#include <cstdio> // fopen
#include <chrono> // see millis()

#include <common.h>
#include <world.h>
#include <ui.h>
#include <entities.h>

/*
 *	TICKS_PER_SEC & MSEC_PER_TICK
 * 
 *	The game's main loop mainly takes care of two things: drawing to the
 *	screen and handling game logic, from user input to world gravity stuff.
 *	The call for rendering is made every time the main loop loops, and then
 *	uses interpolation for smooth drawing to the screen. However, the call
 *	for logic would be preferred to be run every set amount of time.
 * 
 *	The logic loop is currently implemented to run at a certain interval
 *	that we call a 'tick'. As one may now guess, TICKS_PER_SEC defines the
 *	amount of ticks that should be made every second. MSEC_PER_TICK then
 *	does a simple calculation of how many milliseconds elapse per each
 * 	'tick'. Simple math is then done in the main loop using MSEC_PER_TICK
 *	to call the logic handler when necessary.
 * 
*/

#define TICKS_PER_SEC 20
#define MSEC_PER_TICK (1000/TICKS_PER_SEC)

/*
 *	window & mainGLContext
 * 
 *	In order to draw using SDL and its openGL facilities SDL requires
 *	an SDL_Window object, which spawns a window for the program to draw
 *	to. Once the SDL_Window is initialized, an SDL_GLContext is made so
 *	that openGL calls can be made to SDL. The game requires both of these
 *	variables to initialize.
 * 
*/

SDL_Window    *window = NULL;
SDL_GLContext  mainGLContext = NULL;

/*
 *	bgImage contains the GLuint returned when creating a texture for the
 *	background image. Currently there is only one background image for the
 *	main world; this will be changed and bgImage likely removed once better
 *	backgrounds are implemented.
 * 
*/

static GLuint  bgImage;

/*
 *	gameRunning
 * 
 *	This is one of the most important variables in the program. The main
 *	loop of the game is set to break once this variable is set to false.
 *	The only call to modify this variable is made in src/ui.cpp, where it
 *	is set to false if either an SDL_QUIT message is received (the user
 *	closes the window through their window manager) or if escape is pressed.
 * 
*/

bool gameRunning = true;

/*
 *	currentWorld -	This is a pointer to the current world that the player
 * 					is in. Most drawing/entity handling is done through this
 * 					variable. This should only be changed when layer switch
 * 					buttons are pressed (see src/ui.cpp), or when the player
 * 					enters a Structure/Indoor World (see src/ui.cpp again).
 * 
 *	player		 -	This points to a Player object, containing everything for
 * 					the player. Most calls made with currentWorld require a
 * 					Player object as an argument, and glOrtho is set based
 * 					off of the player's coordinates. This is probably the one
 * 					Entity-derived object that is not pointed to in the entity
 * 					array.
 * 
 *	entity		 -	Contains pointers to 'all' entities that have been created in
 * 					the game, including NPCs, Structures, and Mobs. World draws
 * 					and entity handling done by the world cycle through entities
 * 					using this array. Entities made that aren't added to this
 * 					array probably won't be noticable by the game.
 * 
 *	npc			 -	An array of all NPCs in the game. It's not exactly clear how
 * 					NPC initing is done, their constructed in this array, then set
 * 					to be pointed to by entity, then maybe spawned with Entity->spawn().
 * 					See src/entities.cpp for more.
 * 					This variable might be referenced as an extern in other files.
 * 
 *	build		 -	An array of all Structures in the game. Entries in entity point to
 * 					these, allowing worlds to handle the drawing and stuff of these.
 * 					See src/entities.cpp for more.
 * 
 *	mob			 -	An array of all Mobs in the game, entity entries should point to these
 * 					so the world can take care of them. See src/entities.cpp for more.
 * 
*/

World  						*currentWorld=NULL;
Player 						*player;
std::vector<Entity *	>	 entity;
std::vector<NPC			>	 npc;
std::vector<Structures *>	 build;
std::vector<Mob			>	 mob;

