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

#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 "aixlog.hpp"

#include "hexlib.h"
#include "renderer.h"
#include "render_group.h"

#define DEFAULT_VERTEX_SHADER_FILE "../data/default.vs"
#define DEFAULT_FRAGMENT_SHADER_FILE "../data/default.fs"
#define MAX_LIGHTS 10 // NOTE: needs to match the fragment shader source
#define DEFAULT_PALETTE_DIR "../data"
#define DEFAULT_PALETTE_FILE "palette.png"
#define CLEAR_COL_R 75.f / 255.f
#define CLEAR_COL_G 135.f / 255.f
#define CLEAR_COL_B 135.f / 255.f
#define CLEAR_COL_A 1.f

// TODO: add this to json scene properties and render_state
util_RGBA g_clear_col;


// forward declarations
void openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
					GLsizei length, const GLchar* message, const void* userParam);


// interface

bool
renInit(render_state* rs)
{
	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, &rs->handles.currentDisplayMode);
	rs->handles.window =
		SDL_CreateWindow("hexgame", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
							rs->viewport_dims.x, rs->viewport_dims.y, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);

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

	rs->handles.glContext = SDL_GL_CreateContext(rs->handles.window);

	if (!rs->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;
	}

	if (gl3wInit()) {
		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);

	const char* vs_code = utilDumpTextFile(DEFAULT_VERTEX_SHADER_FILE);
	const char* fs_code = utilDumpTextFile(DEFAULT_FRAGMENT_SHADER_FILE);

	bool shader_error = !rgInitShaderProgram(rs->default_shader, vs_code, fs_code);

	utilSafeFree(vs_code);
	utilSafeFree(fs_code);

	if (shader_error) {
		LOG(ERROR) << "Error initializing shader program\n";
		return false;
	}

	rs->max_lights = MAX_LIGHTS;
	rs->lights = UTIL_ALLOC(rs->max_lights, rg_point_light);
	rs->palette_image = utilLoadImage(DEFAULT_PALETTE_DIR, DEFAULT_PALETTE_FILE);

	if (!rgInitGLTexture(rs->palette_id, rs->palette_image)) {
		LOG(ERROR) << "Error creating texture\n";
		return false;
	}

	g_clear_col.R = CLEAR_COL_R;
	g_clear_col.B = CLEAR_COL_B;
	g_clear_col.G = CLEAR_COL_G;
	g_clear_col.A = CLEAR_COL_A;

	return true;
}

void
renFreeBuffers(render_state* rs)
{
	utilSafeFree(rs->lights);
	utilFreeImage(rs->palette_image);
	glDeleteTextures(1, &rs->palette_id);
	rgFree(rs->filled_hex_render_group);
	rgFree(rs->hex_line_render_group);
	rgFree(rs->debug_render_group);
}

bool
renCreateScene(render_state* rs, Entity* entities, uint32 entity_count)
{
	// entities

	for (uint i = 0; i < entity_count; i++) {
		rgInitEntity(&entities[i]);
		entities[i].ren_group->shader = rs->default_shader;
	}

	// debug draw vertices

	uint debug_buf_len = 12; // 4 vertices, 3 floats per vertex
	rs->debug_render_group = rgInitSingle(rs->default_shader, debug_buf_len, true, 0, GL_LINE_LOOP);

	if (rs->debug_render_group == nullptr)
		return false;

	gl_buffer& debug_vertex_buf = rs->debug_render_group->render_objects[0]->vertex_buffer;
	gl_buffer& debug_color_buf = rs->debug_render_group->render_objects[0]->color_buffer;
	gl_buffer& debug_normal_buf = rs->debug_render_group->render_objects[0]->normal_buffer;

	for (uint i = 0; i < debug_buf_len; i += 3) {
		debug_color_buf.buffer[i] = 1.f;
		debug_color_buf.buffer[i + 1] = 0.f;
		debug_color_buf.buffer[i + 2] = 0.f;

		debug_normal_buf.buffer[i] = 0.f;
		debug_normal_buf.buffer[i + 1] = 0.f;
		debug_normal_buf.buffer[i + 2] = 1.f;
	}

	rgBufferData(&debug_vertex_buf, GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER);
	rgBufferData(&debug_color_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);
	rgBufferData(&debug_normal_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);

	return true;
}

void
renRenderFrame(render_state* rs, std::vector<hex_info> *hexes, Entity* entities, uint32 entity_count)
{
	glClearColor(g_clear_col.R, g_clear_col.G, g_clear_col.B, g_clear_col.A);
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

	glm::mat4 m_model = rs->cam.model;
	glm::mat4 m_view = rs->cam.view;
	glm::mat4 m_projection = rs->cam.projection;

	// filled hexes

	// get new colors every frame
	render_group* rg = rs->filled_hex_render_group;
	gl_buffer& color_buf = rg->render_objects[0]->color_buffer;
	// TODO: this needs optimization for large grids, very performance intensive
	hgUpdateColorBuffer(color_buf, hexes);
	rgDraw(rg, m_model, m_view, m_projection,
		rs->lights, rs->num_lights, false, true);

	// hex lines
	rgDraw(rs->hex_line_render_group, m_model, m_view, m_projection,
			rs->lights, rs->num_lights);

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

void
renRenderDebug(render_state* rs, std::vector<Point> &vertices)
{
	GLfloat* buf = rs->debug_render_group->render_objects[0]->vertex_buffer.buffer;
	buf[0] = vertices[0].x; buf[1] = vertices[0].y; buf[2] = 0;
	buf[3] = vertices[1].x; buf[4] = vertices[1].y; buf[2] = 0;
	buf[6] = vertices[2].x; buf[7] = vertices[2].y; buf[8] = 0;
	buf[9] = vertices[3].x; buf[10] = vertices[3].y; buf[11] = 0;

	rgDraw(rs->debug_render_group, rs->cam.model, rs->cam.view,
		rs->cam.projection, rs->lights, rs->num_lights, true);
}


// 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";
}