/*******************************************************************************
 * Copyright (c) 2011, 2015 Wind River Systems 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:
 *     Wind River Systems - initial API and implementation
 *******************************************************************************/
package org.eclipse.debug.internal.ui.viewers.model.provisional;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.TreeMap;

import org.eclipse.core.runtime.Assert;
import org.eclipse.debug.internal.core.IInternalDebugCoreConstants;

/**
 * Virtual item, which is analogous to the SWT's tree item.  This class is used
 * by the {@link VirtualTreeModelViewer}.
 *
 * @see VirtualTreeModelViewer
 * @since 3.8
 */
public class VirtualItem {

    // Data keys for display attributes of an item.
    public static String LABEL_KEY = "LABEL_KEY"; //$NON-NLS-1$
    public static String IMAGE_KEY = "IMAGE_KEY"; //$NON-NLS-1$
    public static String FONT_KEY = "FONT_KEY"; //$NON-NLS-1$
    public static String FOREGROUND_KEY = "FOREGROUND_KEY"; //$NON-NLS-1$
    public static String BACKGROUND_KEY = "BACKGROUND_KEY"; //$NON-NLS-1$

    public static String ELEMENT_DATA_KEY = "element"; //$NON-NLS-1$

    /**
     * Index object of a tree item. It allows the indexes to be modified
     * as items are inserted and removed.
     */
	public static class Index implements Comparable<Object> {
        private Integer fIndexValue;

        public Index(int index) {
            fIndexValue = Integer.valueOf(index);
        }

        @Override
		public boolean equals(Object obj) {
            return obj instanceof Index && ((Index)obj).fIndexValue.equals(fIndexValue);
        }

        @Override
		public int hashCode() {
            return fIndexValue.hashCode();
        }

        public void increment() {
            fIndexValue = Integer.valueOf(fIndexValue.intValue() + 1);
        }

        public void decrement() {
            fIndexValue = Integer.valueOf(fIndexValue.intValue() - 1);
        }

        public int intValue() {
            return fIndexValue.intValue();
        }

        @Override
		public int compareTo(Object obj) {
            return obj instanceof Index ? fIndexValue.compareTo(((Index)obj).fIndexValue) : 0;
        }

        @Override
		public String toString() {
            return fIndexValue.toString();
        }
    }

    /**
     * Parent items of this item.
     */
    final private VirtualItem fParent;

    /**
     * The index of this item.
     */
    final private Index fIndex;

    /**
     * Map of child items.  The key to the map is the item's index, which
     * must be the same object instance as the index in the item.  The tree map
     * keeps the items sorted while allowing indexes (keys) to be modified as
     * child items are inserted and removed.
     */
	private Map<Index, VirtualItem> fItems = new TreeMap<>();

    /**
     * Flag indicating whether this item has child items.
     */
    private boolean fHasItems = false;

    /**
     * Indicates that this item has been expanded.  It should only
     * be set to <code>true</code> if fHasItems is <code>true</code>.
     */
    private boolean fExpanded = false;

    /**
     * The count of child items.  <code>-1</code> indicates that the count
     * is not known.
     */
    private int fItemCount = -1;

    /**
     * The data held by this item.  It includes the element as well as the item
     * display attributes.
     */
	private Map<String, Object> fData = new HashMap<>(1);

    /**
     * Flag indicating that the item needs to have it's label updated.
     */
    private boolean fNeedsLabelUpdate = true;

    /**
     * Flag indicating that the item's count needs to be updated.
     */
    private boolean fNeedsCountUpdate = true;

    /**
     * Flag indicating that the item's element needs to be updated.
     */
    private boolean fNeedsDataUpdate = true;

    /**
     * Indicates that this item has been disposed.
     */
    private boolean fDisposed = false;


    /**
     * Virtual item constructor.
     * @param parent parent virtual item
     * @param index index of the item in the parent
     */
    public VirtualItem(VirtualItem parent, Index index) {
        fParent = parent;
        fIndex = index;
    }

    /**
     * Clears the child item at the given index.
     * @param index index of item to clear.
     */
    public void clear(Index index) {
        VirtualItem item = fItems.remove(index);
        if (item != null) {
            item.dispose();
        }
    }

    /**
     * Clears all child items.
     *
     * @since 3.9
     */
    public void clearAll() {
        fData.clear();
		for (VirtualItem item : fItems.values()) {
			item.dispose();
        }
        fItems.clear();
    }
    /**
     * Returns the parent item.
     * @return parent item.
     */
    public VirtualItem getParent() {
        return fParent;
    }

