precision mediump float;

#define f32 float
#define f64 double
#define u32 uint
#define i32 int
#define b32 bool

#ifdef VERTEX_SHADER
# define varying_param out

layout(location = 0) in vec4 a_color;
layout(location = 1) in vec4 a_tangent;
layout(location = 2) in vec3 a_pos;
layout(location = 3) in vec3 a_normal;
layout(location = 4) in vec2 a_uv0;
layout(location = 5) in vec2 a_uv1;

#else
# define varying_param in

layout(location = 0) out vec4 FragColor;

#define AlbedoTexture u_texture0
#define NormalTexture u_texture1
#define MetallicTexture u_texture2
#define RoughnessTexture u_texture3
#define OcclusionTexture u_texture4
#define EmissionTexture u_texture5
#define HeightTexture u_texture6
#define CubemapTexture u_texture7
#define IrradianceTexture u_texture8
#define PrefilterTexture u_texture9
#define BRDFTexture u_texture10

uniform sampler2D u_texture0;
uniform sampler2D u_texture1;
uniform sampler2D u_texture2;
uniform sampler2D u_texture3;
uniform sampler2D u_texture4;
uniform sampler2D u_texture5;
uniform sampler2D u_texture6;
uniform sampler2D u_texture7;
uniform sampler2D u_texture8;
uniform sampler2D u_texture9;
uniform sampler2D u_texture10;

#endif

#define MMI_Albedo 0
#define MMI_Normal 1
#define MMI_Metallic 2
#define MMI_Roughness 3
#define MMI_Occlusion 4
#define MMI_Emission 5
#define MMI_Height 6
#define MMI_Cubemap 7
#define MMI_Irradiance 8
#define MMI_Prefilter 9
#define MMI_BRDF 10
#define MMI_MAX 11

#define AlbedoMaterial material_maps[MMI_Albedo]
#define NormalMaterial material_maps[MMI_Normal]
#define MetallicMaterial material_maps[MMI_Metallic]
#define RoughnessMaterial material_maps[MMI_Roughness]
#define OcclusionMaterial material_maps[MMI_Occlusion]
#define EmissionMaterial material_maps[MMI_Emission]
#define HeightMaterial material_maps[MMI_Height]
#define CubemapMaterial material_maps[MMI_Cubemap]
#define IrradianceMaterial material_maps[MMI_Irradiance]
#define PrefilterMaterial material_maps[MMI_Prefilter]
#define BRDFMaterial material_maps[MMI_BRDF]

#define VertexMain main
#define FragmentMain main

struct MaterialMap
{
	vec4 color;
	f32  value;
};

layout(location = 0) varying_param vec2 v_uv0;
layout(location = 1) varying_param vec2 v_uv1;
layout(location = 2) varying_param vec3 v_normal;
layout(location = 3) varying_param vec3 v_position;
layout(location = 4) varying_param vec4 v_color;

layout(std140, binding = 0) uniform Globals
{
	mat4 projection;
	mat4 view;
	vec3 camera_position;
	vec3 ambient;
};

layout(std140, binding = 1) uniform ModelState
{
	bool albedo_texture;
	bool normal_texture;
	bool metallic_roughness_texture;
	bool occlusion_texture;
	bool emission_texture;
	bool height_texture;
	bool cubemap_texture;
	bool irradiance_texture;
	bool prefilter_texture;
	bool brdf_texture;
	bool no_material;
};

layout(std140, binding = 2) uniform InstanceState
{
	mat4 model_matrix;
};

layout(std140, binding = 3) uniform Materials
{
	MaterialMap material_maps[MMI_MAX];
};

f32
InverseLerp(f32 v, f32 min_value, f32 max_value)
{
	return (v-min_value) / (max_value-min_value);
}

f32
Remap(f32 v, f32 in_min, f32 in_max, f32 out_min, f32 out_max)
{
	f32 t = InverseLerp(v, in_min, in_max);
	return mix(out_min, out_max, t);
}

#ifdef VERTEX_SHADER

void
VertexMain()
{
	gl_Position = projection * view * model_matrix * vec4(a_pos, 1.0);
	v_uv0       = a_uv0;
	v_normal    = (model_matrix * vec4(a_normal, 0.0f)).xyz;
	v_position  = (model_matrix * vec4(a_pos, 1.0f)).xyz;
	v_color     = a_color;
}

#else

void
FragmentMain()
{
	vec3 normal         = normalize(v_normal);
	vec3 view_direction = normalize(camera_position - v_position);

	vec4 color;
	if(albedo_texture)
	{
		color = texture(AlbedoTexture, v_uv0);
	}
	else if(no_material)
	{
		color = v_color;
	}
	else
	{
		color = AlbedoMaterial.color;
	}

	if(color.a < 0.03f)
	{
		discard;
	}

	vec3 light_pos   = vec3(0.0f, 100000.0f, 0.0f);
	vec3 light_dir   = normalize(light_pos-v_position);
	vec3 light_color = vec3(1.0, 1.0, 0.9);

	// Hemi lighting
	vec3 sky_color = vec3(0.0, 0.3, 0.6);
	vec3 ground_color = vec3(0.6, 0.3, 0.1);

	f32 hemi_mix = Remap(normal.y, -1.0, 1.0, 0.0, 1.0);
	vec3 hemi = mix(ground_color, sky_color, hemi_mix);

	// Diffuse
	f32 dp = max(0.0, dot(light_dir, normal));

	vec3 diffuse = dp * light_color;

	// Phong

	vec3 r = normalize(reflect(-light_dir, normal));
	f32 phong_value = max(0.0, dot(view_direction, r));
	phong_value = pow(phong_value, 32.0);

	vec3 specular = vec3(phong_value);

	vec3 lighting = ambient + hemi + diffuse + specular;
	lighting = pow(lighting, vec3(1.0/2.2));

	FragColor = color * vec4(lighting, 1.0);
}

#endif