Replace parser with Kotlin version
authorDavid ‘Bombe’ Roden <bombe@pterodactylus.net>
Fri, 13 Oct 2017 06:00:21 +0000 (08:00 +0200)
committerDavid ‘Bombe’ Roden <bombe@pterodactylus.net>
Fri, 13 Oct 2017 06:00:21 +0000 (08:00 +0200)
src/main/java/net/pterodactylus/sone/text/SoneTextParser.java [deleted file]
src/main/kotlin/net/pterodactylus/sone/text/SoneTextParser.kt [new file with mode: 0644]

diff --git a/src/main/java/net/pterodactylus/sone/text/SoneTextParser.java b/src/main/java/net/pterodactylus/sone/text/SoneTextParser.java
deleted file mode 100644 (file)
index 39d26db..0000000
+++ /dev/null
@@ -1,431 +0,0 @@
-/*
- * Sone - SoneTextParser.java - Copyright © 2010–2016 David Roden
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package net.pterodactylus.sone.text;
-
-import static com.google.common.base.Optional.absent;
-import static com.google.common.base.Optional.of;
-import static java.util.logging.Logger.getLogger;
-
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.Reader;
-import java.io.StringReader;
-import java.net.MalformedURLException;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-
-import net.pterodactylus.sone.data.Post;
-import net.pterodactylus.sone.data.Sone;
-import net.pterodactylus.sone.data.impl.IdOnlySone;
-import net.pterodactylus.sone.database.PostProvider;
-import net.pterodactylus.sone.database.SoneProvider;
-
-import com.google.common.base.Optional;
-import org.bitpedia.util.Base32;
-
-import freenet.keys.FreenetURI;
-import freenet.support.Base64;
-
-/**
- * {@link Parser} implementation that can recognize Freenet URIs.
- *
- * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
- */
-public class SoneTextParser implements Parser<SoneTextParserContext> {
-
-       /** The logger. */
-       private static final Logger logger = getLogger(SoneTextParser.class.getName());
-
-       /** Pattern to detect whitespace. */
-       private static final Pattern whitespacePattern = Pattern.compile("[\\u000a\u0020\u00a0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u200c\u200d\u202f\u205f\u2060\u2800\u3000]");
-
-       private static class NextLink {
-
-               private final int position;
-               private final String link;
-               private final String remainder;
-               private final LinkType linkType;
-
-               private NextLink(int position, String link, String remainder, LinkType linkType) {
-                       this.position = position;
-                       this.link = link;
-                       this.remainder = remainder;
-                       this.linkType = linkType;
-               }
-
-               public int getPosition() {
-                       return position;
-               }
-
-               public String getLink() {
-                       return link;
-               }
-
-               public String getRemainder() {
-                       return remainder;
-               }
-
-               public LinkType getLinkType() {
-                       return linkType;
-               }
-
-       }
-
-       /**
-        * Enumeration for all recognized link types.
-        *
-        * @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
-        */
-       private enum LinkType {
-
-               KSK("KSK@", true),
-               CHK("CHK@", true),
-               SSK("SSK@", true),
-               USK("USK@", true),
-               HTTP("http://", false),
-               HTTPS("https://", false),
-               SONE("sone://", false),
-               POST("post://", false),
-
-               FREEMAIL("", true) {
-                       @Override
-                       public Optional<NextLink> findNext(String line) {
-                               int nextFreemailSuffix = line.indexOf(".freemail");
-                               if (nextFreemailSuffix < 54) {
-                                       /* 52 chars for the id, 1 on @, at least 1 for the local part. */
-                                       return absent();
-                               }
-                               if (line.charAt(nextFreemailSuffix - 53) != '@') {
-                                       return absent();
-                               }
-                               if (!line.substring(nextFreemailSuffix - 52, nextFreemailSuffix).matches("^[a-z2-7]*$")) {
-                                       return absent();
-                               }
-                               int startOfLocalPart = nextFreemailSuffix - 54;
-                               if (!isAllowedInLocalPart(line.charAt(startOfLocalPart))) {
-                                       return absent();
-                               }
-                               while ((startOfLocalPart > 0) && isAllowedInLocalPart(line.charAt(startOfLocalPart - 1))) {
-                                       startOfLocalPart--;
-                               }
-                               return of(new NextLink(startOfLocalPart, line.substring(startOfLocalPart, nextFreemailSuffix + 9), line.substring(nextFreemailSuffix + 9), this));
-                       }
-
-                       private boolean isAllowedInLocalPart(char character) {
-                               return ((character >= 'A') && (character <= 'Z'))
-                                               || ((character >= 'a') && (character <= 'z'))
-                                               || ((character >= '0') && (character <= '9'))
-                                               || (character == '.') || (character == '-') || (character == '_');
-                       }
-               };
-
-               private final String scheme;
-               private final boolean freenetLink;
-
-               LinkType(String scheme, boolean freenetLink) {
-                       this.scheme = scheme;
-                       this.freenetLink = freenetLink;
-               }
-
-               /**
-                * Returns the scheme of this link type.