    /**
     * @return Returns the index of this item.
     */
    public Index getIndex() {
        return fIndex;
    }

    /**
     * Finds the given item in the child items of this element.
     * @param element Data object of the item to be found.
     * @return Item if found, <code>null</code> if not.
     */
    public VirtualItem findItem(Object element) {
		for (VirtualItem item : fItems.values()) {
			Object nextData = item.getData();
            if ( (element != null && element.equals(nextData)) || (element == null && nextData == null) ) {
				return item;
            }
        }
        return null;
    }

    /**
     * @return Returns whether the data element of this item is stale.
     */
    public boolean needsDataUpdate() {
        return fNeedsDataUpdate;
    }

    /**
     * Marks the item as having a stale data item.
     */
    public void setNeedsDataUpdate() {
        fNeedsDataUpdate = true;
    }

    /**
     * Clears the stale status of the item's data element.
     */
    public void clearNeedsDataUpdate() {
        fNeedsDataUpdate = false;
    }

    /**
     * @return Returns whether the item has stale item count.
     */
    public boolean needsCountUpdate() {
        return fNeedsCountUpdate;
    }

    /**
     * Marks the item as having a stale child count.
     */
    public void setNeedsCountUpdate() {
        fNeedsCountUpdate = true;
        fItemCount = -1;
    }

    /**
     * Clears the stale status of the item's child count.
     */
    public void clearNeedsCountUpdate() {
        fNeedsCountUpdate = false;
    }

    /**
     * @return Returns whether the item has stale label.
     */
    public boolean needsLabelUpdate() {
        return fNeedsLabelUpdate;
    }

    /**
     * Marks the item as having a stale label data.
     */
    public void setNeedsLabelUpdate() {
        fNeedsLabelUpdate = true;
    }

    /**
     * Clears the stale status of the item's label.
     */
    public void clearNeedsLabelUpdate() {
        fNeedsLabelUpdate = false;
    }

    /**
     * @return Returns whether the item has been disposed.
     */
    public boolean isDisposed() {
        return fDisposed;
    }

    /**
     * Disposes the item.
     */
    public void dispose() {
        clearAll();

        fDisposed = true;
        findTree().fireItemDisposed(this);
    }

    /**
     * @param key Key to retrieve data for.
     * @return Returns item data corresponding to given key.
     */
    public Object getData (String key) {
        return fData.get(key);
    }

    /**
     * Sets given data element for given key.
     * @param key Key for data.
     * @param data Data value.
     */
    public void setData(String key, Object data) {
        fData.put(key, data);
    }

    /**
     * Sets the item's data element.
     * @param data Item's new element.
     */
    public void setData(Object data) {
        fData.put(ELEMENT_DATA_KEY, data);
    }

    /**
     * @return Returns item's data element.
     */
    public Object getData () {
        return fData.get(ELEMENT_DATA_KEY);
    }

    /**
     * Marks the given item as expanded or collapsed.
     * @param expanded If true, item will be marked as expanded.
     */
    public void setExpanded(boolean expanded) {
        if (fExpanded == expanded) {
            return;
        }
        fExpanded = expanded;

        if (fExpanded && getItemCount() == -1) {
            setNeedsCountUpdate();
        }


        Assert.isTrue(!fExpanded || hasItems());

        // If collapsed, make sure that all the children are collapsed as well.
        if (!fExpanded) {
			for (VirtualItem item : fItems.values()) {
				item.setExpanded(expanded);
            }
        }
    }

    /**
     * @return Returns item's expanded state.
     */
    public boolean getExpanded() {
        return fExpanded;
    }

    /**
     * Sets the flag indicating whether item has child items.
     * @param hasChildren Set to true if child has items.
     */
    public void setHasItems(boolean hasChildren) {
        fHasItems = hasChildren;
        if (!fHasItems) {
            if (getItemCount() != 0) {
                setItemCount(0);
            }
        } else if (getItemCount() == 0) {
            setItemCount(-1);
        }
    }

    /**
     * @return Returns true if item has child items.
     */
    public boolean hasItems() {
        return fHasItems;
    }

