package cursortoken import ( "encoding/base32" "encoding/json" "go.mongodb.org/mongo-driver/bson/primitive" "gogs.mikescher.com/BlackForestBytes/goext/exerr" "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{}, exerr.New(exerr.TypeCursorTokenDecode, "could not decode token, missing prefix").Str("token", tok).Build() } 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{}, exerr.Wrap(err, "failed to deserialize token").Str("token", tok).Build() } 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 } }