shad-go/retryupdate/update.go

//go:build !solution

package retryupdate

import (
	"errors"
	"fmt"

	"github.com/gofrs/uuid"
	"gitlab.com/slon/shad-go/retryupdate/kvapi"
)

var (
	authError     *kvapi.AuthError
	conflictError *kvapi.ConflictError
)

func UpdateValue(c kvapi.Client, key string, updateFn func(oldValue *string) (newValue string, err error)) error {
	newVersion := uuid.Must(uuid.NewV4())
get:
	for {
		old, err := c.Get(&kvapi.GetRequest{Key: key})
		var value *string
		oldUuid := uuid.Nil
		if err != nil {
			switch {
			case errors.As(err, &authError):
				return err
			case !errors.Is(err, kvapi.ErrKeyNotFound):
				continue
			}
		} else {
			value = &old.Value
			oldUuid = old.Version
		}
		for {
			new, err := updateFn(value)
			if err != nil {
				return err
			}
			_, err = c.Set(&kvapi.SetRequest{
				Key:        key,
				Value:      new,
				OldVersion: oldUuid,
				NewVersion: newVersion,
			})
			if err != nil {
				fmt.Println(err)
				switch {
				case errors.As(err, &conflictError):
					if conflictError.ExpectedVersion == newVersion {
						return nil
					}
					continue get
				case errors.Is(err, kvapi.ErrKeyNotFound):
					value = nil
					oldUuid = uuid.Nil
					continue
				case errors.As(err, &authError):
					return err
				default:
					continue
				}
			}
			return nil
		}
	}
}