/*
    GNU LESSER GENERAL PUBLIC LICENSE
    Copyright (C) 2006 The Lobo Project

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Contact info: lobochief@users.sourceforge.net
 */
package org.lobobrowser.js;

import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;

public class JavaClassWrapperFactory {
  private static JavaClassWrapperFactory instance;
  private final Map<Class<?>, WeakReference<JavaClassWrapper>> classWrappers = new WeakHashMap<>();

  private JavaClassWrapperFactory() {
  }

  public static JavaClassWrapperFactory getInstance() {
    if (instance == null) {
      synchronized (JavaClassWrapperFactory.class) {
        if (instance == null) {
          instance = new JavaClassWrapperFactory();
        }
      }
    }
    return instance;
  }

  public JavaClassWrapper getClassWrapper(final Class<?> clazz) {
    synchronized (this) {
      // WeakHashMaps where the value refers to
      // the key will retain keys. Must make it
      // refer to the value weakly too.
      final WeakReference<?> jcwr = this.classWrappers.get(clazz);
      JavaClassWrapper jcw = null;
      if (jcwr != null) {
        jcw = (JavaClassWrapper) jcwr.get();
      }
      if (jcw == null) {
        // TODO: need to check with the class shutter here. GH #136
        jcw = new JavaClassWrapper(clazz);
        this.classWrappers.put(clazz, new WeakReference<>(jcw));
      }
      return jcw;
    }
  }
}