check for last used address before reducing lookahead size

test/functional/test_framework/wallet_cli_controller.py

@@ -149,8 +149,9 @@ async def create_new_account(self, name: Optional[str] = '') -> str:
     async def select_account(self, account_index: int) -> str:
         return await self._write_command(f"selectaccount {account_index}\n")
 
-    async def set_lookahead_size(self, size: int) -> str:
-        return await self._write_command(f"setlookaheadsize {size}\n")
+    async def set_lookahead_size(self, size: int, force_reduce: bool) -> str:
+        i_know_what_i_am_doing = "i-know-what-i-am-doing" if force_reduce else ""
+        return await self._write_command(f"setlookaheadsize {size} {i_know_what_i_am_doing}\n")
 
     async def new_public_key(self) -> bytes:
         public_key = await self._write_command("newpublickey\n")

test/functional/wallet_set_lookahead_size.py

@@ -131,18 +131,20 @@ async def async_test(self):
             assert_in(f"Coins amount: {coins_to_send}", await wallet.get_balance())
 
             lower_size = random.randint(1, 2)
-            assert_in("Success. Lookahead size has been updated, will rescan the blockchain.", await wallet.set_lookahead_size(lower_size))
+            assert_in(f"Cannot reduce lookahead size to {lower_size} as it is below the last known used key {num_addresses-1}", await wallet.set_lookahead_size(lower_size, False))
+
+            assert_in("Success. Lookahead size has been updated, will rescan the blockchain.", await wallet.set_lookahead_size(lower_size, True))
 
             assert_in("Success", await wallet.sync())
             assert_in(f"Coins amount: 0", await wallet.get_balance())
 
             higher_size = random.randint(num_addresses, num_addresses * 2)
-            assert_in("Success. Lookahead size has been updated, will rescan the blockchain.", await wallet.set_lookahead_size(higher_size))
+            assert_in("Success. Lookahead size has been updated, will rescan the blockchain.", await wallet.set_lookahead_size(higher_size, False))
 
             assert_in("Success", await wallet.sync())
             assert_in(f"Coins amount: {coins_to_send}", await wallet.get_balance())
 
-            assert_in("Lookahead size cannot be 0", await wallet.set_lookahead_size(0))
+            assert_in("Lookahead size cannot be 0", await wallet.set_lookahead_size(0, False))
 
 
 

wallet/src/wallet/mod.rs

@@ -178,6 +178,8 @@ pub enum WalletError {
     DataDepositToBig(usize, usize),
     #[error("Cannot deposit empty data")]
     EmptyDataDeposit,
+    #[error("Cannot reduce lookahead size to {0} as it is below the last known used key {1}")]
+    ReducedLookaheadSize(u32, u32),
 }
 
 /// Result type used for the wallet
@@ -550,7 +552,23 @@ impl<B: storage::Backend> Wallet<B> {
         self.db.unlock_private_keys(password).map_err(WalletError::from)
     }
 
-    pub fn set_lookahead_size(&mut self, lookahead_size: u32) -> WalletResult<()> {
+    pub fn set_lookahead_size(
+        &mut self,
+        lookahead_size: u32,
+        force_reduce: bool,
+    ) -> WalletResult<()> {
+        let last_used = self.accounts.values().fold(None, |last, acc| {
+            let usage = acc.get_addresses_usage();
+            std::cmp::max(last, usage.last_used().map(U31::into_u32))
+        });
+
+        if let Some(last_used) = last_used {
+            ensure!(
+                last_used < lookahead_size || force_reduce,
+                WalletError::ReducedLookaheadSize(lookahead_size, last_used)
+            );
+        }
+
         let mut db_tx = self.db.transaction_rw(None)?;
         db_tx.set_lookahead_size(lookahead_size)?;
         let mut accounts = Self::reset_wallet_transactions(self.chain_config.clone(), &mut db_tx)?;

wallet/src/wallet/tests.rs

@@ -3529,7 +3529,13 @@ fn wallet_set_lookahead_size(#[case] seed: Seed) {
     assert_eq!(coins, block1_amount);
 
