#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
#include <signal.h> //handling ctrl-c
#include <sys/ioctl.h> //terminal size
#include <string.h> // argument parsing

#include "vector.h"
#include "snake.h"
#include "conio.h"
#include "colors.h"

#define UNUSED(x) (void)(x)

/*** GLOBAL VARIABLES ***/
volatile sig_atomic_t INT_CTRL_C = 0; //flag for ctrl-c interrupt
int SCORE = 0;

int boardSize = 15;
int updateInterval = 300000000L;

vectorp_t snakePositions; 
vector_t foodPos;
vector_t lastMoveDir;

void interrupt_handler(int sig); // passed into signal(3) to handle ctrl-c interrupts 

//unsafe functions like printf cannot be called in async interrupt handler
void interrupt_handler(int sig) {
	UNUSED(sig);
	INT_CTRL_C = 1;
}

int main(int argc, char **argv) {
	for (int i = 0; i < argc; i ++) {
		if (strcmp("--version", argv[i]) == 0) {
			printf("snake3, version 1.0\n");
			printf("Copyright 2023 Kai Stevenson\n");
			printf("This software was licensed under the MIT license;\n");
			printf("for more information, see the license file.\n");
			return 0;
		} else if (strcmp("--help", argv[i]) == 0) {
			printf("usage: snake3 [--version] [--help]\n");
			return 0;
		}
	}
	//get terminal size
	struct winsize win;
	ioctl(fileno(stdout), TIOCGWINSZ, &win);
	int width = (int)(win.ws_col);
	int height = (int)(win.ws_row);
	//multiplied by 2 to account for the fact that the board is twice as wide as high
	int smallestAxis = width / 2 < height ? width / 2 : height;
	boardSize = smallestAxis < boardSize ? smallestAxis : boardSize;
	//hide cursor
	printf("\033[?25l");
	//make a new thread handling interrupts
	signal(SIGINT, interrupt_handler); 
	//init values
	snakePositions = init_vectorp(malloc(5 * sizeof(vector_t)), 5);
	snakePositions.vectors[0] = init_vector(5, 5);
	snakePositions.vectors[1] = init_vector(5, 4);
	snakePositions.vectors[2] = init_vector(5, 3);
	snakePositions.vectors[3] = init_vector(4, 3);
	snakePositions.vectors[4] = init_vector(3, 3);
	foodPos = init_vector(7, 9);
	lastMoveDir = init_vector(0, 1);
	srand(time(NULL));
	//clear the screen so as to prevent artifacting
	printf("\033[2J");
	//prepare the pointers which will be used to communicate with the input getting thread
	volatile int* lastInput = calloc(1, sizeof(int));
	int* cancellationToken = calloc(1, sizeof(int));
	//and the wrapper struct
	threadArg_t threadArg;
	threadArg.returnV = (void*)lastInput;
	threadArg.cancellationToken = cancellationToken;
	//create listener thread
	pthread_t listenerID;
	pthread_create(&listenerID, NULL, get_dir_loop, &threadArg);
	//main game logic loop
	while(1) {
		//handle ctrl-c interrupt
		if (INT_CTRL_C) {
			//unhide cursor
			printf("\033[?25h");
			//kill the listener thread
			*cancellationToken = 1;
			printf("Your score was %d. Press any key to exit\n", SCORE);
			pthread_join(listenerID, NULL);
			free(cancellationToken);
			free((int*)lastInput);
			return 0;
		}

