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

// TODO: decide on extension library
//#include <GL/glew.h>
#include <GL/gl3w.h>

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

#include "aixlog.hpp"

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

#define MOVE_SPEED 5.f
#define ROTATE_SPEED 0.005f
#define CAMERA_Z_CLAMP_ANGLE 85.f
//#define PROJ_TYPE ORTHOGRAPHIC
#define PROJ_TYPE PERSPECTIVE
#define DEFAULT_VERTEX_SHADER_FILE "../data/default.vs"
#define DEFAULT_FRAGMENT_SHADER_FILE "../data/default.fs"

const char * LINE_FRAGMENT_SHADER_CODE =
	"#version 330 core\n"
	"out vec3 color;\n"
	"void main()\n"
	"{\n"
	"	color = vec3(0,0,0);\n"
	"}";

const char * DEBUG_FRAGMENT_SHADER_CODE =
	"#version 330 core\n"
	"out vec3 color;\n"
	"void main()\n"
	"{\n"
	"	color = vec3(1,0,0);\n"
	"}";

typedef struct clear_col
{
	real32 R;
	real32 G;
	real32 B;
	real32 A;
} clear_col;
clear_col g_clear_col { 75.f / 255.f, 135.f / 255.f, 135.f / 255.f, 1.f };

typedef struct gl_matrix_info
{
	glm::mat4 projection;
	glm::mat4 view;
	glm::mat4 model;
	glm::mat4 MVP;
} gl_matrix_info;

enum projection_type
{
	PERSPECTIVE,
	ORTHOGRAPHIC,
};

struct camera
{
	glm::vec3 position;
	float hAngle;
	float vAngle;
	glm::vec3 target;
	glm::vec3 forward;
	glm::vec3 up;
	glm::vec3 left;
};


// forward declarations
void initMatrices(projection_type p);
void openglDebugCallback(GLenum source, GLenum type, GLuint id, GLenum severity,
					GLsizei length, const GLchar* message, const void* userParam);
bool initHexGridBuffers(std::vector<hex_info>* hexes);
void fillTriangleBufferFromHex(GLfloat buf[], int idx,  const hex_info &hex);
void fillColorBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes);
void fillHexLineBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes);


// globals
static gl_matrix_info g_scene_matrices;
static render_group* g_filled_hex_render_group;
static render_group* g_hex_line_render_group;
static render_group* g_debug_render_group;
static rg_shader_program g_default_shader;
static rg_shader_program g_line_shader;
// NOTE: entity render_group pointers are kept in the entity struct
static camera g_camera;

// TODO: testing lighting
static renPointLight g_test_light;


// interface

bool
initRenderer(SDL_Handles &handles, v2i vpDims)
{
	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);
	handles.window = 
		SDL_CreateWindow("hexgame", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
							vpDims.x, vpDims.y, SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);

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

	if (gl3wInit()) { // TODO: decide on extension library
		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);
	glEnable(GL_BLEND);
	glBlendEquation(GL_FUNC_ADD);
	glBlendFunc(GL_ONE, GL_SRC_ALPHA);
	glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

	// 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(g_default_shader, vs_code, fs_code);

	utilSafeFree(vs_code);
	utilSafeFree(fs_code);

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

	return true;
}

bool
addTexture(SDL_Handles &handles, const char * path)
{
	// testing
	LOG(INFO) << "Loading image: " << path << "\n";
	SDL_Surface* image = IMG_Load(path);

	if (!image)
	{
		LOG(ERROR) << "IMG_Load: " << IMG_GetError() << "\n";
		return false;
	}

	GLuint tex_id;
	glGenTextures(1, &tex_id);
	glBindTexture(GL_TEXTURE_2D, tex_id);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, image->w, image->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, image->pixels);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

	// store opengl id in SDL_Surface.userdat
	image->userdata = (void*)(intptr_t) tex_id;
	handles.texSurfaces.push_back(image);

	return true;
}

v2f
getUnprojectedCoords(int32 x, int32 y, int32 vp_width, int32 vp_height)
{
	// NOTE: using depth buffer may not be as accurate as doing ray-cast
	GLfloat depth;
	glReadPixels(x, y, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &depth);
	glm::vec4 viewport = glm::vec4(0, 0, vp_width, vp_height);
	glm::vec3 wincoord = glm::vec3(x, y, depth);
	glm::vec3 vU = glm::unProject(wincoord, g_scene_matrices.view, g_scene_matrices.projection, viewport);
	v2f v(vU.x, vU.y);

	return v;
}

v3f
getCameraPosition()
{
	return v3f(g_camera.position.x, g_camera.position.y, g_camera.position.z);
}

bool
createScene(std::vector<hex_info>* hexes, Entity* entities, uint32 entity_count)
{
	// entities

