/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package net.sourceforge.phpdt.internal.core;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import net.sourceforge.phpdt.core.IJavaElement;
import net.sourceforge.phpdt.core.IJavaElementDelta;
import net.sourceforge.phpdt.core.IParent;
import net.sourceforge.phpdt.core.JavaModelException;
import net.sourceforge.phpdt.core.compiler.CharOperation;

/**
 * A java element delta biulder creates a java element delta on a java element
 * between the version of the java element at the time the comparator was
 * created and the current version of the java element.
 * 
 * It performs this operation by locally caching the contents of the java
 * element when it is created. When the method createDeltas() is called, it
 * creates a delta over the cached contents and the new contents.
 */
public class JavaElementDeltaBuilder {
	/**
	 * The java element handle
	 */
	IJavaElement javaElement;

	/**
	 * The maximum depth in the java element children we should look into
	 */
	int maxDepth = Integer.MAX_VALUE;

	/**
	 * The old handle to info relationships
	 */
	Map infos;

	/**
	 * The old position info
	 */
	Map oldPositions;

	/**
	 * The new position info
	 */
	Map newPositions;

	/**
	 * Change delta
	 */
	JavaElementDelta delta;

	/**
	 * List of added elements
	 */
	ArrayList added;

	/**
	 * List of removed elements
	 */
	ArrayList removed;

	/**
	 * Doubly linked list item
	 */
	class ListItem {
		public IJavaElement previous;

		public IJavaElement next;

		public ListItem(IJavaElement previous, IJavaElement next) {
			this.previous = previous;
			this.next = next;
		}
	}

	/**
	 * Creates a java element comparator on a java element looking as deep as
	 * necessary.
	 */
	public JavaElementDeltaBuilder(IJavaElement javaElement) {
		this.javaElement = javaElement;
		this.initialize();
		this.recordElementInfo(javaElement, (JavaModel) this.javaElement
				.getJavaModel(), 0);
	}

	/**
	 * Creates a java element comparator on a java element looking only
	 * 'maxDepth' levels deep.
	 */
	public JavaElementDeltaBuilder(IJavaElement javaElement, int maxDepth) {
		this.javaElement = javaElement;
		this.maxDepth = maxDepth;
		this.initialize();
		this.recordElementInfo(javaElement, (JavaModel) this.javaElement
				.getJavaModel(), 0);
	}

	/**
	 * Repairs the positioning information after an element has been added
	 */
	private void added(IJavaElement element) {
		this.added.add(element);
		ListItem current = this.getNewPosition(element);
		ListItem previous = null, next = null;
		if (current.previous != null)
			previous = this.getNewPosition(current.previous);
		if (current.next != null)
			next = this.getNewPosition(current.next);
		if (previous != null)
			previous.next = current.next;
		if (next != null)
			next.previous = current.previous;
	}

	/**
	 * Builds the java element deltas between the old content of the compilation
	 * unit and its new content.
	 */
	public void buildDeltas() {
		this.recordNewPositions(this.javaElement, 0);
		this.findAdditions(this.javaElement, 0);
		this.findDeletions();
		this.findChangesInPositioning(this.javaElement, 0);
		this.trimDelta(this.delta);
		if (this.delta.getAffectedChildren().length == 0) {
			// this is a fine grained but not children affected -> mark as
			// content changed
			this.delta.contentChanged();
		}
	}

	/**
	 * Finds elements which have been added or changed.
	 */
	private void findAdditions(IJavaElement newElement, int depth) {
		JavaElementInfo oldInfo = this.getElementInfo(newElement);
		if (oldInfo == null && depth < this.maxDepth) {
			this.delta.added(newElement);
			added(newElement);
		} else {
			this.removeElementInfo(newElement);
		}

		if (depth >= this.maxDepth) {
			// mark element as changed
			this.delta.changed(newElement, IJavaElementDelta.F_CONTENT);
			return;
		}

		JavaElementInfo newInfo = null;
		try {
			newInfo = (JavaElementInfo) ((JavaElement) newElement)
					.getElementInfo();
		} catch (JavaModelException npe) {
			return;
		}

		this.findContentChange(oldInfo, newInfo, newElement);

		if (oldInfo != null && newElement instanceof IParent) {

			IJavaElement[] children = newInfo.getChildren();
			if (children != null) {
				int length = children.length;
				for (int i = 0; i < length; i++) {
					this.findAdditions(children[i], depth + 1);
				}
			}
		}
	}

