#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#if 0
#define PART_1
#else
#define PART_2
#endif

#if 0
#define FILE_PATH "example.txt"
#define RULES  2
int WIDTH  = 11;
int HEIGHT = 15;
#else
#define FILE_PATH "input.txt"
#define RULES  12
int WIDTH  = 1311;
int HEIGHT = 895;
#endif

#define BOARD_SZ ((WIDTH)*(HEIGHT))

int *board = NULL;
int rules_val[RULES] = {0};
int rules_axis[RULES] = {0}; // 0 is x; 1 is y

void parse()
{
    FILE *fp = fopen(FILE_PATH, "r");
    if(!fp) {
        fprintf(stderr, "Could not open file: %s", FILE_PATH);
        return;
    }

    board = malloc(BOARD_SZ*sizeof(int));

    char line[256];
    char *tok;
    int read_rules = -1;
    while(fgets(line, sizeof(line), fp) != NULL)
    {
        if(line[0] == '\n') {
            read_rules = 0;
        } else if(read_rules < 0) {
            tok = strtok(line, ",");
            int x = atoi(tok);
            tok = strtok(NULL, ",");
            int y = atoi(tok);

            assert(strtok(NULL, ",") == NULL);
            assert(x >= 0 && x < WIDTH);
            assert(y >= 0 && y < HEIGHT);
            board[y * WIDTH + x] = 1;
        } else {
            tok = strtok(line, "=");
            rules_axis[read_rules] = (tok[11] == 'y');
            tok = strtok(NULL, "=");
            rules_val[read_rules] = atoi(tok);
            read_rules++;
            assert(strtok(NULL, "=") == NULL);
        }
    }

    fclose(fp);
}

void fold(int rules_i)
{
    int *board_cpy = malloc(BOARD_SZ*sizeof(int));

    memcpy(board_cpy, board, BOARD_SZ*sizeof(int));
    free(board);

    int old_width = WIDTH;
    if(rules_axis[rules_i] == 0) WIDTH = (WIDTH-1)/2;
    else                         HEIGHT = (HEIGHT-1)/2;

    board = malloc(BOARD_SZ*sizeof(int));

    for(int i = 0; i < HEIGHT; i++)
    {
        for(int j = 0; j < WIDTH; j++)
        {
            int index = i * WIDTH + j;
            int bc_index = i * old_width + j;
            int mirror;

            if(rules_axis[rules_i] == 0) {
                mirror = i * old_width + (2*rules_val[rules_i] - j);
            } else {
                mirror = ((2*rules_val[rules_i] - i)
                    * old_width) + j;
            }

            board[index] =
                board_cpy[bc_index] +
                board_cpy[mirror];
        }
    }

    free(board_cpy);
}

void print_board()
{
    for(int i = 0; i < HEIGHT; i++)
    {
        for(int j = 0; j < WIDTH; j++)
        {
            if(board[i * WIDTH + j] == 0)
                putc('.', stdout);
            else
                putc('#', stdout);
        }
        putc('\n', stdout);
    }
}

void print_rules()
{
    for(int i = 0; i < RULES; i++)
    {
        char axis;
        if(rules_axis[i] == 0)  axis = 'x';
        else                    axis = 'y';
        printf("fold along %c=%d\n", axis, rules_val[i]);
    }
}

void part_1()
{
    parse();
    fold(0);

    int visible = 0;
    for(int i = 0; i < BOARD_SZ; i++)
    {
        if(board[i] > 0) visible++;
    }

    printf("%d dots are visible\n", visible);
}

void part_2()
{
    parse();
    for(int i = 0; i < RULES; i++)
        fold(i);

    print_board();
}

int main(void)
{

#ifdef PART_1
    part_1();
#endif

#ifdef PART_2
    part_2();
#endif

    free(board);
    return 0;
}