const char* DEFAULT_VERTEX_SHADER = R"VS(
#version 330 core

layout (location = 0) in vec3 vertexPosition_modelspace;
layout (location = 1) in vec3 normal;
layout (location = 2) in vec3 texCoord;

out vec3 fragVertex;
out vec3 fragNormal;
out vec2 fragUV;

uniform mat4 world_transform;
uniform mat4 model;
uniform mat4 view;
uniform mat4 projection;


void main()
{
	fragNormal = vec4(world_transform * vec4(normal, 1)).xyz;
	fragVertex = vertexPosition_modelspace;
	fragUV = texCoord.st;
	gl_Position = projection * view *
		world_transform * model * vec4(vertexPosition_modelspace, 1);
}
)VS";

// TODO: there's a bug here with the array size of 'lights'
// 	with intel opengl, size can be >1000
// 	but with nvidea opengl size of >200 gives the following error:
// 		error C6020: Constant register limit exceeded at sampler;
// 		more than 1024 registers needed to compile program
const char* DEFAULT_FRAGMENT_SHADER = R"FS(
#version 330 core

in vec3 fragVertex;
in vec3 fragNormal;
in vec2 fragUV;

out vec4 color;

uniform mat4 model;
uniform mat3 normal_matrix;
uniform sampler2D sampler;
uniform uint num_lights = 0u;

struct point_light {
	uint light_ID;
	vec3 position;
	vec3 color;
	float intensity;
};

uniform point_light lights[200];


void main()
{
	vec3 normal = normalize(normal_matrix * fragNormal);
	vec3 fragPosition = vec3(model * vec4(fragVertex, 1));
	float totalBrightness = 0;

	for (uint i = 0u; i < num_lights; i++) {
		vec3 surfaceToLight = lights[i].position - fragPosition;
		//float brightness = dot(normal, surfaceToLight) / (length(surfaceToLight) * length(normal));
		float brightness = dot(normal, surfaceToLight) / length(surfaceToLight);
		totalBrightness += brightness;
	}

	color = clamp(totalBrightness, 0, 1) * texture(sampler, fragUV.st);
}
)FS";

const char* SIMPLE_VERTEX_SHADER = R"SVS(
#version 330 core

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 color;

out vec3 frag_color;

uniform mat4 world_transform;
uniform mat4 MVP;


void main()
{
	frag_color = color;
	gl_Position =  MVP * world_transform * vec4(position, 1);
}
)SVS";

const char* SIMPLE_FRAGMENT_SHADER = R"SFS(
#version 330 core

in vec3 frag_color;

out vec4 color;


void main()
{
	color = vec4(frag_color.rgb, 1);
}
)SFS";