/*******************************************************************************
 * Copyright (c) 2007 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 180746)
 *      Boris Bokowski, IBM - initial API and implementation
 *      Matthew Hall - bug 212223
 *      Will Horn - bug 215297
 *      Matthew Hall - bug 208332
 ******************************************************************************/

module org.eclipse.jface.internal.databinding.swt.DelayedObservableValue;

import java.lang.all;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.IStaleListener;
import org.eclipse.core.databinding.observable.ObservableTracker;
import org.eclipse.core.databinding.observable.StaleEvent;
import org.eclipse.core.databinding.observable.value.IObservableValue;
import org.eclipse.core.databinding.observable.value.IValueChangeListener;
import org.eclipse.core.databinding.observable.value.IVetoableValue;
import org.eclipse.core.databinding.observable.value.ValueChangeEvent;
import org.eclipse.core.databinding.observable.value.ValueChangingEvent;
import org.eclipse.core.databinding.observable.value.ValueDiff;
import org.eclipse.jface.databinding.swt.ISWTObservableValue;
import org.eclipse.jface.internal.databinding.provisional.swt.AbstractSWTObservableValue;
import org.eclipse.jface.util.Util;
import org.eclipse.swt.SWT;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Widget;

/**
 * {@link IObservableValue} implementation that wraps any
 * {@link ISWTObservableValue} and delays notification of value change events
 * from the wrapped observable value until a certain time has passed since the
 * last change event, or until a FocusOut event is received from the underlying
 * widget (whichever happens earlier). This class helps to delay validation
 * until the user stops typing. To notify about pending changes, a delayed
 * observable value will fire a stale event when the wrapped observable value
 * fires a change event, but this change is being delayed.
 * 
 * Note that this class will not forward {@link ValueChangingEvent} events from
 * a wrapped {@link IVetoableValue}.
 * 
 * @since 1.2
 */
public class DelayedObservableValue : AbstractSWTObservableValue {
    class ValueUpdater : Runnable {
        private final Object oldValue;

        bool cancel = false;
        bool running = false;

        this(Object oldValue) {
            this.oldValue = oldValue;
        }

        void cancel() {
            cancel = true;
        }

        public void run() {
            if (!cancel)
                try {
                    running = true;
                    internalFireValueChange(oldValue);
                } finally {
                    running = false;
                }
        }
    }

    private IStaleListener staleListener = new class() IStaleListener {
        public void handleStale(StaleEvent staleEvent) {
            if (!updating)
                fireStale();
        }
    };

    private IValueChangeListener valueChangeListener = new class() IValueChangeListener {
        public void handleValueChange(ValueChangeEvent event) {
            if (!updating)
                makeDirty();
        }
    };

    private Listener focusOutListener = new class() Listener {
        public void handleEvent(Event event) {
            // Force update on focus out
            if (dirty)
                internalFireValueChange(cachedValue);
        }
    };

    private final int delay;
    private ISWTObservableValue observable;
    private Control control;

    private bool dirty = true;
    private Object cachedValue = null;

    private bool updating = false;

    private ValueUpdater updater = null;

    /**
     * Constructs a new instance bound to the given
     * <code>ISWTObservableValue</code> and configured to fire change events
     * once there have been no value changes in the observable for
     * <code>delay</code> milliseconds.
     * 
     * @param delayMillis
     * @param observable
     * @throws IllegalArgumentException
     *             if <code>updateEventType</code> is an incorrect type.
     */
    public this(int delayMillis,
            ISWTObservableValue observable) {
        super(observable.getRealm(), observable.getWidget());
        this.delay = delayMillis;
        this.observable = observable;

        observable.addValueChangeListener(valueChangeListener);
        observable.addStaleListener(staleListener);
        Widget widget = observable.getWidget();
        if (null !is cast(Control)widget) {
            control = cast(Control) widget;
            control.addListener(SWT.FocusOut, focusOutListener);
        }

        cachedValue = doGetValue();
    }

    protected Object doGetValue() {
        if (dirty) {
            cachedValue = observable.getValue();
            dirty = false;

            if (updater !is null && !updater.running) {
                fireValueChange(Diffs.createValueDiff(updater.oldValue,
                        cachedValue));
                cancelScheduledUpdate();
            }
        }
        return cachedValue;
    }

    protected void doSetValue(Object value) {
        updating = true;
        try {
            // Principle of least surprise: setValue overrides any pending
            // update from observable.
            dirty = false;
            cancelScheduledUpdate();

            Object oldValue = cachedValue;
            observable.setValue(value);
            // Bug 215297 - target observable could veto or override value
            // passed to setValue(). Make sure we cache whatever is set.
            cachedValue = observable.getValue();

            if (!Util.equals(oldValue, cachedValue))
                fireValueChange(Diffs.createValueDiff(oldValue, cachedValue));
        } finally {
            updating = false;
        }
    }

    public bool isStale() {
        ObservableTracker.getterCalled(this);
        return (dirty && updater !is null) || observable.isStale();
    }

    /**
     * Returns the type of the value from {@link #doGetValue()}, i.e.
     * String.class
     * 
     * @see org.eclipse.core.databinding.observable.value.IObservableValue#getValueType()
     */
    public Object getValueType() {
        return observable.getValueType();
    }

    public void dispose() {
        cancelScheduledUpdate();
        if (observable !is null) {
            observable.dispose();
            observable.removeValueChangeListener(valueChangeListener);
            observable.removeStaleListener(staleListener);
            observable = null;
        }
        if (control !is null) {
            control.removeListener(SWT.FocusOut, focusOutListener);
            control = null;
        }
        super.dispose();
    }

    private void makeDirty() {
        if (!dirty) {
            dirty = true;
            fireStale();
        }
        cancelScheduledUpdate(); // if any
        scheduleUpdate();
    }

    private void cancelScheduledUpdate() {
        if (updater !is null) {
            updater.cancel();
            updater = null;
        }
    }

    private void scheduleUpdate() {
        updater = new ValueUpdater(cachedValue);
        observable.getWidget().getDisplay().timerExec(delay, updater);
    }

    private void internalFireValueChange(Object oldValue) {
        cancelScheduledUpdate();
        fireValueChange(new class(oldValue) ValueDiff {
            Object oldValue_;
            this(Object o){ oldValue_ = o; }
            public Object getOldValue() {
                return oldValue_;
            }

            public Object getNewValue() {
                return getValue();
            }
        });
    }
}