/*******************************************************************************
 * Copyright (c) 2001, 2005 IBM Corporation 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:
 *     IBM Corporation - initial API and implementation
 *     
 *******************************************************************************/
package org.eclipse.wst.html.ui.internal.text;

// taken from package org.eclipse.jdt.ui.text;

import java.io.IOException;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.source.ICharacterPairMatcher;

class JavaPairMatcher implements ICharacterPairMatcher {

	protected char[] fPairs;
	protected IDocument fDocument;
	protected int fOffset;

	protected int fStartPos;
	protected int fEndPos;
	protected int fAnchor;

	protected JavaCodeReader fReader = new JavaCodeReader();
	/**
	 * Stores the source version state.
	 * 
	 * @see Eclipse  3.1
	 */
	private boolean fHighlightAngularBrackets = false;


	public JavaPairMatcher(char[] pairs) {
		fPairs = pairs;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.text.source.ICharacterPairMatcher#match(org.eclipse.jface.text.IDocument,
	 *      int)
	 */
	public IRegion match(IDocument document, int offset) {
		fOffset = offset;

		if(offset < 0 || offset >= document.getLength())
			return null;

		fDocument = document;

		if (fDocument != null && matchPairsAt() && fStartPos != fEndPos)
			return new Region(fStartPos, fEndPos - fStartPos + 1);

		return null;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.text.source.ICharacterPairMatcher#getAnchor()
	 */
	public int getAnchor() {
		return fAnchor;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.text.source.ICharacterPairMatcher#dispose()
	 */
	public void dispose() {
		clear();
		fDocument = null;
		fReader = null;
	}

	/*
	 * @see org.eclipse.jface.text.source.ICharacterPairMatcher#clear()
	 */
	public void clear() {
		if (fReader != null) {
			try {
				fReader.close();
			}
			catch (IOException x) {
				// ignore
			}
		}
	}

	protected boolean matchPairsAt() {

		int i;
		int pairIndex1 = fPairs.length;
		int pairIndex2 = fPairs.length;

		fStartPos = -1;
		fEndPos = -1;

		// get the chars preceding and following the start position
		try {

			char prevChar = fDocument.getChar(Math.max(fOffset - 1, 0));
			// modified behavior for
			// http://dev.eclipse.org/bugs/show_bug.cgi?id=16879
			// char nextChar= fDocument.getChar(fOffset);

			// search for opening peer character next to the activation point
			for (i = 0; i < fPairs.length; i = i + 2) {
				// if (nextChar == fPairs[i]) {
				// fStartPos= fOffset;
				// pairIndex1= i;
				// } else
				if (prevChar == fPairs[i]) {
					fStartPos = fOffset - 1;
					pairIndex1 = i;
				}
			}

			// search for closing peer character next to the activation point
			for (i = 1; i < fPairs.length; i = i + 2) {
				if (prevChar == fPairs[i]) {
					fEndPos = fOffset - 1;
					pairIndex2 = i;
				}
				// else if (nextChar == fPairs[i]) {
				// fEndPos= fOffset;
				// pairIndex2= i;
				// }
			}

			if (fEndPos > -1) {
				fAnchor = RIGHT;
				fStartPos = searchForOpeningPeer(fEndPos, fPairs[pairIndex2 - 1], fPairs[pairIndex2], fDocument);
				if (fStartPos > -1)
					return true;
				else
					fEndPos = -1;
			}
			else if (fStartPos > -1) {
				fAnchor = LEFT;
				fEndPos = searchForClosingPeer(fStartPos, fPairs[pairIndex1], fPairs[pairIndex1 + 1], fDocument);
				if (fEndPos > -1)
					return true;
				else
					fStartPos = -1;
			}

