libTangerine/include/shader.h

#pragma once

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

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


enum UniformType
{
	UNIFORM_SAMPLER,
	UNIFORM_NODE_XFORM,
	UNIFORM_VIEW_XFORM,
	UNIFORM_PROJECTION_XFORM,
	UNIFORM_NORMAL_XFORM,
	UNIFORM_BLOCK_XFORMS,
	UNIFORM_BLOCK_LIGHTS,
	UNIFORM_UNKNOWN,
	UNIFORM_TYPE_COUNT
};

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;
	UniformType uniform_type;
	GLenum gl_type; // NOTE: GL_UNSIGNED_INT, GL_FLOAT_VEC4
	GLint num_elements; // NOTE: 1 unless uniform is an array of base types
	GLint array_stride; // NOTE: bytes between array elements
	GLint uniform_offset; // NOTE: byte offset from beginning of uniform
	char* name;
};

struct GLUniformBlock
{
	GLuint block_id;
	GLint binding_idx;
	UniformType uniform_type;
	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;
};

// TODO: add a note explaining usage when we implement complex entities
struct GLBufferToAttribMapping
{
	GLVertexAttrib* attrib;
	MeshBufferType buf_type;
};

struct ShaderProgram
{
	GLuint prog_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 data_size; // NOTE: size of buffer in bytes
	GLint location; // NOTE: if used as backing for vertex attribute
	GLint 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;
};

struct GLMesh
{
	u32 num_indices;
	GLuint vao_id;
	bool has_texture;
	GLuint tex_id;
	GLenum draw_mode; // NOTE: GL_LINES, GL_TRIANGLES
	GLenum usage; // NOTE: GL_STATIC_DRAW, GL_DYNAMIC_DRAW

	mat4* node_xform;

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

struct Animation;


GLContext* initGLContext(MemoryArena* arena,
	u32 max_shaders,
	u32 max_textures,
	u32 max_ubos);

// TODO: add more notes here describing the internals? This is the entry point
// 	to a complex process of programatically assigning properties to our notion
// 	of what a shader needs ie) uniforms, buffer block bindings, etc
// 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);

GLBuffer* getFreeUBO(GLContext* gl_ctx);

GLBuffer* getUBOByName(GLContext* gl_ctx, const char* name);

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

GLBuffer* initGLBackingBuffer(GLContext* gl_ctx,
	MemoryArena* arena,
	const char* name,
	GLenum data_type,
	u32 buf_size,
	void* data);

void updateGLBuffer(GLBuffer* gl_buf, void* data);

void renderVAO(GLMesh* glmesh,
	mat4* node_xform,
	ShaderProgram* shader,
	GLTexture* gl_tex);

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

GLMesh loadGLMesh(MemoryArena* arena,
	const Mesh& m,
	GLenum draw_mode,
	GLTexture* diffuse_texture,
	u32 num_mappings,
	GLBufferToAttribMapping mappings[]);