var Q = require('q');

/**
 * OKResource!
 * TODO Would be nicer to compose this with an existing resource
 * module, but haven't found a good fit. Should keep an eye on
 * 'resource' by bigcompany for an update.
 */
function OKResource(options) {
  if (!(this instanceof OKResource)) return new OKResource(options);
  options = options || {};
  if (!options.type)
    throw new Error('No resource type provided to OKResource')
  if (!options.schema)
    throw new Error('No schema provided to OKResource');
  if (!options.db)
    throw new Error('No DB provided to OKResource');
  var schema = options.schema;
  var type = options.type;
  this._db = options.db;
  // Define properties which are part of the API
  Object.defineProperty(this, 'schema', {
    value: schema,
    writable: false
  });
  Object.defineProperty(this, 'spec', {
    value: schema.spec,
    writable: false
  });
  Object.defineProperty(this, 'type', {
    value: type,
    writable: false
  });
}

/**
 * Throws an error if data does not conform to schema
 */
OKResource.prototype.assertValid = function(data) {
  this.schema.assertValid(data);
};

OKResource.prototype.all = function() {
  return this._db.getAll(this.type);
};

OKResource.prototype.create = function(data) {
  return this._db.create(this.type, data);
};

OKResource.prototype.destroy = function(data) {
  return this._db.remove(this.type, data.id, data);
};

OKResource.prototype.find = function(query) {
  return this._db.find(this.type, query);
};

OKResource.prototype.get = function(id) {
  return this._db.get(this.type, id);
};

OKResource.prototype.update = function(data) {
  data = data || {};
  return this._db.put(this.type, data.id, data);
};

OKResource.prototype.updateOrCreate = function(data) {
  data = data || {};
  var type = this.type;
  var db = this._db;
  return Q.promise(function(resolve, reject) {
    db.get(type, data.id).then(function(cached) {
      if (cached)
        db.put(type, data.id, data).then(resolve, reject);
      else
        db.create(type, data).then(resolve, reject);
    }, reject);
  });
};

module.exports = OKResource;