/*
 * Copyright (c) 2012, the Dart project authors.
 * 
 * Licensed under the Eclipse Public License v1.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 * 
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.dart.tools.ui.internal.text.dart;

import com.google.dart.tools.ui.DartToolsPlugin;
import com.google.dart.tools.ui.Messages;
import com.google.dart.tools.ui.PreferenceConstants;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.InvalidRegistryObjectException;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.jface.preference.IPreferenceStore;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/**
 * 
 */
public final class ProposalSorterRegistry {
  private static final String EXTENSION_POINT = "dartCompletionProposalSorters"; //$NON-NLS-1$
  private static final String DEFAULT_ID = "com.google.dart.tools.ui.RelevanceSorter"; //$NON-NLS-1$

  private static ProposalSorterRegistry fInstance;

  public static synchronized ProposalSorterRegistry getDefault() {
    if (fInstance == null) {
      fInstance = new ProposalSorterRegistry(
          DartToolsPlugin.getDefault().getPreferenceStore(),
          PreferenceConstants.CODEASSIST_SORTER);
    }
    return fInstance;
  }

  private final IPreferenceStore fPreferenceStore;
  private final String fKey;

  private Map<String, ProposalSorterHandle> fSorters = null;
  private ProposalSorterHandle fDefaultSorter;

  private ProposalSorterRegistry(final IPreferenceStore preferenceStore, final String key) {
    Assert.isTrue(preferenceStore != null);
    Assert.isTrue(key != null);
    fPreferenceStore = preferenceStore;
    fKey = key;
  }

  public ProposalSorterHandle getCurrentSorter() {
    ensureSortersRead();
    String id = fPreferenceStore.getString(fKey);
    ProposalSorterHandle sorter = fSorters.get(id);
    return sorter != null ? sorter : fDefaultSorter;
  }

  public ProposalSorterHandle[] getSorters() {
    ensureSortersRead();
    Collection<ProposalSorterHandle> sorters = fSorters.values();
    return sorters.toArray(new ProposalSorterHandle[sorters.size()]);
  }

  public void select(ProposalSorterHandle handle) {
    Assert.isTrue(handle != null);
    String id = handle.getId();

    fPreferenceStore.setValue(fKey, id);
  }

  private synchronized void ensureSortersRead() {
    if (fSorters != null) {
      return;
    }

    Map<String, ProposalSorterHandle> sorters = new LinkedHashMap<String, ProposalSorterHandle>();
    IExtensionRegistry registry = Platform.getExtensionRegistry();
    List<IConfigurationElement> elements = new ArrayList<IConfigurationElement>(Arrays.asList(registry.getConfigurationElementsFor(
        DartToolsPlugin.getPluginId(),
        EXTENSION_POINT)));

    for (Iterator<IConfigurationElement> iter = elements.iterator(); iter.hasNext();) {
      IConfigurationElement element = iter.next();

      try {

        ProposalSorterHandle handle = new ProposalSorterHandle(element);
        final String id = handle.getId();
        sorters.put(id, handle);
        if (DEFAULT_ID.equals(id)) {
          fDefaultSorter = handle;
        }

      } catch (InvalidRegistryObjectException x) {
        /*
         * Element is not valid any longer as the contributing plug-in was unloaded or for some
         * other reason. Do not include the extension in the list and inform the user about it.
         */
        Object[] args = {element.toString()};
        String message = Messages.format(
            DartTextMessages.CompletionProposalComputerRegistry_invalid_message,
            args);
        IStatus status = new Status(
            IStatus.WARNING,
            DartToolsPlugin.getPluginId(),
            IStatus.OK,
            message,
            x);
        informUser(status);
      }
    }

    fSorters = sorters;
  }

  private void informUser(IStatus status) {
    DartToolsPlugin.log(status);
    String title = DartTextMessages.CompletionProposalComputerRegistry_error_dialog_title;
    String message = status.getMessage();
    MessageDialog.openError(DartToolsPlugin.getActiveWorkbenchShell(), title, message);
  }
}