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

	initMatrices(PROJ_TYPE);

	if (!initHexGridBuffers(hexes))
		return false;

	// debug draw vertices

	uint debug_buf_len = 12; // 4 vertices, 3 floats per vertex
	g_debug_render_group = rgInitSingle(g_default_shader, debug_buf_len, true, 0, GL_LINE_LOOP);

	if (g_debug_render_group == nullptr)
		return false;

	gl_buffer& debug_vertex_buf = g_debug_render_group->render_objects[0]->vertex_buffer;
	gl_buffer& debug_color_buf = g_debug_render_group->render_objects[0]->color_buffer;
	gl_buffer& debug_normal_buf = g_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);

	// lights

	// TODO: load light properties from scene/level files

	//g_test_light.light_ID = glGetUniformLocation(g_entity_render_group.program_id, "light_position");
	if (entities[0].ren_group != nullptr) {
		g_test_light.light_ID = glGetUniformLocation(entities[0].ren_group->shader.program_id, "light_position");
		g_test_light.position = glm::vec3(800, 300, 400); // above center of hexgrid
		g_test_light.direction = glm::vec3(0, 0, 0) - g_test_light.position; // back towards test entity
		g_test_light.color = glm::vec3(1.f, 1.f, 1.f);
		g_test_light.intensity = 1.f;
	}

	return true;
}

void
moveCamera(bool up, bool left, bool down, bool right, bool forward, bool backward)
{
	if (!up && !left && !down && !right && !forward && !backward)
		return;

	glm::vec3 f = g_camera.forward;
	glm::vec3 u = g_camera.up;
	glm::vec3 old = g_camera.position;
	glm::vec3 &p = g_camera.position;
	glm::vec3 v(0.f); // normalized direction
	
	// TODO: still seems like we're adding magnitude when moving in 2 directions
#if 0
	if (forward) v = glm::normalize(v + f);
	if (backward) v = glm::normalize(v - f);
	if (up) v = glm::normalize(v + u);
	if (down) v = glm::normalize(v - u);
	if (left) v -= glm::normalize(glm::cross(f, u));
	if (right) v -= glm::normalize(glm::cross(u, f));
#else
	if (forward) v +=  f;
	if (backward) v -= f;
	if (up) v += u;
	if (down) v -= u;
	if (left) v -= glm::cross(f, u);
	if (right) v -= glm::cross(u, f);
#endif

	p += (v * MOVE_SPEED);
	glm::vec3 diff = old - p;
	g_scene_matrices.view = glm::translate(g_scene_matrices.view, diff);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
}

void
rotateCamera(int32	xrel, int32 yrel)
{
	camera &c = g_camera;
	float &h = c.hAngle;
	float &v = c.vAngle;
	h += ROTATE_SPEED * xrel;
	v -= ROTATE_SPEED * yrel;

	// clamp vAngle to prevent gimbal lock
	float a = glm::radians(CAMERA_Z_CLAMP_ANGLE);
	if (v < (-1 * a)) v = (-1 * a);
	if (v > a) v = a;
	
	c.forward = glm::vec3(
		glm::cos(v) * glm::sin(h),
		glm::cos(v) * glm::cos(h),
		glm::sin(v)
	);

	glm::normalize(c.forward);
	c.up = glm::vec3(0,0,1);
	c.left = glm::normalize(glm::cross(c.forward, c.up));
	c.up = glm::normalize(glm::cross(c.left, c.forward));

	g_scene_matrices.view = glm::lookAt(c.position, c.position + c.forward, c.up);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
}

// NOTE: don't need this yet
void
rollCamera(bool CW, bool CCW)
{
#if 0
	if ((!CW && !CCW) || (CW && CCW))
		return;

	float a = 0.005f;
	if (CW) a *= 1;
	if (CCW) a *= -1;
	camera &c = g_camera;
	glm::mat4 m = glm::rotate(glm::mat4(1.f), a, c.forward);
	glm::vec4 v(c.up.x, c.up.y, c.up.z, 0);
	v = v * m;
	g_camera.up = glm::vec3(v.x, v.y, v.z);
	g_scene_matrices.view *= m;
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model; 
#endif
}

void
renderFrame(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 = g_scene_matrices.model;
	glm::mat4 m_view = g_scene_matrices.view;
	glm::mat4 m_projection = g_scene_matrices.projection;

