#!/usr/bin/env python3

# https://adventofcode.com/2024/day/4

def get_lines(filename: str) -> list:
    with open(filename, "r") as file:
        return [line.strip() for line in file.readlines()]


def get_grid(lines: list) -> list:
    grid = []
    for line in lines:
        row = []
        for char in line:
            row.append(char)
        grid.append(row)
    return grid


def check_xmas_from_pos(grid: list, row: int, col: int,
                        direction: tuple, xmas_letters: list) -> bool:
    if grid[row][col] != xmas_letters[0]:
        # wrong letter, end of recursion
        return False

    if len(xmas_letters) == 1:
        # found the last letter, end of recursion
        return True

    # out of bounds, end of recursion
    new_row = row + direction[0]
    new_col = col + direction[1]
    if new_row < 0 or new_row >= len(grid):
        return False
    if new_col < 0 or new_col >= len(grid[0]):
        return False

    # go deeper into recursion with one less letter on the search string
    return check_xmas_from_pos(grid, new_row, new_col, direction, xmas_letters[1:])


def get_xmas_appearances(grid: list) -> int:
    xmas_appearances = 0
    directions = [(0, 1), (1, 1), (1, 0), (1, -1), (0, -1), (-1, -1), (-1, 0), (-1, 1)]
    xmas_letters = ['X', 'M', 'A', 'S']
    for row in range(len(grid)):
        for col in range(len(grid[0])):
            for direction in directions:
                if check_xmas_from_pos(grid, row, col, direction, xmas_letters):
                    print(f"Found XMAS at position ({row}, {col}) in direction {direction}")
                    xmas_appearances += 1
    return xmas_appearances


def main():
    # lines = get_lines("sample-input.txt")
    lines = get_lines("input.txt")

    grid = get_grid(lines)
    xmas_appearances = get_xmas_appearances(grid)
    print(f"Part 1: The word XMAS appears {xmas_appearances} times.")

if __name__ == '__main__':
    main()