feat: replace network example with wallet bootstrap demo

Author: chavic

examples/network_example.dart

@@ -1,14 +1,71 @@
+import 'dart:io';
+
 import 'package:bdk_dart/bdk.dart';
 
+/// Run with: `dart run examples/network_example.dart`
+///
+/// Prerequisites:
+///  * Generated bindings (`scripts/generate_bindings.sh`)
+///  * Native library (`libbdkffi.*`) discoverable by the Dart process
 void main() {
-  // Create a NetworkExample instance
-  final networkHelper = NetworkExample();
-  
-  // Get the Signet network
-  final signetNetwork = networkHelper.get_signet();
-  
-  // Convert it to string - should print "Signet"
-  final networkName = networkHelper.network_name(signetNetwork);
-  
-  print("Network: $networkName");
-}
+  final network = Network.testnet;
+
+  // 1. Create fresh seed material.
+  final mnemonic = Mnemonic(WordCount.words12);
+  stdout.writeln('Mnemonic: $mnemonic');
+
+  // 2. Turn the mnemonic into descriptor keys for external/change paths.
+  final rootKey = DescriptorSecretKey(network, mnemonic, null);
+  final externalDescriptor =
+      Descriptor.newBip84(rootKey, KeychainKind.external_, network);
+  final changeDescriptor =
+      Descriptor.newBip84(rootKey, KeychainKind.internal, network);
+
+  stdout
+    ..writeln('\nExternal descriptor:\n  $externalDescriptor')
+    ..writeln('Change descriptor:\n  $changeDescriptor');
+
+  // 3. Spin up an in-memory wallet using the descriptors.
+  final persister = Persister.newInMemory();
+  final wallet =
+      Wallet(externalDescriptor, changeDescriptor, network, persister, 25);
+  stdout.writeln('\nWallet ready on ${wallet.network()}');
+
+  // 4. Hand out the next receive address and persist the staged change.
+  final receive = wallet.revealNextAddress(KeychainKind.external_);
+  stdout.writeln(
+      'Next receive address (#${receive.index}): ${receive.address.toString()}');
+  final persisted = wallet.persist(persister);
+  stdout.writeln('Persisted staged wallet changes: $persisted');
+
+  // 5. Try a quick Electrum sync to fetch history/balances.
+  try {
+    stdout.writeln('\nSyncing via Electrum (blockstream.info)…');
+    final client =
+        ElectrumClient('ssl://electrum.blockstream.info:60002', null);
+    final syncRequest = wallet.startSyncWithRevealedSpks().build();
+    final update = client.sync_(syncRequest, 100, true);
+
+    wallet.applyUpdate(update);
+    wallet.persist(persister);
+
+    final balance = wallet.balance();
+    stdout.writeln('Confirmed balance: ${balance.confirmed.toSat()} sats');
+    stdout.writeln('Total balance: ${balance.total.toSat()} sats');
+
+    client.dispose();
+  } catch (error) {
+    stdout.writeln(
+      'Electrum sync failed: $error\n'
+      'Ensure TLS-enabled Electrum access is available, or skip this step.',
+    );
+  }
+
+  // 6. Clean up FFI handles explicitly so long-lived examples don’t leak.
+  wallet.dispose();
+  persister.dispose();
+  externalDescriptor.dispose();
+  changeDescriptor.dispose();
+  rootKey.dispose();
+  mnemonic.dispose();
+}