WalletAppKit: support for restoring a wallet from a seed. The old wallet is moved out of the way.

core/src/main/java/com/google/bitcoin/kits/WalletAppKit.java

@@ -22,6 +22,7 @@ import com.google.bitcoin.net.discovery.DnsDiscovery;
 import com.google.bitcoin.store.BlockStoreException;
 import com.google.bitcoin.store.SPVBlockStore;
 import com.google.bitcoin.store.WalletProtobufSerializer;
+import com.google.bitcoin.wallet.DeterministicSeed;
 import com.google.bitcoin.wallet.KeyChainGroup;
 import com.google.common.collect.ImmutableList;
 import com.google.common.util.concurrent.AbstractIdleService;
@@ -29,7 +30,10 @@ import com.google.common.util.concurrent.MoreExecutors;
 import com.google.common.util.concurrent.Service;
 import com.subgraph.orchid.TorClient;
 import org.bitcoinj.wallet.Protos;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
+import javax.annotation.Nullable;
 import java.io.*;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
@@ -64,6 +68,8 @@ import static com.google.common.base.Preconditions.checkState;
  * out what went wrong more precisely. Same thing if you just use the {@link #startAsync()} method.</p>
  */
 public class WalletAppKit extends AbstractIdleService {
+    protected static final Logger log = LoggerFactory.getLogger(WalletAppKit.class);
+
     protected final String filePrefix;
     protected final NetworkParameters params;
     protected volatile BlockChain vChain;
@@ -83,6 +89,7 @@ public class WalletAppKit extends AbstractIdleService {
     protected boolean useTor = false;   // Perhaps in future we can change this to true.
     protected String userAgent, version;
     protected WalletProtobufSerializer.WalletFactory walletFactory;
+    @Nullable protected DeterministicSeed restoreFromSeed;
 
     public WalletAppKit(NetworkParameters params, File directory, String filePrefix) {
         this.params = checkNotNull(params);
@@ -170,6 +177,19 @@ public class WalletAppKit extends AbstractIdleService {
         return this;
     }
 
+    /**
+     * If a seed is set here then any existing wallet that matches the file name will be renamed to a backup name,
+     * the chain file will be deleted, and the wallet object will be instantiated with the given seed instead of
+     * a fresh one being created. This is intended for restoring a wallet from the original seed. To implement restore
+     * you would shut down the existing appkit, if any, then recreate it with the seed given by the user, then start
+     * up the new kit. The next time your app starts it should work as normal (that is, don't keep calling this each
+     * time).
+     */
+    public WalletAppKit restoreWalletFromSeed(DeterministicSeed seed) {
+        this.restoreFromSeed = seed;
+        return this;
+    }
+
     /**
      * <p>Override this to return wallet extensions if any are necessary.</p>
      *
@@ -217,31 +237,46 @@ public class WalletAppKit extends AbstractIdleService {
                 throw new IOException("Could not create named directory.");
             }
         }
+        log.info("Starting up with directory = {}", directory);
         try {
             File chainFile = new File(directory, filePrefix + ".spvchain");
             boolean chainFileExists = chainFile.exists();
             vWalletFile = new File(directory, filePrefix + ".wallet");
-            boolean shouldReplayWallet = vWalletFile.exists() && !chainFileExists;
+            boolean shouldReplayWallet = (vWalletFile.exists() && !chainFileExists) || restoreFromSeed != null;
-
             vStore = new SPVBlockStore(params, chainFile);
-            if (!chainFileExists && checkpoints != null) {
+            if ((!chainFileExists || restoreFromSeed != null) && checkpoints != null) {
+                // Initialize the chain file with a checkpoint to speed up first-run sync.
+                long time = Long.MAX_VALUE;
+                if (restoreFromSeed != null) {
+                    time = restoreFromSeed.getCreationTimeSeconds();
+                    if (chainFileExists) {
+                        log.info("Deleting the chain file in preparation from restore.");
+                        vStore.close();
+                        if (!chainFile.delete())
+                            throw new Exception("Failed to delete chain file in preparation for restore.");
+                        vStore = new SPVBlockStore(params, chainFile);
+                    }
+                } else {
                     // Ugly hack! We have to create the wallet once here to learn the earliest key time, and then throw it
                     // away. The reason is that wallet extensions might need access to peergroups/chains/etc so we have to
                     // create the wallet later, but we need to know the time early here before we create the BlockChain
                     // object.
-                long time = Long.MAX_VALUE;
                     if (vWalletFile.exists()) {
                         FileInputStream stream = new FileInputStream(vWalletFile);
                         final WalletProtobufSerializer serializer = new WalletProtobufSerializer();
                         final Wallet wallet = serializer.readWallet(params, null, WalletProtobufSerializer.parseToProto(stream));
                         time = wallet.getEarliestKeyCreationTime();
                     }
+                }
                 CheckpointManager.checkpoint(params, checkpoints, vStore, time);
             }
             vChain = new BlockChain(params, vStore);
             vPeerGroup = createPeerGroup();
             if (this.userAgent != null)
                 vPeerGroup.setUserAgent(userAgent, version);
+
+            maybeMoveOldWalletOutOfTheWay();
+
             if (vWalletFile.exists()) {
                 FileInputStream walletStream = new FileInputStream(vWalletFile);
                 try {
@@ -261,7 +296,7 @@ public class WalletAppKit extends AbstractIdleService {
                     walletStream.close();
                 }
             } else {
-                vWallet = walletFactory != null ? walletFactory.create(params, new KeyChainGroup(params)) : new Wallet(params);
+                vWallet = createWallet();
                 vWallet.freshReceiveKey();
                 for (WalletExtension e : provideWalletExtensions()) {
                     vWallet.addExtension(e);
@@ -312,6 +347,35 @@ public class WalletAppKit extends AbstractIdleService {
         }
     }
 
+    protected Wallet createWallet() {
+        KeyChainGroup kcg;
+        if (restoreFromSeed != null)
+            kcg = new KeyChainGroup(params, restoreFromSeed);
+        else
+            kcg = new KeyChainGroup(params);
+        if (walletFactory != null) {
+            return walletFactory.create(params, kcg);
+        } else {
+            return new Wallet(params, kcg);  // default
+        }
+    }
+
+    private void maybeMoveOldWalletOutOfTheWay() {
+        if (restoreFromSeed == null) return;
+        if (!vWalletFile.exists()) return;
+        int counter = 1;
+        File newName;
+        do {
+            newName = new File(vWalletFile.getParent(), "Backup " + counter + " for " + vWalletFile.getName());
+            counter++;
+        } while (newName.exists());
+        log.info("Renaming old wallet file {} to {}", vWalletFile, newName);
+        if (!vWalletFile.renameTo(newName)) {
+            // This should not happen unless something is really messed up.
+            throw new RuntimeException("Failed to rename wallet for restore");
+        }
+    }
+
     protected PeerGroup createPeerGroup() throws TimeoutException {
         if (useTor) {
             return PeerGroup.newWithTor(params, vChain, new TorClient());