/**
    * This file Copyright (c) 2003-2011 Magnolia International
    * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
    *
    *
    * This file is dual-licensed under both the Magnolia
    * Network Agreement and the GNU General Public License.
    * You may elect to use one or the other of these licenses.
    *
   * This file is distributed in the hope that it will be
   * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
   * implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
   * Redistribution, except as permitted by whichever of the GPL
   * or MNA you select, is prohibited.
   *
   * 1. For the GPL license (GPL), you can redistribute and/or
   * modify this file under the terms of the GNU General
   * Public License, Version 3, as published by the Free Software
   * Foundation.  You should have received a copy of the GNU
   * General Public License, Version 3 along with this program;
   * if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * 2. For the Magnolia Network Agreement (MNA), this file
   * and the accompanying materials are made available under the
   * terms of the MNA which accompanies this distribution, and
   * is available at http://www.magnolia-cms.com/mna.html
   *
   * Any modifications to this file must keep this entire header
   * intact.
   *
   */
  package info.magnolia.module;
  
  import info.magnolia.module.model.ModuleDefinition;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import javax.inject.Singleton;
  
  
  /**
   * Keeps references to module descriptors and instances.
   *
   * @author philipp
   * @version $Id: ModuleRegistryImpl.java 46918 2011-06-30 18:59:01Z tmattsson $
   */
  @Singleton
  public class ModuleRegistryImpl implements ModuleRegistry {
      private final Map<String, ModuleEntry> entries;
  
      public ModuleRegistryImpl() {
          // using a LinkedHashMap : module definitions are registered in dependency-order, and we need to keep that order.
          entries = new LinkedHashMap<String, ModuleEntry>();
      }
  
      @Override
      public void registerModuleDefinition(String name, ModuleDefinition moduleDefinition) {
          getOrCreateModuleEntry(name).moduleDefinition = moduleDefinition;
      }
  
      @Override
      public void registerModuleInstance(String name, Object moduleInstance) {
          getOrCreateModuleEntry(name).moduleInstance = moduleInstance;
      }
  
      @Override
      public void registerModuleVersionHandler(String name, ModuleVersionHandler moduleVersionHandler) {
          getOrCreateModuleEntry(name).moduleVersionHandler = moduleVersionHandler;
      }
  
      @Override
      public boolean isModuleRegistered(String name) {
          return entries.containsKey(name);
      }
  
      @Override
      public ModuleDefinition getDefinition(String name) {
          return safeGetModuleEntry(name).moduleDefinition;
      }
  
      @Override
      public Object getModuleInstance(String name) {
          return safeGetModuleEntry(name).moduleInstance;
      }
  
      @Override
      public <T> T getModuleInstance(final Class<T> moduleClass) {
          T module = null;
          for (ModuleEntry m : entries.values()) {
              if (m.moduleInstance != null && moduleClass.isAssignableFrom(m.moduleInstance.getClass())) {
                  if (module != null) {
                      throw new IllegalArgumentException("Multiple modules registered with " + moduleClass.toString() + ".");
                  }
                 module = (T) m.moduleInstance;
             }
         }
         if (module != null) {
             return module;
         }
         throw new IllegalArgumentException("No module registered with " + moduleClass.toString() + ".");
     }
 
     @Override
     public ModuleVersionHandler getVersionHandler(String name) {
         return safeGetModuleEntry(name).moduleVersionHandler;
     }
 
     @Override
     public Set<String> getModuleNames() {
         return Collections.unmodifiableSet(entries.keySet());
     }
 
     @Override
     public List<ModuleDefinition> getModuleDefinitions() {
         // TODO - use something like a Transformer from commons-collections ?
         final List<ModuleDefinition> defs = new ArrayList<ModuleDefinition>();
         for (ModuleEntry mod : entries.values()) {
             defs.add(mod.moduleDefinition);
         }
         return Collections.unmodifiableList(defs);
     }
 
     private ModuleEntry getOrCreateModuleEntry(String name) {
         synchronized (entries) {
             ModuleEntry moduleEntry = entries.get(name);
             if (moduleEntry == null) {
                 moduleEntry = new ModuleEntry();
                 entries.put(name, moduleEntry);
             }
             return moduleEntry;
         }
     }
 
     private ModuleEntry safeGetModuleEntry(String name) {
         synchronized (entries) {
             final ModuleEntry moduleEntry = entries.get(name);
             if (moduleEntry == null) {
                 throw new IllegalArgumentException("No module registered with name \"" + name + "\".");
             }
             return moduleEntry;
         }
     }
 
 
     private static final class ModuleEntry {
 
         private ModuleDefinition moduleDefinition;
 
         private Object moduleInstance;
 
         private ModuleVersionHandler moduleVersionHandler;
 
     }
 }