-                *
-                * @return The scheme of this link type
-                */
-               public String getScheme() {
-                       return scheme;
-               }
-
-               public boolean isFreenetLink() {
-                       return freenetLink;
-               }
-
-               public Optional<NextLink> findNext(String line) {
-                       int nextLinkPosition = line.indexOf(getScheme());
-                       if (nextLinkPosition == -1) {
-                               return absent();
-                       }
-                       int endOfLink = findEndOfLink(line.substring(nextLinkPosition));
-                       return of(new NextLink(nextLinkPosition, line.substring(nextLinkPosition, nextLinkPosition + endOfLink), line.substring(nextLinkPosition + endOfLink), this));
-               }
-
-               private static int findEndOfLink(String line) {
-                       Matcher matcher = whitespacePattern.matcher(line);
-                       int endOfLink = matcher.find() ? matcher.start() : line.length();
-                       while (isPunctuation(line.charAt(endOfLink - 1))) {
-                               endOfLink--;
-                       }
-                       int openParens = 0;
-                       for (int i = 0; i < endOfLink; i++) {
-                               switch (line.charAt(i)) {
-                                       case '(':
-                                               openParens++;
-                                               break;
-                                       case ')':
-                                               openParens--;
-                                               if (openParens < 0) {
-                                                       return i;
-                                               }
-                                       default:
-                               }
-                       }
-                       return endOfLink;
-               }
-
-       }
-
-       /** The Sone provider. */
-       private final SoneProvider soneProvider;
-
-       /** The post provider. */
-       private final PostProvider postProvider;
-
-       /**
-        * Creates a new freenet link parser.
-        *
-        * @param soneProvider
-        *            The Sone provider
-        * @param postProvider
-        *            The post provider
-        */
-       public SoneTextParser(SoneProvider soneProvider, PostProvider postProvider) {
-               this.soneProvider = soneProvider;
-               this.postProvider = postProvider;
-       }
-
-       //
-       // PART METHODS
-       //
-
-       /**
-        * {@inheritDoc}
-        */
-       @Nonnull
-       @Override
-       public Iterable<Part> parse(@Nonnull String source, @Nullable SoneTextParserContext context) {
-               List<Part> parts = new ArrayList<>();
-               try (Reader sourceReader = new StringReader(source);
-                               BufferedReader bufferedReader = new BufferedReader(sourceReader)) {
-                       String line;
-                       boolean lastLineEmpty = true;
-                       int emptyLines = 0;
-                       while ((line = bufferedReader.readLine()) != null) {
-                               if (line.trim().length() == 0) {
-                                       if (lastLineEmpty) {
-                                               continue;
-                                       }
-                                       parts.add(new PlainTextPart("\n"));
-                                       ++emptyLines;
-                                       lastLineEmpty = emptyLines == 2;
-                                       continue;
-                               }
-                               emptyLines = 0;
-                               /*
-                                * lineComplete tracks whether the block you are parsing is the
-                                * first block of the line. this is important because sometimes
-                                * you have to add an additional line break.
