goext/cursortoken/token.go

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2023-06-06 21:18:40 +02:00
package cursortoken
import (
"encoding/base32"
"encoding/json"
"errors"
"go.mongodb.org/mongo-driver/bson/primitive"
"strings"
"time"
)
type Mode string
const (
CTMStart Mode = "START"
CTMNormal Mode = "NORMAL"
CTMEnd Mode = "END"
)
type Extra struct {
Timestamp *time.Time
Id *string
Page *int
PageSize *int
}
type CursorToken struct {
Mode Mode
ValuePrimary string
ValueSecondary string
Direction SortDirection
DirectionSecondary SortDirection
PageSize int
Extra Extra
}
type cursorTokenSerialize 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 Start() CursorToken {
return CursorToken{
Mode: CTMStart,
ValuePrimary: "",
ValueSecondary: "",
Direction: "",
DirectionSecondary: "",
PageSize: 0,
Extra: Extra{},
}
}
func End() CursorToken {
return CursorToken{
Mode: CTMEnd,
ValuePrimary: "",
ValueSecondary: "",
Direction: "",
DirectionSecondary: "",
PageSize: 0,
Extra: Extra{},
}
}
func (c *CursorToken) 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 := cursorTokenSerialize{}
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 Decode(tok string) (CursorToken, error) {
if tok == "" {
return Start(), nil
}
if strings.ToLower(tok) == "@start" {
return Start(), nil
}
if strings.ToLower(tok) == "@end" {
return End(), nil
}
if !strings.HasPrefix(tok, "tok_") {
return CursorToken{}, errors.New("could not decode token, missing prefix")
}
body, err := base32.StdEncoding.DecodeString(tok[len("tok_"):])
if err != nil {
return CursorToken{}, err
}
var tokenDeserialize cursorTokenSerialize
err = json.Unmarshal(body, &tokenDeserialize)
if err != nil {
return CursorToken{}, err
}
token := CursorToken{Mode: CTMNormal}
if tokenDeserialize.ValuePrimary != nil {
token.ValuePrimary = *tokenDeserialize.ValuePrimary
}
if tokenDeserialize.ValueSecondary != nil {
token.ValueSecondary = *tokenDeserialize.ValueSecondary
}
if tokenDeserialize.Direction != nil {
token.Direction = *tokenDeserialize.Direction
}
if tokenDeserialize.DirectionSecondary != nil {
token.DirectionSecondary = *tokenDeserialize.DirectionSecondary
}
if tokenDeserialize.PageSize != nil {
token.PageSize = *tokenDeserialize.PageSize
}
token.Extra.Timestamp = tokenDeserialize.ExtraTimestamp
token.Extra.Id = tokenDeserialize.ExtraId
token.Extra.Page = tokenDeserialize.ExtraPage
token.Extra.PageSize = tokenDeserialize.ExtraPageSize
return token, nil
}
func (c *CursorToken) ValuePrimaryObjectId() (primitive.ObjectID, bool) {
if oid, err := primitive.ObjectIDFromHex(c.ValuePrimary); err == nil {
return oid, true
} else {
return primitive.ObjectID{}, false
}
}
func (c *CursorToken) ValueSecondaryObjectId() (primitive.ObjectID, bool) {
if oid, err := primitive.ObjectIDFromHex(c.ValueSecondary); err == nil {
return oid, true
} else {
return primitive.ObjectID{}, false
}
}