hybrid pagination

pkg/mongo/repository.go

@@ -37,6 +37,7 @@ type PaginatedResult[T any] struct {
 	TotalCount int64  `json:"totalCount"` // Total number of documents matching the filter
 	NextCursor string `json:"nextCursor"` // Base64 encoded cursor for next page
 	HasMore    bool   `json:"hasMore"`    // Whether there are more documents
+	PageOffset int    `json:"pageOffset"` // Zero-based offset of the first item in this page
 }
 
 // Repository defines the interface for MongoDB operations
@@ -144,6 +145,16 @@ func (r *repository[T]) FindAll(ctx context.Context, filter bson.M, pagination P
 		return nil, fmt.Errorf("failed to clone filter for count: %w", err)
 	}
 
+	filtersHash := HashFilter(filter)
+	pageOffset := pagination.Skip
+	if pagination.Cursor != "" {
+		pageCursor, err := decodePageCursor(pagination.Cursor)
+		if err != nil {
+			return nil, err
+		}
+		pageOffset = pageCursor.PageOffset
+	}
+
 	// Build find options
 	findOptions := options.Find().
 		SetSort(sort).
@@ -155,7 +166,7 @@ func (r *repository[T]) FindAll(ctx context.Context, filter bson.M, pagination P
 
 	// Handle cursor-based pagination
 	if pagination.Cursor != "" {
-		cursorFilter, err := r.buildCursorFilter(pagination.Cursor, pagination.SortField, pagination.SortOrder)
+		cursorFilter, err := r.buildCursorFilter(pagination.Cursor, pagination.SortField, pagination.SortOrder, filtersHash)
 		if err != nil {
 			return nil, err
 		}
@@ -209,12 +220,13 @@ func (r *repository[T]) FindAll(ctx context.Context, filter bson.M, pagination P
 	// Generate next cursor
 	var nextCursor string
 	if hasMore && len(items) > 0 {
-		nextCursor, err = r.generateCursor(items[len(items)-1], pagination.SortField, pagination.SortOrder)
+		nextPageOffset := pageOffset + pagination.Limit
+		nextCursor, err = r.generateCursor(items[len(items)-1], pagination.SortField, pagination.SortOrder, filtersHash, nextPageOffset)
 		if err != nil {
 			r.logger.Error("Failed to generate next cursor", map[string]interface{}{
 				"error": err.Error(),
 			})
-			// Don't fail the entire query, just leave cursor empty
+			return nil, fmt.Errorf("failed to generate pagination cursor: %w", err)
 		}
 	}
 
@@ -223,6 +235,7 @@ func (r *repository[T]) FindAll(ctx context.Context, filter bson.M, pagination P
 		TotalCount: totalCount,
 		NextCursor: nextCursor,
 		HasMore:    hasMore,
+		PageOffset: pageOffset,
 	}, nil
 }
 
@@ -454,7 +467,7 @@ func (r *repository[T]) validatePagination(pagination Pagination) error {
 }
 
 // buildCursorFilter builds a filter for cursor-based pagination.
-func (r *repository[T]) buildCursorFilter(cursor, sortField string, sortOrder int) (bson.M, error) {
+func (r *repository[T]) buildCursorFilter(cursor, sortField string, sortOrder int, filtersHash string) (bson.M, error) {
 	pageCursor, err := decodePageCursor(cursor)
 	if err != nil {
 		return nil, err
@@ -462,11 +475,14 @@ func (r *repository[T]) buildCursorFilter(cursor, sortField string, sortOrder in
 	if !pageCursor.matches(sortField, sortOrder) {
 		return nil, fmt.Errorf("%w: cursor does not match requested sort", ErrInvalidCursor)
 	}
+	if pageCursor.FiltersHash != filtersHash {
+		return nil, fmt.Errorf("%w: cursor does not match current filters", ErrInvalidCursor)
+	}
 	return pageCursor.mongoFilter()
 }
 
 // generateCursor generates an opaque cursor from the last document in a page.
-func (r *repository[T]) generateCursor(doc T, sortField string, sortOrder int) (string, error) {
+func (r *repository[T]) generateCursor(doc T, sortField string, sortOrder int, filtersHash string, pageOffset int) (string, error) {
 	docBytes, err := bson.Marshal(doc)
 	if err != nil {
 		return "", fmt.Errorf("failed to marshal document: %w", err)
@@ -487,7 +503,7 @@ func (r *repository[T]) generateCursor(doc T, sortField string, sortOrder int) (
 		return "", err
 	}
 
-	return encodePageCursor(sortField, sortOrder, sortValue, idHex)
+	return encodePageCursor(sortField, sortOrder, sortValue, idHex, filtersHash, pageOffset)
 }
 
 // getModelID extracts the ID from a model