Remove timestamp-reference transaction from start of page (#2189)

Removes the "extra" transaction between pages, fetched for `timestamp` reference:

- Move `slice` into main mapping function.

src/routes/transactions/mappers/transactions-history.mapper.ts

@@ -53,14 +53,25 @@ export class TransactionsHistoryMapper {
     if (transactionsDomain.length == 0) {
       return [];
     }
-    // Must be retrieved before mapping others as we remove it from transactionsDomain
-    const previousTransaction = await this.getPreviousTransaction({
-      offset,
-      transactionsDomain,
-      chainId,
-      safe,
-      onlyTrusted,
-    });
+
+    let previousTransaction: TransactionItem | undefined;
+
+    /**
+     * We insert a {@link DateLabel} between transactions on different days.
+     * On subsequent pages (offset > 0), we fetch the last transaction of previous page
+     * to determine if the first transaction of the current page is on the same day.
+     */
+    if (offset > 0 && transactionsDomain.length > 1) {
+      previousTransaction = await this.getPreviousTransaction({
+        transactionsDomain,
+        chainId,
+        safe,
+        onlyTrusted,
+      });
+
+      // Remove first transaction that was requested to get previous day timestamp
+      transactionsDomain = transactionsDomain.slice(1);
+    }
 
     const mappedTransactions = await this.getMappedTransactions({
       transactionsDomain,
@@ -97,16 +108,11 @@ export class TransactionsHistoryMapper {
   }
 
   private async getPreviousTransaction(args: {
-    offset: number;
     transactionsDomain: TransactionDomain[];
     chainId: string;
     safe: Safe;
     onlyTrusted: boolean;
   }): Promise<TransactionItem | undefined> {
-    // More than 1 element is required to get the previous transaction
-    if (args.offset <= 0 || args.transactionsDomain.length <= 1) {
-      return;
-    }
     const prevDomainTransaction = args.transactionsDomain[0];
     // We map in order to filter last list item against it
     const mappedPreviousTransaction = await this.mapTransaction(
@@ -115,8 +121,6 @@ export class TransactionsHistoryMapper {
       args.safe,
       args.onlyTrusted,
     );
-    // Remove first transaction that was requested to get previous day timestamp
-    args.transactionsDomain = args.transactionsDomain.slice(1);
 
     return Array.isArray(mappedPreviousTransaction)
       ? // All transfers should have same execution date but the last is "true" previous