Trying out paginated cursortoken variant [UNTESTED]

cursortoken/tokenKeySort.go

@@ -0,0 +1,128 @@
+package cursortoken
+
+import (
+	"encoding/base32"
+	"encoding/json"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"time"
+)
+
+type CTKeySort struct {
+	Mode               Mode
+	ValuePrimary       string
+	ValueSecondary     string
+	Direction          SortDirection
+	DirectionSecondary SortDirection
+	PageSize           int
+	Extra              Extra
+}
+
+type cursorTokenKeySortSerialize struct {
+	ValuePrimary       *string        `json:"v1,omitempty"`
+	ValueSecondary     *string        `json:"v2,omitempty"`
+	Direction          *SortDirection `json:"dir,omitempty"`
+	DirectionSecondary *SortDirection `json:"dir2,omitempty"`
+	PageSize           *int           `json:"size,omitempty"`
+
+	ExtraTimestamp *time.Time `json:"ts,omitempty"`
+	ExtraId        *string    `json:"id,omitempty"`
+	ExtraPage      *int       `json:"pg,omitempty"`
+	ExtraPageSize  *int       `json:"sz,omitempty"`
+}
+
+func NewKeySortToken(valuePrimary string, valueSecondary string, direction SortDirection, directionSecondary SortDirection, pageSize int, extra Extra) CursorToken {
+	return CTKeySort{
+		Mode:               CTMNormal,
+		ValuePrimary:       valuePrimary,
+		ValueSecondary:     valueSecondary,
+		Direction:          direction,
+		DirectionSecondary: directionSecondary,
+		PageSize:           pageSize,
+		Extra:              extra,
+	}
+}
+
+func Start() CursorToken {
+	return CTKeySort{
+		Mode:               CTMStart,
+		ValuePrimary:       "",
+		ValueSecondary:     "",
+		Direction:          "",
+		DirectionSecondary: "",
+		PageSize:           0,
+		Extra:              Extra{},
+	}
+}
+
+func End() CursorToken {
+	return CTKeySort{
+		Mode:               CTMEnd,
+		ValuePrimary:       "",
+		ValueSecondary:     "",
+		Direction:          "",
+		DirectionSecondary: "",
+		PageSize:           0,
+		Extra:              Extra{},
+	}
+}
+
+func (c CTKeySort) Token() string {
+
+	if c.Mode == CTMStart {
+		return "@start"
+	}
+	if c.Mode == CTMEnd {
+		return "@end"
+	}
+
+	// We kinda manually implement omitempty for the CursorToken here
+	// because omitempty does not work for time.Time and otherwise we would always
+	// get weird time values when decoding a token that initially didn't have an Timestamp set
+	// For this usecase we treat Unix=0 as an empty timestamp
+
+	sertok := cursorTokenKeySortSerialize{}
+
+	if c.ValuePrimary != "" {
+		sertok.ValuePrimary = &c.ValuePrimary
+	}
+	if c.ValueSecondary != "" {
+		sertok.ValueSecondary = &c.ValueSecondary
+	}
+	if c.Direction != "" {
+		sertok.Direction = &c.Direction
+	}
+	if c.DirectionSecondary != "" {
+		sertok.DirectionSecondary = &c.DirectionSecondary
+	}
+	if c.PageSize != 0 {
+		sertok.PageSize = &c.PageSize
+	}
+
+	sertok.ExtraTimestamp = c.Extra.Timestamp
+	sertok.ExtraId = c.Extra.Id
+	sertok.ExtraPage = c.Extra.Page
+	sertok.ExtraPageSize = c.Extra.PageSize
+
+	body, err := json.Marshal(sertok)
+	if err != nil {
+		panic(err)
+	}
+
+	return "tok_" + base32.StdEncoding.EncodeToString(body)
+}
+
+func (c CTKeySort) valuePrimaryObjectId() (primitive.ObjectID, bool) {
+	if oid, err := primitive.ObjectIDFromHex(c.ValuePrimary); err == nil {
+		return oid, true
+	} else {
+		return primitive.ObjectID{}, false
+	}
+}
+
+func (c CTKeySort) valueSecondaryObjectId() (primitive.ObjectID, bool) {
+	if oid, err := primitive.ObjectIDFromHex(c.ValueSecondary); err == nil {
+		return oid, true
+	} else {
+		return primitive.ObjectID{}, false
+	}
+}