/*******************************************************************************
 * Copyright (c) 2010 SAP AG, Walldorf.
 * 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:
 *     SAP AG - initial API and implementation
 *******************************************************************************/
package org.eclipse.platform.discovery.ui.internal.selector;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.eclipse.jface.viewers.ISelectionChangedListener;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.ITreeSelection;
import org.eclipse.jface.viewers.SelectionChangedEvent;
import org.eclipse.jface.viewers.StructuredSelection;
import org.eclipse.jface.viewers.TreePath;
import org.eclipse.jface.viewers.TreeSelection;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.platform.discovery.core.internal.selectors.IItemSelector;
import org.eclipse.platform.discovery.runtime.api.IDestinationsProvider;
import org.eclipse.platform.discovery.runtime.api.ISearchDestination;
import org.eclipse.platform.discovery.runtime.internal.model.descriptions.IDestinationCategoryDescription;
import org.eclipse.platform.discovery.ui.internal.plugin.DiscoveryUIMessages;
import org.eclipse.platform.discovery.ui.internal.view.IGetControlObject;
import org.eclipse.platform.discovery.ui.internal.view.SearchConsoleView;
import org.eclipse.platform.discovery.ui.internal.view.impl.DestinationsContentProvider;
import org.eclipse.platform.discovery.ui.internal.view.impl.DestinationsLabelProvider;
import org.eclipse.platform.discovery.util.internal.property.IPropertyAttributeListener;
import org.eclipse.platform.discovery.util.internal.property.Property;
import org.eclipse.platform.discovery.util.internal.property.PropertyAttributeChangedEvent;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FormAttachment;
import org.eclipse.swt.layout.FormData;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Label;
import org.eclipse.ui.forms.widgets.FormToolkit;


/**
 * The UI component for selecting search destinations
 * 
 * @author Danail Branekov
 * 
 */
public abstract class SearchDestinationsSelector implements IItemSelector<ISearchDestination, IDestinationCategoryDescription>, IGetControlObject<Control>
{
	private final TreeViewer destinationsTreeViewer;
	private final Property<IStructuredSelection> lastKnownSelection;

	public SearchDestinationsSelector(final Composite parent, final FormToolkit formToolkit, final int secondColumnPosition, final Control topNeighbourControl)
	{
		lastKnownSelection = new Property<IStructuredSelection>();
		lastKnownSelection.set(new StructuredSelection());
		lastKnownSelection.registerValueListener(new SelectionChangedListener(), false);
		
		Label destinationLabel = new Label(parent, SWT.FLAT);
		destinationLabel.setText(DiscoveryUIMessages.SEARCH_IN_LIST_VIEWER_LABEL);
		
		final FormData labelSearchedInFormData = new FormData();
		labelSearchedInFormData.left = new FormAttachment(0, SearchConsoleView.UI_IN_CONTROL_SPACING);
		labelSearchedInFormData.top = new FormAttachment(topNeighbourControl, SearchConsoleView.UI_IN_CONTROL_SPACING);
		destinationLabel.setLayoutData(labelSearchedInFormData);
		
		destinationsTreeViewer = createDestinationsTreeViewer(parent);
		formToolkit.adapt(destinationsTreeViewer.getControl(), true, true);
		final FormData searchInFormData = new FormData();
		searchInFormData.top = new FormAttachment(topNeighbourControl, SearchConsoleView.UI_IN_CONTROL_SPACING);
		searchInFormData.left = new FormAttachment(0, secondColumnPosition + 2*SearchConsoleView.UI_IN_CONTROL_SPACING);
		searchInFormData.right = new FormAttachment(100, -SearchConsoleView.UI_IN_CONTROL_SPACING);
		searchInFormData.height = Math.max(destinationsTreeViewer.getControl().computeSize(SWT.DEFAULT, SWT.DEFAULT).y, treeViewerMinHeight());
		destinationsTreeViewer.getControl().setLayoutData(searchInFormData);
	}

	public ISearchDestination getSelectedItem()
	{
		final Object selectedObject = ((IStructuredSelection) destinationsTreeViewer.getSelection()).getFirstElement();
		if (selectedObject instanceof IDestinationCategoryDescription)
		{
			return null;
		}

		return (ISearchDestination) selectedObject;
	}
	
	private TreeViewer createDestinationsTreeViewer(final Composite parent)
	{
		final TreeViewer viewer = new TreeViewer(parent, SWT.SINGLE | SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER);
		viewer.setContentProvider(new DestinationsContentProvider()
		{
			@Override
			protected List<ISearchDestination> getSearchDestinationsForCategory(final IDestinationCategoryDescription category)
			{
				final List<ISearchDestination> result = new ArrayList<ISearchDestination>();
				for(IDestinationsProvider destinationsProvider : getDestinationProvidersForCategory(category))
				{
					result.addAll(getSearchDestinations(category, destinationsProvider));
				}
				
