/*******************************************************************************
 * Copyright (c) 2000, 2007 QNX Software 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:
 *     QNX Software Systems - Initial API and implementation
 *     Anton Leherbauer (Wind River Systems)
 *******************************************************************************/
package org.eclipse.cdt.internal.ui.text;

import java.util.ArrayList;
import java.util.List;

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

import org.eclipse.core.runtime.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;

/**
 * This class provides the function parameter parsing for the C/C++ Editor hover
 * It is based heavily on the Java class JavaParameterListValidator
 * 
 * @author thomasf
 *
 */
public class CParameterListValidator implements IContextInformationValidator, IContextInformationPresenter {
	private int fPosition;
	private ITextViewer fViewer;
	private IContextInformation fInformation;
	
	private int fCurrentParameter;
	
	public CParameterListValidator() {
	}
	
	/**
	 * @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, 
							 char increment, char decrement, boolean considerNesting) throws BadLocationException {
		
		Assert.isTrue((increment != 0 || decrement != 0) && increment != decrement);
		
		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 (increment != 0) {
						if (curr == increment)
							++ charCount;
					}
					
					if (decrement != 0) {
						if (curr == decrement)
							-- 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() + line.getLength())
				return false;
				
			return (getCharCount(document, fPosition, position, '(', ')', false) >= 0);
			
		} 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, ',', (char) 0, true);
		} catch (BadLocationException x) {
			return false;
		}
		
		if (fCurrentParameter != -1) {
			if (currentParameter == fCurrentParameter)
				return false;
		}
		
		presentation.clear();
		fCurrentParameter= currentParameter;
		
		//Don't presume what has been done to the string, rather use as is
		String s= fInformation.getInformationDisplayString();
		
		int[] commas= computeCommaPositions(s);
		if (commas.length - 2 < fCurrentParameter) {
			presentation.addStyleRange(new StyleRange(0, s.length(), null, null, SWT.NORMAL));
			return true;
		}
		
		int start= commas[fCurrentParameter] + 1;
		int end= commas[fCurrentParameter + 1];
		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;
	}

	private int[] computeCommaPositions(String code) {
		final int length= code.length();
	    int pos= 0;
		List<Integer> positions= new ArrayList<Integer>();
		positions.add(new Integer(-1));
		while (pos < length && pos != -1) {
			char ch= code.charAt(pos);
			switch (ch) {
	            case ',':
		            positions.add(new Integer(pos));
		            break;
	            case '(':
	            	pos= indexOfClosingPeer(code, '(', ')', pos);
	            	break;
	            case '<':
	            	pos= indexOfClosingPeer(code, '<', '>', pos);
	            	break;
	            case '[':
	            	pos= indexOfClosingPeer(code, '[', ']', pos);
	            	break;
	            default:
	            	break;
            }
			if (pos != -1)
				pos++;
		}
		positions.add(new Integer(length));
		
		int[] fields= new int[positions.size()];
		for (int i= 0; i < fields.length; i++)
	        fields[i]= positions.get(i).intValue();
	    return fields;
    }

	private int indexOfClosingPeer(String code, char left, char right, int pos) {
		int level= 0;
		final int length= code.length();
		while (pos < length) {
			char ch= code.charAt(pos);
			if (ch == left) {
				++level;
			} else if (ch == right) {
				if (--level == 0) {
					return pos;
				}
			}
			++pos;
		}
		return -1;
	}
}