		//first, draw the current state of the board
		draw_board();
		//handle player input
		//wait for the specified interval
		struct timespec time;
		time.tv_sec = 0;
		time.tv_nsec = updateInterval;
		nanosleep(&time, NULL);
		//read the most recent value emitted by the listener
		vector_t dir = parse_dir(*(char*)lastInput);
		//if the player inputted a valid direction, use it. otherwise, use his last valid input
		if((dir.mx != 0 || dir.my != 0) && !(dir.mx == 1 && lastMoveDir.mx == -1) && !(dir.mx == -1 && lastMoveDir.mx == 1) && !(dir.my == 1 && lastMoveDir.my == -1) && !(dir.my == -1 && lastMoveDir.my == 1)) {
			lastMoveDir = dir;
		}
		else {
		}
		//check if snake landed on the food
		int ateFood = 0;
		if((snakePositions.vectors[0].mx + lastMoveDir.mx == foodPos.mx) && (snakePositions.vectors[0].my + lastMoveDir.my == foodPos.my)) {
			ateFood = 1;
			SCORE = SCORE + 1;
			if (updateInterval > 50000000) {
				updateInterval -= 20000000;
			}
			//move the food
			while(1) {
				foodPos = init_vector(1 + (rand() % (boardSize - 2)), 1 + (rand() % (boardSize - 2)));
				//if food overlaps snake, try again
				int overlap = 0;
				for(int i = 0; i < snakePositions.length; i++) {
					if((snakePositions.vectors[i].mx == foodPos.mx) && (snakePositions.vectors[i].my == foodPos.my)) {
						overlap = 1;
					}
				}
				if(!overlap) {
					break;
				}
			}
		}
		//move the snake
		vectorp_t newSnakePositions = move_snake(lastMoveDir, ateFood);
		free(snakePositions.vectors);
		snakePositions = newSnakePositions;
		//check if snake landed on self
		int died = 0;
		for(int i = 1; i < snakePositions.length; i++) {
			if(snakePositions.vectors[0].mx == snakePositions.vectors[i].mx && snakePositions.vectors[0].my == snakePositions.vectors[i].my) {
				//game over
				died = 1;
			}
		}
		if(died) {
			break;
		}
	}
	//clear the last getch call from the listener
	*cancellationToken = 1;
	printf("\n%sYou died. Score: %d. Press any key to exit%s\n", RED, SCORE, COLOR_RESET);
	printf("\033[?25h");
	pthread_join(listenerID, NULL);
	free(cancellationToken);
	free((int*)lastInput);
	return 0;
}
void* get_dir_loop(void* threadArg) {
	while(!*(int*)((threadArg_t*)threadArg)->cancellationToken) {
		*(char*)((threadArg_t*)threadArg)->returnV = getch();
	}
	return NULL;
}
//parses WASD or HJKL, returns the necessary deltas to move within a 2d array
vector_t parse_dir(char cDir) {
	if(cDir == 'w' || cDir == 'k') {
		return init_vector(0, -1);
	}
	else if(cDir == 'd' || cDir == 'l') {
		return init_vector(1, 0);
	}
	else if(cDir == 's' || cDir == 'j') {
		return init_vector(0, 1);
	}
	else if(cDir == 'a' || cDir == 'h') {
		return init_vector(-1, 0);
	}
	else {
		return init_vector(0, 0);
	}
}
vectorp_t move_snake(vector_t dir, int lengthen) {
	int newLength = snakePositions.length + (lengthen ? 1 : 0);
	vector_t* newSnakePositions = malloc((newLength * sizeof(vector_t)));
	//wrap around edges
	int nhx = snakePositions.vectors[0].mx + dir.mx;
	nhx = nhx < 0 ? boardSize - 1 : nhx >= boardSize ? 0 : nhx;
	int nhy = snakePositions.vectors[0].my + dir.my;
	nhy = nhy < 0 ? boardSize - 1 : nhy >= boardSize ? 0 : nhy;
	newSnakePositions[0] = init_vector(nhx, nhy);
	for(int i = 1; i < newLength; i++) {
		newSnakePositions[i] = snakePositions.vectors[i - 1];
	}
	return init_vectorp(newSnakePositions, newLength); 
}
void draw_board() {
	//move the cursor to the top left corner of the screen
	printf("\033[0;0H");
	//iterate through and write the board
	for(int r = 0; r < boardSize; r++) {
		for(int c = 0; c < boardSize; c++) {
			//determine the contents of the board position
			int type = 0;
			for(int i = 0; i < snakePositions.length; i++) {
				if(snakePositions.vectors[i].mx == c && snakePositions.vectors[i].my == r) {
					type = i ? 2 : 1;
					break;
				}
				else {
					type = 0;
				}
			}
			if(foodPos.mx == c && foodPos.my == r) {
				type = 3;
			}
			//append the appropriate value
			if(type == 0) {
				//empty square
				printf("` ");
			}
			else if(type == 1) {
				//snake head
				printf("%s@ %s", GRN, COLOR_RESET);
			}
			else if(type == 2) {
				//snake body
				printf("%s* %s", GRN, COLOR_RESET);
			}
			else if(type == 3) {
				//food
				printf("%sF %s", MAG, COLOR_RESET);
			}
		}
		printf("\n");
	}
}