#version 330 core

struct TextureArray {
    sampler2D texture_diffuse[32]; // Array of diffuse textures
    // Add more texture types if needed
};

uniform TextureArray uTextures;           // Array of textures
uniform int uNumDiffuseTextures;         // Number of active diffuse textures

uniform mat4 uLightSpaceMatrix;          // Light space matrix
uniform sampler2D uShadowMap;            // Shadow map texture

in vec2 TexCoord;       // From vertex shader
in vec3 Normal;         // From vertex shader
in vec3 FragPos;        // From vertex shader
in vec4 FragPosLightSpace; // From vertex shader

out vec4 FragColor;     // Final fragment color

// Lighting parameters
struct Light {
    vec3 direction;
    vec3 position;
};
uniform Light light;
uniform vec3 viewPos;    // Position of the camera/viewer

float ShadowCalculation(vec4 fragPosLightSpace)
{
    // Perform perspective divide
    vec3 projCoords = fragPosLightSpace.xyz / fragPosLightSpace.w;

    // Transform to [0,1] range
    projCoords = projCoords * 0.5 + 0.5;

    // Get closest depth value from light's perspective
    float closestDepth = texture(uShadowMap, projCoords.xy).r;

    // Get current fragment's depth
    float currentDepth = projCoords.z;

    // Check whether current frag pos is in shadow
    float bias = 0.005;
    float shadow = currentDepth - bias > closestDepth ? 1.0 : 0.0;

    // Keep the shadow at 0.0 when outside the far plane region of the light's orthographic projection
    if(projCoords.z > 1.0)
        shadow = 0.0;

    return shadow;
}

void main()
{
    // Normalize the normal vector
    vec3 norm = normalize(Normal);
    
    // Calculate the direction from the fragment to the light
    vec3 lightDir = normalize(light.direction);

    // Compute the diffuse intensity
    float diff = max(dot(norm, lightDir), 0.0);
    
    // Initialize diffuse color
    vec4 diffuseColor = vec4(0.0);
    
    // Sample and accumulate diffuse textures
    for(int i = 0; i < uNumDiffuseTextures; ++i)
    {
        diffuseColor += texture(uTextures.texture_diffuse[i], TexCoord);
    }
    
    // Apply the diffuse intensity
    diffuseColor *= diff;
    
    // Simple ambient lighting
    vec3 ambient = 0.1 * diffuseColor.rgb;
    
    // Calculate shadow
    float shadow = ShadowCalculation(FragPosLightSpace);

    // Final color combining ambient and shadowed diffuse components
    vec3 lighting = ambient + (1.0 - shadow) * diffuseColor.rgb;
    FragColor = vec4(lighting, diffuseColor.a);
}