-                                */
-                               boolean lineComplete = true;
-                               while (line.length() > 0) {
-                                       Optional<NextLink> nextLink = findNextLink(line);
-                                       if (!nextLink.isPresent()) {
-                                               if (lineComplete && !lastLineEmpty) {
-                                                       parts.add(new PlainTextPart("\n" + line));
-                                               } else {
-                                                       parts.add(new PlainTextPart(line));
-                                               }
-                                               break;
-                                       }
-                                       LinkType linkType = nextLink.get().getLinkType();
-                                       int next = nextLink.get().getPosition();
-
-                                       /* cut off “freenet:” from before keys. */
-                                       if (linkType.isFreenetLink() && (next >= 8) && (line.substring(next - 8, next).equals("freenet:"))) {
-                                               next -= 8;
-                                               line = line.substring(0, next) + line.substring(next + 8);
-                                       }
-
-                                       /* if there is text before the next item, write it out. */
-                                       if (lineComplete && !lastLineEmpty) {
-                                               parts.add(new PlainTextPart("\n"));
-                                       }
-                                       if (next > 0) {
-                                               parts.add(new PlainTextPart(line.substring(0, next)));
-                                               line = line.substring(next);
-                                       }
-                                       lineComplete = false;
-
-                                       String link = nextLink.get().getLink();
-                                       logger.log(Level.FINER, String.format("Found link: %s", link));
-
-                                       /* if there is no text after the scheme, it’s not a link! */
-                                       if (link.equals(linkType.getScheme())) {
-                                               parts.add(new PlainTextPart(linkType.getScheme()));
-                                               line = line.substring(linkType.getScheme().length());
-                                               continue;
-                                       }
-
-                                       switch (linkType) {
-                                               case SONE:
-                                                       renderSoneLink(parts, link);
-                                                       break;
-                                               case POST:
-                                                       renderPostLink(parts, link);
-                                                       break;
-                                               case KSK:
-                                               case CHK:
-                                               case SSK:
-                                               case USK:
-                                                       renderFreenetLink(parts, link, linkType, context);
-                                                       break;
-                                               case HTTP:
-                                               case HTTPS:
-                                                       renderHttpLink(parts, link, linkType);
-                                                       break;
-                                               case FREEMAIL:
-                                                       renderFreemailLink(parts, link);
-                                       }
-
-                                       line = nextLink.get().getRemainder();
-                               }
-                               lastLineEmpty = false;
-                       }
-               } catch (IOException ioe1) {
-                       // a buffered reader around a string reader should never throw.
-                       throw new RuntimeException(ioe1);
-               }
-               for (int partIndex = parts.size() - 1; partIndex >= 0; --partIndex) {
-                       Part part = parts.get(partIndex);
-                       if (!(part instanceof PlainTextPart) || !"\n".equals(part.getText())) {
-                               break;
-                       }
-                       parts.remove(partIndex);
-               }
-               return parts;
-       }
-
-       public static Optional<NextLink> findNextLink(String line) {
-               int earliestLinkPosition = Integer.MAX_VALUE;
-               NextLink earliestNextLink = null;
-               for (LinkType possibleLinkType : LinkType.values()) {
-                       Optional<NextLink> nextLink = possibleLinkType.findNext(line);
-                       if (nextLink.isPresent()) {
-                               if (nextLink.get().getPosition() < earliestLinkPosition) {
-                                       earliestNextLink = nextLink.get();
-                                       earliestLinkPosition = earliestNextLink.getPosition();
-                               }
-                       }
-               }
-               return Optional.fromNullable(earliestNextLink);
-       }
-
-       private void renderSoneLink(List<Part> parts, String line) {