/*
 *	tickCount contains the number of ticks generated since main loop entrance.
 *	This variable might be used anywhere.
 * 
 *	deltaTime is used for interpolation stuff.
 * 
 *	Pretty sure these variables are considered static as they might be externally
 *	referenced somewhere.
*/

unsigned int tickCount = 0;
unsigned int deltaTime = 0;

/*
 *	names is used to open a file containing all possible NPC names. It is externally
 *	referenced in src/entities.cpp for getting random names.
 *
*/

FILE *names;

/*
 *	These variables are used by SDL_mixer to create sound.
 *	horn is not currently used, although it may be set.
 * 
*/

Mix_Music *music;
Mix_Chunk *horn;

/*
 *	loops is used for texture animation. It is believed to be passed to entity
 *	draw functions, although it may be externally referenced instead.
 * 
*/

unsigned int loops = 0;	// Used for texture animation

/*
 *	initEverything
 * 
 *	Before the main loop, things like the player, entities, and worlds should
 *	be created. This game has not reached the point that these can be scripted
 *	or programmed, so this function substitues for that. It is defined in
 *	src/gameplay.cpp.
 * 
*/

extern void initEverything(void);

/*
 *	mainLoop is in fact the main loop, which runs 'infinitely' (as long as gameRunning
 *	is set). Each loop updates timing values (tickCount and deltaTime), runs logic()
 *	if MSEC_PER_TICK milliseconds have passed, and then runs render().
 * 
 *	logic handles all user input and entity/world physics.
 * 
 *	render handles all drawing to the window, calling draw functions for everything.
 * 
*/

void logic(void);
void render(void);
void mainLoop(void);

/*
 *	millis
 * 
 *	We've encountered many problems when attempting to create delays for triggering
 *	the logic function. As a result, we decided on using the timing libraries given
 *	by <chrono> in the standard C++ library. This function simply returns the amount
 *	of milliseconds that have passed sine the epoch.
 * 
*/
unsigned int millis(void){
	std::chrono::system_clock::time_point now=std::chrono::system_clock::now();
	return std::chrono::duration_cast<std::chrono::milliseconds>(now.time_since_epoch()).count();
}

/*******************************************************************************
 * MAIN ************************************************************************
 *******************************************************************************/
int main(int argc, char *argv[]){
	/*
	 *	Initialize GLEW libraries, and exit if there was an error.
	 *	Not sure what they're for yet.
	 * 
	*/
	
	if(glewInit() < 0){
		std::cout << "GLEW was not able to initialize! Error: " << std::endl;
		return -1;
	}
	
	/*
	 *	(Attempt to) Initialize SDL libraries so that we can use SDL facilities and eventually
	 *	make openGL calls. Exit if there was an error.
	 * 
	*/
	
	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) < 0){
		std::cout << "SDL was not able to initialize! Error: " << SDL_GetError() << std::endl;
		return -1;
	}
	
	// Run SDL_Quit when main returns
    atexit(SDL_Quit);
    
    /*
     *	(Attempt to) Initialize SDL_image libraries with IMG_INIT_PNG so that we can load PNG
     *	textures for the entities and stuff.
     * 
    */
    
    if(!(IMG_Init(IMG_INIT_PNG) & IMG_INIT_PNG)){
		std::cout << "Could not init image libraries! Error: " << IMG_GetError() << std::endl;
		return -1;
	}
	
	// Run IMG_Quit when main returns
	atexit(IMG_Quit);
	
	/*
	 *	(Attempt to) Initialize SDL_mixer libraries for loading and playing music/sound files.
	 * 
	*/
	
	if(Mix_OpenAudio( 44100, MIX_DEFAULT_FORMAT, 2, 2048) < 0){
		std::cout << "SDL_mixer could not initialize! Error: " << Mix_GetError() << std::endl;
	}
	
	// Run Mix_Quit when main returns
	atexit(Mix_Quit);
    
