core/plugins/org.eclipse.dltk.ui/src/org/eclipse/dltk/ui/text/templates/TemplateVariableProcessor.java

/*******************************************************************************
 * Copyright (c) 2009, 2017 xored software, Inc. 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:
 *     xored software, Inc. - initial API and Implementation (Alex Panchenko)
 *******************************************************************************/
package org.eclipse.dltk.ui.text.templates;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;

import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.contentassist.ICompletionProposal;
import org.eclipse.jface.text.contentassist.IContentAssistProcessor;
import org.eclipse.jface.text.contentassist.IContextInformation;
import org.eclipse.jface.text.contentassist.IContextInformationValidator;
import org.eclipse.jface.text.templates.TemplateContextType;
import org.eclipse.jface.text.templates.TemplateVariableResolver;

public class TemplateVariableProcessor implements IContentAssistProcessor {

	private static Comparator<TemplateVariableProposal> fgTemplateVariableProposalComparator = (
			proposal0, proposal1) -> proposal0.getDisplayString()
					.compareTo(proposal1.getDisplayString());

	/** the context type */
	private TemplateContextType fContextType;

	/**
	 * Sets the context type.
	 *
	 * @param contextType
	 *            the context type
	 */
	public void setContextType(TemplateContextType contextType) {
		fContextType = contextType;
	}

	/**
	 * Gets the context type.
	 *
	 * @return the context type
	 */
	public TemplateContextType getContextType() {
		return fContextType;
	}

	@Override
	public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer,
			int documentOffset) {

		if (fContextType == null)
			return null;

		List<TemplateVariableProposal> proposals = new ArrayList<>();

		String text = viewer.getDocument().get();
		int start = getStart(text, documentOffset);
		int end = documentOffset;

		String string = text.substring(start, end);
		int colon = string.indexOf(':');
		boolean includeBrace = true;
		int offset = start;
		String prefix = string;
		if (colon != -1) {
			includeBrace = false;
			offset = start + colon + 1;
			prefix = string.substring(colon + 1);
		} else {
			int escape = string.indexOf("${"); //$NON-NLS-1$
			if (escape != -1) {
				offset = start + escape + 2;
				includeBrace = false;
				prefix = string.substring(escape + 2);
			}
		}
		if (prefix.equals("$")) //$NON-NLS-1$
			prefix = ""; //$NON-NLS-1$

		int length = end - offset;

		for (Iterator<TemplateVariableResolver> iterator = fContextType
				.resolvers(); iterator.hasNext();) {
			TemplateVariableResolver variable = iterator.next();

			if (variable.getType().startsWith(prefix))
				proposals.add(new TemplateVariableProposal(variable, offset,
						length, viewer, includeBrace));
		}

		Collections.sort(proposals, fgTemplateVariableProposalComparator);
		return proposals.toArray(new ICompletionProposal[proposals.size()]);
	}

	/* Guesses the start position of the completion */
	private int getStart(String string, int end) {
		int start = end;

		if (start >= 1 && string.charAt(start - 1) == '$')
			return start - 1;

		while ((start != 0)
				&& Character.isUnicodeIdentifierPart(string.charAt(start - 1)))
			start--;

		if (start >= 1 && string.charAt(start - 1) == ':') {
			start--;
			while ((start != 0) && Character
					.isUnicodeIdentifierPart(string.charAt(start - 1)))
				start--;
		}

		if (start >= 2 && string.charAt(start - 1) == '{'
				&& string.charAt(start - 2) == '$')
			return start - 2;

		return end;
	}

	@Override
	public IContextInformation[] computeContextInformation(ITextViewer viewer,
			int documentOffset) {
		return null;
	}

	@Override
	public char[] getCompletionProposalAutoActivationCharacters() {
		return new char[] { '$' };
	}

	@Override
	public char[] getContextInformationAutoActivationCharacters() {
		return null;
	}

	@Override
	public String getErrorMessage() {
		return null;
	}

	@Override
	public IContextInformationValidator getContextInformationValidator() {
		return null;
	}

}