else
        {
            irradiance = sample_irradiance_fast( normal, v_tangent );
        }

        // Compute the Fresnel term for a perfect mirror reflection with L = R.
        // In this case the halfway vector H = N.
        //
        // We use a modified Fresnel function that dampens specular reflections of very
        // rough surfaces to avoid too bright pixels at grazing angles.
        vec3 F = fresnel_schlick_roughness( N, V, F0, roughness );
        vec3 kS = F;

        // Subtract the amount of reflected light (specular) to get the energy left for
        // absorbed (diffuse) light.
        vec3 kD = vec3(1.) - kS;

        // Metallic surfaces have only a specular reflection.
        kD *= 1.0 - metallic;

        // Premultiplied alpha applied to the diffuse component only
        kD *= alpha;

        // Modulate the incoming lighting with the diffuse color: some wavelengths get absorbed.
        diffuse_ambient = irradiance * baseColor;

        // Ambient light also has a specular part.
        specular_ambient = specular_ibl( V, normal, roughness, F );

        // Ambient occlusion tells us the fraction of sky light that reaches this point.
        if (USE_SPECULAR_AO_ATTENUATION)
        {
            ambient = ao * (kD * diffuse_ambient + specular_ambient);
        }
        else
        {
            // We don't attenuate specular_ambient ambient here with AO which might cause flickering in dark cavities.
            ambient = ao * (kD * diffuse_ambient) + specular_ambient;
        }
    }

    vec3 color = (ambient + Lo) + emissive;

    if ( USE_AMBIENT_DEBUGGING )
    {
        float y = gl_FragCoord.y / resolution.y;
        if( USE_MAP_DEBUGGING && y > 0.5 )
        {
            if ( (y-0.5) < (7.0/7.0/2.0) ) color = vec3(.5) + .5*v_normal_ws;
            if ( (y-0.5) < (6.0/7.0/2.0) ) color = vec3(.5) + .5*normalmap;
            if ( (y-0.5) < (5.0/7.0/2.0) ) color = vec3(ao);
            if ( (y-0.5) < (4.0/7.0/2.0) ) color = vec3(emissive);
            if ( (y-0.5) < (3.0/7.0/2.0) ) color = vec3(metallic);
            if ( (y-0.5) < (2.0/7.0/2.0) ) color = vec3(roughness);
            if ( (y-0.5) < (1.0/7.0/2.0) ) color = baseColor;
        } else {
            float x = gl_FragCoord.x / resolution.x;
            if ( x < 0.33 )
                    color = specular_ambient;
            else if( x > 0.66 )
                    color = diffuse_ambient;
        }
    }

    // dither with noise.
    // float dither = random( uvec3( floatBitsToUint( gl_FragCoord.xy ), frame_count ) );
    // color += BOOST_NOISE * vec3( (-1.0/256.) + (2./256.) * dither );

#if 0 // original
    // basic tonemap and gamma correction
    color = color / ( vec3(1.) + color );
    color = pow( color, vec3(1. / 2.2) );
#elif 0
    // filmic tonemapper
    vec3 linearColor = color;
    vec3 x = max(vec3(0.0), linearColor - 0.004);
    color = (x * (6.2 * x + 0.5)) / (x * (6.2 * x + 1.7) + 0.06);
    // gamma correction
    // color = pow( color, vec3(1. / 2.2) );
#elif 0
    // aces film (CC0, src: https://knarkowicz.wordpress.com/2016/01/06/aces-filmic-tone-mapping-curve/)
    vec3 x = color;
    float a = 2.51f;
    float b = 0.03f;
    float c = 2.43f;
    float d = 0.59f;
    float e = 0.14f;
    color = clamp((x*(a*x+b))/(x*(c*x+d)+e), 0.0, 1.0);
    // gamma correction
#endif
    // color = pow( color, vec3(1. / 2.2) );

    // Technically this alpha may be too transparent, if there is a lot of reflected light we wouldn't
    // see the background, maybe we can approximate it well enough by adding a fresnel term
    fragcolor = vec4( color * shadowing().xyz, alpha );
}

#endif