/*
 * This program is free software; you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
 * Foundation.
 *
 * You should have received a copy of the GNU Lesser General Public License along with this
 * program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
 * or from the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * This program 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.
 *
 * Copyright (c) 2006 - 2009 Pentaho Corporation and Contributors.  All rights reserved.
 */

package org.pentaho.reporting.libraries.resourceloader;

import java.net.URL;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.pentaho.reporting.libraries.base.config.Configuration;
import org.pentaho.reporting.libraries.base.util.ObjectUtilities;

/**
 * Todo: Document Me
 *
 * @author Thomas Morgner
 */
public class DefaultResourceManagerBackend implements ResourceManagerBackend
{
  private static final Log logger = LogFactory.getLog(DefaultResourceManagerBackend.class);

  private ArrayList resourceLoaders;
  private ArrayList resourceBundleLoaders;
  private ArrayList resourceFactories;

  public DefaultResourceManagerBackend()
  {
    resourceLoaders = new ArrayList();
    resourceBundleLoaders = new ArrayList();
    resourceFactories = new ArrayList();
  }

  public synchronized ResourceKey createKey(final Object data, final Map parameters)
      throws ResourceKeyCreationException
  {
    if (data == null)
    {
      throw new NullPointerException("Key data must not be null.");
    }

    final Iterator values = resourceLoaders.iterator();
    while (values.hasNext())
    {
      final ResourceLoader loader = (ResourceLoader) values.next();
      try
      {
        final ResourceKey key = loader.createKey(data, parameters);
        if (key != null)
        {
          return key;
        }
      }
      catch (ResourceKeyCreationException rkce)
      {
        // ignore it.
      }
    }

    throw new ResourceKeyCreationException("Unable to create key: No loader was able to handle the given key data: "
        + data);
  }

  /**
   * Derives a new key from the given resource-key. Only keys for a hierarchical storage system (like file-systems or
   * URLs) can have derived keys. Since LibLoader 0.3.0 only hierarchical keys can be derived. For that, the deriving
   * path must be given as String.
   * <p/>
   * The optional parameter-map will be applied to the derived key after the parent's parameters have been copied to
   * the new key.
   * <p/>
   * Before trying to derive the key, the system tries to interpret the path as absolute key-value.
   *
   * @param parent     the parent key, or null to interpret the path as absolute key.
   * @param path       the relative path, that is used to derive the key.
   * @param parameters a optional map containing resource-key parameters.
   * @return the derived key.
   * @throws ResourceKeyCreationException if deriving the key failed.
   */
  public synchronized ResourceKey deriveKey(final ResourceKey parent, final String path, final Map parameters)
      throws ResourceKeyCreationException
  {
    if (parent == null)
    {
      if (path == null)
      {
        throw new NullPointerException();
      }

      return createKey(path, parameters);
    }

    ResourceKeyCreationException rce = null;
    for (int i = 0; i < resourceBundleLoaders.size(); i++)
    {
      final ResourceBundleLoader bundleLoader = (ResourceBundleLoader) resourceBundleLoaders.get(i);
      if (bundleLoader.isSupportedKey(parent) == false)
      {
        continue;
      }

      try
      {
        final ResourceKey key = bundleLoader.deriveKey(parent, path, parameters);
        if (key != null)
        {
          return key;
        }
      }
      catch (ResourceKeyCreationException rcke)
      {
        rce = rcke;
      }
    }
    
