/*******************************************************************************
 * Copyright (c) 2008 Matthew Hall 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:
 *     Matthew Hall - initial API and implementation (bug 215531)
 *     Matthew Hall - bug 226765
 ******************************************************************************/

module org.eclipse.jface.internal.databinding.viewers.ObservableCollectionContentProvider;

import java.lang.all;

import org.eclipse.core.databinding.observable.IObservable;
import org.eclipse.core.databinding.observable.IObservableCollection;
import org.eclipse.core.databinding.observable.Observables;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.masterdetail.IObservableFactory;
import org.eclipse.core.databinding.observable.masterdetail.MasterDetailObservables;
import org.eclipse.core.databinding.observable.set.IObservableSet;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.observable.value.WritableValue;
import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.databinding.swt.SWTObservables;
import org.eclipse.jface.viewers.AbstractListViewer;
import org.eclipse.jface.viewers.AbstractTableViewer;
import org.eclipse.jface.viewers.IElementComparer;
import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.widgets.Display;

/**
 * NON-API - Abstract base class for content providers where the viewer input is
 * expected to be an {@link IObservableCollection}.
 * 
 * @since 1.2
 */
public abstract class ObservableCollectionContentProvider :
        IStructuredContentProvider {
    private IObservableValue viewerObservable;

    /**
     * Element comparer used by the viewer (may be null).
     */
    protected IElementComparer comparer;

    /**
     * Interface for sending updates to the viewer.
     */
    protected ViewerUpdater viewerUpdater;

    /**
     * Observable set of all elements known to the content provider. Subclasses
     * must add new elements to this set <b>before</b> adding them to the
     * viewer, and must remove old elements from this set <b>after</b> removing
     * them from the viewer.
     */
    protected IObservableSet knownElements;

    private IObservableSet unmodifiableKnownElements;
    private IObservableCollection observableCollection;

    /**
     * Constructs an ObservableCollectionContentProvider
     */
    protected this() {
        final Realm realm = SWTObservables.getRealm(Display.getDefault());
        viewerObservable = new WritableValue(realm);
        viewerUpdater = null;

        // Known elements is a detail set of viewerObservable, so that when we
        // get the viewer instance we can swap in a set that uses its
        // IElementComparer, if any.
        IObservableFactory knownElementsFactory = new class() IObservableFactory {
            public IObservable createObservable(Object target) {
                IElementComparer comparer = null;
                if (null !is cast(StructuredViewer)target)
                    comparer = (cast(StructuredViewer) target).getComparer();
                return ObservableViewerElementSet.withComparer(realm, null,
                        comparer);
            }
        };
        knownElements = MasterDetailObservables.detailSet(viewerObservable,
                knownElementsFactory, null);
        unmodifiableKnownElements = Observables
                .unmodifiableObservableSet(knownElements);

        observableCollection = null;
    }

    public Object[] getElements(Object inputElement) {
        if (observableCollection is null)
            return new Object[0];
        return observableCollection.toArray();
    }

    public void dispose() {
        if (observableCollection !is null)
            removeCollectionChangeListener(observableCollection);

        if (viewerObservable !is null) {
            viewerObservable.setValue(null);
            viewerObservable.dispose();
            viewerObservable = null;
        }
        viewerUpdater = null;
        knownElements = null;
        unmodifiableKnownElements = null;
    }

    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
        setViewer(viewer);
        setInput(newInput);
    }

    private void setViewer(Viewer viewer) {
        viewerUpdater = createViewerUpdater(viewer);
        comparer = getElementComparer(viewer);
        viewerObservable.setValue(viewer); // (clears knownElements)
    }

    private static IElementComparer getElementComparer(Viewer viewer) {
        if (null !is cast(StructuredViewer)viewer)
            return (cast(StructuredViewer) viewer).getComparer();
        return null;
    }

    ViewerUpdater createViewerUpdater(Viewer viewer) {
        if (null !is cast(AbstractListViewer)viewer)
            return new ListViewerUpdater(cast(AbstractListViewer) viewer);
        if (null !is cast(AbstractTableViewer)viewer)
            return new TableViewerUpdater(cast(AbstractTableViewer) viewer);
        throw new IllegalArgumentException(
                "This content provider only works with AbstractTableViewer or AbstractListViewer"); //$NON-NLS-1$
    }

    void setInput(Object input) {
        if (observableCollection !is null) {
            removeCollectionChangeListener(observableCollection);
            observableCollection = null;
        }

        if (input !is null) {
            checkInput(input);
            Assert.isTrue(null !is cast(IObservableCollection)input,
                    "Input must be an IObservableCollection"); //$NON-NLS-1$
            observableCollection = cast(IObservableCollection) input;
            addCollectionChangeListener(observableCollection);
            knownElements.addAll(observableCollection);
        }
    }

    /**
     * Throws an exception if the input is not the correct type.
     * 
     * @param input
     *            the input to check
     */
    protected abstract void checkInput(Object input);

    /**
     * Register for change event notification from the given collection.
     * 
     * @param collection
     *            observable collection to listen to
     */
    protected abstract void addCollectionChangeListener(
            IObservableCollection collection);

    /**
     * Deregisters from change events notification on the given collection.
     * 
     * @param collection
     *            observable collection to stop listening to
     */
    protected abstract void removeCollectionChangeListener(
            IObservableCollection collection);

    /**
     * Returns whether the viewer is disposed. Collection change listeners in
     * subclasses should verify that the viewer is not disposed before sending
     * any updates to the {@link ViewerUpdater viewer updater}.
     * 
     * @return whether the viewer is disposed.
     */
    protected final bool isViewerDisposed() {
        Viewer viewer = cast(Viewer) viewerObservable.getValue();
        return viewer is null || viewer.getControl() is null
                || viewer.getControl().isDisposed();
    }

    /**
     * Returns the set of elements known to this content provider. Label
     * providers may track this set if they need to be notified about additions
     * before the viewer sees the added element, and notified about removals
     * after the element was removed from the viewer. This is intended for use
     * by label providers, as it will always return the items that need labels.
     * 
     * @return unmodifiable observable set of items that will need labels
     */
    public IObservableSet getKnownElements() {
        return unmodifiableKnownElements;
    }
}