-               if (line.length() >= (7 + 43)) {
-                       String soneId = line.substring(7, 50);
-                       Optional<Sone> sone = soneProvider.getSone(soneId);
-                       parts.add(new SonePart(sone.or(new IdOnlySone(soneId))));
-               } else {
-                       parts.add(new PlainTextPart(line));
-               }
-       }
-
-       private void renderPostLink(List<Part> parts, String line) {
-               if (line.length() >= (7 + 36)) {
-                       String postId = line.substring(7, 43);
-                       Optional<Post> post = postProvider.getPost(postId);
-                       if (post.isPresent()) {
-                               parts.add(new PostPart(post.get()));
-                       } else {
-                               parts.add(new PlainTextPart(line.substring(0, 43)));
-                       }
-               } else {
-                       parts.add(new PlainTextPart(line));
-               }
-       }
-
-       private void renderFreenetLink(List<Part> parts, String link, LinkType linkType, @Nullable SoneTextParserContext context) {
-               String name = link;
-               String linkWithoutParameters = link;
-               if (name.indexOf('?') > -1) {
-                       linkWithoutParameters = name = name.substring(0, name.indexOf('?'));
-               }
-               if (name.endsWith("/")) {
-                       name = name.substring(0, name.length() - 1);
-               }
-               try {
-                       FreenetURI uri = new FreenetURI(name);
-                       name = uri.lastMetaString();
-                       if (name == null) {
-                               name = uri.getDocName();
-                       }
-                       if (name == null) {
-                               name = link.substring(0, Math.min(9, link.length()));
-                       }
-                       boolean fromPostingSone = ((linkType == LinkType.SSK) || (linkType == LinkType.USK)) && (context != null) && (context.getPostingSone() != null) && link.substring(4, Math.min(link.length(), 47)).equals(context.getPostingSone().getId());
-                       parts.add(new FreenetLinkPart(link, name, linkWithoutParameters, fromPostingSone));
-               } catch (MalformedURLException mue1) {
-                       /* not a valid link, insert as plain text. */
-                       parts.add(new PlainTextPart(link));
-               } catch (NullPointerException npe1) {
-                       /* FreenetURI sometimes throws these, too. */
-                       parts.add(new PlainTextPart(link));
-               } catch (ArrayIndexOutOfBoundsException aioobe1) {
-                       /* oh, and these, too. */
-                       parts.add(new PlainTextPart(link));
-               }
-       }
-
-       private void renderHttpLink(List<Part> parts, String link, LinkType linkType) {
-               String name = link.substring(linkType == LinkType.HTTP ? 7 : 8);
-               int firstSlash = name.indexOf('/');
-               int lastSlash = name.lastIndexOf('/');
-               if ((lastSlash - firstSlash) > 3) {
-                       name = name.substring(0, firstSlash + 1) + "…" + name.substring(lastSlash);
-               }
-               if (name.endsWith("/")) {
-                       name = name.substring(0, name.length() - 1);
-               }
-               if (((name.indexOf('/') > -1) && (name.indexOf('.') < name.lastIndexOf('.', name.indexOf('/'))) || ((name.indexOf('/') == -1) && (name.indexOf('.') < name.lastIndexOf('.')))) && name.startsWith("www.")) {
-                       name = name.substring(4);
-               }
-               if (name.indexOf('?') > -1) {
-                       name = name.substring(0, name.indexOf('?'));
-               }
-               parts.add(new LinkPart(link, name));
-       }
-
-       private void renderFreemailLink(List<Part> parts, String line) {
-               int separator = line.indexOf('@');
-               String freemailId = line.substring(separator + 1, separator + 53);
-               String identityId = Base64.encode(Base32.decode(freemailId));
-               String emailLocalPart = line.substring(0, separator);
-               parts.add(new FreemailPart(emailLocalPart, freemailId, identityId));
-       }
-
-       private static boolean isPunctuation(char character) {
-               return (character == '.') || (character == ',') || (character == '!') || (character == '?');
-       }
-
-}
diff --git a/src/main/kotlin/net/pterodactylus/sone/text/SoneTextParser.kt b/src/main/kotlin/net/pterodactylus/sone/text/SoneTextParser.kt
new file mode 100644 (file)
index 0000000..68a38ef
--- /dev/null
@@ -0,0 +1,197 @@
+package net.pterodactylus.sone.text
+
+import freenet.keys.FreenetURI
+import freenet.support.Base64
+import net.pterodactylus.sone.data.Sone
+import net.pterodactylus.sone.data.impl.IdOnlySone
+import net.pterodactylus.sone.database.PostProvider
+import net.pterodactylus.sone.database.SoneProvider
+import net.pterodactylus.sone.text.LinkType.CHK
+import net.pterodactylus.sone.text.LinkType.FREEMAIL
+import net.pterodactylus.sone.text.LinkType.HTTP
+import net.pterodactylus.sone.text.LinkType.HTTPS
+import net.pterodactylus.sone.text.LinkType.KSK
+import net.pterodactylus.sone.text.LinkType.POST
+import net.pterodactylus.sone.text.LinkType.SONE
+import net.pterodactylus.sone.text.LinkType.SSK
+import net.pterodactylus.sone.text.LinkType.USK
+import net.pterodactylus.sone.utils.let
+import org.bitpedia.util.Base32
+import java.net.MalformedURLException
+
+/**
+ * [Parser] implementation that can recognize Freenet URIs.
