spacetalky問題回答

spacetalky.js

#! /usr/bin/env node

var fs = require('fs');
var readline = require('readline');

if (process.argv.length !== 3) {
  console.log("usage:command <file path>");
  process.exit(1);
}

var filePath = process.argv[2];

var rl = readline.createInterface({
  input:  fs.createReadStream(filePath, {encoding: 'utf8'}),
  output:  {},
});

rl.on('line',  function(line) {
  answer = answerString(line);
  console.log(answer);
});

function answerString(line) {
  if (!canEncode(line)) {
    return 'X:' + line;
  } else {
    return stretchString(line) + ':' + line;
  }
}

function stretchString(str) {
  if (str.length % 2 !== 0) throw "illegal argument";

  var array = str.splitN(2);
  var arrayStretched = array.map(function (e) {
    return stretchTwoChar(e);
  });
  return arrayStretched.join('');
}

function toDecimal(c) {
  if (c === undefined) throw "argument error";
  var s = 'abcdefghijklmnopqrstuvwxyz';
  return s.indexOf(c) + 1;
}

function stretchTwoChar(str) {
  var first = str[0];
  var repeat = toDecimal(str[1]);
  var newStr = '';
  for (var i = 0; i < repeat; i++) {
    newStr += first;
  }
  return newStr;
}

function canEncode(str) {
  var last = '';

  if (str.length % 2 === 1) return false;

  for (var i = 0; i < str.length; i += 2) {
    if (last === str[i] && str[i - 1] !== 'z') return false;
    last = str[i];
  }
  return true;
}

String.prototype.splitN = function (n) {
  var a = [];

  var begin = 0;
  var i = 0;
  for (; i < this.length; i++) {
    if (i !== 0 && i % n == 0) {
      a.push(this.substring(begin, i));
      begin = i;
    }
  }
  a.push(this.substring(begin));
  return a;
}