import { promises as fsPromises } from "node:fs";

async function asyncReadFile(filename) {
    try {
        const contents = await fsPromises.readFile(filename, "utf-8");

        const arr = contents.split(/\r?\n/);

        return arr;
    } catch (err) {
        console.error(err);
    }
}

const countAdjacentRolls = (rows) => {
    const newData = structuredClone(rows);
    let countWithLessThanFourAdjacent = 0;

    rows.forEach((row, rowIndex) => {
        row.forEach((val, colIndex) => {
            if (val !== "@") return;

            let adjacentCount = 0;

            if (rowIndex > 0 && rows[rowIndex - 1][colIndex] === "@")
                adjacentCount++; // UM
            if (
                rowIndex > 0 &&
                colIndex < row.length - 1 &&
                rows[rowIndex - 1][colIndex + 1] === "@"
            )
                adjacentCount++; // UR
            if (colIndex < row.length - 1 && row[colIndex + 1] === "@")
                adjacentCount++; // MR
            if (
                rowIndex < rows.length - 1 &&
                colIndex < row.length - 1 &&
                rows[rowIndex + 1][colIndex + 1] === "@"
            )
                adjacentCount++; // DR
            if (
                rowIndex < rows.length - 1 &&
                rows[rowIndex + 1][colIndex] === "@"
            )
                adjacentCount++; // DM
            if (
                rowIndex < rows.length - 1 &&
                colIndex > 0 &&
                rows[rowIndex + 1][colIndex - 1] === "@"
            )
                adjacentCount++; // DL
            if (colIndex > 0 && row[colIndex - 1] === "@") adjacentCount++; // LM
            if (
                rowIndex > 0 &&
                colIndex > 0 &&
                rows[rowIndex - 1][colIndex - 1] === "@"
            )
                adjacentCount++; // UL

            if (adjacentCount < 4) {
                countWithLessThanFourAdjacent++;
                newData[rowIndex][colIndex] = "x";
            } else newData[rowIndex][colIndex] = "@";
        });
    });

    return {
        count: countWithLessThanFourAdjacent,
        newRows: newData,
    };
};

const useTestData = false;

const testDataToParse = `
..@@.@@@@.
@@@.@.@.@@
@@@@@.@.@@
@.@@@@..@.
@@.@@@@.@@
.@@@@@@@.@
.@.@.@.@@@
@.@@@.@@@@
.@@@@@@@@.
@.@.@@@.@.
`;

const dataToParse = await asyncReadFile("../input.txt");

let rollData = useTestData
    ? testDataToParse
          .trim()
          .split("\n")
          .map((val) => Array.from(val))
    : dataToParse.map((val) => Array.from(val));

let lastCount = -1;
let totalCount = 0;

while (lastCount !== 0) {
    const { count, newRows } = countAdjacentRolls(rollData);

    console.log(`Found ${count}`);

    if (useTestData)
        console.log("\n", {
            newRows: newRows.map((row) => row.join("")).join(`\n`),
        });

    totalCount += count;
    lastCount = count;
    rollData = newRows;
}

console.log(`Final count: ${totalCount}`);