goext/wmo/pagination.go
2023-06-07 17:57:03 +02:00

88 lines
2.7 KiB
Go

package wmo
import (
"errors"
"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{"$lt": valueSecondary}},
}})
sort = append(sort, bson.E{Key: fieldPrimary, Value: -1})
}
}
pipeline := make([]bson.D, 0, 3)
if token.Mode == ct.CTMStart {
// no gt/lt condition
} else if token.Mode == ct.CTMNormal {
pipeline = append(pipeline, bson.D{{Key: "$match", Value: bson.M{"$or": cond}}})
} else if token.Mode == ct.CTMEnd {
// false
pipeline = append(pipeline, bson.D{{Key: "$match", Value: bson.M{"$expr": bson.M{"$eq": bson.A{"1", "0"}}}}})
} else {
return nil, errors.New("unknown ct mode: " + string(token.Mode))
}
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
}