     let less_than_last_used = rng.gen_range(1..=last_used);
-    wallet.set_lookahead_size(less_than_last_used).unwrap();
+    let err = wallet.set_lookahead_size(less_than_last_used, false).unwrap_err();
+    assert_eq!(
+        err,
+        WalletError::ReducedLookaheadSize(less_than_last_used, last_used)
+    );
+
+    wallet.set_lookahead_size(less_than_last_used, true).unwrap();
 
     scan_wallet(&mut wallet, BlockHeight::new(0), vec![block1.clone()]);
     let coins = get_coin_balance_for_acc(&wallet, DEFAULT_ACCOUNT_INDEX);
@@ -3539,7 +3545,7 @@ fn wallet_set_lookahead_size(#[case] seed: Seed) {
     assert_eq!(usage.last_issued(), None);
 
     let more_than_last_used = rng.gen_range(last_used + 1..100);
-    wallet.set_lookahead_size(more_than_last_used).unwrap();
+    wallet.set_lookahead_size(more_than_last_used, false).unwrap();
 
     scan_wallet(&mut wallet, BlockHeight::new(0), vec![block1.clone()]);
     let coins = get_coin_balance_for_acc(&wallet, DEFAULT_ACCOUNT_INDEX);

wallet/wallet-cli-lib/src/commands/helper_types.rs

@@ -358,3 +358,8 @@ impl CliIsUnfreezable {
         }
     }
 }
+
+#[derive(Debug, Clone, Copy, ValueEnum)]
+pub enum CliForceReduce {
+    IKnowWhatIAmDoing,
+}

wallet/wallet-cli-lib/src/commands/mod.rs

@@ -46,8 +46,9 @@ use crate::{
 
 use self::helper_types::{
     format_delegation_info, format_pool_info, parse_coin_amount, parse_pool_id, parse_token_amount,
-    parse_token_id, parse_utxo_outpoint, print_coin_amount, to_per_thousand, CliIsFreezable,
-    CliIsUnfreezable, CliStoreSeedPhrase, CliUtxoState, CliUtxoTypes, CliWithLocked,
+    parse_token_id, parse_utxo_outpoint, print_coin_amount, to_per_thousand, CliForceReduce,
+    CliIsFreezable, CliIsUnfreezable, CliStoreSeedPhrase, CliUtxoState, CliUtxoTypes,
+    CliWithLocked,
 };
 
 #[derive(Debug, Parser)]
@@ -102,6 +103,10 @@ pub enum WalletCommand {
     SetLookaheadSize {
         // The new lookahead size
         lookahead_size: u32,
+
+        // Forces the reduction of lookahead size even below the known last used address
+        // the new wallet can lose track of known addresses and balance
+        i_know_what_i_am_doing: Option<CliForceReduce>,
     },
 
     /// Returns the node chainstate
@@ -686,9 +691,17 @@ impl CommandHandler {
                 ))
             }
 
-            WalletCommand::SetLookaheadSize { lookahead_size } => {
+            WalletCommand::SetLookaheadSize {
+                lookahead_size,
+                i_know_what_i_am_doing,
+            } => {
+                let force_reduce = match i_know_what_i_am_doing {
+                    Some(CliForceReduce::IKnowWhatIAmDoing) => true,
+                    None => false,
+                };
+
                 self.controller()?
-                    .set_lookahead_size(lookahead_size)
+                    .set_lookahead_size(lookahead_size, force_reduce)
                     .map_err(WalletCliError::Controller)?;
 
                 Ok(ConsoleCommand::Print(

wallet/wallet-controller/src/lib.rs

@@ -353,11 +353,15 @@ impl<T: NodeInterface + Clone + Send + Sync + 'static, W: WalletEvents> Controll
     /// # Returns
     ///
     /// This method returns an error if you try to set lookahead size to 0
-    pub fn set_lookahead_size(&mut self, lookahead_size: u32) -> Result<(), ControllerError<T>> {
+    pub fn set_lookahead_size(
+        &mut self,
+        lookahead_size: u32,
+        force_reduce: bool,
+    ) -> Result<(), ControllerError<T>> {
         utils::ensure!(lookahead_size > 0, ControllerError::InvalidLookaheadSize);
 
         self.wallet
-            .set_lookahead_size(lookahead_size)
+            .set_lookahead_size(lookahead_size, force_reduce)
             .map_err(ControllerError::WalletError)
     }