const fs = require('fs/promises');

const sum = (arr) => arr.reduce((total, num) => total+num, 0);
const arrayOfLength = n => Array.from(Array(n).keys()).map(() => {});

const main = async () => {
  const input = (await fs.readFile("./input.txt", 'utf8')).split("\n");

  const coord = ([x, y]) => {

    if(isNaN(x) || typeof y === "undefined") {
      throw new Error("");
    }
    return `${x}-${y}`;
  };

  let sandUnitCount = 0;


  const fillPath = ([x1, y1], [x2, y2]) => {
    const fillIns = [];
    if(x1 === x2) {
      const yDiff = y2 - y1;
      for(let y = y1; y !== y2; y = y + (Math.abs(yDiff)/yDiff))  {
        fillIns.push(coord([x1, y]));
      }
    } else {
      const xDiff = x2 - x1;

      for(let x = x1; x !== x2; x = x + (xDiff/Math.abs(xDiff)))  {
        fillIns.push(coord([x, y1]));
      }
    }
    return fillIns;

  };
  const grid = input.reduce((obj, row, i) => {
    if(row === "" ) {
      return obj;
    }
    const path = row.split(" -> ");
    for(let i = 0; i < path.length - 1; i++) {
      const start = path[i].split(",").map(x => parseInt(x));
      const end = path[i + 1].split(",").map(x => parseInt(x));

      const filledIn = fillPath(start, end);
      filledIn.forEach(x => obj[x] = "#")
    }
    const lastRock = path[path.length - 1].split(",").map(x => parseInt(x))
    obj[coord(lastRock)] = "#";

    return obj;
  }, {})

  const sandFall = (x, y) => {
    if(y === 174) {
      return [x, y];
    }
    if(!grid[coord([x, y + 1])]) {
      return sandFall(x, y + 1);
    }
    if(!grid[coord([x - 1, y + 1])]) {
      return sandFall(x - 1, y + 1);
    }
    if(!grid[coord([x + 1, y + 1])]) {
      return sandFall(x + 1, y + 1);
    }
    return [x, y];
  };

  const print = () => {
      for(let y = 0; y < 175; ++y) {
        console.log(arrayOfLength(100).map((_, i) => grid[coord([i + 450, y])] || ".").join(""));
      }
      console.log("\n\n\n")
      console.log("Sand count: ", sandUnitCount);
  };

  while(true) {
    const loc = sandFall(500, 0);
    sandUnitCount++;
    grid[coord(loc)] = "o";
    console.log("Location of sand: ", loc);
    if(loc[0] === 500 && loc[1] === 0) {
      break;
    }
  }
  console.log("Answer: ", sandUnitCount);
  print();
}

main();