implement synchronized Tracker structure

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

@@ -31,7 +31,7 @@ public class Torrent {
 		}
 	}
 	
-	public <T extends Collection<Peer>> void updatePeers(T src) {
+	public <T extends Collection<Peer>> void putPeers(T src) {
 		for (Peer peer : src) {
 			peers.put(peer);
 		}

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

@@ -0,0 +1,48 @@
+package com.mykola2312.retracker.tracker;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+
+/* Tracker meant to be called from multiple running threads,
+ * so thread-safety ensured by synchronized methods.
+ */
+public class Tracker {
+	private HashMap<InfoHash, Torrent> torrents = new HashMap<InfoHash, Torrent>();
+	
+	/* Adds peer to torrent's PeerSet. If no such Torrent present,
+	 * creates the Torrent.
+	 */
+	public synchronized void announcePeer(InfoHash infoHash, Peer peer) {
+		Torrent torrent = torrents.get(infoHash);
+		if (torrent != null) {
+			torrent.putPeers(List.of(peer));
+		} else {
+			// create torrent and initiate PeerSet with first announced peer
+			torrent = new Torrent(infoHash, peer);
+			torrents.put(torrent.getInfoHash(), torrent);
+		}
+	}
+	
+	/* Adds multiple peers to torrent. If no such Torrent present,
+	 * creates the torrent.
+	 */
+	public synchronized <T extends Collection<Peer>> void announcePeers(InfoHash infoHash, T src) {
+		Torrent torrent = torrents.get(infoHash);
+		if (torrent != null) {
+			torrent.putPeers(src);
+		} else {
+			torrent = new Torrent(infoHash);
+			torrent.putPeers(src);
+			torrents.put(torrent.getInfoHash(), torrent);
+		}
+	}
+	
+	// Get list of peers at this very moment.
+	public synchronized <T extends Collection<Peer>> void getPeers(InfoHash infoHash, T dst) {
+		Torrent torrent = torrents.get(infoHash);
+		if (torrent != null) {
+			torrent.copyPeers(dst);
+		}
+	}
+}

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

@@ -31,7 +31,7 @@ public class TorrentTest {
 		
 		List<Peer> src = Arrays.asList(new Peer(newAddress("127.0.0.1", 1337)),
 										new Peer(newAddress("127.0.0.1", 1338)));
-		torrent.updatePeers(src);
+		torrent.putPeers(src);
 		{
 			ArrayList<Peer> copy = new ArrayList<Peer>();
 			torrent.copyPeers(copy);

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

@@ -0,0 +1,74 @@
+package com.mykola2312.retracker.tracker;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.UnknownHostException;
+import java.util.ArrayList;
+
+import org.junit.jupiter.api.Test;
+
+public class TrackerTest {
+	private static InetSocketAddress newAddress(String addr, int port) throws UnknownHostException {
+		return new InetSocketAddress(InetAddress.getByName(addr), port);
+	}
+	
+	class TrackerJob implements Runnable {
+		private Tracker tracker;
+		private InfoHash infoHash;
+		private Peer peer;
+		
+		public TrackerJob(Tracker tracker, InfoHash infoHash, Peer peer) {
+			this.tracker = tracker;
+			this.infoHash = infoHash;
+			this.peer = peer;
+		}
+
+		@Override
+		public void run() {
+			tracker.announcePeer(infoHash, peer);
+		}
+	}
+	
+	@Test
+	public void testTrackerPutAndGet() throws Exception {
+		final InfoHash infoHash = new InfoHash();
+		infoHash.fromString("360775c6629eb06e60d90201aed1b7bc49a1ce16");
+		
+		Tracker tracker = new Tracker();
+		
+		ArrayList<Thread> threads = new ArrayList<Thread>();
+		for (int i = 0; i < 32; i++) {
+			TrackerJob job = new TrackerJob(tracker, infoHash,
+					new Peer(newAddress("127.0.0.1", 1337 + i)));
+			Thread thread = new Thread(job);
+			thread.start();
+			threads.add(thread);
+			
+		}
+		
+		// wait for all threads to finish
+		for (Thread thread : threads) {
+			thread.join();
+		}
+		
+		ArrayList<Peer> peers = new ArrayList<Peer>(32);
+		tracker.getPeers(infoHash, peers);
+		
+		assertEquals(32, peers.size());
+		
+		// check if every port present
+		for (int i = 0; i < 32; i++) {
+			int port = 1337 + i;
+			boolean peerPortPresent = false;
+			for (Peer peer : peers) {
+				if (peer.getAddress().getPort() == port) {
+					peerPortPresent = true;
+				}
+			}
+			
+			assertEquals(true, peerPortPresent);
+		}
+	}
+}