function DillerDao(client) {

  var deviceColumns = 'id, key, created_timestamp';
  var propertyColumns = 'id, device, key, created_timestamp';

  function deviceByKey(key) {
    return client.oneOrNone("SELECT " + deviceColumns + " FROM device WHERE key=$1", key);
  }

  function insertDevice(key) {
    return client.one("INSERT INTO device(id, key, created_timestamp) VALUES(DEFAULT, $1, CURRENT_TIMESTAMP) RETURNING " + deviceColumns, key);
  }

  function devicePropertyByDeviceIdAndKey(deviceId, key) {
    return client.oneOrNone('SELECT id FROM device_property WHERE device=$1 AND key=$2', [deviceId, key]);
  }

  function insertDeviceProperty(deviceId, key) {
    return client.oneOrNone('INSERT INTO device_property(id, device, key, created_timestamp) VALUES(DEFAULT, $1, $2, CURRENT_TIMESTAMP) RETURNING ' + propertyColumns, [deviceId, key]);
  }

  function updatePropertyName(id, name) {
    return client.none('UPDATE device_property SET name=$1 WHERE id=$2', name, id);
  }

  function updatePropertyDescription(id, description) {
    return client.none('UPDATE device_property SET description=$1 WHERE id=$2', description, id);
  }

  function insertValue(propertyId, value) {
    return client.none('INSERT INTO value(property, timestamp, value) VALUES($1, CURRENT_TIMESTAMP, $2)', [propertyId, value]);
  }

  return {
    deviceByKey: deviceByKey,
    insertDevice: insertDevice,

    devicePropertyByDeviceIdAndKey: devicePropertyByDeviceIdAndKey,
    insertDeviceProperty: insertDeviceProperty,
    updatePropertyName: updatePropertyName,
    updatePropertyDescription: updatePropertyDescription,

    insertValue: insertValue
  }
}

module.exports = DillerDao;