/**
 * @license
 * Copyright 2019 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @fileoverview Fields can be created based on a JSON definition. This file
 *    contains methods for registering those JSON definitions, and building the
 *    fields based on JSON.
 * @author bekawestberg@gmail.com (Beka Westberg)
 */
'use strict';

goog.provide('Blockly.fieldRegistry');

goog.require('Blockly.registry');

goog.requireType('Blockly.IRegistrableField');


/**
 * Registers a field type.
 * Blockly.fieldRegistry.fromJson uses this registry to
 * find the appropriate field type.
 * @param {string} type The field type name as used in the JSON definition.
 * @param {!Blockly.IRegistrableField} fieldClass The field class containing a
 *     fromJson function that can construct an instance of the field.
 * @throws {Error} if the type name is empty, the field is already
 *     registered, or the fieldClass is not an object containing a fromJson
 *     function.
 */
Blockly.fieldRegistry.register = function(type, fieldClass) {
  Blockly.registry.register(Blockly.registry.Type.FIELD, type, fieldClass);
};

/**
 * Unregisters the field registered with the given type.
 * @param {string} type The field type name as used in the JSON definition.
 */
Blockly.fieldRegistry.unregister = function(type) {
  Blockly.registry.unregister(Blockly.registry.Type.FIELD, type);
};

/**
 * Construct a Field from a JSON arg object.
 * Finds the appropriate registered field by the type name as registered using
 * Blockly.fieldRegistry.register.
 * @param {!Object} options A JSON object with a type and options specific
 *     to the field type.
 * @return {Blockly.Field} The new field instance or null if a field wasn't
 *     found with the given type name
 * @package
 */
Blockly.fieldRegistry.fromJson = function(options) {
  var fieldObject = /** @type {?Blockly.IRegistrableField} */ (
    Blockly.registry.getObject(Blockly.registry.Type.FIELD, options['type']));
  if (!fieldObject) {
    console.warn('Blockly could not create a field of type ' + options['type'] +
      '. The field is probably not being registered. This could be because' +
      ' the file is not loaded, the field does not register itself (Issue' +
      ' #1584), or the registration is not being reached.');
    return null;
  }
  return fieldObject.fromJson(options);
};