	// filled hexes

	// get new colors every frame
	render_group* rg = g_filled_hex_render_group;
	gl_buffer& color_buf = rg->render_objects[0]->color_buffer;
	fillColorBuffer(color_buf.buffer, color_buf.buffer_len, hexes);
	rgDraw(rg, m_model, m_view, m_projection,
		g_test_light.position, g_test_light.light_ID);

	// hex lines
	rgDraw(g_hex_line_render_group, m_model, m_view, m_projection,
			g_test_light.position, g_test_light.light_ID);

	// entities
	for (uint i = 0; i < entity_count; i++) {
		rgDraw(entities[i].ren_group, entities[i].world_transform , m_view, m_projection,
			g_test_light.position, g_test_light.light_ID);
	}
}

void
renderDebug(std::vector<Point> &vertices)
{
	GLfloat* buf = g_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(g_debug_render_group, g_scene_matrices.model, g_scene_matrices.view,
		g_scene_matrices.projection, g_test_light.position, g_test_light.light_ID, true);
}

void
freeBuffers()
{
	std::vector<render_group*> groups = {
		g_filled_hex_render_group,
		g_hex_line_render_group,
		g_debug_render_group,
	};
	
	for (render_group* group : groups)
		rgFree(group);
}


// internal

void
initMatrices(projection_type p)
{
	// TODO: many constants used here should be passed as args

	if (p == PERSPECTIVE)
	{
		g_scene_matrices.projection = glm::infinitePerspective(
			glm::radians(60.f), // FoV
			16.f / 9.f, // ascpect ratio
			0.1f // near clip plane
		);

		g_camera.position = glm::vec3(640,0,100);
		g_camera.target = glm::vec3(640,500,0);
		//g_camera.target = glm::vec3(0,0,0);
		// inital rotation should match target direction
		glm::vec3 &p = g_camera.position;
		glm::vec3 &t = g_camera.target;
		g_camera.hAngle = 0;
		g_camera.vAngle = glm::atan((t.z - p.z) / (t.y - p.y));

		//////
		// TODO: add call to rotate camera here to remove duplicate code
		camera &c = g_camera;
		float &h = c.hAngle;
		float &v = c.vAngle;
		c.forward = glm::vec3(
			glm::cos(v) * glm::sin(h),
			glm::cos(v) * glm::cos(h),
			glm::sin(v)
		);

		glm::normalize(c.forward);
		//////

		g_camera.up = glm::vec3(0,1,0);
		g_camera.left = glm::normalize(glm::cross(g_camera.up, g_camera.forward));
		g_camera.up = glm::normalize(glm::cross(g_camera.forward, g_camera.left));

		g_scene_matrices.view = glm::lookAt(
			g_camera.position, // camera position
			g_camera.position + g_camera.forward,
			g_camera.up // "up" vector
		);
	}
	else // ORTHO
	{
		// left, right, bottom, top, zNear, zFar
		g_scene_matrices.projection = glm::ortho(0.f, 1280.0f, 0.f, 720.0f, 0.1f, 100.0f);
		g_scene_matrices.view = glm::lookAt(
			glm::vec3(0.0f, 0.0f, 1.0f),	// camera position
			glm::vec3(0.0f, 0.0f, 0.0f),	// look at position
			glm::vec3(0,1,0)				// "up" vector
		);
	}

	g_scene_matrices.model = glm::mat4(1.0f);
	g_scene_matrices.MVP = g_scene_matrices.projection * g_scene_matrices.view * g_scene_matrices.model;
}

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
initHexGridBuffers(std::vector<hex_info>* hexes)
{
	// TODO: index duplicate vertices
	// 6 triangles * 3 vertices per triangle * 3 floats per vertex = 54
	uint line_vertices_per_hex = 6 * 2; // 12 vertices since we're using line segments atm
	uint line_buf_len = hexes->size() * line_vertices_per_hex * 3; // 3 floats per vertex
	uint vbuf_len = hexes->size() * 6 * 3 * 3;

	g_filled_hex_render_group = rgInitSingle(g_default_shader, vbuf_len, true);

	if (g_filled_hex_render_group == nullptr)
		return false;

	gl_buffer& vbuf = g_filled_hex_render_group->render_objects[0]->vertex_buffer;
	gl_buffer& cbuf = g_filled_hex_render_group->render_objects[0]->color_buffer;
	gl_buffer& normal_buf = g_filled_hex_render_group->render_objects[0]->normal_buffer;

	for (uint i = 0; i < hexes->size(); i++)
		fillTriangleBufferFromHex(vbuf.buffer, i * 54, (*hexes)[i]);

	rgBufferData(&vbuf,	GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER);
	fillColorBuffer(cbuf.buffer, vbuf_len, hexes);
	rgBufferData(&cbuf, GL_DYNAMIC_DRAW, GL_ARRAY_BUFFER);