		}
		catch (BadLocationException x) {
		}
		catch (IOException x) {
		}

		return false;
	}

	protected int searchForClosingPeer(int offset, int openingPeer, int closingPeer, IDocument document) throws IOException {
		if (openingPeer == '<' && !(fHighlightAngularBrackets && isTypeParameterBracket(offset, document)))
			return -1;

		fReader.configureForwardReader(document, offset + 1, document.getLength(), true, true);

		int stack = 1;
		int c = fReader.read();
		while (c != JavaCodeReader.EOF) {
			if (c == openingPeer && c != closingPeer)
				stack++;
			else if (c == closingPeer)
				stack--;

			if (stack == 0)
				return fReader.getOffset();

			c = fReader.read();
		}

		return -1;
	}


	protected int searchForOpeningPeer(int offset, int openingPeer, int closingPeer, IDocument document) throws IOException {
		if (openingPeer == '<' && !fHighlightAngularBrackets)
			return -1;

		fReader.configureBackwardReader(document, offset, true, true);

		int stack = 1;
		int c = fReader.read();
		while (c != JavaCodeReader.EOF) {
			if (c == closingPeer && c != openingPeer)
				stack++;
			else if (c == openingPeer)
				stack--;

			if (stack == 0) {
				if (closingPeer == '>' && !isTypeParameterBracket(fReader.getOffset(), document))
					return -1;
				return fReader.getOffset();
			}

			c = fReader.read();
		}

		return -1;
	}

	/**
	 * Checks if the angular bracket at <code>offset</code> is a type
	 * parameter bracket.
	 * 
	 * @param offset
	 *            the offset of the opening bracket
	 * @param document
	 *            the document
	 * @return <code>true</code> if the bracket is part of a type parameter,
	 *         <code>false</code> otherwise
	 * @see Eclipse  3.1
	 */
	private boolean isTypeParameterBracket(int offset, IDocument document) {
		/*
		 * type parameter come after braces (closing or opening), semicolons,
		 * or after a Type name (heuristic: starts with capital character, or
		 * after a modifier keyword in a method declaration (visibility,
		 * static, synchronized, final)
		 */

		try {
			IRegion line = document.getLineInformationOfOffset(offset);

			JavaHeuristicScanner scanner = new JavaHeuristicScanner(document);
			int prevToken = scanner.previousToken(offset - 1, line.getOffset());
			int prevTokenOffset = scanner.getPosition() + 1;
			String previous = prevToken == Symbols.TokenEOF ? null : document.get(prevTokenOffset, offset - prevTokenOffset).trim();

			if (prevToken == Symbols.TokenLBRACE || prevToken == Symbols.TokenRBRACE || prevToken == Symbols.TokenSEMICOLON || prevToken == Symbols.TokenSYNCHRONIZED || prevToken == Symbols.TokenSTATIC || (prevToken == Symbols.TokenIDENT && isTypeParameterIntroducer(previous)) || prevToken == Symbols.TokenEOF)
				return true;
		}
		catch (BadLocationException e) {
			return false;
		}

		return false;
	}

	/**
	 * Returns <code>true</code> if <code>identifier</code> is an
	 * identifier that could come right before a type parameter list. It uses
	 * a heuristic: if the identifier starts with an upper case, it is assumed
	 * a type name. Also, if <code>identifier</code> is a method modifier,
	 * it is assumed that the angular bracket is part of the generic type
	 * parameter of a method.
	 * 
	 * @param identifier
	 *            the identifier to check
	 * @return <code>true</code> if the identifier could introduce a type
	 *         parameter list
	 * @see Eclipse  3.1
	 */
	private boolean isTypeParameterIntroducer(String identifier) {
		return identifier.length() > 0 && (Character.isUpperCase(identifier.charAt(0)) || identifier.startsWith("final") //$NON-NLS-1$
					|| identifier.startsWith("public") //$NON-NLS-1$
					|| identifier.startsWith("public") //$NON-NLS-1$
					|| identifier.startsWith("protected") //$NON-NLS-1$
		|| identifier.startsWith("private")); //$NON-NLS-1$
	}
}