docmlet/org.eclipse.statet.docmlet.wikitext.commonmark.core/src/org/eclipse/statet/internal/docmlet/wikitext/commonmark/core/References.java

/*=============================================================================#
 # Copyright (c) 2020 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.docmlet.wikitext.commonmark.core;

import static org.eclipse.statet.internal.docmlet.wikitext.commonmark.core.CommonRegex.isWhitespace;

import java.net.URLDecoder;
import java.nio.charset.StandardCharsets;

import com.google.common.escape.Escaper;
import com.google.common.net.UrlEscapers;

import org.eclipse.statet.jcommons.lang.NonNullByDefault;
import org.eclipse.statet.jcommons.lang.Nullable;
import org.eclipse.statet.jcommons.text.core.BasicTextRegion;


@NonNullByDefault
public class References {
	
	
	public static final String REF_LABEL_REGEX= "(?:\\\\.|[^\\[\\]]){0,1000}";
	
	private static final String D_QUOTED_TITLE_REGEX= "\"(?:\\\\.|[^\"])*\"";
	private static final String S_QUOTED_TITLE_REGEX= "'(?:\\\\.|[^'])*'";
	private static final String PARENS_TITLE_REGEX= "\\((?:\\\\.|[^\\)])*\\)";
	
	public static final String REF_TITLE_REGEX= D_QUOTED_TITLE_REGEX + "|" + S_QUOTED_TITLE_REGEX + "|" + PARENS_TITLE_REGEX;
	
	
	public static class LinkDestination extends BasicTextRegion {
		
		private final String escapedUri;
		
		public LinkDestination(final int startOffset, final int endOffset, final String escapedUri) {
			super(startOffset, endOffset);
			this.escapedUri= escapedUri;
		}
		
		public String getEscapedUri() {
			return this.escapedUri;
		}
		
	}
	
	public static @Nullable LinkDestination readLinkDestination(final String text, int offset) {
		final int beginOffset= offset;
		while (offset < text.length() && isWhitespace(text.charAt(offset))) {
			offset++;
		}
		if (offset < text.length()) {
			if (text.charAt(offset) == '<') {
				offset++;
				final int linkBeginOffset= offset;
				ITER_CHARS: for (; offset < text.length(); offset++) {
					switch (text.charAt(offset)) {
					case '\n':
					case '\r':
						return null;
					case '\\':
						offset++;
						if (offset < text.length()) {
							switch (text.charAt(offset)) {
							case '\n':
							case '\r':
								return null;
							default:
								continue ITER_CHARS;
							}
						}
					case '<':
						return null;
					case '>':
						return new LinkDestination(beginOffset, offset + 1,
								text.substring(linkBeginOffset, offset) );
					default:
						continue ITER_CHARS;
					}
				}
				return null;
			}
			else {
				final int linkBeginOffset= offset;
				int bracketLevels= 0;
				ITER_CHARS: for (; offset < text.length(); offset++) {
					switch (text.charAt(offset)) {
					case 0x00:
					case 0x01:
					case 0x02:
					case 0x03:
					case 0x04:
					case 0x05:
					case 0x06:
					case 0x07:
					case 0x08:
					case '\t':
					case '\n':
					case 0x0B:
					case 0x0C:
					case '\r':
					case 0x0E:
					case 0x0F:
					case 0x10:
					case 0x11:
					case 0x12:
					case 0x13:
					case 0x14:
					case 0x15:
					case 0x16:
					case 0x17:
					case 0x18:
					case 0x19:
					case 0x1A:
					case 0x1B:
					case 0x1C:
					case 0x1D:
					case 0x1E:
					case 0x1F:
					case ' ':
						break ITER_CHARS;
					case '\\':
						offset++;
						if (offset < text.length()) {
							switch (text.charAt(offset)) {
							case 0x00:
							case 0x01:
							case 0x02:
							case 0x03:
							case 0x04:
							case 0x05:
							case 0x06:
							case 0x07:
							case 0x08:
							case '\t':
							case '\n':
							case 0x0B:
							case 0x0C:
							case '\r':
							case 0x0E:
							case 0x0F:
							case 0x10:
							case 0x11:
							case 0x12:
							case 0x13:
							case 0x14:
							case 0x15:
							case 0x16:
							case 0x17:
							case 0x18:
							case 0x19:
							case 0x1A:
							case 0x1B:
							case 0x1C:
							case 0x1D:
							case 0x1E:
							case 0x1F:
							case ' ':
								return null;
							default:
								continue ITER_CHARS;
							}
						}
					case '(':
						bracketLevels++;
						continue ITER_CHARS;
					case ')':
						if (--bracketLevels < 0) {
							break ITER_CHARS;
						}
						continue ITER_CHARS;
					default:
						continue ITER_CHARS;
					}
				}
				return new LinkDestination(beginOffset, offset,
						text.substring(linkBeginOffset, offset) );
			}
		}
		return null;
	}
	
	public static String normalizeUri(final String uri) {
		try {
			final String decoded= URLDecoder.decode(uri, StandardCharsets.UTF_8.name());
			final Escaper escaper= UrlEscapers.urlFragmentEscaper();
			final int indexOfHash= decoded.indexOf('#');
			if (indexOfHash != -1) {
				String uriWithHash= escaper.escape(decoded.substring(0, indexOfHash)) + '#';
				if ((indexOfHash + 1) < decoded.length()) {
					uriWithHash+= escaper.escape(decoded.substring(indexOfHash + 1));
				}
				return uriWithHash;
			}
			return escaper.escape(decoded);
		} catch (final Exception e) {
			return uri;
		}
	}
	
	
	private References() {
	}
	
}