feat(migration): enhance primary key handling and add GIN index support in migration writer

pkg/writers/pgsql/migration_writer_test.go

@@ -97,6 +97,89 @@ func TestWriteMigration_ArrayDefault(t *testing.T) {
 	}
 }
 
+func TestWriteMigration_GinIndexOnTextUsesTrigramOperatorClass(t *testing.T) {
+	current := models.InitDatabase("testdb")
+	currentSchema := models.InitSchema("public")
+	current.Schemas = append(current.Schemas, currentSchema)
+
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+
+	table := models.InitTable("articles", "public")
+	titleCol := models.InitColumn("title", "articles", "public")
+	titleCol.Type = "text"
+	table.Columns["title"] = titleCol
+
+	index := &models.Index{
+		Name:    "idx_articles_title_gin",
+		Type:    "gin",
+		Columns: []string{"title"},
+	}
+	table.Indexes[index.Name] = index
+
+	modelSchema.Tables = append(modelSchema.Tables, table)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "USING gin (title gin_trgm_ops)") {
+		t.Fatalf("expected GIN text index to include gin_trgm_ops, got:\n%s", output)
+	}
+}
+
+func TestWriteMigration_GinIndexOnTextArrayDoesNotUseTrigramOperatorClass(t *testing.T) {
+	current := models.InitDatabase("testdb")
+	currentSchema := models.InitSchema("public")
+	current.Schemas = append(current.Schemas, currentSchema)
+
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+
+	table := models.InitTable("plans", "public")
+	tagsCol := models.InitColumn("tags", "plans", "public")
+	tagsCol.Type = "text[]"
+	table.Columns["tags"] = tagsCol
+
+	index := &models.Index{
+		Name:    "idx_plans_tags",
+		Type:    "gin",
+		Columns: []string{"tags"},
+	}
+	table.Indexes[index.Name] = index
+
+	modelSchema.Tables = append(modelSchema.Tables, table)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(&writers.WriterOptions{})
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, current); err != nil {
+		t.Fatalf("WriteMigration failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "USING gin (tags)") {
+		t.Fatalf("expected GIN array index without explicit trigram opclass, got:\n%s", output)
+	}
+	if strings.Contains(output, "gin_trgm_ops") {
+		t.Fatalf("did not expect gin_trgm_ops for text[] migration index, got:\n%s", output)
+	}
+}
+
 func TestWriteMigration_WithAudit(t *testing.T) {
 	// Current database (empty)
 	current := models.InitDatabase("testdb")
@@ -322,3 +405,46 @@ func TestWriteMigration_NumericConstraintNames(t *testing.T) {
 		t.Error("Migration missing FOREIGN KEY")
 	}
 }
+
+func TestNewMigrationWriter_NilOptions(t *testing.T) {
+	writer, err := NewMigrationWriter(nil)
+	if err != nil {
+		t.Fatalf("NewMigrationWriter(nil) returned error: %v", err)
+	}
+	if writer == nil {
+		t.Fatal("expected writer instance")
+	}
+	if writer.options == nil {
+		t.Fatal("expected default writer options to be initialized")
+	}
+}
+
+func TestWriteMigration_NilCurrentTreatsDatabaseAsEmpty(t *testing.T) {
+	model := models.InitDatabase("testdb")
+	modelSchema := models.InitSchema("public")
+
+	table := models.InitTable("users", "public")
+	idCol := models.InitColumn("id", "users", "public")
+	idCol.Type = "integer"
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+
+	modelSchema.Tables = append(modelSchema.Tables, table)
+	model.Schemas = append(model.Schemas, modelSchema)
+
+	var buf bytes.Buffer
+	writer, err := NewMigrationWriter(nil)
+	if err != nil {
+		t.Fatalf("Failed to create writer: %v", err)
+	}
+	writer.writer = &buf
+
+	if err := writer.WriteMigration(model, nil); err != nil {
+		t.Fatalf("WriteMigration with nil current failed: %v", err)
+	}
+
+	output := buf.String()
+	if !strings.Contains(output, "CREATE TABLE") {
+		t.Fatalf("expected CREATE TABLE in migration output, got:\n%s", output)
+	}
+}