implement InfoHash torrent data type

notes.txt

@@ -17,5 +17,8 @@ When there is need to expose local tracker a tracker endpoint should be declare
 is HTTP or UDP server responsing to BitTorrent announces just like if it was any other regular torrent tracker.
 
 
+Announce request coming from local peer contains local (peer) data: ID, uploaded, downloaded, and so on.
+Announce response contains peer set.
+
 Maven exec with args:
 	mvn exec:java -Dexec.args=''

pom.xml

@@ -70,6 +70,11 @@
     	<artifactId>jackson-databind</artifactId>
     	<version>2.18.0</version>
     </dependency>
+    <dependency>
+    	<groupId>commons-codec</groupId>
+    	<artifactId>commons-codec</artifactId>
+    	<version>1.17.1</version>
+    </dependency>
   </dependencies>
 
   <build>

src/main/java/com/mykola2312/retracker/App.java

@@ -24,8 +24,8 @@ public class App {
 	private static final Logger log = LoggerFactory.getLogger(App.class);
 	
 	public static void main(String[] args) {
-		final Option logDirOpt = new Option("l", "log", true, "log dir path");
 		final Option configFileOpt = new Option("c", "config", true, "config.json path");
+		final Option logDirOpt = new Option("l", "log", true, "log dir path");
 		final Options options = new Options()
 				.addOption(configFileOpt)
 				.addOption(logDirOpt);

src/main/java/com/mykola2312/retracker/tracker/InfoHash.java

@@ -0,0 +1,70 @@
+package com.mykola2312.retracker.tracker;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.BitSet;
+
+import org.apache.commons.codec.DecoderException;
+import org.apache.commons.codec.net.URLCodec;
+
+public class InfoHash {
+	public static final int HASH_LENGTH = 20;
+	
+	private byte[] hash = null;
+	
+	public InfoHash() {
+		this.hash = null;
+	}
+	
+	public InfoHash(byte[] hash) {
+		this.hash = hash;
+	}
+	
+	public byte[] bytes() {
+		return this.hash;
+	}
+	
+	public void fromURLEncoded(String urlParam) throws DecoderException {
+		this.hash = URLCodec.decodeUrl(urlParam.getBytes());
+	}
+	
+	public String toURLEncoded() {
+		return new String(URLCodec.encodeUrl(new BitSet(), this.hash), StandardCharsets.US_ASCII);
+	}
+	
+	public void fromString(String hashString) throws Exception {
+		if (hashString.length() != InfoHash.HASH_LENGTH * 2) {
+			throw new Exception(String.format("hash is not 40 characters length: %s, %d", hashString, hashString.length()));
+		}
+		
+		char[] bytePair = new char[2];
+		hash = new byte[InfoHash.HASH_LENGTH];
+		for (int i = 0; i < InfoHash.HASH_LENGTH; i++) {
+			hashString.getChars(i*2, i*2 + 2, bytePair, 0);
+			hash[i] = (byte)Short.parseShort(new String(bytePair), 16);
+		}
+	}
+	
+	@Override
+	public String toString() {
+		StringBuilder out = new StringBuilder();
+		for (int i = 0; i < InfoHash.HASH_LENGTH; i++) {
+			out.append(String.format("%02x", hash[i]));
+		}
+		
+		return out.toString();
+	}
+	
+	@Override
+	public boolean equals(Object o) {
+		if (o == this) return true;
+		if (!(o instanceof InfoHash)) return false;
+		InfoHash other = (InfoHash)o;
+		return Arrays.equals(this.hash, other.hash);
+	}
+	
+	@Override
+	public final int hashCode() {
+		return this.hash != null ? Arrays.hashCode(this.hash) : 0;
+	}
+}

src/test/java/com/mykola2312/retracker/tracker/InfoHashTest.java

@@ -0,0 +1,67 @@
+package com.mykola2312.retracker.tracker;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class InfoHashTest {
+	@Test
+	public void testHashString() {
+		final String hashString = "360775c6629eb06e60d90201aed1b7bc49a1ce16";
+		
+		assertDoesNotThrow(() -> {
+			InfoHash hash = new InfoHash();
+			
+			hash.fromString(hashString);
+			assertEquals(hashString, hash.toString());
+		});
+	}
+	
+	@Test
+	public void testHashEquals() {
+		final String hashString = "360775c6629eb06e60d90201aed1b7bc49a1ce16";
+		
+		assertDoesNotThrow(() -> {
+			InfoHash hashOne = new InfoHash();
+			InfoHash hashTwo = new InfoHash();
+			
+			hashOne.fromString(hashString);
+			hashTwo.fromString(hashString);
+			
+			assertEquals(true, hashOne.equals(hashTwo));
+		});
+	}
+	
+	@Test
+	public void testHashCode() {
+		final String hashString = "360775c6629eb06e60d90201aed1b7bc49a1ce16";
+		
+		assertDoesNotThrow(() -> {
+			InfoHash hashOne = new InfoHash();
+			InfoHash hashTwo = new InfoHash();
+			
+			hashOne.fromString(hashString);
+			hashTwo.fromString(hashString);
+			
+			assertEquals(true, hashOne.hashCode() == hashTwo.hashCode());
+		});
+	}
+	
+	@Test
+	public void testURLEncode() {
+		final String hashString = "360775c6629eb06e60d90201aed1b7bc49a1ce16";
+		
+		assertDoesNotThrow(() -> {
+			InfoHash first = new InfoHash();
+			first.fromString(hashString);
+			
+			InfoHash second = new InfoHash();
+			second.fromURLEncoded(first.toURLEncoded());
+			
+			System.out.printf("url encoded hash: %s\n", first.toURLEncoded());
+			
+			assertEquals(first, second);
+		});
+	}
+}