merge.js

var prompt = require("prompt");

var array = [
  [0, 0, 0, 0, 0],
  [0, 16, 0, 0, 0],
  [0, 4, 0, 0, 0],
  [16, 32, 0, 0, 0],
  [8, 16, 0, 0, 0],
  [4, 8, 4, 0, 0],
];

function insert(i, j, value) {
  array[i][j] = value;
}

function display() {
  console.log(array);
}

function checkPossibilities(i, j) {
  let left = false;
  let right = false;
  let bottom = false;

  if (j > 0) {
    if (array[i][j] === array[i][j - 1]) {
      left = true;
    }
  }

  if (j < 4) {
    if (array[i][j] === array[i][j + 1]) {
      right = true;
    }
  }

  if (i < 5) {
    if (array[i][j] === array[i + 1][j]) {
      bottom = true;
    }
  }
  return { left, right, bottom };
}

function mergeLeft(i, j) {
  array[i][j] = array[i][j] * 2;
  array[i][j - 1] = 0;
}

function mergeRight(i, j) {
  array[i][j] = array[i][j] * 2;
  array[i][j + 1] = 0;
}

function mergeBottom(i, j) {
  array[i][j] = array[i][j] * 2;
  array[i + 1][j] = 0;
}

function merge(i, j, left, right, bottom) {
  if (left) {
    mergeLeft(i, j);
  }
  if (right) {
    mergeRight(i, j);
  }
  if (bottom) {
    mergeBottom(i, j);
  }
}

function finalShift(i, j) {
  let x = i;
  if (i < 5) {
    if (array[i + 1][j] === 0) {
      array[i + 1][j] = array[i][j];
      array[i][j] = 0;
      x = x + 1;
    }
  }
  return x;
}

function shiftDown(x, y) {
  i = x;
  j = y;
  let temp;
  for (i = x; i > 0; i--) {
    if (array[i - 1][j] !== 0) {
      array[i][j] = array[i - 1][j];
      array[i - 1][j] = 0;
    }
  }
}

// display();

// let { left, right, bottom } = checkPossibilities(4, 2);

// merge(4, 2, left, right, bottom);

// finalShift(4, 2);

// shiftDown(5, 1);

// display();

async function main() {
  display();
  // This json object is used to configure what data will be retrieved from command line.
  var prompt_attributes = [
    {
      name: "i",
    },
    {
      name: "j",
    },
    {
      name: "value",
    },
  ];

  let game_over = false;
  let lock;

  while (!game_over && !lock) {
    prompt.start();

    // Start the prompt to read user input.
    lock = true;

    // Prompt and get user input then display those data in console.
    let next = async function () {
      return new Promise((resolve, reject) => {
        prompt.get(prompt_attributes, function (err, result) {
          if (err) {
            reject(err);
          } else {
            console.log("Command-line:");

            var i = parseInt(result.i);
            var j = parseInt(result.j);
            var value = parseInt(result.value);
            insert(i, j, value);
            let exit = false;

            while (!exit) {
              let { left, right, bottom } = checkPossibilities(i, j);
              merge(i, j, left, right, bottom);
              if (left) {
                shiftDown(i, j - 1);
              }
              if (right) {
                shiftDown(i, j + 1);
              }
              i = finalShift(i, j);
              if (!left && !right && !bottom) {
                exit = true;
              }
            }

            resolve(false);
          }
        });
      });
    };

    lock = await next();
    display();
  }
}

main()
  .then(() => {
    console.log("....");
  })
  .catch((err) => {
    console.log(err);
  });