/r/dailyprogrammer problem #162 [easy + intermediate + hard]

162.js

#!/usr/bin/env node

// See http://www.reddit.com/r/dailyprogrammer/comments/25o2bd/5162014_challenge_162_hard_novel_compression_pt_3/

// Usage:
//         ./162 -c input.txt -o compressed.txt
//         ./162 -d compressed.txt -o output.txt

var fs    = require("fs");
var stdio = require("stdio"); // npm install stdio
var args  = stdio.getopt({
  compress: {key: "c", args: 0, description: "compress a file"},
  decompress: {key: "d", args: 0, description: "decompress a string"},
  outputFile: {key: "o", args: 1, description: "a file to output the data"}
});

function compress(input) {
  input.replace(/--|[^ a-zA-Z.,\-?!;:\n]|([.,?!;:]+)[a-z]+\1|( |[A-Z]+)[a-z]+[A-Z]+/, function() {
    throw "Error: invalid input";
  });
  var dictionary = [];
  input = input.replace(/([\n.,?\-!;:])/g, " $1 ");
  input.match(/[a-zA-Z]+/g).forEach(function(e) {
    if (dictionary.indexOf(e.toLowerCase()) === -1)
      dictionary.push(e.toLowerCase());
  });
  return dictionary.join(" ") + " -> " + input.split(/ +/).map(function(e) {
    return /[.,?!\-;:]/.test(e) ? e :
    dictionary.indexOf(e.toLowerCase()).toString().replace(/-1/, "R") +
    e.replace(/^([A-Z]){2,}$/, "!").replace(/^[A-Z]/g, "^").replace(/[^^!]+/, "");
  }).concat("E").join(" ");
}

function decompress(data, words) {
  if (typeof words === "string") words = words.split(/ +/);
  return data.replace(/R/g, " \n ").replace(/([0-9]+)/g, function(e) { return words[parseInt(e)]; })
    .replace(/(\S+)!/g,  function(e) { return e.slice(0, -1).toUpperCase(); })
    .replace(/(\S+)\^/g, function(e) { return e[0].toUpperCase() + e.slice(1, -1); }).split(/ +/)
    .slice(0, -2).join(" ").replace(/ - /g, "-").replace(/ ([,.?!])/g, "$1")
    .replace(/( +)?\n( +)/g, "\n").replace(/(\n| )+$/, "");
}

var argLen = Object.keys(args).length - 2;
function openFile(fname, callback) {
  fs.readFile(fname, "utf8", function(err, data) {
    callback(data);
  });
}

if (!args.hasOwnProperty("outputFile")) {
  return false;
}

if (args.hasOwnProperty("compress") && args.args && args.args.length && argLen === 3) {
  openFile(args.args[0], function(data) {
    fs.writeFileSync(args.outputFile, compress(data));
  });
} else if (args.hasOwnProperty("decompress") && argLen === 3) {
  openFile(args.args[0], function(data) {
    var a = data.split(" -> ");
    if (a.length === 2) {
      fs.writeFileSync(args.outputFile, decompress(a[1], a[0]));
    }
  });
}