	/**
	 * Looks for changed positioning of elements.
	 */
	private void findChangesInPositioning(IJavaElement element, int depth) {
		if (depth >= this.maxDepth || this.added.contains(element)
				|| this.removed.contains(element))
			return;

		if (!isPositionedCorrectly(element)) {
			this.delta.changed(element, IJavaElementDelta.F_REORDER);
		}

		if (element instanceof IParent) {
			JavaElementInfo info = null;
			try {
				info = (JavaElementInfo) ((JavaElement) element)
						.getElementInfo();
			} catch (JavaModelException npe) {
				return;
			}

			IJavaElement[] children = info.getChildren();
			if (children != null) {
				int length = children.length;
				for (int i = 0; i < length; i++) {
					this.findChangesInPositioning(children[i], depth + 1);
				}
			}
		}
	}

	/**
	 * The elements are equivalent, but might have content changes.
	 */
	private void findContentChange(JavaElementInfo oldInfo,
			JavaElementInfo newInfo, IJavaElement newElement) {
		if (oldInfo instanceof MemberElementInfo
				&& newInfo instanceof MemberElementInfo) {
			if (((MemberElementInfo) oldInfo).getModifiers() != ((MemberElementInfo) newInfo)
					.getModifiers()) {
				this.delta.changed(newElement, IJavaElementDelta.F_MODIFIERS);
			} else if (oldInfo instanceof SourceMethodElementInfo
					&& newInfo instanceof SourceMethodElementInfo) {
				if (!CharOperation
						.equals(((SourceMethodElementInfo) oldInfo)
								.getReturnTypeName(),
								((SourceMethodElementInfo) newInfo)
										.getReturnTypeName())) {
					this.delta.changed(newElement, IJavaElementDelta.F_CONTENT);
				}
			} else if (oldInfo instanceof SourceFieldElementInfo
					&& newInfo instanceof SourceFieldElementInfo) {
				if (!CharOperation.equals(((SourceFieldElementInfo) oldInfo)
						.getTypeName(), ((SourceFieldElementInfo) newInfo)
						.getTypeName())) {
					this.delta.changed(newElement, IJavaElementDelta.F_CONTENT);
				}
			}
		}
		if (oldInfo instanceof SourceTypeElementInfo
				&& newInfo instanceof SourceTypeElementInfo) {
			SourceTypeElementInfo oldSourceTypeInfo = (SourceTypeElementInfo) oldInfo;
			SourceTypeElementInfo newSourceTypeInfo = (SourceTypeElementInfo) newInfo;
			if (!CharOperation.equals(oldSourceTypeInfo.getSuperclassName(),
					newSourceTypeInfo.getSuperclassName())
					|| !CharOperation.equals(oldSourceTypeInfo
							.getInterfaceNames(), newSourceTypeInfo
							.getInterfaceNames())) {
				this.delta.changed(newElement, IJavaElementDelta.F_SUPER_TYPES);
			}
		}
	}

	/**
	 * Adds removed deltas for any handles left in the table
	 */
	private void findDeletions() {
		Iterator iter = this.infos.keySet().iterator();
		while (iter.hasNext()) {
			IJavaElement element = (IJavaElement) iter.next();
			this.delta.removed(element);
			this.removed(element);
		}
	}

	private JavaElementInfo getElementInfo(IJavaElement element) {
		return (JavaElementInfo) this.infos.get(element);
	}

	private ListItem getNewPosition(IJavaElement element) {
		return (ListItem) this.newPositions.get(element);
	}

	private ListItem getOldPosition(IJavaElement element) {
		return (ListItem) this.oldPositions.get(element);
	}

	private void initialize() {
		this.infos = new HashMap(20);
		this.oldPositions = new HashMap(20);
		this.newPositions = new HashMap(20);
		this.putOldPosition(this.javaElement, new ListItem(null, null));
		this.putNewPosition(this.javaElement, new ListItem(null, null));
		this.delta = new JavaElementDelta(javaElement);

