//////////////////////////////////////////////////////////////////////////////

#ifdef VERTEX

layout (location = 0) in vec3 a_position;
layout (location = 1) in vec3 a_normal;
layout (location = 2) in vec2 a_texcoord;

uniform mat4 u_proj;
uniform mat4 u_view;
uniform mat4 u_model;

out vec3 v_fragpos;
out vec2 v_texcoord;
out vec3 v_normal;

void main()
{
	v_fragpos = vec3(u_model * vec4(a_position, 1.0f));
	v_normal = mat3(transpose(inverse(u_model))) * a_normal;
	v_texcoord = a_texcoord;

	gl_Position = u_proj * u_view * u_model * vec4(a_position, 1.0f);
}

#endif

//////////////////////////////////////////////////////////////////////////////

#ifdef FRAGMENT

#define MAX_LIGHT_COUNT 30

struct light_t {
	vec3 position;
	vec3 color;
	float intensity;
	float radius;
};

in vec3 v_fragpos;
in vec2 v_texcoord;
in vec3 v_normal;

out vec4 f_color;

uniform sampler2D u_texture;
uniform int u_light_count;
uniform light_t u_lights[MAX_LIGHT_COUNT];

float attenuate(float dist, float radius)
{
	float val = 1.0f - ((dist*dist)/(radius*radius));

	return clamp(val, 0.0f, 1.0f);
}

vec3 calc_light(light_t light, vec3 frag_normal, vec3 frag_pos)
{
	vec3 light_dir = normalize(light.position - frag_pos);
	float distance = length(light.position-frag_pos);
	vec3 light_color = light.color * light.intensity * attenuate(distance, light.radius);

	vec3 diffuse = light_color * max(dot(normalize(frag_normal), light_dir), 0.0f);

	return diffuse;
}

void main()
{
	vec3 ambient_light = vec3(0.05f);
	vec3 frag_normal = normalize(v_normal);
	vec3 diffuse_light = vec3(0.0f);

	for (int i = 0; i < u_light_count; i++)
	{
		diffuse_light += calc_light(u_lights[i], frag_normal, v_fragpos);
	}

	vec4 total_light = vec4(ambient_light + diffuse_light, 1.0f);

	vec4 tex_color = texture(u_texture, v_texcoord);
	f_color = total_light * tex_color;
}

#endif

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