feat(enable-banking): safe pending transaction merge with sync re-import prevention (#1709)

* feat(enable-banking): safe pending transaction merge with sync re-import prevention

* preserve all merged pending IDs across syncs

* fix(enable-banking): harden merge locking, safe logging, and non-blocking index

* fix(enable-banking): use safe external ID in invalid currency log

* refactor(models): centralize pending transaction SQL logic

Move the SQL fragment used to identify pending transactions from the `Entry` model to a constant in the `Transaction` model. This improves maintainability and ensures that the logic for determining if a transaction is pending is defined in a single location.

* fix(enable-banking): drop dead manual_merge index, use lateral join for excluded IDs

* No net schema changes

---------

Co-authored-by: Juan José Mata <jjmata@jjmata.com>

app/models/enable_banking_account/transactions/processor.rb

@@ -15,6 +15,7 @@ class EnableBankingAccount::Transactions::Processor
     Rails.logger.info "EnableBankingAccount::Transactions::Processor - Processing #{total_count} transactions for enable_banking_account #{enable_banking_account.id}"
 
     imported_count = 0
+    skipped_count = 0
     failed_count = 0
     errors = []
 
@@ -22,8 +23,43 @@ class EnableBankingAccount::Transactions::Processor
       Account::ProviderImportAdapter.new(enable_banking_account.current_account)
     end
 
+    # Pre-fetch external_ids that were manually merged and must not be re-imported.
+    # One query per sync; O(1) Set lookup per transaction — avoids N+1.
+    # Uses a lateral jsonb_array_elements join to extract only the ID strings in SQL,
+    # avoiding loading full extra blobs into Ruby. Handles both Array (current) and
+    # Hash (legacy) formats via jsonb_typeof.
+    excluded_ids = if enable_banking_account.current_account
+      Transaction.joins(:entry)
+                 .where(entries: { account_id: enable_banking_account.current_account.id })
+                 .where("transactions.extra ? 'manual_merge'")
+                 .joins(
+                   Arel.sql(<<~SQL.squish)
+                     CROSS JOIN LATERAL jsonb_array_elements(
+                       CASE jsonb_typeof(transactions.extra->'manual_merge')
+                       WHEN 'array'  THEN transactions.extra->'manual_merge'
+                       WHEN 'object' THEN jsonb_build_array(transactions.extra->'manual_merge')
+                       ELSE '[]'::jsonb
+                       END
+                     ) AS merge_elem
+                   SQL
+                 )
+                 .pluck(Arel.sql("merge_elem->>'merged_from_external_id'"))
+                 .compact
+                 .to_set
+    else
+      Set.new
+    end
+
     enable_banking_account.raw_transactions_payload.each_with_index do |transaction_data, index|
       begin
+        ext_id = EnableBankingEntry::Processor.compute_external_id(transaction_data)
+
+        if ext_id && excluded_ids.include?(ext_id)
+          Rails.logger.info("EnableBankingAccount::Transactions::Processor - Skipping re-import of manually merged pending transaction: #{ext_id}")
+          skipped_count += 1
+          next
+        end
+
         result = EnableBankingEntry::Processor.new(
           transaction_data,
           enable_banking_account: enable_banking_account,
@@ -56,6 +92,7 @@ class EnableBankingAccount::Transactions::Processor
       success: failed_count == 0,
       total: total_count,
       imported: imported_count,
+      skipped: skipped_count,
       failed: failed_count,
       errors: errors
     }