feat: tool and scripts to interactively explore webgraph

Add more utility methods to save data in files, to map host names
to registered domains and to translate from/to reverse domain name
notation.

src/main/java/org/commoncrawl/webgraph/explore/Graph.java

@@ -19,9 +19,11 @@
 import java.util.stream.Stream;
 
 import org.commoncrawl.webgraph.CountingMergedIntIterator;
+import org.commoncrawl.webgraph.HostToDomainGraph;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import crawlercommons.domains.EffectiveTldFinder;
 import it.unimi.dsi.fastutil.io.BinIO;
 import it.unimi.dsi.fastutil.longs.LongArrayList;
 import it.unimi.dsi.lang.MutableString;
@@ -343,4 +345,59 @@ public static String getTopLevelDomain(String reversedDomainName) {
 		}
 		return reversedDomainName;
 	}
+
+	/**
+	 * Get the registered domain for a host name based on the ICANN section of the
+	 * <a href="https://www.publicsuffix.org/">public suffix list</a>.
+	 * 
+	 * @see EffectiveTldFinder
+	 * 
+	 * @param hostName host name, e.g. <code>www.example.org.uk</code>
+	 * @param strict   if true return null instead of <code>hostName</code> if no
+	 *                 valid public suffix is detected
+	 * @return the domain name below the public suffix, e.g.
+	 *         <code>example.org.uk</code>
+	 */
+	public static String getRegisteredDomain(String hostName, boolean strict) {
+		return EffectiveTldFinder.getAssignedDomain(hostName, strict, true);
+	}
+
+	/**
+	 * Get the registered domain for a host name, both in
+	 * <a href= "https://en.wikipedia.org/wiki/Reverse_domain_name_notation">reverse
+	 * domain name notation</a>.
+	 * 
+	 * @see #getRegisteredDomain(String, boolean)
+	 * 
+	 * @param reversedHostName host name in reverse domain name notation, e.g.
+	 *                         <code>uk.ork.example.www</code>
+	 * @param strict           if true return null instead of
+	 *                         <code>reversedHostName</code> if no valid public
+	 *                         suffix is detected
+	 * @return the domain name below the public suffix, e.g.
+	 *         <code>uk.org.example</code> (in reverse domain name notation)
+	 */
+	public static String getRegisteredDomainReversed(String reversedHostName, boolean strict) {
+		String hostName = reverseDomainName(reversedHostName);
+		String domainName = getRegisteredDomain(hostName, strict);
+		if (strict && domainName == null) {
+			return null;
+		} else if (hostName.equals(domainName)) {
+			return reversedHostName;
+		}
+		return reverseDomainName(domainName);
+	}
+
+	/**
+	 * Reverse or "unreverse" a host/domain name: <code>com.example.www</code> is
+	 * reversed to <code>www.example.com</code> and vice versa.
+	 * 
+	 * @param domain name
+	 * @return domain name with <a href=
+	 *         "https://en.wikipedia.org/wiki/Reverse_domain_name_notation">reverse
+	 *         domain name notation</a> (un)applied
+	 */
+	private static String reverseDomainName(String reversedDomainName) {
+		return HostToDomainGraph.reverseHost(reversedDomainName);
+	}
 }

src/main/java/org/commoncrawl/webgraph/explore/GraphExplorer.java

@@ -15,6 +15,7 @@
 import java.util.function.Function;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
+import java.util.stream.LongStream;
 import java.util.stream.Stream;
 
 import org.commoncrawl.webgraph.CountingMergedIntIterator;
@@ -215,6 +216,24 @@ public void saveVerticesToFile(IntStream vertexIDs, String fileName) {
 		}
 	}
 
+	public void saveVerticesToFile(LongStream vertexIDs, String fileName) {
+		try (PrintStream out = new PrintStream(Files.newOutputStream(Paths.get(fileName)), false,
+				StandardCharsets.UTF_8)) {
+			vertexIDs.forEach(id -> out.println(g.vertexIdToLabel(id)));
+		} catch (IOException e) {
+			LOG.error("Failed to write vertices to file {}", fileName, e);
+		}
+	}
+
+	public void saveToFile(Stream<String> strings, String fileName) {
+		try (PrintStream out = new PrintStream(Files.newOutputStream(Paths.get(fileName)), false,
+				StandardCharsets.UTF_8)) {
+			strings.forEach(out::println);
+		} catch (IOException e) {
+			LOG.error("Failed to write strings to file {}", fileName, e);
+		}
+	}
+
 	public void saveCountsToFile(Stream<Entry<String, Long>> counts, String fileName) {
 		try (PrintStream out = new PrintStream(Files.newOutputStream(Paths.get(fileName)), false,
 				StandardCharsets.UTF_8)) {