    /*
     *	Create a window for SDL to draw to. Most parameters are the default, except for the
     *	following which are defined in include/common.h:
     * 
     *	GAME_NAME		the name of the game that is displayed in the window title bar
     *	SCREEN_WIDTH	the width of the created window
     *	SCREEN_HEIGHT	the height of the created window
     *	FULLSCREEN		makes the window fullscreen
     * 
    */
    
    window = SDL_CreateWindow(GAME_NAME,
							  SDL_WINDOWPOS_UNDEFINED,	// Spawn the window at random (undefined) x and y coordinates
							  SDL_WINDOWPOS_UNDEFINED,	//
							  SCREEN_WIDTH,
							  SCREEN_HEIGHT,
							  SDL_WINDOW_SHOWN | SDL_WINDOW_OPENGL
#ifdef FULLSCREEN
							  | SDL_WINDOW_FULLSCREEN
#endif // FULLSCREEN
                              );
    
    /*
     *	Exit if the window cannot be created
    */
    
    if(window==NULL){
		std::cout << "The window failed to generate! SDL_Error: " << SDL_GetError() << std::endl;
        return -1;
    }
    
    /*
     *	Create the SDL OpenGL context. Once created, we are allowed to use OpenGL functions.
     *	Saving this context to mainGLContext does not appear to be necessary as mainGLContext
     *	is never referenced again.
     * 
    */
    
    if((mainGLContext = SDL_GL_CreateContext(window)) == NULL){
		std::cout << "The OpenGL context failed to initialize! SDL_Error: " << SDL_GetError() << std::endl;
        return -1;
    }
	
	/*
	 *	Initialize the FreeType libraries and select what font to use using functions from the ui
	 *	namespace, defined in include/ui.h and src/ui.cpp. These functions should abort with errors
	 *	if they have error.
	 * 
	*/
	
	ui::initFonts();
	ui::setFontFace("ttf/Perfect DOS VGA 437.ttf");		// as in gamedev/ttf/<font>
	
	/*
	 *	Initialize the random number generator. At the moment, initRand is a macro pointing to libc's
	 *	srand, and its partner getRand points to rand. This is because having our own random number
	 *	generator may be favorable in the future, but at the moment is not implemented.
	 * 
	*/
	
	initRand(millis());

	/*
	 *	Do some basic setup for openGL. Enable double buffering, switch to by-pixel coordinates,
	 *	setup the alpha channel for textures/transparency, and finally hide the system's mouse
	 *	cursor so that we may draw our own.
	 * 
	*/
	
	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
	
	glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);
	
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	
	SDL_ShowCursor(SDL_DISABLE);

	/*
	 *	TODO - Initialize shaders n' stuff
	*/

	/*
	
	GLuint fragShader;
	GLuint shaderProgram;

	const GLchar *shaderSource = "shader.frag";
	GLint bufferln = GL_FALSE;

	shaderProgram = glCreateProgram();
	fragShader = glCreateShader(GL_FRAGMENT_SHADER);
	
	glShaderSource(fragShader, 1, &shaderSource, NULL);
	glCompileShader(fragShader);
	glGetShaderiv(fragShader, GL_COMPILE_STATUS, &bufferln);
	
	if(bufferln == GL_TRUE){
		std::cout << "Error compiling shader" << std::endl;
	}
	
	glAttachShader(shaderProgram, fragShader);
	glLinkProgram(shaderProgram);
	glValidateProgram(shaderProgram);

	//glEnable(GL_DEPTH_TEST);
	//glEnable(GL_MULTISAMPLE);
	
	*/

	/*
	 *	Open the names file containing potential names for NPCs and store it in the names file
	 *	pointer. This will be reference by getName in src/entities.cpp when NPCs are spawned. 
	 * 
	*/
	
	names = fopen("assets/names_en-us", "r+");
	
	/*
	 *	Create all the worlds, entities, mobs, and the player. This function is defined in
	 *	src/gameplay.cpp
	 * 
	*/
	
	initEverything();
	
	/*
	 *	Open a test background music file and sound. The background music is then played indefinitely
	 *	while the sound is never referenced again.
	 * 
	*/
	
	music = Mix_LoadMUS("assets/BennyHillTheme.wav");			// as in gamedev/assets/<sound>
	horn  = Mix_LoadWAV("assets/air-horn-club-sample_1.wav");	//
	
	Mix_VolumeMusic(15);		// Set the volume
	Mix_PlayMusic( music, -1 );	// Play music forever
	
