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 useTestData = false;

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

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

const rows = useTestData
    ? testDataToParse
          .trim()
          .split("\n")
          .map((val) => Array.from(val))
    : dataToParse.map((val) => Array.from(val));
const newData = Array.from({ length: rows.length }, () =>
    new Array(rows[0].length).fill(".")
);

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] = "@";
    });
});

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

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