fetch params from download.z.cash on demand to reduce app size (#2879)

add restore height to seed screen

cw_zcash/lib/src/zcash_taddress_rotation.dart

@@ -313,6 +313,7 @@ class ZcashTaddressRotation {
 
         final recipient = Recipient(recipientBuilder.toBytes());
         final fee = FeeT(fee: 10000, minFee: 0, maxFee: 0, scheme: 0);
+        await ZcashWalletBase.loadProver();
         final txPlan = await ZcashWalletService.runInDbMutex(
           () => WarpApi.prepareTx(
             coin,

cw_zcash/lib/src/zcash_wallet.dart

@@ -11,6 +11,7 @@ import 'package:cw_core/sync_status.dart';
 import 'package:cw_core/transaction_direction.dart';
 import 'package:cw_core/transaction_priority.dart';
 import 'package:cw_core/utils/print_verbose.dart';
+import 'package:cw_core/utils/proxy_wrapper.dart';
 import 'package:cw_core/wallet_addresses.dart';
 import 'package:cw_core/wallet_base.dart';
 import 'package:cw_core/wallet_credentials.dart';
@@ -220,6 +221,7 @@ abstract class ZcashWalletBase
 
     // pools parameter: bitmask for which pools to use for sending
     // 1=Transparent, 2=Sapling, 4=Orchard, 7=All pools
+    await ZcashWalletBase.loadProver();
     // Using 7 (all pools) allows spending from any pool type
     final txPlan = await ZcashWalletService.runInDbMutex(
       () => WarpApi.prepareTx(
@@ -333,6 +335,8 @@ abstract class ZcashWalletBase
       "privateViewKey": backup.fvk,
       "uvk": backup.uvk,
       "tsk": backup.tsk,
+      if (lastKnownRestoreHeight != null)
+        "restoreHeight": lastKnownRestoreHeight.toString(),
     };
   }
 
@@ -354,12 +358,14 @@ abstract class ZcashWalletBase
   bool get hasRescan => true;
 
   static Future<void> storeZcashHeight(final int height) async {
+    lastKnownRestoreHeight = height;
     final zcashDir = await pathForWalletTypeDir(type: WalletType.zcash);
     final zcashInitialSync = File(p.join(zcashDir, ".initial-sync-marker"));
     zcashInitialSync.writeAsBytesSync([0x00]);
     zcashInitialSync.writeAsStringSync(height.toString(), mode: FileMode.writeOnlyAppend);
   }
 
+  static int? lastKnownRestoreHeight = null;
   static Future<int?> loadZcashHeight() async {
     final zcashDir = await pathForWalletTypeDir(type: WalletType.zcash);
     final zcashInitialSync = File(p.join(zcashDir, ".initial-sync-marker"));
@@ -371,7 +377,8 @@ abstract class ZcashWalletBase
       return null;
     }
     final heightString = String.fromCharCodes(bytes.skip(1));
-    return int.tryParse(heightString);
+    lastKnownRestoreHeight = int.tryParse(heightString);
+    return lastKnownRestoreHeight;
   }
 
   static int zashiAnnouncedBlockHeight = 2419420;
@@ -749,6 +756,7 @@ abstract class ZcashWalletBase
 
     final recipient = Recipient(recipientBuilder.toBytes());
     final fee = FeeT(fee: 10000, minFee: 0, maxFee: 0, scheme: 0);
+    await ZcashWalletBase.loadProver();
     final txPlan = await ZcashWalletService.runInDbMutex(
       () => WarpApi.prepareTx(
         coin,
@@ -1039,13 +1047,45 @@ abstract class ZcashWalletBase
     } catch (e) {
       printV("zec init failed: $e");
     } // do not fail on network exception
-    final spend = await rootBundle.load('scripts/zcash_lib/assets/sapling-spend.params');
-    final output = await rootBundle.load('scripts/zcash_lib/assets/sapling-output.params');
-    WarpApi.initProver(spend.buffer.asUint8List(), output.buffer.asUint8List());
+    await loadZcashHeight();
+
+    unawaited(loadProver());
+
     await ZcashTaddressRotation.init();
     await ZcashTransactionInfo.init();
     _initialized = true;
   }
+  
+  static bool isProverLoaded = false;
+  static Future<void> loadProver() async {
+    Uint8List? spend;
+    Uint8List? output;
+    final cacheDir = await getApplicationCacheDirectory();
+    try {
+      final spendBundle = await rootBundle.load('scripts/zcash_lib/assets/sapling-spend.params');
+      final outputBundle = await rootBundle.load('scripts/zcash_lib/assets/sapling-output.params');
+      spend = spendBundle.buffer.asUint8List();
+      output = outputBundle.buffer.asUint8List();
+      if (spend.length == 0 || output.length == 0) throw Exception("NUH UH");
+      spend = await File(cacheDir.path+"/sapling-spend.params").readAsBytesSync();
+      output = await File(cacheDir.path+"/sapling-output.params").readAsBytesSync();
+      if (spend.length == 0 || output.length == 0) throw Exception("NUH UH");
+    } catch (e) {
+      printV("$e. Fine, I'll download them.");
+      final spendResponse = await ProxyWrapper().get(
+        clearnetUri: Uri.parse("https://download.z.cash/downloads/sapling-spend.params"),
+      );
+      final outputResponse = await ProxyWrapper().get(
+        clearnetUri: Uri.parse("https://download.z.cash/downloads/sapling-output.params"),
+      );
+      spend = spendResponse.bodyBytes;
+      output = outputResponse.bodyBytes;
+      await File(cacheDir.path+"/sapling-spend.params").writeAsBytes(spend);
+      await File(cacheDir.path+"/sapling-output.params").writeAsBytes(output);
+    }
+    WarpApi.initProver(spend, output);
+    isProverLoaded = true;
+  }
 
   static Future<int> getBlockHeightByTime(final DateTime time) async {
     final genesisTime = DateTime.utc(2016, 10, 28);

lib/src/screens/wallet_keys/wallet_keys_page.dart

@@ -183,7 +183,7 @@ class _WalletKeysPageBodyState extends State<WalletKeysPageBody>
   Widget _buildSeedTab(BuildContext context, bool isLegacySeed) {
     return Column(
       children: [
-        if (isLegacySeedOnly || isLegacySeed || widget.walletKeysViewModel.isBitcoin) ...[
+        if (isLegacySeedOnly || isLegacySeed ||widget.walletKeysViewModel.shouldShowHeightBox) ...[
           _buildHeightBox(),
           const SizedBox(height: 20),
         ],

lib/view_model/wallet_keys_view_model.dart

@@ -62,7 +62,9 @@ abstract class WalletKeysViewModelBase with Store {
   }
 
   bool get isBitcoin => _wallet.type == WalletType.bitcoin;
-
+  
+  // this is incomplete, needs legacy seed toggle for XMR
+  bool get shouldShowHeightBox => [WalletType.bitcoin, WalletType.zcash].contains(_wallet.type);
   final ObservableList<StandartListItem> items;
 
   @observable
@@ -318,6 +320,9 @@ abstract class WalletKeysViewModelBase with Store {
     if (_wallet.type == WalletType.wownero) {
       return wownero!.getRestoreHeight(_wallet)?.toString();
     }
+    if (_wallet.type == WalletType.zcash) {
+      return zcash!.getKeys(_wallet)["restoreHeight"]?.toString();
+    }
     if (_restoreHeightByTransactions != 0)
       return getRoundedRestoreHeight(_restoreHeightByTransactions);
     if (_restoreHeight != 0) return _restoreHeight.toString();