/*
 * libTangerine, a small, modern openGL renderer specializing in flat shaded,
 * 	solid color models using pallete textures. See README for build instructions
 * 	and look in the examples folder for... examples
 */

/*
* === TODO: ===
* - try to improve the setup interface for examples
*   	see if we can remove some boilerplate with more helpers, or
*   	re-organizing
* - add orbit function to camera, see orbitPositionZ0 in example
*   	maybe implement with quaternion, so we can set arbitrary orbit axis
* - update camera interal state and rotations to use quaternions
* - add scene abstrastion for RenderState
* - add an example of dynamically switching shaders for an entity
* - fix debug load times (either by using cgltf, or hiding tinygltf.h)
* - RenderGroups and Entities need to come into and out of existence during
*  		gameplay. So, we need to extend MemoryArena to be a pool allocator
*  		instead of an allocate only linear allocator
* - resizable arrays for entities and asset system (^ see above)
* - add libTangerine namespace?
* - make a test case for overflowing default array sizes, rg->assets
*	  	rg_info->groups, render_group->enitities, rg->textures
* - test for video memory leaking since we're not actually deleting GLBuffers
*   	anywhere
* - look for glm::mat4 in structs, and replace with pointers (easier debugging)
* - defaults include for various #defines
* - make separate shaders for per vertex, and per pixel/fragment lighting
* 		see red book chapter 7
* - add a bloom/blur render to texture shader for light sources?
* 		https://learnopengl.com/Advanced-Lighting/Bloom
*
* === TODONE: ===
*  - don't allocate Asset structure on asset arena
*    - store on RenderState as reference
*  - store asset arena to asset structure
*  - condense get_X_ByPath functions with assetLoad functions
*    - move to asset interface
*  - load diffuse texture automatically when loading a model
*  - move entity structure and functions to new file?
*  - load diffuse texture into OpenGL, and store GLTexture structure onto
*    GLContext
*	- need a cache algorithm starting in initEntity()
*		- check for GLTexture by path hash
*		- load texture into gl if not cached
*		- pass result GLTexture to loadGLMesh()
*  - update loadScene function with textured models, and test texture loading
*  - work on cleaner interface for initEntity and loadScene...
*  - add a LOGF macro for printf style logging
*		- replace instances of printf
*  - rename data structures to be in the new format, eg) UpperCaseStyleNames
*  - rename instances of 'model_xform' that refer to a mesh node to something
*  		like node_xform. model_xform should be reserved for the entity node
*  - move default shaders out of git-lfs
*  - full lighting model
*  		- add buffer backed storage for light arrays in GLSL
*  		- remove hard-coded values in full_lighting.frag
*  		- test buffer backed lights, probably need to pad any scalars/vec3s
*  		- add point light type with tweakable attenuation parameters
*  - test complex entities
*  		- need a separate GLBufferToAttribMapping for each mesh on an entity
*  		- maybe fixed now with MeshBufferType enum and getMeshData()
*  - allow entities to have an empty diffuse texture (see initEntity())
*  - use dynamic shader parsing to set 'sampler_id' for shaders with textures
*  - add ambient light to LightsBuffer structure
*  		- remember to update offsets in initLights()
*  - use rg_arena for store GLMeshes, see initGLMesh()
*  - merge back into libTangerine
* - merge render_group_fix branch back into master
*/


#pragma once

#include <SDL2/SDL.h>


// NOTE: optional compile-time defines:
// 	TANGERINE_GL_DEBUG_QUIET  disable extra debug messages from openGL


#include "asset.h"
#include "camera.h"
#include "entity.h"
#include "dumbLog.h"
#include "GLDebug.h"
#include "input.h"
#include "shader.h"
#include "types.h"
#include "util.h"


struct SDLHandles
{
	SDL_Window* window;
	SDL_GLContext sdl_gl_ctx;
	SDL_DisplayMode display_mode;
	u32 SDL_flags;
};

struct RenderGroup
{
	ShaderProgram* shader;
	u32 num_entities;
	u32 max_entities;
	Entity* entities;
	char* name;
};

// TODO: node/tree structure for entities
#if 0
struct Node;

struct Scene
{
	MemoryArena* rg_arena;
	u32 num_render_groups;
	u32 max_render_groups;
	RenderGroup* render_groups;

	u32 num_point_lights;
	u32 max_point_lights;
	PointLight* p_lights;

	u32 num_d_lights;
	u32 max_d_lights;
	DirectionalLight* d_lights;

	u32 num_spot_lights;
	u32 max_spot_lights;
	SpotLight* s_lights;

	Node root_node;

	Camera cam;
};
#endif

struct GLClearColor
{
	GLfloat R;
	GLfloat G;
	GLfloat B;
	GLfloat A;
};

// NOTE: structure to match the layout of the 'lights' uniform in a shader
// 	all the pointers are pointers into the address space of 'buffer'. the vec4
// 	pointers are required to start on 16 byte boundaries as per layout std140,
// 	so there may be some padding added between the 'header', and the start of
// 	the arrays
// NOTE: this is also very fragile. Since c/c++ doesn't support reflection, we
// 	need to manually update 'initLights()' if we ever update this structure.
// 	And remember to update the 'padding' if the number of 'header' attributes
// 	change
struct LightsBuffer
{
	u32 buf_size;
	u32* max_p_lights;
	u32* active_p_lights;
	u32* max_d_lights;
	u32* active_d_lights;

	vec4* ambient_color;

	vec4* pl_positions;
	vec4* pl_colors;
	uvec4* pl_intensities;

	vec4* dl_directions;
	vec4* dl_colors;
	uvec4* dl_intensities;

	void* buffer;
};

struct RenderState
{
	bool running;
	GLClearColor clear_col;
	SDLHandles handles;
	GLContext* gl_ctx;
	Assets assets;
	uvec2 window_dims;