	/*
	 *	Load a temporary background image.
	*/
	
	bgImage=loadTexture("assets/bg.png");
	
	/*
	 *	Load sprites used in the inventory menu. See src/inventory.cpp
	*/
	
	initInventorySprites();
	
	/**************************
	****     GAMELOOP      ****
	**************************/
	
	while(gameRunning){
		mainLoop();
	}
	
	/**************************
	****   CLOSE PROGRAM   ****
	**************************/
	
    /*
     *  Close the window and free resources
    */
    
    fclose(names);
    
    SDL_GL_DeleteContext(mainGLContext);
    SDL_DestroyWindow(window);
    
    return 0;	// Calls everything passed to atexit
}

/*
 *	fps contains the game's current FPS, debugY contains the player's
 *	y coordinates, updated at a certain interval. These are used in
 *	the debug menu (see below).
 * 
*/

static unsigned int fps=0;
static float debugY=0;

void mainLoop(void){
	static unsigned int debugDiv=0;			// A divisor used to update the debug menu if it's open
	
	static unsigned int prevTime    = 0,	// Used for timing operations
						currentTime = 0,	//
						prevPrevTime= 0;	// shit
						
	unsigned int i;							// Used for `for` loops
	
	if(!currentTime){						// Initialize currentTime if it hasn't been
		currentTime=millis();
		prevPrevTime=currentTime;
	}
	
	/*
	 *	Update timing values. This is crucial to calling logic and updating the window (basically
	 *	the entire game).
	*/
	
	prevTime	= currentTime;
	currentTime = millis();
	deltaTime	= currentTime - prevTime;

	/*
	 *	Run the logic handler if MSEC_PER_TICK milliseconds have passed.
	*/
	
	if(prevPrevTime + MSEC_PER_TICK >= currentTime){
		logic();
		prevPrevTime = currentTime;
	}

	/*
	 *	Update player and entity coordinates.
	*/
	
	player->loc.y+= player->vel.y				*deltaTime;
	player->loc.x+=(player->vel.x*player->speed)*deltaTime;
	
	for(int i=0;i<=entity.size();i++){
		
		entity[i]->loc.x += entity[i]->vel.x * deltaTime;
		entity[i]->loc.y += entity[i]->vel.y * deltaTime;
		
			 if(entity[i]->vel.x<0)entity[i]->left=true;
		else if(entity[i]->vel.x>0)entity[i]->left=false;
	}
	
	/*
	 * 	Update debug variables if necessary
	*/
	
	if(++debugDiv==20){
		debugDiv=0;
		
		fps=1000/deltaTime;
		
	}else if(!(debugDiv%10)){
		debugY = player->loc.y;
	}
	
	render();	// Call the render loop
}

void render(){
	/*
	 *	TODO fix this dense garbage ANDY :D lol hahahaha XDSSDSDDDDD
	*/
													//a matrix is a blank canvas for the computer to draw on, the matrices are stored in a "stack"
													//GL_PROJECTION has 2 matrices
													//GL_MODELVIEW has 32 matrices
	glMatrixMode(GL_PROJECTION); 					//set the matrix mode as projection so we can set the ortho size and the camera settings later on
	glPushMatrix(); 								//push the  matrix to the top of the matrix stack
	glLoadIdentity(); 								//replace the entire matrix stack with the updated GL_PROJECTION mode
	glOrtho(player->loc.x-SCREEN_WIDTH/2,player->loc.x+SCREEN_WIDTH/2,0,SCREEN_HEIGHT,-1,1);
	glMatrixMode(GL_MODELVIEW); 					//set the matrix to modelview so we can draw objects
	glPushMatrix(); 								//push the  matrix to the top of the matrix stack
	glLoadIdentity(); 								//replace the entire matrix stack with the updated GL_MODELVIEW mode
	glPushMatrix();									//basically here we put a blank canvas (new matrix) on the screen to draw on
	glPushAttrib( GL_DEPTH_BUFFER_BIT | GL_LIGHTING_BIT );
	glClear(GL_COLOR_BUFFER_BIT); 					//clear the matrix on the top of the stack