    // First, try to derive the resource directly. This makes sure, that we preserve the parent's context.
    // If a file is derived, we assume that the result will be a file; and only if that fails we'll try to
    // query the other contexts. If the parent is an URL-context, the result is assumed to be an URL as well.
    for (int i = 0; i < resourceLoaders.size(); i++)
    {
      final ResourceLoader loader = (ResourceLoader) resourceLoaders.get(i);
      if (loader.isSupportedKey(parent) == false)
      {
        continue;
      }
      try
      {
        final ResourceKey key = loader.deriveKey(parent, path, parameters);
        if (key != null)
        {
          return key;
        }
      }
      catch (ResourceKeyCreationException rcke)
      {
        rce = rcke;
      }
    }

    if (path != null)
    {
      // Second, try to load the key as absolute value.
      // This assumes, that we have no catch-all implementation.
      for (int i = 0; i < resourceLoaders.size(); i++)
      {
        final ResourceLoader loader = (ResourceLoader) resourceLoaders.get(i);
        final ResourceKey key = loader.createKey(path, parameters);
        if (key != null)
        {
          return key;
        }
      }
    }

    final ResourceKey secondParent = parent.getParent();
    if (secondParent != null)
    {
      // Desperate measures: Maybe the key is relative to the bundle. 
      for (int i = 0; i < resourceLoaders.size(); i++)
      {
        final ResourceLoader loader = (ResourceLoader) resourceLoaders.get(i);
        if (loader.isSupportedKey(secondParent) == false)
        {
          continue;
        }
        try
        {
          final ResourceKey key = loader.deriveKey(secondParent, path, parameters);
          if (key != null)
          {
            return key;
          }
        }
        catch (ResourceKeyCreationException rcke)
        {
          rce = rcke;
        }
      }
    }

    if (rce != null)
    {
      throw rce;
    }
    throw new ResourceKeyCreationException("Unable to create key: No such schema or the key was not recognized.");
  }

  /**
   * Tries to find the first resource-loader that would be able to process the key.
   *
   * @param key the resource-key.
   * @return the resourceloader for that key, or null, if no resource-loader is able to process the key.
   */
  private ResourceLoader findBySchema(final ResourceKey key)
  {
    for (int i = 0; i < resourceLoaders.size(); i++)
    {
      final ResourceLoader loader = (ResourceLoader) resourceLoaders.get(i);
      if (loader.isSupportedKey(key))
      {
        return loader;
      }
    }
    return null;
  }

  public synchronized URL toURL(final ResourceKey key)
  {
    if (key == null)
    {
      throw new NullPointerException();
    }
    final ResourceLoader loader = findBySchema(key);
    if (loader == null)
    {
      return null;
    }
    return loader.toURL(key);
  }

  public synchronized Resource create(final ResourceManager frontEnd, final ResourceData data,
      final ResourceKey context, final Class[] target) throws ResourceLoadingException, ResourceCreationException
  {
    if (frontEnd == null)
    {
      throw new NullPointerException();
    }
    if (data == null)
    {
      throw new NullPointerException("Data must not be null.");
    }

    // AutoMode ..
    if (target == null)
    {
      return autoCreateResource(frontEnd, data, context);
    }

    ResourceCreationException exception = null;
    final int factoryCount = resourceFactories.size();
    final ResourceFactory[] factories = (ResourceFactory[]) resourceFactories
        .toArray(new ResourceFactory[factoryCount]);
    for (int targetIdx = 0; targetIdx < target.length; targetIdx++)
    {
      final Class targetClass = target[targetIdx];
      for (int i = 0; i < factoryCount; i++)
      {
        final ResourceFactory fact = factories[i];
        if (isSupportedTarget(targetClass, fact) == false)
        {
          // Unsupported keys: Try the next factory ..
          continue;
        }

        try
        {
          return fact.create(frontEnd, data, context);
        }
        catch (ContentNotRecognizedException ce)
        {
          // Ignore it, unless it is the last one.
        }
        catch (ResourceCreationException rex)
        {
          // ignore it, try the next factory ...
          exception = rex;
          if (logger.isDebugEnabled())
          {
            logger.debug("Failed at " + fact.getClass() + ": ", rex);
          }
        }
      }
    }

    if (exception != null)
    {
      throw exception;
    }
    throw new ContentNotRecognizedException("None of the selected factories was able to handle the given data: "
        + data.getKey());
  }

