var languages = require('languages4translatewiki')
  , fs = require('fs')
  , path = require('path')
  , _ = require('underscore')
  , npm = require('npm')
  , plugins = require('ep_etherpad-lite/static/js/pluginfw/plugins.js').plugins
  , semver = require('semver')
  , existsSync = semver.gt(process.version, '0.7.0') ? fs.existsSync : path.existsSync
;


// returns all existing messages merged together and grouped by langcode
// {es: {"foo": "string"}, en:...}
function getAllLocales() {
  var locales2paths = {};

  // Puts the paths of all locale files contained in a given directory
  // into `locales2paths` (files from various dirs are grouped by lang code)
  // (only json files with valid language code as name)
  function extractLangs(dir) {
    if(!existsSync(dir)) return;
    var stat = fs.lstatSync(dir);
    if (!stat.isDirectory() || stat.isSymbolicLink()) return;

    fs.readdirSync(dir).forEach(function(file) {
      file = path.resolve(dir, file);
      stat = fs.lstatSync(file);
      if (stat.isDirectory() || stat.isSymbolicLink()) return;

      var ext = path.extname(file)
      , locale = path.basename(file, ext).toLowerCase();

      if ((ext == '.json') && languages.isValid(locale)) {
        if(!locales2paths[locale]) locales2paths[locale] = [];
        locales2paths[locale].push(file);
      }
    });
  }

  //add core supported languages first
  extractLangs(npm.root+"/ep_etherpad-lite/locales");
  
  //add plugins languages (if any)
  for(var pluginName in plugins) extractLangs(path.join(npm.root, pluginName, 'locales'));

  // Build a locale index (merge all locale data)
  var locales = {}
  _.each (locales2paths, function(files, langcode) {
    locales[langcode]={};

    files.forEach(function(file) {
     var fileContents = JSON.parse(fs.readFileSync(file,'utf8'));
      _.extend(locales[langcode], fileContents);
    });
  });

  return locales;
}

// returns a hash of all available languages availables with nativeName and direction
// e.g. { es: {nativeName: "español", direction: "ltr"}, ... }
function getAvailableLangs(locales) {
  var result = {};
  _.each(_.keys(locales), function(langcode) {
    result[langcode] = languages.getLanguageInfo(langcode);
  });
  return result;
}

// returns locale index that will be served in /locales.json
var generateLocaleIndex = function (locales) {
  var result = _.clone(locales) // keep English strings
  _.each(_.keys(locales), function(langcode) {
    if (langcode != 'en') result[langcode]='locales/'+langcode+'.json';
  });
  return JSON.stringify(result);
}


exports.expressCreateServer = function(n, args) {

  //regenerate locales on server restart
  var locales = getAllLocales();
  var localeIndex = generateLocaleIndex(locales);
  exports.availableLangs = getAvailableLangs(locales);

  args.app.get ('/locales/:locale', function(req, res) {
    //works with /locale/en and /locale/en.json requests
    var locale = req.params.locale.split('.')[0];
    if (exports.availableLangs.hasOwnProperty(locale)) {
      res.setHeader('Content-Type', 'application/json; charset=utf-8');
      res.send('{"'+locale+'":'+JSON.stringify(locales[locale])+'}');
    } else {
      res.send(404, 'Language not available');
    }
  })
  
  args.app.get('/locales.json', function(req, res) {
    res.setHeader('Content-Type', 'application/json; charset=utf-8');
    res.send(localeIndex);
  })
  
}