		// if building a delta on a compilation unit or below,
		// it's a fine grained delta
		if (javaElement.getElementType() >= IJavaElement.COMPILATION_UNIT) {
			this.delta.fineGrained();
		}

		this.added = new ArrayList(5);
		this.removed = new ArrayList(5);
	}

	/**
	 * Inserts position information for the elements into the new or old
	 * positions table
	 */
	private void insertPositions(IJavaElement[] elements, boolean isNew) {
		int length = elements.length;
		IJavaElement previous = null, current = null, next = (length > 0) ? elements[0]
				: null;
		for (int i = 0; i < length; i++) {
			previous = current;
			current = next;
			next = (i + 1 < length) ? elements[i + 1] : null;
			if (isNew) {
				this.putNewPosition(current, new ListItem(previous, next));
			} else {
				this.putOldPosition(current, new ListItem(previous, next));
			}
		}
	}

	/**
	 * Returns whether the elements position has not changed.
	 */
	private boolean isPositionedCorrectly(IJavaElement element) {
		ListItem oldListItem = this.getOldPosition(element);
		if (oldListItem == null)
			return false;

		ListItem newListItem = this.getNewPosition(element);
		if (newListItem == null)
			return false;

		IJavaElement oldPrevious = oldListItem.previous;
		IJavaElement newPrevious = newListItem.previous;
		if (oldPrevious == null) {
			return newPrevious == null;
		} else {
			return oldPrevious.equals(newPrevious);
		}
	}

	private void putElementInfo(IJavaElement element, JavaElementInfo info) {
		this.infos.put(element, info);
	}

	private void putNewPosition(IJavaElement element, ListItem position) {
		this.newPositions.put(element, position);
	}

	private void putOldPosition(IJavaElement element, ListItem position) {
		this.oldPositions.put(element, position);
	}

	/**
	 * Records this elements info, and attempts to record the info for the
	 * children.
	 */
	private void recordElementInfo(IJavaElement element, JavaModel model,
			int depth) {
		if (depth >= this.maxDepth) {
			return;
		}
		JavaElementInfo info = (JavaElementInfo) JavaModelManager
				.getJavaModelManager().getInfo(element);
		if (info == null) // no longer in the java model.
			return;
		this.putElementInfo(element, info);

		if (element instanceof IParent) {
			IJavaElement[] children = info.getChildren();
			if (children != null) {
				insertPositions(children, false);
				for (int i = 0, length = children.length; i < length; i++)
					recordElementInfo(children[i], model, depth + 1);
			}
		}
	}

	/**
	 * Fills the newPositions hashtable with the new position information
	 */
	private void recordNewPositions(IJavaElement newElement, int depth) {
		if (depth < this.maxDepth && newElement instanceof IParent) {
			JavaElementInfo info = null;
			try {
				info = (JavaElementInfo) ((JavaElement) newElement)
						.getElementInfo();
			} catch (JavaModelException npe) {
				return;
			}

			IJavaElement[] children = info.getChildren();
			if (children != null) {
				insertPositions(children, true);
				for (int i = 0, length = children.length; i < length; i++) {
					recordNewPositions(children[i], depth + 1);
				}
			}
		}
	}

	/**
	 * Repairs the positioning information after an element has been removed
	 */
	private void removed(IJavaElement element) {
		this.removed.add(element);
		ListItem current = this.getOldPosition(element);
		ListItem previous = null, next = null;
		if (current.previous != null)
			previous = this.getOldPosition(current.previous);
		if (current.next != null)
			next = this.getOldPosition(current.next);
		if (previous != null)
			previous.next = current.next;
		if (next != null)
			next.previous = current.previous;

	}

	private void removeElementInfo(IJavaElement element) {
		this.infos.remove(element);
	}

	public String toString() {
		StringBuffer buffer = new StringBuffer();
		buffer.append("Built delta:\n"); //$NON-NLS-1$
		buffer.append(this.delta.toString());
		return buffer.toString();
	}

	/**
	 * Trims deletion deltas to only report the highest level of deletion
	 */
	private void trimDelta(JavaElementDelta delta) {
		if (delta.getKind() == IJavaElementDelta.REMOVED) {
			IJavaElementDelta[] children = delta.getAffectedChildren();
			for (int i = 0, length = children.length; i < length; i++) {
				delta.removeAffectedChild((JavaElementDelta) children[i]);
			}
		} else {
			IJavaElementDelta[] children = delta.getAffectedChildren();
			for (int i = 0, length = children.length; i < length; i++) {
				trimDelta((JavaElementDelta) children[i]);
			}
		}
	}
}
