/**
 * fifteen.c
 *
 * Computer Science 50
 * Problem Set 3
 *
 * Implements Game of Fifteen (generalized to d x d).
 *
 * Usage: fifteen d
 *
 * whereby the board's dimensions are to be d x d,
 * where d must be in [DIM_MIN,DIM_MAX]
 *
 * Note that usleep is obsolete, but it offers more granularity than
 * sleep and is simpler to use than nanosleep; `man usleep` for more.
 */

#define _XOPEN_SOURCE 500

#include <cs50.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

// constants
#define DIM_MIN 3
#define DIM_MAX 9

// board
int board[DIM_MAX][DIM_MAX];

// dimensions
int d;

// prototypes
void clear(void);
void greet(void);
void init(void);
void draw(void);
bool move(int tile);
bool won(void);

int main(int argc, string argv[])
{
    // ensure proper usage
    if (argc != 2)
    {
        printf("Usage: fifteen d\n");
        return 1;
    }

    // ensure valid dimensions
    d = atoi(argv[1]);
    if (d < DIM_MIN || d > DIM_MAX)
    {
        printf("Board must be between %i x %i and %i x %i, inclusive.\n",
            DIM_MIN, DIM_MIN, DIM_MAX, DIM_MAX);
        return 2;
    }

    // open log
    FILE* file = fopen("log.txt", "w");
    if (file == NULL)
    {
        return 3;
    }

    // greet user with instructions
    greet();

    // initialize the board
    init();

    // accept moves until game is won
    while (true)
    {
        // clear the screen
        clear();

        // draw the current state of the board
        draw();

        // log the current state of the board (for testing)
        for (int i = 0; i < d; i++)
        {
            for (int j = 0; j < d; j++)
            {
                fprintf(file, "%i", board[i][j]);
                if (j < d - 1)
                {
                    fprintf(file, "|");
                }
            }
            fprintf(file, "\n");
        }
        fflush(file);

        // check for win
        if (won())
        {
            printf("ftw!\n");
            break;
        }

        // prompt for move
        printf("Tile to move: ");
        int tile = GetInt();

        // quit if user inputs 0 (for testing)
        if (tile == 0)
        {
            break;
        }

        // log move (for testing)
        fprintf(file, "%i\n", tile);
        fflush(file);

        // move if possible, else report illegality
        if (!move(tile))
        {
            printf("\nIllegal move.\n");
            usleep(500000);
        }

        // sleep thread for animation's sake
        usleep(500000);
    }

    // close log
    fclose(file);

    // success
    return 0;
}

/**
 * Clears screen using ANSI escape sequences.
 */
void clear(void)
{
    printf("\033[2J");
    printf("\033[%d;%dH", 0, 0);
}

/**
 * Greets player.
 */
void greet(void)
{
    clear();
    printf("WELCOME TO GAME OF FIFTEEN\n");
    usleep(2000000);
}

/**
 * Initializes the game's board with tiles numbered 1 through d*d - 1
 * (i.e., fills 2D array with values but does not actually print them).
 */
void init(void)
{
    int n = (d*d) - 1;
    int i, j = 0;

    for(i = 0; i < d; i++)
    {
        for(j = 0; j < d; j++)
        {
            board[i][j] = n;
            n--;

        }

    }

    if(d % 2 == 0)
    {
        // if number of tiles is odd swaps the position of 2 and 1
        int swap;
        swap = board[d-1][d-2];
        board[d-1][d-2] = board[d-1][d-3];
        board[d-1][d-3] = swap;
    }
}

/**
 * Prints the board in its current state.
 */
void draw(void)
{
    int i, j = 0;
    for(i = 0; i < d; i++)
    {
        for(j = 0; j < d; j++)
        {
            printf("%2d  ", board[i][j]);

        }
        printf("\n\n");
    }

}

/**
 * If tile borders empty space, moves tile and returns true, else
 * returns false.
 */
bool move(int tile)
{
     int i, j, temp, blank_i, blank_j;

    // searching for the tile

    // rows
    for (i = 0; i < d; i++)
    {
        // coloumns
        for (j = 0; j < d; j++)
        {
                // finding the tile
                if (board[i][j] == tile)
                {

                        // searching for the blank

                        // rows
                        for (blank_i = 0; blank_i < d; blank_i++)
                        {
                            // coloumns
                            for (blank_j = 0; blank_j < d; blank_j++)
                            {
                                // finding the blank
                                if (board[blank_i][blank_j] == 0)
                                {
                                    // making sure the move is legal
                                    if ((i == blank_i && j+1 == blank_j) || (i == blank_i && j-1 == blank_j) ||
                                    (i+1 == blank_i && j == blank_j) || (i-1 == blank_i && j == blank_j))
                                    {
                                        // swapping the tile and the 0 (blank)
                                        temp = board[i][j];
                                        board[i][j] = board[blank_i][blank_j];
                                        board[blank_i][blank_j] = temp;
                                        return true;
                                    }
                                }
                            }
                        }

                }
        }
    }
     return false;
}

/**
 * Returns true if game is won (i.e., board is in winning configuration),
 * else false.
 */
bool won(void)
{
    int i, j = 0;
    for(i = 0; i < d; i++)
    {
        for(j = 0; j < d; j++)
        {
            if(board[i][j+1] != board[i][j] - 1)
            {
                return false;
            }

        }

    }
    return true;
}