#!/usr/bin/env node
  'use strict';
  
  /* globals Set */
  /*!
   * Script to update version number references in the project.
   * Copyright 2015 Twitter, Inc.
   * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
   */
  var fs = require('fs');
  var path = require('path');
  var sh = require('shelljs');
  sh.config.fatal = true;
  var sed = sh.sed;
  
  // Blame TC39... https://github.com/benjamingr/RegExp.escape/issues/37
  RegExp.quote = function (string) {
    return string.replace(/[-\\^$*+?.()|[\]{}]/g, '\\$&');
  };
  RegExp.quoteReplacement = function (string) {
    return string.replace(/[$]/g, '$$');
  };
  
  var DRY_RUN = false;
  
  function walkAsync(directory, excludedDirectories, fileCallback, errback) {
    if (excludedDirectories.has(path.parse(directory).base)) {
      return;
    }
    fs.readdir(directory, function (err, names) {
      if (err) {
        errback(err);
        return;
      }
      names.forEach(function (name) {
        var filepath = path.join(directory, name);
        fs.lstat(filepath, function (err, stats) {
          if (err) {
            process.nextTick(errback, err);
            return;
          }
          if (stats.isSymbolicLink()) {
            return;
          }
          else if (stats.isDirectory()) {
            process.nextTick(walkAsync, filepath, excludedDirectories, fileCallback, errback);
          }
          else if (stats.isFile()) {
            process.nextTick(fileCallback, filepath);
          }
        });
      });
    });
  }
  
  function replaceRecursively(directory, excludedDirectories, allowedExtensions, original, replacement) {
    original = new RegExp(RegExp.quote(original), 'g');
    replacement = RegExp.quoteReplacement(replacement);
    var updateFile = !DRY_RUN ? function (filepath) {
      if (allowedExtensions.has(path.parse(filepath).ext)) {
        sed('-i', original, replacement, filepath);
      }
    } : function (filepath) {
      if (allowedExtensions.has(path.parse(filepath).ext)) {
        console.log('FILE: ' + filepath);
      }
      else {
        console.log('EXCLUDED:' + filepath);
      }
    };
    walkAsync(directory, excludedDirectories, updateFile, function (err) {
      console.error('ERROR while traversing directory!:');
      console.error(err);
      process.exit(1);
    });
  }
  
  function main(args) {
    if (args.length !== 2) {
      console.error('USAGE: change-version old_version new_version');
      console.error('Got arguments:', args);
      process.exit(1);
    }
    var oldVersion = args[0];
    var newVersion = args[1];
    var EXCLUDED_DIRS = new Set([
      '.git',
      'node_modules',
      'vendor'
    ]);
    var INCLUDED_EXTENSIONS = new Set([
      // This extension whitelist is how we avoid modifying binary files
      '',
      '.css',
      '.html',
      '.js',
      '.json',
      '.less',
      '.md',
      '.nuspec',
      '.ps1',
      '.scss',
      '.txt',
      '.yml'
    ]);
    replaceRecursively('.', EXCLUDED_DIRS, INCLUDED_EXTENSIONS, oldVersion, newVersion);
  }
  
  main(process.argv.slice(2));