v0.0.133

wmo/pagination.go

@@ -0,0 +1,69 @@
+package wmo
+
+import (
+	"go.mongodb.org/mongo-driver/bson"
+	ct "gogs.mikescher.com/BlackForestBytes/goext/cursortoken"
+)
+
+func CreatePagination[TData any](coll *Coll[TData], token ct.CursorToken, fieldPrimary string, sortPrimary ct.SortDirection, fieldSecondary *string, sortSecondary *ct.SortDirection, pageSize *int) ([]bson.D, error) {
+
+	cond := bson.A{}
+	sort := bson.D{}
+
+	valuePrimary, err := coll.getTokenValueAsMongoType(token.ValuePrimary, fieldPrimary)
+	if err != nil {
+		return nil, err
+	}
+
+	if sortPrimary == ct.SortASC {
+		// We sort ASC on <field> - so we want all entries newer ($gt) than the $primary
+		cond = append(cond, bson.M{fieldPrimary: bson.M{"$gt": valuePrimary}})
+		sort = append(sort, bson.E{Key: fieldPrimary, Value: +1})
+	} else if sortPrimary == ct.SortDESC {
+		// We sort DESC on <field> - so we want all entries older ($lt) than the $primary
+		cond = append(cond, bson.M{fieldPrimary: bson.M{"$lt": valuePrimary}})
+		sort = append(sort, bson.E{Key: fieldPrimary, Value: -1})
+	}
+
+	if fieldSecondary != nil && sortSecondary != nil && *fieldSecondary != fieldPrimary {
+
+		valueSecondary, err := coll.getTokenValueAsMongoType(token.ValueSecondary, *fieldSecondary)
+		if err != nil {
+			return nil, err
+		}
+
+		if *sortSecondary == ct.SortASC {
+
+			// the conflict-resolution condition, for entries with the _same_ <field> as the $primary we take the ones with a greater $secondary (= newer)
+			cond = append(cond, bson.M{"$and": bson.A{
+				bson.M{fieldPrimary: valuePrimary},
+				bson.M{*fieldSecondary: bson.M{"$gt": valueSecondary}},
+			}})
+
+			sort = append(sort, bson.E{Key: fieldPrimary, Value: +1})
+
+		} else if *sortSecondary == ct.SortDESC {
+
+			// the conflict-resolution condition, for entries with the _same_ <field> as the $primary we take the ones with a smaller $secondary (= older)
+			cond = append(cond, bson.M{"$and": bson.A{
+				bson.M{fieldPrimary: valuePrimary},
+				bson.M{*fieldSecondary: bson.M{"$lt": valueSecondary}},
+			}})
+
+			sort = append(sort, bson.E{Key: fieldPrimary, Value: -1})
+
+		}
+	}
+
+	pipeline := make([]bson.D, 0, 3)
+
+	pipeline = append(pipeline, bson.D{{Key: "$match", Value: bson.M{"$or": cond}}})
+
+	pipeline = append(pipeline, bson.D{{Key: "$sort", Value: sort}})
+
+	if pageSize != nil {
+		pipeline = append(pipeline, bson.D{{Key: "$limit", Value: int64(*pageSize + 1)}})
+	}
+
+	return pipeline, nil
+}