08. Array Manipulator

function executeCommandsOverArray(integers, commands) {
  let currentCommand = commands.shift();

  function add(arr, tokens) {
    arr.splice(tokens[0], 0, Number(tokens[1]));
    return arr;
  }

  function addMany(arr, tokens) {
    // може и със spread operator
    let index = tokens.shift();

    for (let element of tokens) {
      arr.splice(index++, 0, element);
    }

    return arr;
  }

  function remove(arr, tokens) {
    arr.splice(Number(tokens[0]), 1);
    return arr;
  }

  function shift(arr, tokens) {
    let position = Number(tokens[0]);
    while (position > 0) {
      let element = arr.shift();
      arr.push(element);
      position--;
    }
    return arr;
  }

  function sumPairs(arr) {
    let output = [];
    while (arr.length > 0) {
      let a = arr.shift() || 0;
      let b = arr.shift() || 0;

      output.push(a + b);
    }

    return output;
  }

  while (currentCommand !== "print") {
    let tokens = currentCommand.split(" ");

    switch (tokens.shift()) {
      case "add":
        integers = add(integers, tokens);
        break;

      case "addMany":
        integers = addMany(integers, tokens);
        break;

      case "contains":
        console.log(integers.indexOf(Number(tokens[0])));

        break;

      case "remove":
        integers = remove(integers, tokens);

        break;

      case "shift":
        integers = shift(integers, tokens);
        break;

      case "sumPairs":
        integers = sumPairs(integers);
        break;
    }

    currentCommand = commands.shift();
  }

  return `[ ${integers.join(", ")} ]`;
}