implement PeerSet type with peer local & remote conflict resolving

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

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+package com.mykola2312.retracker.tracker;
+
+import java.net.InetSocketAddress;
+import java.util.HashMap;
+import java.util.Iterator;
+
+public class PeerSet extends HashMap<InetSocketAddress, Peer> implements Iterable<Peer> {
+	private static final long serialVersionUID = -6175727375850698818L;
+
+	public PeerSet() {
+		super();
+	}
+	
+	public PeerSet(int initialCapacity) {
+		super(initialCapacity);
+	}
+	
+	/* Peer add contract: will override existing peer
+	 * only in favor of new locally announced peer,
+	 * in other words PeerType.LOCAL will always overwrite PeerType.REMOTE
+	 */
+	public void put(Peer peer) {
+		InetSocketAddress key = peer.getAddress();
+		// check for existing peer
+		Peer found = get(key);
+		if (found != null && found.getType() == PeerType.REMOTE) {
+			remove(key);
+		}
+		
+		put(key, peer);
+	}
+	
+	public Peer get(InetSocketAddress addr) {
+		return super.get(addr);
+	}
+	
+	public Peer get(Peer peer) {
+		return get(peer.getAddress());
+	}
+	
+	@Override
+	public Iterator<Peer> iterator() {
+		return values().iterator();
+	}
+}

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

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+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.Iterator;
+
+import org.junit.jupiter.api.Test;
+
+public class PeerSetTest {
+	private static InetSocketAddress newAddress(String addr, int port) throws UnknownHostException {
+		return new InetSocketAddress(InetAddress.getByName(addr), port);
+	}
+	
+	@Test
+	public void testPeerAddContract() throws UnknownHostException {
+		PeerSet set = new PeerSet(1);
+		
+		set.put(new Peer(newAddress("127.0.0.1", 1337))); // remote
+		assertEquals(PeerType.REMOTE, set.get(newAddress("127.0.0.1", 1337)).getType());
+		
+		// override with local peer
+		set.put(new Peer(newAddress("127.0.0.1", 1337), null)); // local
+		assertEquals(PeerType.LOCAL, set.get(newAddress("127.0.0.1", 1337)).getType());
+	}
+	
+	@Test
+	public void testIterator() throws UnknownHostException {
+		PeerSet set = new PeerSet(2);
+		set.put(new Peer(newAddress("127.0.0.1", 1337)));
+		set.put(new Peer(newAddress("127.0.0.1", 1338)));
+		
+		Iterator<Peer> it = set.iterator();
+		
+		assertEquals(true, it.hasNext());
+		assertEquals(1337, it.next().getAddress().getPort());
+		
+		assertEquals(true, it.hasNext());
+		assertEquals(1338, it.next().getAddress().getPort());
+	}
+}