const inputFile = await Bun.file("input").text();

const lines = inputFile.split("\n").filter((x) => x);

function between(x: number, min: number, max: number): boolean {
  return x >= min && x < max;
}

function countMs(str: string) {
  return (str.match(/M/g) || []).length;
}

function countSs(str: string) {
  return (str.match(/S/g) || []).length;
}

let xmasCount = 0;

for (let lineIdx = 0; lineIdx < lines.length; lineIdx++) {
  for (let charIdx of lines[lineIdx]
    .matchAll(/A/g)
    .toArray()
    .map((m) => m.index)) {
    let charPositions = [
      [lineIdx - 1, charIdx - 1], // up left
      [lineIdx - 1, charIdx + 1], // up right
      [lineIdx + 1, charIdx - 1], // down left
      [lineIdx + 1, charIdx + 1], // down right
    ].filter(
      ([li, ci]) =>
        between(li, 0, lines.length) && between(ci, 0, lines[lineIdx].length),
    );

    if (charPositions.length === 4) {
      let corners = "";
      for (let [li, ci] of charPositions) {
        corners += lines[li][ci];
      }

      if (countMs(corners) == 2 && countSs(corners) == 2) {
        xmasCount += 1;
      }
    }
  }
}

console.log(xmasCount);

export {};