//  DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
//
//   Copyright 2016-2018 Pascal ECHEMANN.
//
//   Licensed under the Apache License, Version 2.0 (the "License");
//   you may not use this file except in compliance with the License.
//   You may obtain a copy of the License at
//
//       http://www.apache.org/licenses/LICENSE-2.0
//
//   Unless required by applicable law or agreed to in writing, software
//   distributed under the License is distributed on an "AS IS" BASIS,
//   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//   See the License for the specific language governing permissions and
//   limitations under the License.

import {JsletMethodDescriptor} from "../reflect/JsletMethodDescriptor";
import {JsletMethod} from "../reflect/JsletMethod";
import {SingletonErrorFactory} from "../utils/SingletonErrorFactory";

/**
 * A helper singleton that creates new <code>JsletMethodDescriptor</code>
 * instances.
 */
export class JsletMethodDescriptorBuilder {

  //////////////////////////////////////////////////////////////////////////////
  // Constructor function
  //////////////////////////////////////////////////////////////////////////////

  /**
   * Creates a new <code>JsletMethodDescriptorBuilder</code> instance.
   */
  constructor() {
    if(JsletMethodDescriptorBuilder._locked ||
                                        JsletMethodDescriptorBuilder.INSTANCE) {
      new SingletonErrorFactory().throw(JsletMethodDescriptorBuilder);
    }
    JsletMethodDescriptorBuilder._locked = true;
  }
  
  //////////////////////////////////////////////////////////////////////////////
  // Singleton managment
  //////////////////////////////////////////////////////////////////////////////

  /**
   * Prevents <code>JsletMethodDescriptorBuilder</code> illegal instanciations.
   */
  private static _locked:boolean = true;

  /**
   * The <code>JsletMethodDescriptorBuilder</code> singleton instance reference.
   */
  private static INSTANCE:JsletMethodDescriptorBuilder = null;

  /**
   * Returns a reference to the <code>JsletMethodDescriptorBuilder</code>
   * singleton.
   *
   * @return {JsletMethodDescriptorBuilder} a reference to the
   *                        <code>JsletMethodDescriptorBuilder</code> singleton.
   */
  public static getInstance():JsletMethodDescriptorBuilder {
    if(JsletMethodDescriptorBuilder.INSTANCE === null) {
      JsletMethodDescriptorBuilder._locked = false;
      JsletMethodDescriptorBuilder.INSTANCE = 
                                             new JsletMethodDescriptorBuilder();
    }
    return JsletMethodDescriptorBuilder.INSTANCE;
  }

  //////////////////////////////////////////////////////////////////////////////
  // Public methods
  //////////////////////////////////////////////////////////////////////////////

  /**
   * Creates and returns a new <code>JsletMethodDescriptor</code> instance.
   * 
   * @param {JsletMethod} jsletMethod the jslet method associated with the
   *                                  decorated  method.
   * @param {string} key the name of the decorated method.
   * @param {PropertyDescriptor} descriptor the property descriptor associated
   *                                        with the decorated method.
   * @return {JsletMethodDescriptor} a new <code>JsletMethodDescriptor</code>
   *                                 instance.
   */
  public build(jsletMethod:JsletMethod, key:string,
                          descriptor:PropertyDescriptor):JsletMethodDescriptor {
    const methodDesc:JsletMethodDescriptor = new JsletMethodDescriptor();
    methodDesc.jsletMethod = jsletMethod;
    methodDesc.name = key;
    methodDesc.action = descriptor.value;
    return methodDesc;
  }
};