/*******************************************************************************
 * Copyright (c) 2000, 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 net.sourceforge.phpdt.internal.ui.text.java;


import org.eclipse.swt.SWT;
import org.eclipse.swt.custom.StyleRange;

import org.eclipse.jface.text.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.TextPresentation;
import org.eclipse.jface.text.contentassist.IContextInformation;
import org.eclipse.jface.text.contentassist.IContextInformationPresenter;
import org.eclipse.jface.text.contentassist.IContextInformationValidator;



public class JavaParameterListValidator implements IContextInformationValidator, IContextInformationPresenter {

	private int fPosition;
	private ITextViewer fViewer;
	private IContextInformation fInformation;

	private int fCurrentParameter;



	public JavaParameterListValidator() {
	}

	/**
	 * @see IContextInformationValidator#install(IContextInformation, ITextViewer, int)
	 * @see IContextInformationPresenter#install(IContextInformation, ITextViewer, int)
	 */
	public void install(IContextInformation info, ITextViewer viewer, int documentPosition) {
		fPosition= documentPosition;
		fViewer= viewer;
		fInformation= info;

		fCurrentParameter= -1;
	}

	private int getCommentEnd(IDocument d, int pos, int end) throws BadLocationException {
		while (pos < end) {
			char curr= d.getChar(pos);
			pos++;
			if (curr == '*') {
				if (pos < end && d.getChar(pos) == '/') {
					return pos + 1;
				}
			}
		}
		return end;
	}

	private int getStringEnd(IDocument d, int pos, int end, char ch) throws BadLocationException {
		while (pos < end) {
			char curr= d.getChar(pos);
			pos++;
			if (curr == '\\') {
				// ignore escaped characters
				pos++;
			} else if (curr == ch) {
				return pos;
			}
		}
		return end;
	}

	private int getCharCount(IDocument document, int start, int end, String increments, String decrements, boolean considerNesting) throws BadLocationException {

		Assert.isTrue((increments.length() != 0 || decrements.length() != 0) && !increments.equals(decrements));

		int nestingLevel= 0;
		int charCount= 0;
		while (start < end) {
			char curr= document.getChar(start++);
			switch (curr) {
				case '/':
					if (start < end) {
						char next= document.getChar(start);
						if (next == '*') {
							// a comment starts, advance to the comment end
							start= getCommentEnd(document, start + 1, end);
						} else if (next == '/') {
							// '//'-comment: nothing to do anymore on this line
							start= end;
						}
					}
					break;
				case '*':
					if (start < end) {
						char next= document.getChar(start);
						if (next == '/') {
							// we have been in a comment: forget what we read before
							charCount= 0;
							++ start;
						}
					}
					break;
				case '"':
				case '\'':
					start= getStringEnd(document, start, end, curr);
					break;
				default:

					if (considerNesting) {

						if ('(' == curr)
							++ nestingLevel;
						else if (')' == curr)
							-- nestingLevel;

						if (nestingLevel != 0)
							break;
					}

					if (increments.indexOf(curr) >= 0) {
						++ charCount;
					}

					if (decrements.indexOf(curr) >= 0) {
						-- charCount;
					}
			}
		}

		return charCount;
	}

	/**
	 * @see IContextInformationValidator#isContextInformationValid(int)
	 */
	public boolean isContextInformationValid(int position) {

		try {
			if (position < fPosition)
				return false;

			IDocument document= fViewer.getDocument();
			IRegion line= document.getLineInformationOfOffset(fPosition);

			if (position < line.getOffset() || position >= document.getLength())
				return false;

			return getCharCount(document, fPosition, position, "(<", ")>", false) >= 0;  //$NON-NLS-1$//$NON-NLS-2$

		} catch (BadLocationException x) {
			return false;
		}
	}

	/**
	 * @see IContextInformationPresenter#updatePresentation(int, TextPresentation)
	 */
	public boolean updatePresentation(int position, TextPresentation presentation) {

		int currentParameter= -1;

		try {
			currentParameter= getCharCount(fViewer.getDocument(), fPosition, position, ",", "", true);  //$NON-NLS-1$//$NON-NLS-2$
		} catch (BadLocationException x) {
			return false;
		}

		if (fCurrentParameter != -1) {
			if (currentParameter == fCurrentParameter)
				return false;
		}

		presentation.clear();
		fCurrentParameter= currentParameter;

		String s= fInformation.getInformationDisplayString();
		int start= 0;
		int occurrences= 0;
		while (occurrences < fCurrentParameter) {
			int found= s.indexOf(',', start);
			if (found == -1)
				break;
			start= found + 1;
			++ occurrences;
		}

		if (occurrences < fCurrentParameter) {
			presentation.addStyleRange(new StyleRange(0, s.length(), null, null, SWT.NORMAL));
			return true;
		}

		if (start == -1)
			start= 0;

		int end= s.indexOf(',', start);
		if (end == -1)
			end= s.length();

		if (start > 0)
			presentation.addStyleRange(new StyleRange(0, start, null, null, SWT.NORMAL));

		if (end > start)
			presentation.addStyleRange(new StyleRange(start, end - start, null, null, SWT.BOLD));

		if (end < s.length())
			presentation.addStyleRange(new StyleRange(end, s.length() - end, null, null, SWT.NORMAL));

		return true;
	}
}