/*******************************************************************************
 * Copyright (c) 2009 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
 *     Zend Technologies
 *******************************************************************************/
package org.eclipse.php.internal.ui.editor.contentassist;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.*;
import org.eclipse.jface.text.contentassist.IContextInformation;
import org.eclipse.jface.text.contentassist.IContextInformationExtension;
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;

public class PHPContextInformationValidator implements IContextInformationValidator, IContextInformationPresenter {

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

	@Override
	public void install(IContextInformation info, ITextViewer viewer, int offset) {
		fInformation = info;
		fViewer = viewer;
		if (info instanceof IContextInformationExtension) {
			fPosition = ((IContextInformationExtension) info).getContextInformationPosition();
		} else {
			fPosition = offset - 1;
		}

		// Work around for bug 253901.
		fPosition++;

		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;
	}

	@Override
	public boolean isContextInformationValid(int offset) {
		try {
			if (offset < fPosition)
				return false;

			IDocument document = fViewer.getDocument();
			IRegion line = document.getLineInformationOfOffset(fPosition);
			// offset could equals to document's length
			if (offset < line.getOffset() || offset > document.getLength())
				return false;

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

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

	@Override
	public boolean updatePresentation(int offset, TextPresentation presentation) {
		int currentParameter = -1;

		IDocument document = fViewer.getDocument();

		int parameterStartPosition = fPosition;
		try {
			for (int i = parameterStartPosition; i < offset; i++) {
				if (document.getChar(parameterStartPosition) == '(') {
					++parameterStartPosition;
					break;
				}
			}
		} catch (BadLocationException x) {
		}

		try {
			currentParameter = getCharCount(document, parameterStartPosition, offset, ",", "", true); //$NON-NLS-1$//$NON-NLS-2$
		} catch (BadLocationException x) {
			return false;
		}

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

		presentation.clear();
		fCurrentParameter = currentParameter;

		// this check was added in order to workaround bug
		// https://bugs.eclipse.org/bugs/show_bug.cgi?id=191849
		// when it will be resolved this check can be removed.
		if (fInformation == null) {
			return false;
		}
		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;
	}

}