goext/cursortoken/token.go

package cursortoken

import (
	"encoding/base32"
	"encoding/json"
	"gogs.mikescher.com/BlackForestBytes/goext/exerr"
	"strconv"
	"strings"
	"time"
)

type CursorToken interface {
	Token() string
	IsStart() bool
	IsEnd() bool
}

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
}

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.ToLower(tok) == "$end" {
		return PageEnd(), nil
	}
	if strings.HasPrefix(tok, "$") && len(tok) > 1 {
		n, err := strconv.ParseInt(tok[1:], 10, 64)
		if err != nil {
			return nil, exerr.Wrap(err, "failed to deserialize token").Str("token", tok).WithType(exerr.TypeCursorTokenDecode).Build()
		}
		return Page(int(n)), nil
	}

	if strings.HasPrefix(tok, "tok_") {

		body, err := base32.StdEncoding.DecodeString(tok[len("tok_"):])
		if err != nil {
			return nil, err
		}

		var tokenDeserialize cursorTokenKeySortSerialize
		err = json.Unmarshal(body, &tokenDeserialize)
		if err != nil {
			return nil, exerr.Wrap(err, "failed to deserialize token").Str("token", tok).WithType(exerr.TypeCursorTokenDecode).Build()
		}

		token := CTKeySort{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

	} else {
		return nil, exerr.New(exerr.TypeCursorTokenDecode, "could not decode token, missing/unknown prefix").Str("token", tok).Build()
	}
}