--- Day 4: Ceres Search ---

"Looks like the Chief's not here. Next!" One of The Historians pulls out a device and pushes the only button on it. After a brief flash, you recognize the interior of the Ceres monitoring station!

As the search for the Chief continues, a small Elf who lives on the station tugs on your shirt; she'd like to know if you could help her with her word search (your puzzle input). She only has to find one word: XMAS.

This word search allows words to be horizontal, vertical, diagonal, written backwards, or even overlapping other words. It's a little unusual, though, as you don't merely need to find one instance of XMAS - you need to find all of them. Here are a few ways XMAS might appear, where irrelevant characters have been replaced with .:

..X...
.SAMX.
.A..A.
XMAS.S
.X....
The actual word search will be full of letters instead. For example:

MMMSXXMASM
MSAMXMSMSA
AMXSXMAAMM
MSAMASMSMX
XMASAMXAMM
XXAMMXXAMA
SMSMSASXSS
SAXAMASAAA
MAMMMXMMMM
MXMXAXMASX
In this word search, XMAS occurs a total of 18 times; here's the same word search again, but where letters not involved in any XMAS have been replaced with .:

....XXMAS.
.SAMXMS...
...S..A...
..A.A.MS.X
XMASAMX.MM
X.....XA.A
S.S.S.S.SS
.A.A.A.A.A
..M.M.M.MM
.X.X.XMASX
Take a look at the little Elf's word search. How many times does XMAS appear?

Your puzzle answer was 2434.

--- Part Two ---

The Elf looks quizzically at you. Did you misunderstand the assignment?

Looking for the instructions, you flip over the word search to find that this isn't actually an XMAS puzzle; it's an X-MAS puzzle in which you're supposed to find two MAS in the shape of an X. One way to achieve that is like this:

M.S
.A.
M.S
Irrelevant characters have again been replaced with . in the above diagram. Within the X, each MAS can be written forwards or backwards.

Here's the same example from before, but this time all of the X-MASes have been kept instead:

.M.S......
..A..MSMS.
.M.S.MAA..
..A.ASMSM.
.M.S.M....
..........
S.S.S.S.S.
.A.A.A.A..
M.M.M.M.M.
..........
In this example, an X-MAS appears 9 times.

Flip the word search from the instructions back over to the word search side and try again. How many times does an X-MAS appear?
const fs = require('fs');

// Read the input file and create the grid
const data = fs.readFileSync('input.txt', 'utf8');
const lines = data.trim().split('\n');
const grid = lines.map(line => line.trim().split(''));

const numRows = grid.length;
const numCols = grid[0].length;
let count = 0;

// Directions for diagonals
const dir1 = [-1, -1]; // Top-left to bottom-right
const dir2 = [-1,  1]; // Top-right to bottom-left

for (let row = 0; row < numRows; row++) {
    for (let col = 0; col < numCols; col++) {
      if (grid[row][col] === 'A') {
        let valid1 = false;
        let valid2 = false;
  
        // Check diagonal from top-left to bottom-right
        // Check diagonal from top-left to bottom-right
if (
    row - 1 >= 0 && col - 1 >= 0 &&
    row + 1 < numRows && col + 1 < numCols &&
    (
      (grid[row - 1][col - 1] === 'M' && grid[row + 1][col + 1] === 'S') ||
      (grid[row - 1][col - 1] === 'S' && grid[row + 1][col + 1] === 'M')
    )
  ) {
    valid1 = true;
  }
  
  // Check diagonal from top-right to bottom-left
  if (
    row - 1 >= 0 && col + 1 < numCols &&
    row + 1 < numRows && col - 1 >= 0 &&
    (
      (grid[row - 1][col + 1] === 'M' && grid[row + 1][col - 1] === 'S') ||
      (grid[row - 1][col + 1] === 'S' && grid[row + 1][col - 1] === 'M')
    )
  ) {
    valid2 = true;
  }
  
  // If both diagonals form 'MAS' or 'SAM', increment count
  if (valid1 && valid2) {
    count++;
  }
      }
    }
  }
  
  console.log(`Number of X-MAS patterns found: ${count}`);