#include <vector>
#include <cmath> // trig functions

#if defined (_WIN32)
	#include <SDL.h>
#else
	#include <SDL2/SDL.h>
#endif
#include <glm/glm.hpp>
#include <glm/geometric.hpp>
#include <glm/gtc/matrix_transform.hpp>

#include "dumbLog.h"
#include "renderer.h"
#include "default_shaders.cpp"

#define MAX_LIGHTS 10 // NOTE: needs to match the fragment shader source
#define CLEAR_COL_R 55.f / 255.f
#define CLEAR_COL_G 55.f / 255.f
#define CLEAR_COL_B 55.f / 255.f
#define CLEAR_COL_A 1.f
#define DEFAULT_WIDTH 1280
#define DEFAULT_HEIGHT 720
#define USE_SECOND_MONITOR 0


// forward declarations
void openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
					GLsizei length, const GLchar* message, const void* userParam);
bool initSDL(SDL_Handles& handles);
bool createWindow(SDL_Handles& handles, v2i& viewport_dims);
bool initContext(SDL_Handles& handles);
bool initGlOptions();
void setDefaults(render_state* rs);


// interface

render_state*
renInit()
{
	render_state* rs = UTIL_ALLOC(1, render_state);
	setDefaults(rs);

	if (initSDL(rs->handles) &&
		createWindow(rs->handles, rs->viewport_dims) &&
		initContext(rs->handles) &&
		initGlOptions() &&
		rgInitShaderProgram(rs->default_shader, DEFAULT_VERTEX_SHADER, DEFAULT_FRAGMENT_SHADER))
	{
		return rs;
	} else {
		LOG(Error) << "renderer initialization failed, aborting\n";
		return nullptr;
	}
}

void
renShutdown(render_state* rs)
{
	utilSafeFree(rs->lights);
	SDL_GL_DeleteContext(rs->handles.glContext);
	SDL_DestroyWindow(rs->handles.window);
	SDL_Quit();
}

void
renRenderFrame(render_state* rs, Entity* entities, uint32 entity_count)
{
	glClearColor(rs->clear_col.R, rs->clear_col.G, rs->clear_col.B, rs->clear_col.A);
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

	// entities
	for (uint i = 0; i < entity_count; i++) {
		rgDraw(entities[i].ren_group,
			entities[i].world_transform,
			rs->cam.view,
			rs->cam.projection,
			rs->lights,
			rs->num_lights
		);
	}
}


// internal

void
openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
					GLsizei length, const GLchar* message, const void* userParam)
{
	LOG((type == GL_DEBUG_TYPE_ERROR) ? Error : Debug)
		<< (type == GL_DEBUG_TYPE_ERROR ? "** GL Error **" : "")
		<< ", type: " << type
		<< ", severity: " << severity
		<< ", message: " << message << "\n";
}

bool
initSDL(SDL_Handles& handles)
{
	if (SDL_Init(SDL_INIT_VIDEO) != 0) {
		LOG(Error) << "Error, SDL_Init: " << SDL_GetError() << "\n";
		return false;
	}

	SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
	SDL_GetCurrentDisplayMode(0, &handles.currentDisplayMode);

	return true;
}

bool
createWindow(SDL_Handles& handles, v2i& viewport_dims)
{
	uint display_id = 0;
	if (USE_SECOND_MONITOR && SDL_GetNumVideoDisplays() > 1)
		display_id = 1;

	handles.window = SDL_CreateWindow(
		"hexgame",
		SDL_WINDOWPOS_CENTERED_DISPLAY(display_id),
		SDL_WINDOWPOS_CENTERED_DISPLAY(display_id),
		viewport_dims.x,
		viewport_dims.y,
		SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE
	);

	if (!handles.window) {
		LOG(Error) << "Error creating window: " << SDL_GetError() << "\n";
		return false;
	}

	return true;
}

bool
initContext(SDL_Handles& handles)
{
	handles.glContext = SDL_GL_CreateContext(handles.window);

	if (!handles.glContext) {
		LOG(Error) << "Error creating glContext: " << SDL_GetError() << "\n";
		return false;
	}

	if (SDL_GL_SetSwapInterval(1) != 0) {	// vsync
		LOG(Error) << "SDL Errors: " << SDL_GetError() << "\n";
		return false;
	}

	return true;
}

bool
initGlOptions()
{
	if (glewInit()) {
		LOG(Error) << "failed to initialize OpenGL\n";
		return false;
	}

	LOG(Info) << "opengl vendor: " << glGetString(GL_VENDOR) << "\n";
	LOG(Info)<< "opengl renderer: " << glGetString(GL_RENDERER) << "\n";
	LOG(Info) << "opengl version: " << glGetString(GL_VERSION) << "\n";

	glEnable(GL_DEPTH_TEST);
	glEnable(GL_LINE_SMOOTH);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
#if 0
	// TODO: blending messes up rendering with mesa on intel graphics 4000
	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFunc(GL_ONE, GL_SRC_ALPHA);
#endif

	// TODO: glDebugMessageCallback is only availabe  from >v4.3
	//  check and warn if context doesn't support this function here
	glEnable (GL_DEBUG_OUTPUT);
	glDebugMessageCallback((GLDEBUGPROC) openglDebugCallback, 0);
	// hide VRAM debug messages
	glDebugMessageControl(GL_DONT_CARE, 33361, GL_DONT_CARE, 0, 0, GL_FALSE);

	return true;
}

void
setDefaults(render_state* rs)
{
	rs->viewport_dims = v2i(DEFAULT_WIDTH, DEFAULT_HEIGHT);
	rs->max_lights = MAX_LIGHTS;
	rs->lights = UTIL_ALLOC(rs->max_lights, rg_point_light);
	rs->clear_col.R = CLEAR_COL_R;
	rs->clear_col.B = CLEAR_COL_B;
	rs->clear_col.G = CLEAR_COL_G;
	rs->clear_col.A = CLEAR_COL_A;
}