fix: prevent overwrite when document has multiple files

main_test.go

@@ -19,3 +19,41 @@ func TestConfigFilePathUsesXDGConfigDir(t *testing.T) {
 		t.Fatalf("expected %q, got %q", want, got)
 	}
 }
+
+func TestArchiveDestinationIndexesMultipleAttachmentsAndPreservesDistinctFiles(t *testing.T) {
+	directory := t.TempDir()
+	sourcePath := filepath.Join(t.TempDir(), "source.pdf")
+	if err := os.WriteFile(sourcePath, []byte("source"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	got, alreadyArchived, err := archiveDestination(directory, "Document", "pdf", 2, sourcePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if alreadyArchived || got != filepath.Join(directory, "Document.1.pdf") {
+		t.Fatalf("expected first indexed destination, got %q (already archived: %t)", got, alreadyArchived)
+	}
+
+	if err := os.WriteFile(got, []byte("different"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	got, alreadyArchived, err = archiveDestination(directory, "Document", "pdf", 2, sourcePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if alreadyArchived || got != filepath.Join(directory, "Document.2.pdf") {
+		t.Fatalf("expected second indexed destination, got %q (already archived: %t)", got, alreadyArchived)
+	}
+
+	if err := os.WriteFile(got, []byte("source"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	got, alreadyArchived, err = archiveDestination(directory, "Document", "pdf", 2, sourcePath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !alreadyArchived || got != filepath.Join(directory, "Document.2.pdf") {
+		t.Fatalf("expected matching indexed destination, got %q (already archived: %t)", got, alreadyArchived)
+	}
+}