/*******************************************************************************
 * Copyright (c) 2000, 2015 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
 *******************************************************************************/
package org.eclipse.cdt.autotools.ui.editors;

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

/**
 * This class provides the macro call parameter parsing for the Autoconf Editor hover
 * It is modified from the CDT class CParameterListValidator
 * 
 * @author jjohnstn
 *
 */
public class AutoconfMacroParameterListValidator implements IContextInformationValidator, IContextInformationPresenter {
	private int fPosition;
	private ITextViewer fViewer;
	private IContextInformation fInformation;
	
	private int fCurrentParameter;
	
	public AutoconfMacroParameterListValidator() {
	}
	
	@Override
	public void install(IContextInformation info, ITextViewer viewer, int documentPosition) {
		
		fPosition= documentPosition;
		fViewer= viewer;
		fInformation= info;
		
		fCurrentParameter= -1;
	}
	
	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);
		
		// There are two nesting levels to worry about.  Arguments can be
		// quoted with [] which means to treat the contents as one arg.
		// As well, macro calls can be nested within macro calls so we
		// have to handle parentheses.
		int macroQuotingLevel = 0; // Pertaining to '[' and ']' quoted args.
		int macroNestingLevel = -1; // Set to -1 to take into account first ( for function call
		int charCount = 0;
		while (start < end) {
			char curr = document.getChar(start++);
			switch (curr) {
				case 'd':
					if (start < end - 2) {
						char next= document.getChar(start);
						if (next == 'n') {
							// a comment starts, advance to the comment end
							next = document.getChar(start + 1);
							if (next == 'l')
							// dnl-comment: nothing to do anymore on this line 
								start= end;
						}
					}
					break;
				case '"':
				case '\'':
					start= getStringEnd(document, start, end, curr);
					break;
				default:
					if ('[' == curr)
						++ macroQuotingLevel;
					else if (']' == curr)
						-- macroQuotingLevel;
					if (macroQuotingLevel != 0)
						break;
					if (considerNesting) {
						if ('(' == curr)
							++ macroNestingLevel;
						else if (')' == curr) {
							-- macroNestingLevel;
						}
						if (macroNestingLevel != 0)
							break;
					}
					if (increment != 0) {
						if (curr == increment) {
							++charCount;
						}
					}
					
					if (decrement != 0) {
						if (curr == decrement) {
							-- charCount;
						}
					}
			}
		}
		
		return charCount;
	}
	
	@Override
	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;
		}
	}
	
	@Override
	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();
		
		//@@@ This is obviously going to have problems with functions such
		//int myfunction(int (*function_argument)(void * extra, int param), void * extra)
		//int myfunction(/*A comment, indeed */int a);
		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;
	}
}