#version 330 core

in vec3 frag_pos;
in vec3 frag_normal;
in vec2 frag_uv;

out vec4 color;

layout (std140) uniform matrices
{
	mat4 view_xform;
	mat4 proj_xform;
	mat4 normal_xform;
};

uniform mat4 node_xform;
uniform sampler2D sampler;

struct PointLight
{
	vec3 pos;
	vec3 color;
	float intensity;
};

struct DirectionalLight
{
	vec3 direction;
	vec3 color;
	float intensity;
};

// FIXME: probably want a buffer-backed UBO for lights in case we have more
// 	than one shader that does lighting calculations
//uniform PointLight lights[32];
// FIXME: hard-coded values for testing
const DirectionalLight dl1 =
	DirectionalLight(vec3(-2, 1, 3), vec3(1,1,1), 1);
const vec4 ambient_color = vec4(0.1, 0.1, 0.1, 1);

const PointLight pl1 = PointLight(vec3(-20, 10, 30), vec3(1, 1, 1), 800);


void main()
{
#if 1 // directional light
	vec3 light_direction = normalize(dl1.direction);
	float diffuse_factor = clamp(dot(frag_normal, light_direction), 0, 1);
	vec4 diffuse_color = dl1.intensity * vec4(dl1.color * diffuse_factor, 1);
#else // point light
	vec3 light_direction = pl1.pos - frag_pos;
	float len = length(light_direction);
	light_direction = normalize(light_direction);
	float diffuse_factor = dot(frag_normal, light_direction) / pow(len, 2);
	diffuse_factor = clamp(diffuse_factor, 0, 1);
	vec4 diffuse_color = pl1.intensity * vec4(pl1.color * diffuse_factor, 1);
#endif

	color = (ambient_color + diffuse_color) * texture(sampler, frag_uv.st);
}