r/org.eclipse.statet.r.core/src/org/eclipse/statet/internal/r/core/RdTextContentDescriber.java

/*=============================================================================#
 # Copyright (c) 2008, 2019 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.internal.r.core;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.core.runtime.QualifiedName;
import org.eclipse.core.runtime.content.IContentDescription;
import org.eclipse.core.runtime.content.IContentType;

import org.eclipse.statet.ecommons.io.TextContentDescriber;


/**
 * Detects encoding of Rd file based on optional \encoding element
 * The \encoding element must be the first command in Rd file
 */
public class RdTextContentDescriber extends TextContentDescriber {
	
	
	private static final QualifiedName[] SUPPORTED_OPTIONS= new QualifiedName[] {
		IContentDescription.CHARSET, 
		IContentDescription.BYTE_ORDER_MARK,
	};
	
	
	private static String ENCODING_COMMAND_NAME= "encoding"; //$NON-NLS-1$
	private static Pattern BRACKET_CONTENT_PATTERN= Pattern.compile("\\s*\\{\\s*(\\S*)\\s*\\}.*"); //$NON-NLS-1$
	
	
	public RdTextContentDescriber() {
	}
	
	
	@Override
	public QualifiedName[] getSupportedOptions() {
		return SUPPORTED_OPTIONS;
	}
	
	@Override
	public int describe(final Reader contents, final IContentDescription description) throws IOException {
		if (description != null && description.isRequested(IContentDescription.CHARSET)) {
			final BufferedReader reader= new BufferedReader(contents);
			final String encoding= searchEncoding(reader);
			if (encoding == null) {
				return INDETERMINATE;
			}
			description.setProperty(IContentDescription.CHARSET, encoding);
		}
		return VALID;
	}
	
	@Override
	public int describe(final InputStream contents, final IContentDescription description) throws IOException {
		final byte[] bom= getByteOrderMark(contents);
		String baseEncoding= "UTF-8"; // "ISO-8859-1"; //$NON-NLS-1$
		if (bom != null) {
			if (bom == IContentDescription.BOM_UTF_16BE) {
				baseEncoding= "UTF-16BE"; //$NON-NLS-1$
			}
			else if (bom == IContentDescription.BOM_UTF_16LE) {
				baseEncoding= "UTF-16LE"; //$NON-NLS-1$
			}
			else if (bom == IContentDescription.BOM_UTF_8) {
				baseEncoding= "UTF-8"; //$NON-NLS-1$
			}
			
			if (description != null && description.isRequested(IContentDescription.BYTE_ORDER_MARK)) {
				description.setProperty(IContentDescription.BYTE_ORDER_MARK, bom);
			}
		}
		if (description != null && description.isRequested(IContentDescription.CHARSET)) {
			final BufferedReader reader= new BufferedReader(
					new InputStreamReader(contents, baseEncoding) );
			final String encoding= searchEncoding(reader);
			if (encoding == null) {
				return INDETERMINATE;
			}
			final IContentType contentType= description.getContentType();
			if (contentType == null || !encoding.equals(contentType.getDefaultCharset())) {
				description.setProperty(IContentDescription.CHARSET, encoding);
			}
		}
		return VALID;
	}
	
	private String searchEncoding(final BufferedReader reader) throws IOException {
		String line;
		ITER_LINES: while ((line= reader.readLine()) != null) {
			ITER_CHARS: for (int i= 0; i < line.length(); i++) {
				switch (line.charAt(i)) {
				case ' ':
				case '\t':
					continue ITER_CHARS;
				case '%':
					continue ITER_LINES;
				case '\\':
					if (line.regionMatches(i + 1, ENCODING_COMMAND_NAME, 0, ENCODING_COMMAND_NAME.length())) {
						final Matcher matcher= BRACKET_CONTENT_PATTERN.matcher(line.substring(i + 1 + ENCODING_COMMAND_NAME.length()));
						if (matcher.matches()) {
							return matcher.group(1);
						}
					}
					break ITER_LINES;
				default:
					break ITER_LINES;
				}
			}
		}
		return null;
	}
	
}