docmlet/org.eclipse.statet.docmlet.wikitext.commonmark.ui/src/org/eclipse/statet/docmlet/wikitext/commonmark/ui/CommonmarkCompletionExtension.java

/*=============================================================================#
 # Copyright (c) 2015, 2018 Stephan Wahlbrink and others.
 # 
 # This program and the accompanying materials are made available under the
 # terms of the Eclipse Public License 2.0 which is available at
 # https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
 # which is available at https://www.apache.org/licenses/LICENSE-2.0.
 # 
 # SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
 # 
 # Contributors:
 #     Stephan Wahlbrink <sw@wahlbrink.eu> - initial API and implementation
 #=============================================================================*/

package org.eclipse.statet.docmlet.wikitext.commonmark.ui;

import java.util.Locale;

import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;

import org.eclipse.statet.docmlet.wikitext.commonmark.core.ParseHelper;
import org.eclipse.statet.docmlet.wikitext.core.markup.IMarkupLanguage;
import org.eclipse.statet.docmlet.wikitext.ui.sourceediting.IMarkupCompletionExtension;
import org.eclipse.statet.ltk.ui.sourceediting.assist.AssistInvocationContext;


public class CommonmarkCompletionExtension implements IMarkupCompletionExtension {
	
	
	private final ParseHelper helper= new ParseHelper();
	
	
	public CommonmarkCompletionExtension() {
	}
	
	
	@Override
	public CompletionType getLinkAnchorLabel(final AssistInvocationContext context, final IMarkupLanguage markupLanguage) {
		try {
			final IDocument document= context.getDocument();
			final int endOffset= context.getOffset();
			int startOffset= endOffset;
			while (startOffset > 0) {
				final char c= document.getChar(--startOffset);
				if (Character.isLetterOrDigit(c) || c == '-' || c == '_' || c == ':' || c == '.') {
					continue;
				}
				if (c == '#' && startOffset > 0 && document.getChar(startOffset - 1) != '\\') {
					startOffset++;
					return new CompletionType(document.get(startOffset, endOffset - startOffset));
				}
				break;
			}
		}
		catch (final BadLocationException e) {}
		return null;
	}
	
	@Override
	public CompletionType getLinkRefLabel(final AssistInvocationContext context, final IMarkupLanguage markupLanguage) {
		try {
			final IDocument document= context.getDocument();
			final int endOffset= context.getInvocationOffset();
			int startOffset= endOffset;
			final int lookupBound= Math.max(startOffset - 1000, 0);
			while (startOffset > lookupBound) {
				final char c= document.getChar(--startOffset);
				if (c == '[' && !isEscaped(document, startOffset)) {
					startOffset= forwardBlank(document, ++startOffset, endOffset);
					final String sourcePrefix= document.get(startOffset, endOffset - startOffset);
					final String lookupPrefix= normalizeLabel(sourcePrefix);
					return new CompletionType(sourcePrefix, lookupPrefix);
				}
				if (c != '\n' || c != '\r') {
					continue;
				}
				break;
			}
		}
		catch (final BadLocationException e) {}
		return null;
	}
	
	private boolean isEscaped(final IDocument document, int offset) throws BadLocationException {
		int count= 0;
		while (offset > 0) {
			if (document.getChar(--offset) == '\\') {
				count++;
			}
			else {
				break;
			}
		}
		return (count % 2) == 1;
	}
	
	private int forwardBlank(final IDocument document, int offset, final int endOffset) throws BadLocationException {
		while (offset < endOffset) {
			final char c= document.getChar(offset);
			if (c == ' ' || c == '\t') {
				offset++;
				continue;
			}
			break;
		}
		return offset;
	}
	
	private String normalizeLabel(String label) {
		if (label.isEmpty()) {
			return "";
		}
		label= this.helper.collapseWhitespace(label);
		if (label.isEmpty()) {
			return "";
		}
		return label.toLowerCase(Locale.ROOT);
	}
	
}