	// cheat at vertex normals since all hexes lay flat on z-axis

	for (uint i = 0; i < vbuf_len; i += 3) {
		normal_buf.buffer[i] = 0.f;
		normal_buf.buffer[i + 1] = 0.f;
		normal_buf.buffer[i + 2] = 1.f;
	}
	rgBufferData(&normal_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);

	// hex lines

	g_hex_line_render_group = rgInitSingle(g_default_shader, line_buf_len, true, 0, GL_LINES);

	if (g_hex_line_render_group == nullptr)
		return false;

	gl_buffer& line_buf = g_hex_line_render_group->render_objects[0]->vertex_buffer;
	gl_buffer& line_color_buf = g_hex_line_render_group->render_objects[0]->color_buffer;
	gl_buffer& line_normal_buf = g_hex_line_render_group->render_objects[0]->normal_buffer;
	fillHexLineBuffer(line_buf.buffer, line_buf_len, hexes);
	rgBufferData(&line_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);

	for (uint i = 0; i < line_buf_len; i++)
		line_color_buf.buffer[i] = 0.f;

	rgBufferData(&line_color_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);

	for (uint i = 0; i < line_buf_len; i += 3) {
		line_normal_buf.buffer[i] = 0.f;
		line_normal_buf.buffer[i + 1] = 0.f;
		line_normal_buf.buffer[i + 2] = 1.f;
	}

	rgBufferData(&line_normal_buf, GL_STATIC_DRAW, GL_ARRAY_BUFFER);

	return true;
}

void
fillTriangleBufferFromHex(GLfloat buf[], int idx,  const hex_info &hex)
{
	// triangles
	for (int i = 0; i < 6; i++)
	{
		// vertex 0
		buf[idx + 0] = (GLfloat) hex.XPos;
		buf[idx + 1] = (GLfloat) hex.YPos;
		buf[idx + 2] = (GLfloat) 0.f;

		// vertex 1
		buf[idx + 3] = (GLfloat) hex.vertices[i].x;
		buf[idx + 4] = (GLfloat) hex.vertices[i].y;
		buf[idx + 5] = (GLfloat) 0.f;

		if (i == 5)	// re-use the first point for the last triangle
		{
			// vertex 2
			buf[idx + 6] = (GLfloat) hex.vertices[0].x;
			buf[idx + 7] = (GLfloat) hex.vertices[0].y;
			buf[idx + 8] = (GLfloat) 0.f;
		}
		else
		{
			// vertex 2
			buf[idx + 6] = (GLfloat) hex.vertices[i + 1].x;
			buf[idx + 7] = (GLfloat) hex.vertices[i + 1].y;
			buf[idx + 8] = (GLfloat) 0.f;
		}

		// we've added 9 GLfloats per loop
		idx += 9;
	}
}

void
fillColorBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes)
{
	int buf_idx;
	int buf_len_per_hex = 54; // NOTE: 3 * 3 * 6
	GLfloat color_buf[3];
	for (int i = 0; i < (int) hexes->size(); i++)
	{
		buf_idx = i * buf_len_per_hex;
		hex_info hxi = (*hexes)[i];
		// TODO: check performance of this since we call multiple times per frame
		// 	maybe can cache glfloat triplets somewhere
		utilConvertColor(color_buf, hxi.current_color);

		for (int j = 0; j < buf_len_per_hex; j+=3)
		{
			buf[buf_idx + j] = color_buf[0];
			buf[buf_idx + j + 1] = color_buf[1];
			buf[buf_idx + j + 2] = color_buf[2];
		}
	}
}

void
fillHexLineBuffer(GLfloat buf[], int len, std::vector<hex_info>* hexes)
{
	Point p1, p2;
	int idx = 0;
	for (int i = 0; i < (int) hexes->size(); i++)
	{
		hex_info hxi = (*hexes)[i];
		for (int j = 0; j < 6; j ++)
		{
			if (j == 5) // wrap
			{
				p1 = hxi.vertices[j];
				p2 = hxi.vertices[0];
			}
			else
			{
				p1 = hxi.vertices[j];
				p2 = hxi.vertices[j + 1];
			}

			buf[idx + 0] = p1.x;
			buf[idx + 1] = p1.y;
			buf[idx + 2] = 0.f;
			buf[idx + 3] = p2.x;
			buf[idx + 4] = p2.y;
			buf[idx + 5] = 0.f;
			idx += 6;
		}
	}
}