var Q = require('q');
var fs = require('fs');
var path = require('path');
var glob = require('glob');
var stringify = require('json-to-html');
var Liquid = require('liquid-node');

/**
 * Define any custom liquid filters here.
 */
var filters = {

  /**
   * Return a string formatted version of a JSON object.
   * Useful for quick debugging of template data.
   */
  prettify: function(obj) {
    try {
      return '<pre>' + stringify(obj) + '</pre>';
    } catch (e) {
      return 'Error prettifying';
    }
  },

  /**
   * Serialize Javascript objects into a JSON string
   */
  stringify: function(obj) {
    try {
      return JSON.stringify(obj);
    } catch (e) {
      return 'Error stringifying';
    }
  },

};

/**
 * Manages templates. Only supports Mustache currently/
 */
function OKTemplateRepo(options) {
  options = options || {};
  var root = this._root = options.root || 'templates';
  var ext = 'liquid';
  var cache = this._cache = {};
  var engine = this._engine = new Liquid.Engine;
  engine.registerFilters(filters);
  engine.fileSystem = new Liquid.LocalFileSystem(root, ext);
  this._populateCache(engine, cache, ext);
}

OKTemplateRepo.prototype.getTemplate = function getTemplate(name) {
  return this._cache[name];
}

/**
 * Go through our template dir and read the template files
 * into memory as strings.
 * Assumes all templates fit into memory.
 */
OKTemplateRepo.prototype._populateCache = function _populateCache(engine, cache, ext) {
  var self = this;
  var files = glob.sync(this._root + '/*.' + ext);
  files.forEach(function eachFile(file) {
    var name = path.basename(file, '.' + ext);
    var templateString = fs.readFileSync(file, {encoding: 'UTF8'});
    cache[name] = {
      name: name,
      templateString: templateString,
      render: function(data) {
        return Q.promise(function(resolve, reject) {
        // TODO Not sure if this caches parsed templates behind the scenes?
          engine.parseAndRender(templateString, data)
            .then(resolve)
            .catch(reject);
        });
      }
    }
  });
}

module.exports = OKTemplateRepo;