/*
 * Copyright 2005 by Oracle USA
 * 500 Oracle Parkway, Redwood Shores, California, 94065, U.S.A.
 * All rights reserved.
 */
package javax.ide.extension.spi;

import java.net.URI;

import java.util.logging.Level;
import javax.ide.extension.ElementName;
import javax.ide.extension.ElementStartContext;
import javax.ide.extension.ElementVisitor;
import javax.ide.extension.ExtensionHook;
import javax.ide.net.URIFactory;
import javax.ide.net.VirtualFileSystem;
import javax.ide.util.MetaClass;

/**
 * The hook-handler-hook implementation. This implementation takes a
 * <tt>DefaultHookVisitorFactory</tt> in its constructor and registers
 * handlers for custom hooks through this factory.
 */
public class HookHandlerHook extends ExtensionHook
{
  public static final ElementName ELEMENT = new ElementName( 
    MANIFEST_XMLNS, "hook-handler-hook" );
  private final DefaultHookVisitorFactory _factory;

  private final ElementName HOOKHANDLER = new ElementName(
    MANIFEST_XMLNS, "hook-handler" );

  private ElementVisitor _hookHandlerVisitor = new HookHandlerVisitor();

  /**
   * Constructs a new HookHandlerHook. 
   * 
   * @param hookFactory the hook factory. Must not be null.
   */
  public HookHandlerHook( DefaultHookVisitorFactory hookFactory )
  {
    if ( hookFactory == null )
    {
      throw new NullPointerException( "hookFactory is null" );
    }
    _factory = hookFactory;
  }
  
  public void start( ElementStartContext context )
  {
    context.registerChildVisitor( HOOKHANDLER, _hookHandlerVisitor );
  }
  
  private class HookHandlerVisitor extends ElementVisitor
  {
    public void start( ElementStartContext context )
    {
      String tagName = context.getAttributeValue( "tag-name" );
      if ( tagName == null || ( tagName = tagName.trim()) == "" )
      {
        log( context, Level.SEVERE, "Missing required attribute 'tag-name'" );
        return;
      }
      
      String handlerClass = context.getAttributeValue( "handler-class" );
      if ( handlerClass == null || ( handlerClass = handlerClass.trim() ) == "" )
      {
        log( context, Level.SEVERE, "Missing required attribute 'handler-class'" );
        return;
      }
      
      String namespace = context.getAttributeValue( "namespace" );
      if ( namespace == null || ( namespace = namespace.trim() )  == "" )
      {
        log( context, Level.SEVERE, "Missing required attribute 'namespace'" );
        return;
      }
      
      String schemaLocation = context.getAttributeValue( "schema-location" );
      
      if ( schemaLocation != null && schemaLocation.trim().length() > 0 )
      {
        // Attempt to find the schema in the jar.
        URI sourceUri = context.getExtensionSourceURI();
        URI schemaUri = URIFactory.newJarURI( sourceUri, "META-INF/" + schemaLocation.replace( '\\', '/' ) );
        if ( !VirtualFileSystem.getVirtualFileSystem().exists( schemaUri ) )
        {
          log( context, Level.SEVERE, "Schema not found: " + 
               VirtualFileSystem.getVirtualFileSystem().getPlatformPathName( schemaUri ) );
          schemaLocation = null;
        }
      }
         
      
      ElementName elementName = new ElementName( namespace, tagName );
      if ( _factory.isNameRegistered( elementName ) )
      {
        // For now we consider this to be an error rather than allowing
        // handlers to be subverted by downstream extensions.
        log( context, Level.SEVERE, "A custom hook is already registered for " +
          elementName.getNamespaceURI()+":"+elementName.getLocalName() );
        return;
      }

      MetaClass mc = new MetaClass( Thread.currentThread().getContextClassLoader(), 
        handlerClass );
      
      Object hookInstance = null;
      try
      {
        hookInstance = mc.newInstance();
      }
      catch ( ClassNotFoundException cnfe )
      {
        log( context, Level.SEVERE, "Custom hook class "+handlerClass+" not found." );
        return;
      }
      catch ( InstantiationException ie )
      {
        log( context, Level.SEVERE,
          "Custom hook class "+handlerClass+
          " cannot be instantiated."
        );
        // TODO print these to a logger or somewhere more sensible.
        ie.printStackTrace();
      }
      catch ( IllegalAccessException iae )
      {
        log( context, Level.SEVERE,
          "Custom hook class "+handlerClass+
          " is not public or does not have a public no argument constructor."
        );
        iae.printStackTrace();
      }
      
      if ( hookInstance != null )
      {
        try
        {
          ExtensionHook hook = (ExtensionHook) hookInstance;
          _factory.registerHook( elementName, hook );
          hook.setSchemaLocation( schemaLocation );
          hook.setProvider( getExtension( context ).getID() );
        }
        catch ( ClassCastException cce )
        {
          log( context, Level.SEVERE,
            "Custom hook class "+handlerClass+
            " is not derived from "+ExtensionHook.class.getName()
          );
        }
      }
    }
  }
}