#ifndef SHADOWMAP_GLSL
#define SHADOWMAP_GLSL

#include "utils.glsl"

uniform bool u_shadow_receiver;
uniform float u_cascade_distances[MAX_LIGHTS * NUM_SHADOW_CASCADES];
uniform samplerCube shadowMap[MAX_LIGHTS];
uniform sampler2D shadowMap2D[MAX_LIGHTS * NUM_SHADOW_CASCADES];
uniform sampler3D shadow_offsets;
uniform int shadow_filter_size;
uniform int shadow_window_size;
uniform float shadow_offset_radius;

// const float bias_modifier[NUM_SHADOW_CASCADES] = float[NUM_SHADOW_CASCADES](0.95, 0.35, 0.20, 0.1, 0.1, 0.1);
const float bias_modifier[NUM_SHADOW_CASCADES] = float[NUM_SHADOW_CASCADES](1.0, 6.0, 9.0, 16.0);
// const float bias_modifier[NUM_SHADOW_CASCADES] = float[NUM_SHADOW_CASCADES](0.95, 0.35, 0.20, 0.15);

//// From http://fabiensanglard.net/shadowmappingVSM/index.php
float shadow_vsm(float distance, vec3 dir, int light_index, float min_variance, float variance_transition) {
    distance = distance/200;
    
    // Define offsets for 3x3 PCF
    vec3 offsets[9] = vec3[9](
        vec3(-1, -1, 0) * 0.01,
        vec3( 0, -1, 0) * 0.01,
        vec3( 1, -1, 0) * 0.01,
        vec3(-1,  0, 0) * 0.01,
        vec3( 0,  0, 0) * 0.01,
        vec3( 1,  0, 0) * 0.01,
        vec3(-1,  1, 0) * 0.01,
        vec3( 0,  1, 0) * 0.01,
        vec3( 1,  1, 0) * 0.01
    );
    
    float shadow = 0.0;

    // Perform 3x3 PCF
    for (int i = 0; i < 9; i++) {
        vec3 sampleDir = dir + offsets[i] * (rand(vec2(v_position_ws.x + offsets[i].x, v_position_ws.y + offsets[i].y))*1.75f + 1.25f);
        vec2 moments = texture(shadowMap[light_index], sampleDir).rg;

        // If the shadow map is sampled outside of its bounds, add 1.0
        if (moments.x == 1.0 && moments.y == 1.0) {
            shadow += 1.0;
            continue;
        }
        
        // Surface is fully lit if the current fragment is before the light occluder
        if (distance <= moments.x) {
            shadow += 1.0;
            continue;
        }
        
        // Calculate VSM for this sample
        float p = step(distance, moments.x);
        float variance = max(moments.y - (moments.x * moments.x), min_variance);
        float d = distance - moments.x;
        float p_max = linstep(variance_transition, 1.0, variance / (variance + d*d));
        
        shadow += min(max(p, p_max), 1.0);
    }
    
    // Average the results
    return shadow / 9.0;
}

float shadow_csm(float distance, vec3 lightDir, int light_index, float shadow_bias, float normal_bias) {
    // Determine which cascade to use
    int cascade_index = -1;
    int min_cascades_range = light_index * NUM_SHADOW_CASCADES;
    int max_cascades_range = min_cascades_range + NUM_SHADOW_CASCADES;
    for (int i = min_cascades_range; i < max_cascades_range; i++) {
        if (distance < u_cascade_distances[i]) {
            cascade_index = i;
            break;
        }
    }
    if (cascade_index == -1) {
        cascade_index = max_cascades_range - 1;
    }

    light_t light = u_lights[light_index];
    int matrix_index = cascade_index - min_cascades_range;

    vec4 fragPosLightSpace = light.shadow_matrix[matrix_index] * vec4(v_position_ws, 1.0);

    // Perform perspective divide
    vec3 projCoords = fragPosLightSpace.xyz / fragPosLightSpace.w;
    
    // Transform to [0,1] range
    projCoords = projCoords * 0.5 + 0.5;
    vec4 sc = vec4(projCoords, 1.0);

    float currentDepth = projCoords.z;

    if (currentDepth > 1.0) {
        return 1.0;
    }

    // Calculate bias
    vec3 normal = normalize(vneye.xyz);
    float bias = max(normal_bias * bias_modifier[matrix_index] * (1.0 - dot(normal, lightDir)), shadow_bias);
    bias *= 1 / (u_cascade_distances[cascade_index]);
 
    // CSM
    float shadow = 0.0;
    vec2 texelSize = 1.0 / textureSize(shadowMap2D[cascade_index], 0);

    // Get the offset coordinates
    ivec3 ofs_coord = ivec3(0);
    vec2 ofs = mod(gl_FragCoord.xy, vec2(shadow_window_size));
    ofs_coord.yz = ivec2(ofs);
    float ofs_sum = 0.0;
    int samples_div2 = int(shadow_filter_size * shadow_filter_size / 2.0);

    for (int i = 0; i < 4; i++) {
        ofs_coord.x = i;
        vec4 offsets = texelFetch(shadow_offsets, ofs_coord, 0) * shadow_offset_radius;
        sc.xy = projCoords.xy + offsets.rg * texelSize;
        float csmDepth = texture(shadowMap2D[cascade_index], sc.xy).r;
        ofs_sum += currentDepth - bias > csmDepth ? 1.0 : 0.0;

        sc.xy = projCoords.xy + offsets.ba * texelSize;
        csmDepth = texture(shadowMap2D[cascade_index], sc.xy).r;
        ofs_sum += currentDepth - bias > csmDepth ? 1.0 : 0.0;
    }

    float shadow_sum = ofs_sum / 8.0;

    if (shadow_sum != 0.0 && shadow_sum != 1.0) {
        for (int i = 4; i < samples_div2; i++) {
            ofs_coord.x = i;
            vec4 offsets = texelFetch(shadow_offsets, ofs_coord, 0) * shadow_offset_radius;
            sc.xy = projCoords.xy + offsets.rg * texelSize;
            float csmDepth = texture(shadowMap2D[cascade_index], sc.xy).r;
            ofs_sum += currentDepth - bias > csmDepth ? 1.0 : 0.0;

            sc.xy = projCoords.xy + offsets.ba * texelSize;
            csmDepth = texture(shadowMap2D[cascade_index], sc.xy).r;
            ofs_sum += currentDepth - bias > csmDepth ? 1.0 : 0.0;
        }

        shadow_sum = ofs_sum / (samples_div2 * 2.0);
    }
    return 1.0 - shadow_sum;
}

vec4 shadowmap(int idx, in vec4 peye, in vec4 neye) {
    vec3 fragment = vec3(peye);
    float shadowFactor = 1.0;
    light_t light = u_lights[idx];

    if (light.processed_shadows) {
        if (light.type == LIGHT_DIRECTIONAL) {
            shadowFactor = shadow_csm(-peye.z, light.dir, idx, light.shadow_bias, light.normal_bias);
        } else if (light.type == LIGHT_POINT || light.type == LIGHT_SPOT) {
            vec3 light_pos = (view * vec4(light.pos, 1.0)).xyz;
            vec3 dir = light_pos - fragment;
            vec4 sc = inv_view * vec4(dir, 0.0);
            shadowFactor = shadow_vsm(length(dir), -sc.xyz, idx, light.min_variance, light.variance_transition);
        }
    }

    return vec4(vec3(shadowFactor), 1.0);
}

vec4 shadowing(int idx) {
    if (u_shadow_receiver) {
        return shadowmap(idx, vpeye, vneye);
    } else {
        return vec4(1.0);
    }
}

#endif