    /**
     * Sets the item's child count.
     * @param count Child count.
     */
    public void setItemCount(int count) {
        fItemCount = count;
		for (Iterator<Entry<Index, VirtualItem>> itr = fItems.entrySet().iterator(); itr.hasNext();) {
			Entry<Index, VirtualItem> entry = itr.next();
            int index = entry.getKey().intValue();
            if (index >= count) {
                VirtualItem item = entry.getValue();
                item.dispose();
                itr.remove();
            }
        }
        if (fItemCount == 0) {
            if (hasItems()) {
                setHasItems(false);
            }
            if (getExpanded()) {
                setExpanded(false);
            }
        } else {
            if (!hasItems()) {
                setHasItems(true);
            }
        }
    }

    /**
     * @return  Returns item's child count.
     */
    public int getItemCount() {
        return fItemCount;
    }

    /**
     * Returns the child item at given index.  Child item is created if needed.
     *
     * @param index Index of the child item.
     * @return Child item.
     */
    public VirtualItem getItem(Index index) {
        ensureItems();

        VirtualItem item = fItems.get(index);
        if (item == null) {
            item = new VirtualItem(this, index);
            fItems.put(index, item);
        }
        return item;
    }

    /**
     * @return Returns true if any of the child items need a data update.
     */
    public boolean childrenNeedDataUpdate() {
        if (getItemCount() == 0) {
            return false;
        }
        if (fItems == null || fItems.size() != fItemCount) {
            return true;
        }
		for (VirtualItem child : fItems.values()) {
            if (child.needsDataUpdate()) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns an array of current child items.  The returned array contains
     * only the items that have been created.  It may not contain as many items as the
     * item count.
     *
     * @return Child items array.
     */
    public VirtualItem[] getItems() {
        return fItems.values().toArray(new VirtualItem[fItems.size()]);
    }

    /**
     * Adds a child item at the given index position.
     * @param position The index position to inser the new item at.
     * @return Returns the added item.
     */
    public VirtualItem addItem(int position) {
        if (!fHasItems) {
            fHasItems = true;
        }
        if (fItemCount < 0) {
            fItemCount = 0;
        }

        // Increment all items with an index higher than the given position.
        fItemCount++;
        ensureItems();
		for (Index childIndex : fItems.keySet()) {
            if (childIndex.intValue() >= position) {
                childIndex.increment();
            }
        }

        // Note: the same index object used to create the item has to
        // be used as the key into the map.
        Index childIndex = new Index(position);
        VirtualItem newChild = new VirtualItem(this, childIndex);
        fItems.put(childIndex, newChild);
        return newChild;
    }

    /**
     * Removes the item at the given index.
     * @param position Index of the item to remove.
     */
    public void remove(Index position) {
        fItemCount--;
        if (fItemCount < 0) {
            fHasItems = false;
        }

        ensureItems();

        VirtualItem removedItem = null;
		for (Iterator<Entry<Index, VirtualItem>> itr = fItems.entrySet().iterator(); itr.hasNext();) {
			Entry<Index, VirtualItem> entry = itr.next();
            Index childIndex = entry.getKey();
            if (childIndex.intValue() > position.intValue()) {
                childIndex.decrement();
            } else if (childIndex.intValue() == position.intValue()) {
                removedItem = entry.getValue();
                removedItem.dispose();
                itr.remove();
            }
        }
    }

    private void ensureItems() {
        if (fItems == null) {
			fItems = new HashMap<>(Math.max(1, Math.min(fItemCount, 16)));
        }
    }

    private VirtualTree findTree() {
        VirtualItem item = this;
        while (!(item instanceof VirtualTree)) {
            item = item.fParent;
        }
        return (VirtualTree)item;
    }

    @Override
	public String toString() {
        StringBuffer buffer = new StringBuffer();
        toStringItem(buffer, IInternalDebugCoreConstants.EMPTY_STRING);
        return buffer.toString();
    }

    void toStringItem(StringBuffer buffer, String indent) {
        buffer.append(indent);
        buffer.append(toStringElement());
        buffer.append("\n"); //$NON-NLS-1$
        indent = indent + "  "; //$NON-NLS-1$
        for (int i = 0; i < fItemCount; i++) {
            VirtualItem item = fItems.get(new Index(i));
            if (item != null) {
                item.toStringItem(buffer, indent);
            } else {
                buffer.append("<no item>\n"); //$NON-NLS-1$
            }
        }
    }

    private String toStringElement() {
        String[] label = (String[])fData.get(LABEL_KEY);
        if (label != null && label.length != 0) {
            return label[0];
        }
        Object data = fData.get(ELEMENT_DATA_KEY);
        if (data != null) {
            return data.toString();
        }
        return "<no data>"; //$NON-NLS-1$
    }
}