	/**************************
	**** RENDER STUFF HERE ****
	**************************/

	/*
	 *  Draw a temporary background image
	*/

	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D,bgImage);
	
	glBegin(GL_QUADS);
		glTexCoord2i(0,1);glVertex2i(-SCREEN_WIDTH*2,0);
		glTexCoord2i(1,1);glVertex2i( SCREEN_WIDTH*2,0);
		glTexCoord2i(1,0);glVertex2i( SCREEN_WIDTH*2,SCREEN_HEIGHT);
		glTexCoord2i(0,0);glVertex2i(-SCREEN_WIDTH*2,SCREEN_HEIGHT);
	glEnd();
	
	glDisable(GL_TEXTURE_2D);
	
	/*
	 *	Call the world's draw function, drawing the player, the world, and entities. Also
	 *	draw the player's inventory if it exists.
	*/

	player->near=true;			// Draw the player's name
	
	currentWorld->draw(player);
	
	player->inv->draw();

	/*
	 *	Draw UI elements. As of 10/20/2015 this includes the player's health bar and the dialog box.
	*/
	
	ui::draw();

	/*
	 *	Draw the debug overlay if it has been enabled.
	*/

	if(ui::debug){
		
		ui::setFontSize(16);
		
		ui::putText(player->loc.x-SCREEN_WIDTH/2,
					SCREEN_HEIGHT-ui::fontSize,
					"FPS: %d\nG:%d\nRes: %ux%u\nE: %d\nPOS: (x)%+.2f\n     (y)%+.2f\nQc: %u",
					fps,
					player->ground,
					SCREEN_WIDTH,
					SCREEN_HEIGHT,
					entity.size(),
					player->loc.x,
					debugY,			// The player's y coordinate
					player->qh.current.size()
					);
					
	}
	
	glColor3ub(255,255,255);							// Draw the mouse
	glBegin(GL_TRIANGLES);								//
		glVertex2i(ui::mouse.x,ui::mouse.y);			//
		glVertex2i(ui::mouse.x+HLINE*3.5,ui::mouse.y);	//
		glVertex2i(ui::mouse.x,ui::mouse.y-HLINE*3.5);	//
	glEnd();											//

	/**************************
	****  END RENDERING   ****
	**************************/

	glPopMatrix(); 									//take the matrix(s) off the stack to pass them to the renderer
	SDL_GL_SwapWindow(window); 						//give the stack to SDL to render it
}

void logic(){	
	ui::handleEvents();				// Handle keyboard / mouse input
	currentWorld->detect(player);	// Handle gravity and world bounds
	
	for(int i=0;i<=entity.size();i++){	// Loop through the whole entity stack
		if(entity[i]->alive){			// If the entity is alive
			switch(entity[i]->type){
			case NPCT:	// Handle NPCs
			
				if(entity[i]->canMove)entity[i]->wander((rand()%120 + 30), &entity[i]->vel); // Make the NPC wander
				
				// Check if the NPC is near the player and handle potential interaction
				if(pow((entity[i]->loc.x - player->loc.x),2) + pow((entity[i]->loc.y - player->loc.y),2) <= pow(40*HLINE,2)){	// NPC in range
					if(ui::mouse.x >= entity[i]->loc.x && ui::mouse.x <= entity[i]->loc.x + entity[i]->width &&	// Mouse is hovering over NPC
					   ui::mouse.y >= entity[i]->loc.y && ui::mouse.y <= entity[i]->loc.y + entity[i]->width){
						entity[i]->near=true; // Allows the NPC's name to be drawn
						if(SDL_GetMouseState(NULL, NULL)&SDL_BUTTON(SDL_BUTTON_RIGHT)){	// If right click
							entity[i]->interact();				// Interact with the player
							//Mix_PlayChannel( -1, horn, 0);	// Audio feedback
						}
					}else entity[i]->near=false;
				}
				break;
			case MOBT:	// Handle mobs
				entity[i]->wander((rand()%240 + 15),&entity[i]->vel);	// Make the mob wander
				break;
			default:
				break;
			}
		}
	}
	loops++;
}