#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 <math.h> /* time calculations */

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

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

/*** GLOBAL VARIABLES ***/
volatile sig_atomic_t intCtrlC = 0; /* flag for ctrl-c interrupt */
int speed = 3;
int score = 0;
int boardSize = 15;
int updateInterval = 300000000L;
int obstacleSize = 2;
vectorp_t obstaclePositions;
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);
	intCtrlC = 1;
}

int main(int argc, char **argv) {
	/* parsing arguments */
	char *last_flag;
	int was_flag = 0;
	int obstacles = 2;
	for(int i = 1; i < argc; i++) {
		if(strcmp("--version", argv[i]) == 0) {
			printf("snake3, version 2.0\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] [--size board_size] [--speed speed] [--obstacles obstacles]\n");
			return 0;
		}
		else if(strcmp("--size", argv[i]) == 0 || strcmp("--speed", argv[i]) == 0 || strcmp("--obstacles", argv[i]) == 0) {
			last_flag = argv[i];
			was_flag = 1;
		}
		else if(was_flag) {
			if(strcmp("--size", last_flag) == 0) {
				boardSize = atoi(argv[i]);
				if(boardSize < 3) {
					fprintf(stderr, "%sboard size too small or argument invalid, please try again.%s\n", RED, COLOR_RESET);
					exit(1);
				}
			}
			else if(strcmp("--speed", last_flag) == 0) {
				speed = atoi(argv[i]);
				if(speed <= 0) {
					fprintf(stderr, "%sspeed level must be greater than zero and integer. Please try again.%s\n", RED, COLOR_RESET);
					exit(1);
				}
				else if(speed > 10) {
					fprintf(stderr, "%sspeed must not be greater than ten. Please try again.%s\n", RED, COLOR_RESET);
					exit(1);
				}
			}
			else if(strcmp("--obstacles", last_flag) == 0) {
				obstacles = atoi(argv[i]);
				if(obstacles < 0) {
					fprintf(stderr, "%sobstacle count cannot be negative. Please try again.%s\n", RED, COLOR_RESET);
					exit(1);
				}
			}
			was_flag = 0;
		}
		else {
			printf("usage: snake3 [--version] [--help]\n");
			exit(1);
		}
	}
	/* check argument compatibility */
	if(obstacles * 2 > boardSize) {
		fprintf(stderr, "%stoo many obstacles. Please try again.%s\n", RED, COLOR_RESET);
		exit(1);
	}
	/* 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);
	int opc = (int)pow(obstacleSize, 2) * obstacles;
	obstaclePositions = init_vectorp(malloc(opc * sizeof(vector_t)), opc);
	srand(time(NULL));
	/* place the obstacles */
	/* TODO: make this less recursive */
	int opi = 0;
	for(int i = 0; i < obstacles; i++) {
		while(1) {
			vector_t basePos = init_vector((rand() % (boardSize - (obstacleSize - 1))), (rand() % (boardSize - (obstacleSize - 1))));
			/* if obstacle overlaps snake, try again */
			int overlap = 0;
			for(int r = 0; r < obstacleSize; r++) {
				for(int c = 0; c < obstacleSize; c++) {
					vector_t voxelPos = init_vector(basePos.mx + c, basePos.my + r);
					for(int j = 0; j < snakePositions.length; j++) {
						if((snakePositions.vectors[j].mx == voxelPos.mx) && (snakePositions.vectors[j].my == voxelPos.my)) {
							overlap = 1;
						}
					}
					if(foodPos.mx == voxelPos.mx && foodPos.my == voxelPos.my) {
							overlap = 1;
					}
				}
			}
			if(overlap) {
				continue;
			}
			for(int r = 0; r < obstacleSize; r++) {
				for(int c = 0; c < obstacleSize; c++) {
					vector_t voxelPos = init_vector(basePos.mx + c, basePos.my + r);
					obstaclePositions.vectors[opi] = voxelPos;
					opi++;
				}
			}
			break;
		}
	}
	/* 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(intCtrlC) {
			goto EXIT;
		}

		/* 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 = round((float)updateInterval / ((float)speed / 3));
		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;
		}
		/* check if snake landed on an obstacle */
		int ateFood = 0;
		/* check if snake landed on the food */
		if((snakePositions.vectors[0].mx + lastMoveDir.mx == foodPos.mx) && (snakePositions.vectors[0].my + lastMoveDir.my == foodPos.my)) {
			ateFood = 1;
			score += 1;
			if(updateInterval > 100000000) {
				updateInterval -= 10000000;
			}
			/* move the food */
			while(1) {
				foodPos = init_vector(1 + (rand() % (boardSize - 2)), 1 + (rand() % (boardSize - 2)));
				/* if food overlaps snake or obstacles, 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;
					}
				}
				for(int i = 0; i < obstaclePositions.length; i++) {
					if((obstaclePositions.vectors[i].mx == foodPos.mx) && (obstaclePositions.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 */
		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 */
				goto EXIT;
			}
		}
		for(int i = 0; i < obstaclePositions.length; i++) {
			if((snakePositions.vectors[0].mx + lastMoveDir.mx == obstaclePositions.vectors[i].mx) && (snakePositions.vectors[0].my + lastMoveDir.my == obstaclePositions.vectors[i].my)) {
				goto EXIT;
			}
		}
	}
EXIT:
	/* 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;
			/* 0=horizontal, 1=vertical, 2=diagonal slant right, 3=diagonal slant left */
			int tailOrientation = 0;
			for(int i = 0; i < snakePositions.length; i++) {
				if(snakePositions.vectors[i].mx == c && snakePositions.vectors[i].my == r) {
					if(i > 0) {
						type = 2;
						/* get the delta to the connecting tail */
						int dx;
						int dy;
						if(i < snakePositions.length - 1) {
							dx = snakePositions.vectors[i - 1].mx - snakePositions.vectors[i + 1].mx;
							dy = snakePositions.vectors[i - 1].my - snakePositions.vectors[i + 1].my;
						}
						else {
							dx = snakePositions.vectors[i - 1].mx - c;
							dy = snakePositions.vectors[i - 1].my - r;
						}
						if(dy == 0) {
							tailOrientation = 0;
						}
						else if(dx == 0) {
							tailOrientation = 1;
						}
						else if((dx == 1 && dy == 1) || (dx == -1 && dy == -1)) {
							tailOrientation = 3;
						}
						else if((dx == -1 && dy == 1) || (dx == 1 && dy == -1)) {
							tailOrientation = 2;
						}
					}
					else {
						type = 1;
					}
					break;
				}
			}
			if(foodPos.mx == c && foodPos.my == r) {
				type = 3;
			}
			for(int i = 0; i < obstaclePositions.length; i++) {
				if(obstaclePositions.vectors[i].mx == c && obstaclePositions.vectors[i].my == r) {
					type = 4;
					break;
				}
			}
			/* 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 */
				char bodyChar = tailOrientation == 0 ? '-'
					: tailOrientation == 1 ? '|'
					: tailOrientation == 2 ? '/'
					: tailOrientation == 3 ? '\\'
					: '*';
				printf("%s%c %s", GRN, bodyChar, COLOR_RESET);
			}
			else if(type == 3) {
				/* food */
				printf("%sF %s", MAG, COLOR_RESET);
			}
			else if(type == 4) {
				/* obstacle */
				printf("%s# %s", MAG, COLOR_RESET);
			}
		}
		printf("\n");
	}
}