/*******************************************************************************
 * 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 207858)
 *     Matthew Hall - bug 226765
 ******************************************************************************/

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

import java.lang.all;

import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import org.eclipse.core.databinding.observable.IObservable;
import org.eclipse.core.databinding.observable.IObservableCollection;
import org.eclipse.core.databinding.observable.IObservablesListener;
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.databinding.viewers.TreeStructureAdvisor;
import org.eclipse.jface.util.Util;
import org.eclipse.jface.viewers.AbstractTreeViewer;
import org.eclipse.jface.viewers.IElementComparer;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.widgets.Display;

/**
 * NON-API - Abstract base class for {@link ITreeContentProvider}s which use an
 * {@link IObservableFactory observable collection factory} to provide the
 * elements of a tree. Each observable collection obtained from the factory is
 * observed such that changes in the collection are reflected in the viewer.
 * 
 * @since 1.2
 */
public abstract class ObservableCollectionTreeContentProvider :
        ITreeContentProvider {
    private Realm realm;

    private IObservableValue viewerObservable;

    /**
     * Interfaces for sending updates to the viewer.
     */
    protected TreeViewerUpdater viewerUpdater;

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

    private IObservableSet knownElements;
    private IObservableSet unmodifiableKnownElements;

    private IObservableFactory /* <IObservableCollection> */collectionFactory;

    private Map /* <Object element, TreeNode node> */elementNodes;

    private TreeStructureAdvisor structureAdvisor;

    /**
     * Constructs an ObservableCollectionTreeContentProvider using the given
     * parent provider and collection factory.
     * 
     * @param collectionFactory
     *            observable factory that produces an IObservableList of
     *            children for a given parent element.
     * @param structureAdvisor
     */
    protected this(
            IObservableFactory collectionFactory,
            TreeStructureAdvisor structureAdvisor) {
        this.structureAdvisor = structureAdvisor;
        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) {
                return ObservableViewerElementSet.withComparer(realm, null,
                        getElementComparer(cast(Viewer) target));
            }
        };
        knownElements = MasterDetailObservables.detailSet(viewerObservable,
                knownElementsFactory, null);
        unmodifiableKnownElements = Observables
                .unmodifiableObservableSet(knownElements);

        Assert
                .isNotNull(collectionFactory,
                        "Collection factory cannot be null"); //$NON-NLS-1$
        this.collectionFactory = collectionFactory;
    }

    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
        if (elementNodes !is null && !elementNodes.isEmpty()) {
            // Ensure we flush any observable collection listeners
            TreeNode[] oldNodes = new TreeNode[elementNodes.size()];
            elementNodes.values().toArray(oldNodes);
            for (int i = 0; i < oldNodes.length; i++)
                oldNodes[i].dispose();
            elementNodes.clear();
            elementNodes = null;
        }

        setViewer(viewer);
    }

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

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

    private static TreeViewerUpdater createViewerUpdater(Viewer viewer) {
        if (null !is cast(AbstractTreeViewer)viewer)
            return new TreeViewerUpdater(cast(AbstractTreeViewer) viewer);
        throw new IllegalArgumentException(
                "This content provider only works with AbstractTreeViewer"); //$NON-NLS-1$
    }

    public Object getParent(Object element) {
        if (structureAdvisor !is null) {
            Object parentFromAdvisor = structureAdvisor.getParent(element);
            if (parentFromAdvisor !is null) {
                return parentFromAdvisor;
            }
        }
        TreeNode node = getExistingNode(element);
        if (node !is null)
            return node.getParent();
        return null;
    }

    public Object[] getElements(Object input) {
        return getChildren(input);
    }

    public Object[] getChildren(Object element) {
        Object[] children = getOrCreateNode(element).getChildren();
        for (int i = 0; i < children.length; i++)
            getOrCreateNode(children[i]).addParent(element);
        return children;
    }

    public bool hasChildren(Object element) {
        if (structureAdvisor !is null) {
            Boolean hasChildren = structureAdvisor.hasChildren(element);
            if (hasChildren !is null) {
                return hasChildren.booleanValue();
            }
        }
        return getOrCreateNode(element).hasChildren();
    }

    protected TreeNode getOrCreateNode(Object element) {
        TreeNode node = getExistingNode(element);
        if (node is null) {
            node = new TreeNode(element);
        }
        return node;
    }

    protected TreeNode getExistingNode(Object element) {
        TreeNode node = cast(TreeNode) elementNodes.get(element);
        return node;
    }