  private boolean isSupportedTarget(final Class target, final ResourceFactory fact)
  {
    final Class factoryType = fact.getFactoryType();
    if (target != null && target.isAssignableFrom(factoryType))
    {
      return true;
    }
    return false;
  }

  private Resource autoCreateResource(final ResourceManager frontEnd, final ResourceData data, final ResourceKey context)
      throws ResourceLoadingException, ResourceCreationException
  {
    final Iterator it = resourceFactories.iterator();
    while (it.hasNext())
    {
      final ResourceFactory fact = (ResourceFactory) it.next();
      try
      {
        final Resource res = fact.create(frontEnd, data, context);
        if (res != null)
        {
          return res;
        }
      }
      catch (ResourceCreationException rex)
      {
        // ignore it, try the next factory ...
      }
    }
    throw new ResourceCreationException("No known factory was able to handle the given data.");
  }

  public boolean isResourceUnchanged(final ResourceManager frontEnd, final Resource resource)
      throws ResourceLoadingException
  {
    if (frontEnd == null)
    {
      throw new NullPointerException();
    }
    if (resource == null)
    {
      throw new NullPointerException();
    }

    final ResourceKey[] deps = resource.getDependencies();
    for (int i = 0; i < deps.length; i++)
    {
      final ResourceKey dep = deps[i];
      final long version = resource.getVersion(dep);
      if (version == -1)
      {
        // non-versioning key, ignore it.
        continue;
      }

      final ResourceData data = frontEnd.load(dep);
      if (data.getVersion(frontEnd) != version)
      {
        // oh, my bad, an outdated or changed entry.
        // We have to re-read the whole thing.
        return false;
      }
    }
    // all versions have been confirmed to be valid. Nice, we can use the
    // cached product.
    return true;
  }

  /**
   * Tries to find the first resource-bundle-loader that would be able to process the key.
   *
   * @param key the resource-key.
   * @return the resourceloader for that key, or null, if no resource-loader is able to process the key.
   * @throws ResourceLoadingException if an error occured.
   */
  public synchronized ResourceBundleData loadResourceBundle(final ResourceManager frontEnd, final ResourceKey key)
      throws ResourceLoadingException
  {
    if (frontEnd == null)
    {
      throw new NullPointerException();
    }
    if (key == null)
    {
      throw new NullPointerException();
    }

    for (int i = 0; i < resourceBundleLoaders.size(); i++)
    {
      final ResourceBundleLoader loader = (ResourceBundleLoader) resourceBundleLoaders.get(i);
      final ResourceBundleData resourceBundle = loader.loadBundle(frontEnd, key);
      if (resourceBundle != null)
      {
        return resourceBundle;
      }
    }
    return null;
  }

  public ResourceData loadRawData(final ResourceManager frontEnd, final ResourceKey key)
      throws UnrecognizedLoaderException, ResourceLoadingException
  {
    if (frontEnd == null)
    {
      throw new NullPointerException();
    }
    if (key == null)
    {
      throw new NullPointerException();
    }

    final ResourceLoader loader = findBySchema(key);
    if (loader == null)
    {
      throw new UnrecognizedLoaderException("Invalid key: No resource-loader registered for schema: " + key.getSchema());
    }
    logger.debug("Loaded " + key);
    return loader.load(key);
  }

  public void registerDefaultFactories()
  {
    final Configuration config = LibLoaderBoot.getInstance().getGlobalConfig();
    final Iterator itType = config.findPropertyKeys(ResourceManager.FACTORY_TYPE_PREFIX);
    while (itType.hasNext())
    {
      final String key = (String) itType.next();
      final String factoryClass = config.getConfigProperty(key);

      final Object maybeFactory = ObjectUtilities.loadAndInstantiate(factoryClass, ResourceManager.class,
          ResourceFactory.class);
      if (maybeFactory instanceof ResourceFactory == false)
      {
        continue;
      }

      final ResourceFactory factory = (ResourceFactory) maybeFactory;
      factory.initializeDefaults();
      registerFactory(factory);
    }
  }

