#version 450

const int MAX_LIGHTS = 4;

struct Light {
    vec4 direction;
    vec4 color;
};

layout(location = 0) in vec2 fragUV;
layout(location = 1) in vec3 fragNormal;
layout(location = 2) in vec3 fragWorldPos;

layout(location = 0) out vec4 outColor;

layout(set = 0, binding = 0) uniform UniformBufferObject {
    mat4 view;
    mat4 proj;
    vec4 ambientColor;
    Light lights[MAX_LIGHTS];
} ubo;

layout(set = 1, binding = 0) uniform sampler2D texSampler;

void main() {
    vec3 albedo = texture(texSampler, fragUV).rgb;
    vec3 N = normalize(fragNormal);

    vec3 result = ubo.ambientColor.rgb * albedo;

    for (int i = 0; i < MAX_LIGHTS; ++i) {
        vec3 L = normalize(-ubo.lights[i].direction.xyz);
        float diff = max(dot(N, L), 0.0);
        result += ubo.lights[i].color.rgb * ubo.lights[i].color.a * diff * albedo;
    }

    outColor = vec4(result, 1.0);
}