SCM-Manager/scm-webapp/src/main/java/sonia/scm/plugin/ExtensionBinder.java

/**
 * Copyright (c) 2010, Sebastian Sdorra
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. Neither the name of SCM-Manager; nor the names of its
 *    contributors may be used to endorse or promote products derived from this
 *    software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * http://bitbucket.org/sdorra/scm-manager
 *
 */



package sonia.scm.plugin;

//~--- non-JDK imports --------------------------------------------------------

import com.google.inject.Binder;
import com.google.inject.Singleton;
import com.google.inject.binder.AnnotatedBindingBuilder;
import com.google.inject.binder.ScopedBindingBuilder;
import com.google.inject.multibindings.Multibinder;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import sonia.scm.EagerSingleton;
import sonia.scm.util.Util;

/**
 *
 * @author Sebastian Sdorra
 */
@SuppressWarnings("unchecked")
public final class ExtensionBinder
{

  private static final String TYPE_LOOSE_EXT = "loose extension";
  private static final String TYPE_REST_RESOURCE = "rest resource";
  private static final String AS_EAGER_SINGLETON = " as eager singleton";

  /**
   * the logger for ExtensionBinder
   */
  private static final Logger logger = LoggerFactory.getLogger(ExtensionBinder.class);

  public ExtensionBinder(Binder binder)
  {
    this.binder = binder;
  }

  public void bind(ExtensionCollector collector)
  {
    logger.debug("bind extensions to extension points");

    for (ExtensionPointElement epe : collector.getExtensionPointElements())
    {
      bindExtensionPoint(collector, epe);
    }

    logger.debug("bind loose extensions");
    bindLooseExtensions(collector.getLooseExtensions());
    logger.debug("bind rest providers");
    bindRestProviders(collector.getRestProviders());
    logger.debug("bind rest resources");
    bindRestResource(collector.getRestResources());
  }

  private void bindExtensionPoint(ExtensionCollector collector,
    ExtensionPointElement epe)
  {
    if (epe.isAutoBind())
    {
      if (epe.isMultiple())
      {
        bindMultiExtensionPoint(epe, collector.byExtensionPoint(epe));
      }
      else
      {
        Class extension = collector.oneByExtensionPoint(epe);

        if (extension != null)
        {
          bindSingleInstance(epe, extension);
        }
        else
        {
          logger.warn("could not find extension for extension point {}",
            epe.getClazz());
        }
      }
    }
    else
    {
      logger.debug("bind type of {} is manual", epe.getClazz());
    }
  }

  private void bindLooseExtensions(Iterable<Class> extensions)
  {
    for (Class extension : extensions)
    {
      singleBind(TYPE_LOOSE_EXT, extension);
    }
  }

  private void bindMultiExtensionPoint(ExtensionPointElement extensionPoint, Iterable<Class> extensions)
  {
    Class extensionPointClass = extensionPoint.getClazz();

    logger.debug("create multibinder for {}", extensionPointClass.getName());

    Multibinder multibinder = Multibinder.newSetBinder(binder, extensionPointClass);
    for (Class extensionClass : extensions)
    {
      boolean eagerSingleton = isEagerSingleton(extensionClass);

      if (logger.isDebugEnabled())
      {
        String as = Util.EMPTY_STRING;

        if (eagerSingleton)
        {
          as = AS_EAGER_SINGLETON;
        }

        logger.debug("bind {} to multibinder of {}{}", extensionClass.getName(),
          extensionPointClass.getName(), as);
      }

      ScopedBindingBuilder sbb = multibinder.addBinding().to(extensionClass);

      if (eagerSingleton)
      {
        sbb.asEagerSingleton();
      }
    }
  }

  private void bindRestProviders(Iterable<Class> restProviders)
  {
    for (Class restProvider : restProviders)
    {
      logger.debug("bind rest provider {}", restProvider);
      binder.bind(restProvider).in(Singleton.class);
    }
  }

  private void bindRestResource(Iterable<Class> restResources)
  {
    for (Class restResource : restResources)
    {
      singleBind(TYPE_REST_RESOURCE, restResource);
    }
  }

  private void bindSingleInstance(ExtensionPointElement extensionPoint,
    Class extensionClass)
  {
    Class extensionPointClass = extensionPoint.getClazz();
    boolean eagerSingleton = isEagerSingleton(extensionClass);

    if (logger.isDebugEnabled())
    {
      String as = Util.EMPTY_STRING;

      if (eagerSingleton)
      {
        as = AS_EAGER_SINGLETON;
      }

      logger.debug("bind {} to {}{}", extensionClass.getName(),
        extensionPointClass.getName(), as);
    }

    ScopedBindingBuilder sbb =
      binder.bind(extensionPointClass).to(extensionClass);

    if (eagerSingleton)
    {
      sbb.asEagerSingleton();
    }
  }

  private void singleBind(String type, Class extension)
  {
    StringBuilder log = new StringBuilder();

    log.append("bind ").append(type).append(" ").append(extension);

    AnnotatedBindingBuilder abb = binder.bind(extension);

    if (isEagerSingleton(extension))
    {
      log.append(AS_EAGER_SINGLETON);
      abb.asEagerSingleton();
    }

    if (logger.isDebugEnabled()) {
      logger.debug(log.toString());
    }
  }

  private boolean isEagerSingleton(Class extensionClass)
  {
    return extensionClass.isAnnotationPresent(EagerSingleton.class);
  }

  private final Binder binder;
}