  public void registerDefaultLoaders()
  {
    final Configuration config = LibLoaderBoot.getInstance().getGlobalConfig();
    final Iterator it = config.findPropertyKeys(ResourceManager.LOADER_PREFIX);
    while (it.hasNext())
    {
      final String key = (String) it.next();
      final String value = config.getConfigProperty(key);
      final ResourceLoader loader = (ResourceLoader) ObjectUtilities.loadAndInstantiate(value, ResourceManager.class,
          ResourceLoader.class);
      if (loader != null)
      {
        //Log.debug("Registering loader for " + loader.getSchema());
        registerLoader(loader);
      }
    }

    final Iterator bit = config.findPropertyKeys(ResourceManager.BUNDLE_LOADER_PREFIX);
    while (bit.hasNext())
    {
      final String key = (String) bit.next();
      final String value = config.getConfigProperty(key);
      final ResourceBundleLoader loader = (ResourceBundleLoader) ObjectUtilities.loadAndInstantiate(value,
          ResourceManager.class, ResourceBundleLoader.class);
      if (loader != null)
      {
        //Log.debug("Registering loader for " + loader.getSchema());
        registerBundleLoader(loader);
      }
    }
  }

  public void registerBundleLoader(final ResourceBundleLoader loader)
  {
    if (loader == null)
    {
      throw new NullPointerException("ResourceLoader must not be null.");
    }
    resourceBundleLoaders.add(loader);
  }

  public void registerLoader(final ResourceLoader loader)
  {
    if (loader == null)
    {
      throw new NullPointerException("ResourceLoader must not be null.");
    }
    resourceLoaders.add(loader);
  }

  public void registerFactory(final ResourceFactory factory)
  {
    if (factory == null)
    {
      throw new NullPointerException("ResourceFactory must not be null.");
    }
    resourceFactories.add(factory);
  }

  /**
   * Converts a serialized version of a <code>ResourceKey</code> into an actual <code>ResourceKey</code>
   * by locating the proper <code>ResourceLoader</code> that can perform the deserialization.
   *
   * @param bundleKey
   *@param serializedKey the String serialized key to be deserialized  @returns the <code>ResourceKey</code> that has been deserialized
   * @throw ResourceKeyCreationException indicates an error trying to create the <code>ResourceKey</code>
   *   from the deserialized version
   */
  public ResourceKey deserialize(final ResourceKey bundleKey, String serializedKey) throws ResourceKeyCreationException
  {
    if (serializedKey == null)
    {
      throw new NullPointerException("Key data must not be null.");
    }

    final Iterator values = resourceLoaders.iterator();
    while (values.hasNext())
    {
      final ResourceLoader loader = (ResourceLoader) values.next();
      if (loader.isSupportedDeserializer(serializedKey))
      {
        final ResourceKey key = loader.deserialize(bundleKey, serializedKey);
        return key;
      }
    }

    throw new ResourceKeyCreationException
        ("Unable to create key: No loader was able to handle the deserialization of the given key data: " + serializedKey);
  }

  /**
   * Creates a String version of the <code>ResourceKey</code> that can be deserialized with the
   * <code>deserialize()</code> method.
   * @param bundleKey
   *@param key @throw ResourceException indicates an error trying to serialize the key
   * @throw NullPointerException indicates the supplied key is <code>null</code>
   */
  public String serialize(final ResourceKey bundleKey, final ResourceKey key) throws ResourceException
  {
    if (key == null)
    {
      throw new NullPointerException("Key data must not be null.");
    }

    final Iterator values = resourceLoaders.iterator();
    while (values.hasNext())
    {
      final ResourceLoader loader = (ResourceLoader) values.next();
      if (loader.isSupportedKey(key))
      {
        return loader.serialize(bundleKey, key);
      }
    }

    throw new ResourceException("Unable to find resource loader for specified key: " + key);
  }

}