	MemoryArena* rg_arena;
	u32 num_render_groups;
	u32 max_render_groups;
	RenderGroup* render_groups;

	// TODO: should we have a 'scene' abstraction here?
	// 	could have render groups, lights, camera
	// 	could match up with gltf scene graph where everyting is part of a node
	LightsBuffer* lights_buf;
	Camera* camera;
};


#define DEFAULT_WIDTH 1280
#define DEFAULT_HEIGHT 720
#define DEFAULT_SDL_FLAGS SDL_INIT_VIDEO
#define DEFAULT_MODEL_COUNT 256
#define DEFAULT_TEXTURE_COUNT 64
#define DEFAULT_SHADER_COUNT 64
#define DEFAULT_UBO_COUNT 32
#define DEFAULT_RENDER_GROUP_COUNT 256
#define DEFAULT_CLEAR_COLOR { 0.2, 0.2, 0.2, 1 }
#define DEFAULT_AMBIENT_COLOR { 0.1, 0.1, 0.1, 1 }
#define DEFAULT_MAX_LIGHTS 32 // NOTE: needs to match NUM_LIGHTS in shaders
RenderState* initRenderState(const char* window_title = "tangerine",
	uvec2 window_dims = uvec2(DEFAULT_WIDTH, DEFAULT_HEIGHT),
	u32 SDL_flags = DEFAULT_SDL_FLAGS,
	GLClearColor clear_col = DEFAULT_CLEAR_COLOR,
	vec4 ambient_color = DEFAULT_AMBIENT_COLOR,
	u32 max_models = DEFAULT_MODEL_COUNT,
	u32 max_textures = DEFAULT_TEXTURE_COUNT,
	u32 max_shaders = DEFAULT_SHADER_COUNT,
	u32 max_render_groups = DEFAULT_RENDER_GROUP_COUNT,
	u32 max_ubos = DEFAULT_UBO_COUNT,
	u32 max_lights = DEFAULT_MAX_LIGHTS);

void freeRenderState(RenderState*& rs);

#define DEFAULT_ENTITY_COUNT 256
void initRenderGroup(RenderGroup* rg,
		MemoryArena* arena,
		ShaderProgram* shader,
		u32 num_entities = DEFAULT_ENTITY_COUNT,
		const char* name = "");

void freeRenderGroup(RenderGroup* rg, MemoryArena* arena);

RenderGroup* getFreeRenderGroup(RenderState* rs);

RenderGroup* getRenderGroupByName(RenderState* rs, const char* name);

Entity* getFreeEntity(RenderGroup* rg);

Entity* getEntityByName(RenderGroup* rg, const char* name);

// NOTE: callback function signature to use with renDoRenderLoop()
typedef void (*frame_callback_fn) (RenderState*, void*);

// NOTE: There are 2 callbacks to use here, cb_func_pre is called before
// 	the call to renRenderFrame(), cb_fun_post is called after
// NOTE: if you use cb_func_pre, you will have to use SDL_PollEvent() manually
// 	and at minimum set rs->running = false on SDL_QUIT event
void doRenderLoop(RenderState* rs,
	uint framerate = 60,
	frame_callback_fn cb_func_pre = nullptr,
	frame_callback_fn cb_func_post = nullptr,
	void* user_data = nullptr);

void renderFrame(RenderState* rs, const GLClearColor& clear_col);


//  NOTE: automatic loading of default shaders

struct ShaderInit
{
	const char* name;
	const char* vert_path;
	const char* frag_path;
};

#define SHADER_INIT_COUNT 4
#define TEXTURE_ONLY_SHADER_INIT { "texture_only", \
	"../data/texture_only.vert", \
	"../data/texture_only.frag" }
#define FULL_LIGHTING_SHADER_INIT { "full_lighting", \
	"../data/full_lighting.vert", \
	"../data/full_lighting.frag" }
#define DEBUG_SHADER_INIT { "debug", \
	"../data/debug.vert", \
	"../data/debug.frag", }
#define COLORED_VERT_SHADER_INIT { "colored_vertices", \
	"../data/colored_vertices.vert", \
	"../data/colored_vertices.frag", }
const ShaderInit SHADER_INIT_LIST[SHADER_INIT_COUNT]
{
	TEXTURE_ONLY_SHADER_INIT,
	FULL_LIGHTING_SHADER_INIT,
	DEBUG_SHADER_INIT,
	COLORED_VERT_SHADER_INIT
};

bool loadDefaultShaders(RenderState* rs,
	u32 num_shaders = SHADER_INIT_COUNT,
	const ShaderInit shaders[] = SHADER_INIT_LIST);

// NOTE: only useful if the shader attribute names match the names in the
// 	default	shaders. If loading a custom shader, this may not work as expected,
// 	and you should use getVertexAttribByName instead
GLVertexAttrib* getVertexAttribByType(ShaderProgram* shader,
	MeshBufferType buf_type);