    protected bool isViewerDisposed() {
        Viewer viewer = cast(Viewer) viewerObservable.getValue();
        return viewer is null || viewer.getControl() is null
                || viewer.getControl().isDisposed();
    }

    public void dispose() {
        if (elementNodes !is null) {
            if (!elementNodes.isEmpty()) {
                TreeNode[] nodes = new TreeNode[elementNodes.size()];
                elementNodes.values().toArray(nodes);
                for (int i = 0; i < nodes.length; i++) {
                    nodes[i].dispose();
                }
                elementNodes.clear();
            }
            elementNodes = null;
        }
        if (viewerObservable !is null) {
            viewerObservable.setValue(null);
            viewerObservable.dispose();
            viewerObservable = null;
        }
        viewerUpdater = null;
        comparer = null;
        knownElements = null;
        unmodifiableKnownElements = null;
        collectionFactory = null;
    }

    /**
     * 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;
    }

    /**
     * Returns a listener which, when a collection change event is received,
     * updates the tree viewer through the {@link #viewerUpdater} field, and
     * maintains the adds and removes parents from the appropriate tree nodes.
     * 
     * @param parentElement
     *            the element that is the parent element of all elements in the
     *            observable collection.
     * @return a listener which updates the viewer when change events occur.
     */
    protected abstract IObservablesListener createCollectionChangeListener(
            Object parentElement);

    /**
     * Registers the change listener to receive change events for the specified
     * observable collection.
     * 
     * @param collection
     *            the collection to observe for changes
     * @param listener
     *            the listener that will receive collection change events.
     */
    protected abstract void addCollectionChangeListener(
            IObservableCollection collection, IObservablesListener listener);

    /**
     * Unregisters the change listener from receving change events for the
     * specified observable collection.
     * 
     * @param collection
     *            the collection to stop observing.
     * @param listener
     *            the listener to remove
     */
    protected abstract void removeCollectionChangeListener(
            IObservableCollection collection, IObservablesListener listener);

    protected final class TreeNode {
        private Object element;

        private Object parent;
        private Set parentSet;

        private IObservableCollection children;

        private IObservablesListener listener;

        this(Object element) {
            Assert.isNotNull(element, "element cannot be null"); //$NON-NLS-1$
            this.element = element;
            knownElements.add(element);
            elementNodes.put(element, this);
        }

        Object getElement() {
            return element;
        }

        private bool equal(Object left, Object right) {
            if (comparer is null)
                return Util.equals(left, right);
            return comparer.equals(left, right);
        }

        public void addParent(Object newParent) {
            if (parent is null) {
                parent = newParent;
            } else if (!equal(parent, newParent)) {
                if (parentSet is null) {
                    parentSet = ViewerElementSet.withComparer(comparer);
                    parentSet.add(parent);
                }
                parentSet.add(newParent);
            }
        }

        public void removeParent(Object oldParent) {
            if (parentSet !is null)
                parentSet.remove(oldParent);

            if (equal(parent, oldParent)) {
                if (parentSet is null || parentSet.isEmpty()) {
                    parent = null;
                } else {
                    Iterator iterator = parentSet.iterator();
                    parent = iterator.next();
                    iterator.remove();
                }
            }

            if (parentSet !is null && parentSet.isEmpty())
                parentSet = null;

            if (parent is null) {
                dispose();
            }
        }

        private Object getParent() {
            return parent;
        }

        private void initChildren() {
            if (children is null) {
                children = cast(IObservableCollection) collectionFactory
                        .createObservable(element);
                if (children is null) {
                    listener = null;
                    children = Observables.emptyObservableSet(realm);
                } else {
                    Assert
                            .isTrue(Util.equals(realm, children.getRealm()),
                                    "Children observable collection must be on the Display realm"); //$NON-NLS-1$
                    listener = createCollectionChangeListener(element);
                    addCollectionChangeListener(children, listener);
                }
            }
        }

        bool hasChildren() {
            initChildren();
            return !children.isEmpty();
        }

        Object[] getChildren() {
            initChildren();
            return children.toArray();
        }

        private void dispose() {
            if (element !is null) {
                elementNodes.remove(element);
                knownElements.remove(element);
            }
            if (children !is null) {
                for (Iterator iterator = children.iterator(); iterator
                        .hasNext();) {
                    TreeNode child = getExistingNode(iterator.next());
                    if (child !is null)
                        child.removeParent(element);
                }
                if (listener !is null)
                    removeCollectionChangeListener(children, listener);
                children.dispose();
                children = null;
            }
            element = null;
            parent = null;
            if (parentSet !is null) {
                parentSet.clear();
                parentSet = null;
            }
        }
    }
}