				return result;
			}
		});
		viewer.setLabelProvider(new DestinationsLabelProvider());
		viewer.addSelectionChangedListener(new ISelectionChangedListener()
		{
			@Override
			public void selectionChanged(final SelectionChangedEvent event)
			{
				// filter out empty selection events - registered listeners have to be notified, but the selection property needs to remain unchanged
				// Also, empty selection can happen only via API - the user is not capable of delesecting everything
				if(event.getSelection().isEmpty())
				{
					handleSelectionChange(null);
					return;
				}
				lastKnownSelection.set((IStructuredSelection) event.getSelection());
			}
		});

		return viewer;
	}


	@Override
	public Control getControl() {
		return destinationsTreeViewer.getControl();
	}

	@Override
	public void setInput(List<IDestinationCategoryDescription> input)
	{
		updateInternal(input);
	}
	
	@SuppressWarnings("unchecked")
	public void update()
	{
		updateInternal((List<IDestinationCategoryDescription>) destinationsTreeViewer.getInput());
	}
	
	private void updateInternal(final List<IDestinationCategoryDescription> input)
	{
		destinationsTreeViewer.setInput(input);
		refreshAndExpandTreeViewer(destinationsTreeViewer);
		if(!input.isEmpty())
		{
			restoreLastKnownSelection(destinationsTreeViewer);
		}
		
		if (input.size() == 1) 
		{
			final Set<ISearchDestination> result = new HashSet<ISearchDestination>();
			for(IDestinationsProvider destinationsProvider : getDestinationProvidersForCategory(input.iterator().next()))
			{
				result.addAll(getSearchDestinations(input.iterator().next(), destinationsProvider));
			}
			if (result.size() == 1) 
			{
				destinationsTreeViewer.setSelection(new StructuredSelection(result.iterator().next()));
			}
		}
	}
	
	private void refreshAndExpandTreeViewer(TreeViewer viewer)
	{
		viewer.refresh();
		viewer.expandAll();
	}

	/**
	 * Restores the last known selection
	 */
	private void restoreLastKnownSelection(final TreeViewer viewer)
	{
		viewer.setSelection(lastKnownSelection.get(), true);
		lastKnownSelection.set((IStructuredSelection)viewer.getSelection());
	}
	
	public void setEnabled(boolean enabled)
	{
		destinationsTreeViewer.getControl().setEnabled(enabled);
	}
	
	@Override
	public boolean isEnabled()
	{
		return destinationsTreeViewer.getControl().isEnabled();
	}
	
	/**
	 * Retrieves a set of destination providers which are capable of providing destinations for the category specified
	 * 
	 * @param category
	 *            the destination category
	 * @return a set of destination provider descriptions
	 */
	protected abstract Set<IDestinationsProvider> getDestinationProvidersForCategory(final IDestinationCategoryDescription category);

	/**
	 * Retrieves a list of search destinations which are relevant to the destination category and destination provider specified
	 * 
	 * @param category
	 *            the destination category
	 * @param destinationsProvider
	 *            the destinations provider
	 * @return a set of search destinations
	 */
	protected abstract List<ISearchDestination> getSearchDestinations(final IDestinationCategoryDescription category,
									final IDestinationsProvider destinationsProvider);
	
	private class SelectionChangedListener implements IPropertyAttributeListener<IStructuredSelection>
	{
		@Override
		public void attributeChanged(final PropertyAttributeChangedEvent<IStructuredSelection> event)
		{
			final IStructuredSelection selection = event.getNewAttribute();
			if (selection.isEmpty() || !(selection.getFirstElement() instanceof ISearchDestination))
			{
				handleSelectionChange(null);
				return;
			}

			handleSelectionChange((ISearchDestination)selection.getFirstElement());
		}
	}
	
	protected int treeViewerMinHeight()
	{
		// TODO: Maybe take a percentage of screen size!?
		return 80;
	}
	
	public IDestinationCategoryDescription getActiveDestinationCategory() {
		IStructuredSelection selection = lastKnownSelection.get();
		
		if(!(selection instanceof TreeSelection)) {
			//this means initial empty selection
			return null;
		}
		
		TreeSelection treeSelection = (TreeSelection) selection;
		
		Object selectedElement = treeSelection.getFirstElement();
		if (selectedElement instanceof IDestinationCategoryDescription) {
			return (IDestinationCategoryDescription)selectedElement;
		}
		
		if(selectedElement instanceof ISearchDestination) {
			TreePath pathToSelected = treeSelection.getPathsFor(selectedElement)[0];
			assert pathToSelected.getFirstSegment() instanceof IDestinationCategoryDescription;
			return (IDestinationCategoryDescription) pathToSelected.getFirstSegment() ;
		}
		
		return null;
	}
}