Fix overflow when computing prune threshold

It would happen if the number of block to keep is greater than the
highest stored block range root start.

Author: Alenar

internal/mithril-persistence/src/database/provider/cardano_transaction/delete_cardano_transaction.rs

@@ -1,3 +1,4 @@
+use anyhow::Context;
 use sqlite::Value;
 
 use mithril_common::entities::BlockNumber;
@@ -36,18 +37,22 @@ impl<'conn> DeleteCardanoTransactionProvider<'conn> {
         Self { connection }
     }
 
-    fn get_prune_condition(&self, threshold: BlockNumber) -> WhereCondition {
-        let threshold = Value::Integer(threshold.try_into().unwrap());
+    fn get_prune_condition(&self, threshold: BlockNumber) -> StdResult<WhereCondition> {
+        let threshold = Value::Integer(
+            threshold
+                .try_into()
+                .with_context(|| format!("Failed to convert threshold `{threshold}` to i64"))?,
+        );
 
-        WhereCondition::new("block_number < ?*", vec![threshold])
+        Ok(WhereCondition::new("block_number < ?*", vec![threshold]))
     }
 
     /// Prune the cardano transaction data below the given threshold.
     pub fn prune(
         &self,
         threshold: BlockNumber,
     ) -> StdResult<EntityCursor<CardanoTransactionRecord>> {
-        let filters = self.get_prune_condition(threshold);
+        let filters = self.get_prune_condition(threshold)?;
 
         self.find(filters)
     }

internal/mithril-persistence/src/database/repository/cardano_transaction_repository.rs

@@ -297,7 +297,7 @@ impl CardanoTransactionRepository {
             .await?
         {
             let provider = DeleteCardanoTransactionProvider::new(&self.connection);
-            let threshold = highest_block_range_start - number_of_blocks_to_keep;
+            let threshold = highest_block_range_start.saturating_sub(number_of_blocks_to_keep);
             provider.prune(threshold)?.next();
         }
 
@@ -897,6 +897,12 @@ mod tests {
         let transaction_result = repository.get_all().await.unwrap();
         assert_eq!(cardano_transactions.len(), transaction_result.len());
 
+        // Pruning with a number of block to keep greater than the highest block range start should
+        // do nothing.
+        repository.prune_transaction(10_000_000).await.unwrap();
+        let transaction_result = repository.get_all_transactions().await.unwrap();
+        assert_eq!(cardano_transactions, transaction_result);
+
         // Since the highest block range start is 45, pruning with 20 should remove transactions
         // with a block number strictly below 25.
         repository.prune_transaction(20).await.unwrap();