/*******************************************************************************
 * Copyright (c) 2005, 2008 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
module org.eclipse.jface.internal.databinding.provisional.swt.TableUpdater;

import java.lang.all;

import org.eclipse.core.databinding.observable.ChangeEvent;
import org.eclipse.core.databinding.observable.IChangeListener;
import org.eclipse.core.databinding.observable.IObservable;
import org.eclipse.core.databinding.observable.ObservableTracker;
import org.eclipse.core.databinding.observable.list.IListChangeListener;
import org.eclipse.core.databinding.observable.list.IObservableList;
import org.eclipse.core.databinding.observable.list.ListChangeEvent;
import org.eclipse.core.databinding.observable.list.ListDiffEntry;
import org.eclipse.core.runtime.Assert;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Table;
import org.eclipse.swt.widgets.TableItem;

/**
 * NON-API - This class can be used to update a table with automatic dependency
 * tracking.
 * 
 * @since 1.1
 * 
 * @noextend This class is not intended to be subclassed by clients. (We do
 *           encourage experimentation for non-production code and are
 *           interested in feedback though.)
 * 
 */
public abstract class TableUpdater {

    private class UpdateRunnable : Runnable, IChangeListener,
            DisposeListener {
        private TableItem item;

        private bool dirty = false;

        private IObservable[] dependencies = new IObservable[0];

        private final Object element;

        this(TableItem item, Object element) {
            this.item = item;
            this.element = element;
            item.addDisposeListener(this);
        }

        // Runnable implementation. This method runs at most once per repaint
        // whenever the
        // value gets marked as dirty.
        public void run() {
            if (table !is null && !table.isDisposed() && item !is null
                    && !item.isDisposed()) {
                if (table.isVisible()) {
                    int tableHeight = table.getClientArea().height;
                    int numVisibleItems = tableHeight / table.getItemHeight();
                    int indexOfItem = table.indexOf(item);
                    int topIndex = table.getTopIndex();
                    if (indexOfItem >= topIndex
                            && indexOfItem <= topIndex + numVisibleItems) {
                        updateIfNecessary(indexOfItem);
                        return;
                    }
                }
                table.clear(table.indexOf(item));
            }
        }

        private void updateIfNecessary(int indexOfItem) {
            if (dirty) {
                dependencies = ObservableTracker.runAndMonitor(dgRunnable( (int indexOfItem_) {
                        updateItem(indexOfItem_, item, element);
                }, indexOfItem), this, null);
                dirty = false;
            }
        }

        // IChangeListener implementation (listening to the ComputedValue)
        public void handleChange(ChangeEvent event) {
            // Whenever this updator becomes dirty, schedule the run() method
            makeDirty();
        }

        protected final void makeDirty() {
            if (!dirty) {
                dirty = true;
                stopListening();
                SWTUtil.runOnce(table.getDisplay(), this);
            }
        }

        private void stopListening() {
            // Stop listening for dependency changes
            for (int i = 0; i < dependencies.length; i++) {
                IObservable observable = dependencies[i];

                observable.removeChangeListener(this);
            }
        }

        // DisposeListener implementation
        public void widgetDisposed(DisposeEvent e) {
            stopListening();
            dependencies = null;
            item = null;
        }
    }

    private class PrivateInterface : Listener, DisposeListener {

        // Listener implementation
        public void handleEvent(Event e) {
            if (e.type is SWT.SetData) {
                UpdateRunnable runnable = cast(UpdateRunnable) e.item.getData();
                if (runnable is null) {
                    runnable = new UpdateRunnable(cast(TableItem) e.item, list.get(e.index));
                    e.item.setData(runnable);
                    runnable.makeDirty();
                } else {
                    runnable.updateIfNecessary(e.index);
                }
            }
        }

        // DisposeListener implementation
        public void widgetDisposed(DisposeEvent e) {
            this.outer.dispose();
        }

    }

    private PrivateInterface privateInterface = new PrivateInterface();

    private Table table;

    private IListChangeListener listChangeListener = new class() IListChangeListener {
        public void handleListChange(ListChangeEvent event) {
            ListDiffEntry[] differences = event.diff.getDifferences();
            for (int i = 0; i < differences.length; i++) {
                ListDiffEntry entry = differences[i];
                if (entry.isAddition()) {
                    TableItem item = new TableItem(table, SWT.NONE, entry
                            .getPosition());
                    UpdateRunnable updateRunnable = new UpdateRunnable(item, entry.getElement());
                    item.setData(updateRunnable);
                    updateRunnable.makeDirty();
                } else {
                    table.getItem(entry.getPosition()).dispose();
                }
            }
        }
    };

    private IObservableList list;

    /**
     * Creates an updator for the given control.
     * 
     * @param table
     *            table to update
     * @param list
     * @since 1.2
     */
    public this(Table table, IObservableList list) {
        this.table = table;
        this.list = list;
        Assert.isLegal((table.getStyle() & SWT.VIRTUAL) !is 0,
                "TableUpdater requires virtual table"); //$NON-NLS-1$

        table.setItemCount(list.size());
        list.addListChangeListener(listChangeListener);

        table.addDisposeListener(privateInterface);
        table.addListener(SWT.SetData, privateInterface);
    }

    /**
     * This is called automatically when the control is disposed. It may also be
     * called explicitly to remove this updator from the control. Subclasses
     * will normally extend this method to detach any listeners they attached in
     * their constructor.
     */
    public void dispose() {
        table.removeDisposeListener(privateInterface);
        table.removeListener(SWT.SetData, privateInterface);
        list.removeListChangeListener(listChangeListener);
        table = null;
        list = null;
    }

    /**
     * Updates the control. This method will be invoked once after the updator
     * is created, and once before any repaint during which the control is
     * visible and dirty.
     * 
     * <p>
     * Subclasses should overload this method to provide any code that changes
     * the appearance of the widget.
     * </p>
     * 
     * @param index
     * @param item
     *            the item to update
     * @param element
     * @since 1.2
     */
    protected abstract void updateItem(int index, TableItem item, Object element);

}