/*******************************************************************************
 * Copyright (c) 2014, 2015 Google, Inc and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 * 	   Sergey Prigogin (Google) - initial API and implementation
 *******************************************************************************/
package org.eclipse.cdt.internal.ui.util;

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

import org.eclipse.core.commands.AbstractHandler;
import org.eclipse.core.commands.ExecutionEvent;
import org.eclipse.core.commands.ExecutionException;
import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.core.resources.IResource;
import org.eclipse.core.resources.mapping.ResourceMapping;
import org.eclipse.core.resources.mapping.ResourceTraversal;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.ui.IEditorInput;
import org.eclipse.ui.ISources;
import org.eclipse.ui.IWorkbenchWindow;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.handlers.HandlerUtil;
import org.eclipse.ui.handlers.IHandlerService;
import org.eclipse.ui.ide.ResourceUtil;

import org.eclipse.cdt.ui.CUIPlugin;

import org.eclipse.cdt.internal.core.AdapterUtil;

/**
 * Base class for command handlers operating on resources.
 */
public abstract class AbstractResourceActionHandler extends AbstractHandler {
  private IEvaluationContext evaluationContext;
  private IStructuredSelection selection;

  public void setSelection(ISelection selection) {
    this.selection = convertSelection(null, selection);
  }

  @Override
  public void setEnabled(Object evaluationContext) {
    this.evaluationContext = (IEvaluationContext) evaluationContext;
    selection = convertSelection(this.evaluationContext, null);
  }

  protected IStructuredSelection getSelection() {
    if (selection == null) {
      selection = convertSelection(evaluationContext, null);
    }
    return selection;
  }

  protected static IStructuredSelection getSelection(ExecutionEvent event) throws ExecutionException {
    Object selection = HandlerUtil.getActiveMenuSelection(event);
    if (selection == null) {
      selection = HandlerUtil.getCurrentSelectionChecked(event);
    }
    if (selection instanceof ITextSelection) {
      IEditorInput editorInput = HandlerUtil.getActiveEditorInputChecked(event);
      IResource resource = ResourceUtil.getResource(editorInput);
      if (resource != null) {
        return new StructuredSelection(resource);
      }

      resource = ResourceUtil.getFile(editorInput);
      if (resource != null) {
        return new StructuredSelection(resource);
      }
    }
    if (selection instanceof IStructuredSelection) {
      return (IStructuredSelection) selection;
    }
    return StructuredSelection.EMPTY;
  }

  private static IStructuredSelection convertSelection(IEvaluationContext context,
      Object selection) {
    if (selection == null) {
      if (context == null) {
        return StructuredSelection.EMPTY;
      }
      selection = context.getVariable(ISources.ACTIVE_MENU_SELECTION_NAME);
      if (!(selection instanceof ISelection)) {
        selection = context.getVariable(ISources.ACTIVE_CURRENT_SELECTION_NAME);
      }
    }
    if (selection instanceof ITextSelection) {
      if (context == null) {
        context = getEvaluationContext();
      }
      IResource resource =
          ResourceUtil.getResource(context.getVariable(ISources.ACTIVE_EDITOR_INPUT_NAME));
      if (resource != null) {
        return new StructuredSelection(resource);
      }
    }
    if (selection instanceof IStructuredSelection) {
      return (IStructuredSelection) selection;
    }
    return StructuredSelection.EMPTY;
  }

  private static IEvaluationContext getEvaluationContext() {
    IWorkbenchWindow activeWindow = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
    if (activeWindow == null) {
      return null;
    }
    IHandlerService service = activeWindow.getService(IHandlerService.class);
    return service.getCurrentState();
  }

  /**
   * Returns the selected resources.
   */
  protected Collection<IResource> getSelectedResources() {
    return getSelectedResources(getSelection());
  }

  /**
   * Returns the selected resources.
   */
  protected static Collection<IResource> getSelectedResources(ExecutionEvent event) throws ExecutionException {
    IStructuredSelection selection = getSelection(event);
    return getSelectedResources(selection);
  }

  private static Collection<IResource> getSelectedResources(IStructuredSelection selection) {
    Set<IResource> result = new LinkedHashSet<IResource>();
    for (Object obj : selection.toList()) {
      IResource resource = AdapterUtil.adapt(obj, IResource.class);
      if (resource != null) {
        result.add(resource);
      } else {
        result.addAll(extractResourcesFromMapping(obj));
      }
    }
    return result;
  }

  /**
   * Extracts resources associated with a {@link ResourceMapping}.
   *
   * @param obj an object adaptable to {@link ResourceMapping}
   * @return a list of resources associated with the mapping
   */
  private static List<IResource> extractResourcesFromMapping(Object obj) {
    ResourceMapping mapping = AdapterUtil.adapt(obj, ResourceMapping.class);
    if (mapping != null) {
      try {
        ResourceTraversal[] traversals = mapping.getTraversals(null, null);
        for (ResourceTraversal traversal : traversals) {
          return Arrays.asList(traversal.getResources());
        }
      } catch (CoreException e) {
        CUIPlugin.log(e);
      }
    }
    return Collections.emptyList();
  }
}