+ */
+class SoneTextParser(private val soneProvider: SoneProvider?, private val postProvider: PostProvider?) {
+
+       fun parse(source: String, context: SoneTextParserContext?) =
+                       source.split("\n")
+                                       .dropWhile { it.trim() == "" }
+                                       .dropLastWhile { it.trim() == "" }
+                                       .mergeMultipleEmptyLines()
+                                       .flatMap { splitLineIntoParts(it, context) }
+                                       .removeEmptyPlainTextParts()
+                                       .mergeAdjacentPlainTextParts()
+
+       private fun splitLineIntoParts(line: String, context: SoneTextParserContext?) =
+                       generateSequence(PlainTextPart("") as Part to line) { remainder ->
+                               if (remainder.second == "")
+                                       null
+                               else
+                                       LinkType.values()
+                                                       .mapNotNull { it.findNext(remainder.second) }
+                                                       .minBy { it.position }
+                                                       .let {
+                                                               when {
+                                                                       it == null -> PlainTextPart(remainder.second) to ""
+                                                                       it.position == 0 -> it.toPart(context) to it.remainder
+                                                                       else -> PlainTextPart(remainder.second.substring(0, it.position)) to (it.link + it.remainder)
+                                                               }
+                                                       }
+                       }.map { it.first }.toList()
+
+       private fun NextLink.toPart(context: SoneTextParserContext?) = when (linkType) {
+               KSK, CHK -> try {
+                       FreenetURI(link).let { freenetUri ->
+                               FreenetLinkPart(
+                                               link,
+                                               if (freenetUri.isKSK) {
+                                                       freenetUri.guessableKey
+                                               } else {
+                                                       freenetUri.metaString ?: freenetUri.docName ?: link.substring(0, 9)
+                                               },
+                                               link.split('?').first()
+                               )
+                       }
+               } catch (e: MalformedURLException) {
+                       PlainTextPart(link)
+               }
+               SSK, USK ->
+                       try {
+                                FreenetLinkPart(link, FreenetURI(link).docName, trusted = context?.routingKey?.contentEquals(FreenetURI(link).routingKey) == true)
+                       } catch (e: MalformedURLException) {
+                               PlainTextPart(link)
+                       }
+               SONE -> link.substring(7).let { SonePart(soneProvider?.getSone(it)?.orNull() ?: IdOnlySone(it)) }
+               POST -> postProvider?.getPost(link.substring(7))?.let { PostPart(it) } ?: PlainTextPart(link)
+               FREEMAIL -> link.indexOf('@').let { atSign ->
+                       link.substring(atSign + 1, link.length - 9).let { freemailId ->
+                               FreemailPart(link.substring(0, atSign), freemailId, freemailId.decodedId)
+                       }
+               }
+               HTTP, HTTPS -> LinkPart(link, link
+                               .withoutProtocol
+                               .withoutWwwPrefix
+                               .withoutUrlParameters
+                               .withoutMiddlePathComponents
+                               .withoutTrailingSlash)
+       }
+
+}
+
+private fun List<String>.mergeMultipleEmptyLines() = fold(emptyList<String>()) { previous, current ->
+       if (previous.isEmpty()) {
+               previous + current
+       } else {
+               if ((previous.last() == "\n") && (current == "")) {
+                       previous
+               } else {
+                       previous + ("\n" + current)
+               }
+       }
+}
+
+private fun List<Part>.mergeAdjacentPlainTextParts() = fold(emptyList<Part>()) { parts, part ->
+       if ((parts.lastOrNull() is PlainTextPart) && (part is PlainTextPart)) {
+               parts.dropLast(1) + PlainTextPart(parts.last().text + part.text)
+       } else {
+               parts + part
+       }
