var Q = require('q');
var format = require('util').format;
var low = require('lowdb');
low.mixin(low.mixin(require('underscore-db')));

/**
 * OKDB!
 * Minimal interface over a database of named collections of documents.
 */
function OKDB(options) {
  if (!(this instanceof OKDB)) return new OKDB(options);
  options = options || {};
  var type;
  if (typeof options === 'string')
    type = options;
  else
    type = options.type;
  if (!type)
    throw new Error('No DB type provided');
  switch (type) {
    case 'fs':
      return FSDB(options);
    default:
      throw new Error('Invalid DB type');
  }
}

/**
 * DB implementation backed by a JSON file.
 * TODO Incomplete
 */
function FSDB(options) {
  if (!(this instanceof FSDB)) return new FSDB(options);
  options = options || {};
  var name = options.name || 'db';
  var filename = name + '.json';
  this._db = low(filename);
}

FSDB.prototype._resolve = function(data, success) {
  success = typeof success === 'undefined' ? true : success;
  return Q.Promise(function resolvePromise(resolve, reject) {
    if (success)
      resolve(data);
    else
      reject(data);
  });
};

FSDB.prototype.get = function(collection, id) {
  var data = this._db(collection).get(id);
  return this._resolve(data);
};

FSDB.prototype.getMeta = function() {
  var data = this._db('meta').first();
  return this._resolve(data || {});
};

FSDB.prototype.getAll = function(collection) {
  var data = this._db(collection).toArray();
  return this._resolve(data || []);
};

module.exports = OKDB;