Automatically set up fast catchup time on a PeerGroup when wallets are added. Resolves issue 183.

core/src/main/java/com/google/bitcoin/core/AbstractWalletEventListener.java

@@ -91,9 +91,14 @@ public abstract class AbstractWalletEventListener implements WalletEventListener
         onChange();
     }
 
+    public void onKeyAdded(ECKey key) {
+        onChange();
+    }
+
     /**
      * Called by the other default method implementations when something (anything) changes in the wallet.
      */
     public void onChange() {
     }
+
 }

core/src/main/java/com/google/bitcoin/core/PeerGroup.java

@@ -339,18 +339,41 @@ public class PeerGroup {
     }
 
     /**
-     * Link the given wallet to this PeerGroup. This is used for two purposes:
+     * <p>Link the given wallet to this PeerGroup. This is used for three purposes:</p>
      * <ol>
      *   <li>So the wallet receives broadcast transactions.</li>
      *   <li>Announcing pending transactions that didn't get into the chain yet to our peers.</li>
+     *   <li>Set the fast catchup time using {@link PeerGroup#setFastCatchupTimeSecs(long)}, to optimize chain
+     *       download.</li>
      * </ol>
+     * <p>Note that this should be done before chain download commences because if you add a wallet with keys earlier
+     * than the current chain head, the relevant parts of the chain won't be redownloaded for you.</p>
      */
     public synchronized void addWallet(Wallet wallet) {
-        if (wallet == null)
+        Preconditions.checkNotNull(wallet);
-            throw new IllegalArgumentException("wallet is null");
         wallets.add(wallet);
         addEventListener(wallet.getPeerEventListener());
         announcePendingWalletTransactions(Collections.singletonList(wallet), peers);
+
+        // Don't bother downloading block bodies before the oldest keys in all our wallets. Make sure we recalculate
+        // if a key is added. Of course, by then we may have downloaded the chain already. Ideally adding keys would
+        // automatically rewind the block chain and redownload the blocks to find transactions relevant to those keys,
+        // all transparently and in the background. But we are a long way from that yet.
+        wallet.addEventListener(new AbstractWalletEventListener() {
+            @Override
+            public void onKeyAdded(ECKey key) {
+                recalculateFastCatchupTime();
+            }
+        });
+        recalculateFastCatchupTime();
+    }
+
+    private synchronized void recalculateFastCatchupTime() {
+        long earliestKeyTime = Long.MAX_VALUE;
+        for (Wallet w : wallets) {
+            earliestKeyTime = Math.min(earliestKeyTime, w.getEarliestKeyCreationTime());
+        }
+        setFastCatchupTimeSecs(earliestKeyTime);
     }
 
     /**
@@ -738,6 +761,16 @@ public class PeerGroup {
         }
     }
 
+    /**
+     * Returns the current fast catchup time. The contents of blocks before this time won't be downloaded as they
+     * cannot contain any interesting transactions. If you use {@link PeerGroup#addWallet(Wallet)} this just returns
+     * the min of the wallets earliest key times.
+     * @return a time in seconds since the epoch
+     */
+    public synchronized long getFastCatchupTimeSecs() {
+        return fastCatchupTimeSecs;
+    }
+
     protected synchronized void handlePeerDeath(final Peer peer) {
         if (!isRunning()) {
             log.info("Peer death while shutting down");

core/src/main/java/com/google/bitcoin/core/Wallet.java

@@ -1194,9 +1194,15 @@ public class Wallet implements Serializable {
     /**
      * Adds the given ECKey to the wallet. There is currently no way to delete keys (that would result in coin loss).
      */
-    public synchronized void addKey(ECKey key) {
+    public synchronized void addKey(final ECKey key) {
         checkArgument(!keychain.contains(key), "Key already present");
         keychain.add(key);
+        EventListenerInvoker.invoke(eventListeners, new EventListenerInvoker<WalletEventListener>() {
+            @Override
+            public void invoke(WalletEventListener listener) {
+                listener.onKeyAdded(key);
+            }
+        });
     }
 
     /**

core/src/main/java/com/google/bitcoin/core/WalletEventListener.java

@@ -99,4 +99,10 @@ public interface WalletEventListener {
      * @param tx
      */
     void onTransactionConfidenceChanged(Wallet wallet, Transaction tx);
+
+    /**
+     * Called by the {@link Wallet#addKey(ECKey)} method on whatever the calling thread was.
+     * @param key
+     */
+    void onKeyAdded(ECKey key);
 }

core/src/test/java/com/google/bitcoin/core/PeerGroupTest.java

@@ -24,6 +24,7 @@ import org.junit.Test;
 import java.io.IOException;
 import java.math.BigInteger;
 import java.net.InetSocketAddress;
+import java.util.Date;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.concurrent.BlockingQueue;
@@ -306,6 +307,25 @@ public class PeerGroupTest extends TestWithNetworkConnections {
         assertTrue(n3.outbound() instanceof InventoryMessage);
         peerGroup.stop();
     }
+
+    @Test
+    public void testWalletCatchupTime() throws Exception {
+        // Check the fast catchup time was initialized to something around the current runtime. The wallet was
+        // already added to the peer in setup.
+        long time = new Date().getTime() / 1000;
+        assertTrue(peerGroup.getFastCatchupTimeSecs() > time - 10000);
+        Wallet w2 = new Wallet(params);
+        ECKey key1 = new ECKey();
+        key1.setCreationTimeSeconds(time - 86400);  // One day ago.
+        w2.addKey(key1);
+        peerGroup.addWallet(w2);
+        assertEquals(peerGroup.getFastCatchupTimeSecs(), time - 86400);
+        // Adding a key to the wallet should update the fast catchup time.
+        ECKey key2 = new ECKey();
+        key2.setCreationTimeSeconds(time - 100000);
+        w2.addKey(key2);
+        assertEquals(peerGroup.getFastCatchupTimeSecs(), time - 100000);
+    }
     
     private void disconnectAndWait(MockNetworkConnection conn) throws IOException, InterruptedException {
         conn.disconnect();