feat(gl): detect duplicate transaction versions

application/reconciliation/service.go

@@ -32,6 +32,7 @@ func Run(ctx context.Context, repository Repository, pageSize int) (Report, erro
 		pageSize = 100
 	}
 	report := Report{Invalid: make([]Issue, 0)}
+	seen := make(map[string]string)
 	for offset := 0; ; offset += pageSize {
 		journals, err := repository.List(ctx, ledger.JournalFilter{Limit: pageSize, Offset: offset})
 		if err != nil {
@@ -43,6 +44,12 @@ func Run(ctx context.Context, repository Repository, pageSize int) (Report, erro
 				report.Invalid = append(report.Invalid, Issue{JournalID: journal.ID, Error: err.Error()})
 				continue
 			}
+			key := journal.SourceService + "\x00" + journal.SourceTransactionID + "\x00" + fmt.Sprint(journal.EventVersion)
+			if previous, exists := seen[key]; exists {
+				report.Invalid = append(report.Invalid, Issue{JournalID: journal.ID, Error: fmt.Sprintf("duplicate source transaction/version; first journal %s", previous)})
+				continue
+			}
+			seen[key] = journal.ID
 			report.Valid++
 		}
 		if len(journals) < pageSize {

application/reconciliation/service_test.go

@@ -41,3 +41,16 @@ func TestRunScansAndReportsInvalidJournals(t *testing.T) {
 		t.Fatalf("unexpected report: %+v", report)
 	}
 }
+
+func TestRunReportsDuplicateTransactionVersions(t *testing.T) {
+	first := validJournal()
+	second := validJournal()
+	second.ID = "j2"
+	report, err := Run(context.Background(), repositoryStub{pages: [][]ledger.Journal{{first, second}}}, 10)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if report.Valid != 1 || len(report.Invalid) != 1 {
+		t.Fatalf("unexpected report: %+v", report)
+	}
+}