/*
 * (c) Copyright IBM Corp. 2000, 2001.
 * All Rights Reserved.
 */
package net.sourceforge.phpdt.internal.corext.textmanipulation;

import org.eclipse.core.runtime.CoreException;

// import net.sourceforge.phpdt.internal.corext.Assert;

/**
 * A text edit that moves text inside a text buffer.
 */
public final class MoveTextEdit extends TextEdit {

	/* package */static class TargetMark extends NopTextEdit {
		private MoveTextEdit fMoveTextEdit;

		public TargetMark(TextRange range, MoveTextEdit edit) {
			super(range);
			fMoveTextEdit = edit;
		}

		/* package */MoveTextEdit getMoveTextEdit() {
			return fMoveTextEdit;
		}

		public TextEdit perform(TextBuffer buffer) throws CoreException {
			fMoveTextEdit.internalPerform(buffer);
			return super.perform(buffer);
		}

		public TextEdit copy() {
			// Assert.isTrue(false, "This should never happen"); //$NON-NLS-1$
			return super.copy();
		}
	}

	private TextRange fTarget;

	private TextRange fSource;

	private int fPerformCounter;

	/**
	 * Creates a new <code>MoveTextEdit</code>. The text edit doesn't support
	 * overlapping moves. So for a
	 * <code>MoveTextEdit</code> <code>destination &lt;= offset && 
	 * offset + length - 1 &lt;= destination</code>
	 * must be <code>true</code>.
	 * 
	 * @param offset
	 *            the offset of the text to be moved
	 * @param length
	 *            the text length to be moved
	 * @param destination
	 *            the destination offset
	 */
	public MoveTextEdit(int offset, int length, int destination) {
		// Assert.isTrue(destination <= offset || offset + length <=
		// destination);
		fSource = new TextRange(offset, length);
		fTarget = new TextRange(destination);
	}

	/**
	 * Creates a new <code>MoveTextEdit</code> with the given source and
	 * target range.
	 * 
	 * @param source
	 *            the source
	 * @param target
	 *            the target
	 */
	private MoveTextEdit(TextRange source, TextRange target) {
		fSource = source;
		fTarget = target;
	}

	/**
	 * Returns the move text edit's source range. This method returns the same
	 * range as <code>TextEdit#getTextRange()</code>
	 * 
	 * @return the edit's source range
	 */
	public TextRange getSourceRange() {
		return fSource;
	}

	/**
	 * Returns the move text edit's target range.
	 * 
	 * @return the edit's target range
	 */
	public TextRange getTargetRange() {
		return fTarget;
	}

	/*
	 * non Java-doc
	 * 
	 * @see TextEdit#getTextRange()
	 */
	public TextRange getTextRange() {
		return fSource;
	}

	/*
	 * non Java-doc
	 * 
	 * @see TextEdit#connect(TextBufferEditor)
	 */
	public void connect(TextBufferEditor editor) throws CoreException {
		editor.add(new TargetMark(fTarget, this));
	}

	/*
	 * non Java-doc
	 * 
	 * @see TextEdit#perform(TextBuffer)
	 */
	public TextEdit perform(TextBuffer buffer) throws CoreException {
		internalPerform(buffer);
		return new MoveTextEdit(fTarget, fSource);
	}

	/*
	 * non Java-doc
	 * 
	 * @see TextEdit#copy()
	 */
	public TextEdit copy() {
		TextRange source = getSourceRange();
		TextRange target = getTargetRange();
		return new MoveTextEdit(source.fOffset, source.fLength, target.fOffset);
	}

	// ---- Helper method
	// ---------------------------------------------------------------------------------

	private void internalPerform(TextBuffer buffer) throws CoreException {
		// Assert.isTrue(fPerformCounter < 2);
		if (++fPerformCounter == 2) {
			TextRange source = getSourceRange();
			TextRange target = getTargetRange();
			String current = buffer.getContent(source.fOffset, source.fLength);
			buffer.replace(source, ""); //$NON-NLS-1$
			buffer.replace(target, current);
		}
	}

	/* package */boolean isUpMove() {
		return fSource.fOffset < fTarget.fOffset;
	}

	/* package */boolean isDownMove() {
		return fSource.fOffset > fTarget.fOffset;
	}

	/* package */TextRange getChildRange() {
		int offset = fSource.fOffset;
		int length = fSource.fLength;
		int destination = fTarget.fOffset;
		if (destination <= offset)
			return new TextRange(destination, offset + length - destination);
		else
			return new TextRange(offset, destination - offset);
	}
}