#pragma once

#include <SDL2/SDL.h>
#include <GL/glew.h>
#include <glm/glm.hpp>

#include "types.h"
#include "util.h"


struct GLUniform
{
	// NOTE: would be nice to use idx as the location parameter because it seems
	// 	to match when the uniform isn't part of a uniform block, at least with
	// 	intel mesa driver, but apparently that's not guarantied
	GLuint idx;
	GLint location;
	GLint block_idx;
	GLenum data_type;
	GLint data_size;
	GLint num_elements;
	char* name;
};

struct GLUniformBlock
{
	GLuint block_id;
	GLint binding_idx;
	GLuint num_uniforms;
	GLUniform* uniforms;
	char* name;
};

enum MeshBufferType
{
	VERTEX,
	NORMAL,
	UV,
	COLOR,
	MESH_BUFFER_TYPE_COUNT
};

// NOTE: we need another struct for vertex attributes that mirrors GLBuffer
// 	because an attribute is associated with a ShaderProgram while a buffer is
// 	associated with the vertex data passed to glBufferData()
struct GLVertexAttrib
{
	MeshBufferType buf_type;
	GLenum data_type;
	GLenum component_type;
	u32 num_components;
	GLuint location;
	char* name;
};

struct GLBufferToAttribMapping
{
	GLVertexAttrib* attrib;
	MeshBufferType buf_type;
};

struct ShaderProgram
{
	GLuint prog_id;
	GLuint xforms_ubo_id;
	GLuint node_xform_id;
	GLint sampler_id;

	u32 num_blocks;
	GLUniformBlock* uniform_blocks;

	u32 num_uniforms;
	GLUniform* uniforms;

	u32 num_vertex_attribs;
	GLVertexAttrib* vertex_attribs;
	GLBufferToAttribMapping* attrib_mappings;

	char* name;
	u64 hash; // NOTE: hash of vs filpath + fs filepath concat
};

struct GLBuffer
{
	GLuint id;
	GLenum target;
	GLenum data_type;
	GLuint location; // NOTE: if used as backing for vertex attribute
	GLuint binding_idx; // NOTE: if used as backing from uniform buffer object
	char* name;
};

struct GLTexture
{
	GLuint id;
	GLenum pixel_format; // NOTE: GL_RGB or GL_RGBA
	u32 width;
	u32 height;
	u64 filepath_hash;
};

struct GLContext
{
	GLuint binding_count;
	GLint max_binding_points;
	GLint max_vertex_blocks;
	GLint max_fragment_blocks;
	GLint max_ublock_size;
	GLint max_vertex_attribs;

	u32 max_ubos;
	u32 num_ubos;
	GLBuffer* uniform_buffers;

	u32 max_shaders;
	u32 num_shaders;
	ShaderProgram* shaders;

	u32 max_textures;
	u32 num_textures;
	GLTexture* textures;
};

// TODO: rename to GLMesh
struct GLmesh
{
	u32 num_indices;
	GLuint vao_id;
	GLuint tex_id;
	GLenum draw_mode; // NOTE: GL_LINES, GL_TRIANGLES
	GLenum usage; // NOTE: GL_STATIC_DRAW, GL_DYNAMIC_DRAW

	glm::mat4* node_xform;

	u32 num_vertex_attrib_buffers;
	GLBuffer* vertex_attrib_buffers;
	GLBuffer* element_buf;
};

struct Animation;

struct PointLight
{
	glm::vec3 position;
	glm::vec3 color;
	u32 intensity;
};

struct Transforms
{
	glm::mat4 view_xform;
	glm::mat4 proj_xform;
	glm::mat4 normal_xform;
};


const float DEFAULT_FOV = 60.f;
const float NEAR_CLIP_PLANE = 5.f;
const float DEFAULT_ASPECT_RATIO = 16.f / 9.f;
const glm::vec3 DEFAULT_CAM_POS = { 0, 0, 30.f };
const glm::vec3 DEFAULT_LOOK_POS = { 0, 0, 0 };


// NOTE: every shader program is assumed to have one uniform block named
// 	"matrices" that contains the projection and view matrices, and one uniform
// 	named "node_xform" for the node matrix
bool addShaderProgram(MemoryArena* arena,
	GLContext* gl_ctx,
	const char* vs,
	const char* fs,
	const char* name);

ShaderProgram* getShaderByName(const char* name, GLContext* gl_ctx);

ShaderProgram* getShaderByID(GLContext* gl_ctx, GLuint prog_id);

ShaderProgram* getShaderByHash(GLContext* gl_ctx, u64 hash);

ShaderProgram* getFreeShader(GLContext* gl_ctx);

GLTexture* getGLTexture(GLContext* gl_ctx, Texture* diffuse_img);

void renderVAO(GLmesh* glmesh,
	glm::mat4* node_xform,
	ShaderProgram* shader,
	GLuint tex_id = 0);

GLVertexAttrib* getVertexAttribByName(ShaderProgram* shader, const char* name);

GLmesh loadGLMesh(const Mesh& m,
	GLenum draw_mode,
	GLuint diffuse_texture_id,
	u32 num_mappings,
	GLBufferToAttribMapping mappings[]);

void initTransforms(MemoryArena* arena,
	Transforms* xforms,
	GLBuffer* xform_ubo,
	GLContext* gl_ctx,
	float fov = DEFAULT_FOV,
	float near_clip_plane = NEAR_CLIP_PLANE,
	float aspect_ratio = DEFAULT_ASPECT_RATIO,
	glm::vec3 cam_pos = DEFAULT_CAM_POS,
	glm::vec3 look_pos = DEFAULT_LOOK_POS);