Add legacy hierarchy fallback for pre-migration databases.

Handle missing course_sub_categories table by serving hierarchy data from legacy categories/courses queries so content pages keep loading until unified hierarchy migration is applied.

Made-with: Cursor

internal/web_server/handlers/hierarchy_handler.go

@@ -74,6 +74,15 @@ type createSubModulePracticeReq struct {
 	IsActive      *bool   `json:"is_active"`
 }
 
+type legacyHierarchyRow struct {
+	CategoryID      int64   `json:"category_id"`
+	CategoryName    string  `json:"category_name"`
+	SubCategoryID   *int64  `json:"sub_category_id"`
+	SubCategoryName *string `json:"sub_category_name"`
+	CourseID        *int64  `json:"course_id"`
+	CourseTitle     *string `json:"course_title"`
+}
+
 func toText(v *string) pgtype.Text {
 	if v == nil {
 		return pgtype.Text{Valid: false}
@@ -113,6 +122,13 @@ func intOrNil(v *int32) interface{} {
 func (h *Handler) UnifiedHierarchy(c *fiber.Ctx) error {
 	rows, err := h.analyticsDB.GetCoursesWithHierarchy(c.Context())
 	if err != nil {
+		if isMissingCourseSubCategoryTableErr(err) {
+			legacyRows, legacyErr := h.buildLegacyHierarchyRows(c)
+			if legacyErr != nil {
+				return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{Message: "Failed to load hierarchy", Error: legacyErr.Error()})
+			}
+			return c.JSON(domain.Response{Message: "Unified hierarchy retrieved successfully", Data: legacyRows})
+		}
 		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{Message: "Failed to load hierarchy", Error: err.Error()})
 	}
 	return c.JSON(domain.Response{Message: "Unified hierarchy retrieved successfully", Data: rows})
@@ -135,11 +151,88 @@ func (h *Handler) UnifiedHierarchyByCourse(c *fiber.Ctx) error {
 	}
 	rows, err := h.analyticsDB.GetFullHierarchyByCourseID(c.Context(), courseID)
 	if err != nil {
+		if isMissingCourseSubCategoryTableErr(err) {
+			course, getCourseErr := h.analyticsDB.GetCourseByID(c.Context(), courseID)
+			if getCourseErr != nil {
+				return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{Message: "Failed to load course hierarchy", Error: getCourseErr.Error()})
+			}
+			return c.JSON(domain.Response{
+				Message: "Course hierarchy retrieved successfully",
+				Data: []map[string]interface{}{
+					{
+						"course_id":        course.ID,
+						"course_title":     course.Title,
+						"level_id":         nil,
+						"cefr_level":       nil,
+						"module_id":        nil,
+						"module_title":     nil,
+						"sub_module_id":    nil,
+						"sub_module_title": nil,
+					},
+				},
+			})
+		}
 		return c.Status(fiber.StatusInternalServerError).JSON(domain.ErrorResponse{Message: "Failed to load course hierarchy", Error: err.Error()})
 	}
 	return c.JSON(domain.Response{Message: "Course hierarchy retrieved successfully", Data: rows})
 }
 
+func isMissingCourseSubCategoryTableErr(err error) bool {
+	if err == nil {
+		return false
+	}
+	return strings.Contains(strings.ToLower(err.Error()), "relation \"course_sub_categories\" does not exist")
+}
+
+func (h *Handler) buildLegacyHierarchyRows(c *fiber.Ctx) ([]legacyHierarchyRow, error) {
+	categories, err := h.analyticsDB.GetAllCourseCategories(c.Context(), dbgen.GetAllCourseCategoriesParams{
+		Offset: pgtype.Int4{Int32: 0, Valid: true},
+		Limit:  pgtype.Int4{Int32: 10000, Valid: true},
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	out := make([]legacyHierarchyRow, 0, len(categories))
+	for _, cat := range categories {
+		courses, courseErr := h.analyticsDB.GetCoursesByCategory(c.Context(), dbgen.GetCoursesByCategoryParams{
+			CategoryID: cat.ID,
+			Offset:     pgtype.Int4{Int32: 0, Valid: true},
+			Limit:      pgtype.Int4{Int32: 10000, Valid: true},
+		})
+		if courseErr != nil {
+			return nil, courseErr
+		}
+
+		if len(courses) == 0 {
+			out = append(out, legacyHierarchyRow{
+				CategoryID:      cat.ID,
+				CategoryName:    cat.Name,
+				SubCategoryID:   nil,
+				SubCategoryName: nil,
+				CourseID:        nil,
+				CourseTitle:     nil,
+			})
+			continue
+		}
+
+		for _, course := range courses {
+			courseID := course.ID
+			courseTitle := course.Title
+			out = append(out, legacyHierarchyRow{
+				CategoryID:      cat.ID,
+				CategoryName:    cat.Name,
+				SubCategoryID:   nil,
+				SubCategoryName: nil,
+				CourseID:        &courseID,
+				CourseTitle:     &courseTitle,
+			})
+		}
+	}
+
+	return out, nil
+}
+
 // CreateCourseSubCategory godoc
 // @Summary Create course sub-category
 // @Description Creates a sub-category under a course category