hybrid pagination

pkg/mongo/cursor.go

@@ -13,15 +13,17 @@ const pageCursorVersion = 1
 
 // pageCursor is an opaque pagination token for keyset (cursor) pagination.
 type pageCursor struct {
-	V         int    `json:"v"`
-	SortField string `json:"sort_field"`
-	SortOrder int    `json:"sort_order"`
-	ValueType string `json:"value_type"` // i64, f64, str, oid
-	SortValue string `json:"sort_value"`
-	ID        string `json:"id"`
+	V           int    `json:"v"`
+	SortField   string `json:"sort_field"`
+	SortOrder   int    `json:"sort_order"`
+	ValueType   string `json:"value_type"` // i64, f64, str, oid
+	SortValue   string `json:"sort_value"`
+	ID          string `json:"id"`
+	FiltersHash string `json:"filters_hash,omitempty"`
+	PageOffset  int    `json:"page_offset,omitempty"`
 }
 
-func encodePageCursor(sortField string, sortOrder int, sortValue interface{}, id string) (string, error) {
+func encodePageCursor(sortField string, sortOrder int, sortValue interface{}, id, filtersHash string, pageOffset int) (string, error) {
 	if sortField == "" {
 		return "", fmt.Errorf("%w: sort field is required", ErrInvalidCursor)
 	}
@@ -35,22 +37,28 @@ func encodePageCursor(sortField string, sortOrder int, sortValue interface{}, id
 	}
 
 	payload, err := json.Marshal(pageCursor{
-		V:         pageCursorVersion,
-		SortField: sortField,
-		SortOrder: sortOrder,
-		ValueType: valueType,
-		SortValue: sortValueStr,
-		ID:        id,
+		V:           pageCursorVersion,
+		SortField:   sortField,
+		SortOrder:   sortOrder,
+		ValueType:   valueType,
+		SortValue:   sortValueStr,
+		ID:          id,
+		FiltersHash: filtersHash,
+		PageOffset:  pageOffset,
 	})
 	if err != nil {
 		return "", fmt.Errorf("failed to marshal cursor: %w", err)
 	}
 
-	return base64.StdEncoding.EncodeToString(payload), nil
+	return base64.RawURLEncoding.EncodeToString(payload), nil
 }
 
 func decodePageCursor(encoded string) (*pageCursor, error) {
-	cursorBytes, err := base64.StdEncoding.DecodeString(encoded)
+	cursorBytes, err := base64.RawURLEncoding.DecodeString(encoded)
+	if err != nil {
+		// Accept standard Base64 cursors issued before URL-safe encoding.
+		cursorBytes, err = base64.StdEncoding.DecodeString(encoded)
+	}
 	if err != nil {
 		return nil, fmt.Errorf("%w: invalid cursor encoding", ErrInvalidCursor)
 	}