+}
+
+private fun List<Part>.removeEmptyPlainTextParts() = filterNot { it == PlainTextPart("") }
+
+private val String.decodedId: String get() = Base64.encode(Base32.decode(this))
+private val String.withoutProtocol get() = substring(indexOf("//") + 2)
+private val String.withoutUrlParameters get() = split('?').first()
+
+private val String.withoutWwwPrefix
+       get() = split("/")
+                       .replaceFirst { it.split(".").dropWhile { it == "www" }.joinToString(".") }
+                       .joinToString("/")
+
+private fun <T> List<T>.replaceFirst(replacement: (T) -> T) = mapIndexed { index, element ->
+       if (index == 0) replacement(element) else element
+}
+
+private val String.withoutMiddlePathComponents
+       get() = split("/").let {
+               if (it.size > 2) {
+                       "${it.first()}/…/${it.last()}"
+               } else {
+                       it.joinToString("/")
+               }
+       }
+private val String.withoutTrailingSlash get() = if (endsWith("/")) substring(0, length - 1) else this
+private val SoneTextParserContext.routingKey: ByteArray? get() = postingSone?.routingKey
+private val Sone.routingKey: ByteArray get() = Base64.decode(id)
+
+private enum class LinkType(private val scheme: String, private val freenetLink: Boolean) {
+
+       KSK("KSK@", true),
+       CHK("CHK@", true),
+       SSK("SSK@", true),
+       USK("USK@", true),
+       HTTP("http://", false),
+       HTTPS("https://", false),
+       SONE("sone://", false) {
+               override fun validateLinkLength(length: Int) = length.takeIf { it == 50 }
+       },
+       POST("post://", false),
+       FREEMAIL("", true) {
+               override fun findNext(line: String): NextLink? {
+                       val nextFreemailSuffix = line.indexOf(".freemail").takeIf { it >= 54 } ?: return null
+                       if (line[nextFreemailSuffix - 53] != '@') return null
+                       if (!line.substring(nextFreemailSuffix - 52, nextFreemailSuffix).matches(Regex("^[a-z2-7]*\$"))) return null
+                       val firstCharacterIndex = generateSequence(nextFreemailSuffix - 53) {
+                               it.minus(1).takeIf { (it >= 0) && line[it].validLocalPart }
+                       }.lastOrNull() ?: return null
+                       return NextLink(firstCharacterIndex, this, line.substring(firstCharacterIndex, nextFreemailSuffix + 9), line.substring(nextFreemailSuffix + 9))
+               }
+
+               private val Char.validLocalPart get() = (this in ('A'..'Z')) || (this in ('a'..'z')) || (this in ('0'..'9')) || (this == '-') || (this == '_') || (this == '.')
+       };
+
+       open fun findNext(line: String): NextLink? {
+               val nextLinkPosition = line.indexOf(scheme).takeIf { it != -1 } ?: return null
+               val endOfLink = line.substring(nextLinkPosition).findEndOfLink().validate() ?: return null
+               val link = line.substring(nextLinkPosition, nextLinkPosition + endOfLink)
+               val realNextLinkPosition = if (freenetLink && line.substring(0, nextLinkPosition).endsWith("freenet:")) nextLinkPosition - 8 else nextLinkPosition
+               return NextLink(realNextLinkPosition, this, link, line.substring(nextLinkPosition + endOfLink))
+       }
+
+       private fun String.findEndOfLink() =
+                       substring(0, whitespace.find(this)?.range?.start ?: length)
+                                       .dropLastWhile(::isPunctuation)
+                                       .upToFirstUnmatchedParen()
+
+       private fun Int.validate() = validateLinkLength(this)
+       protected open fun validateLinkLength(length: Int) = length.takeIf { it > scheme.length }
+
+       private fun String.upToFirstUnmatchedParen() =
+                       foldIndexed(Pair<Int, Int?>(0, null)) { index, (openParens, firstUnmatchedParen), currentChar ->
+                               when (currentChar) {
+                                       '(' -> (openParens + 1) to firstUnmatchedParen
+                                       ')' -> ((openParens - 1) to (if (openParens == 0) (firstUnmatchedParen ?: index) else firstUnmatchedParen))
+                                       else -> openParens to firstUnmatchedParen
+                               }
+                       }.second ?: length
+
+}
+
+private val punctuationChars = listOf('.', ',', '?', '!')
+private fun isPunctuation(char: Char) = char in punctuationChars
+
+private val whitespace = Regex("[\\u000a\u0020\u00a0\u1680\u180e\u2000\u2001\u2002\u2003\u2004\u2005\u2006\u2007\u2008\u2009\u200a\u200b\u200c\u200d\u202f\u205f\u2060\u2800\u3000]")
+
+private data class NextLink(val position: Int, val linkType: LinkType, val link: String, val remainder: String)