pulid.go

// Copyright 2019-present Facebook
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package pulid implements the pulid type.
// A pulid is an identifier that is a two-byte prefixed ULIDs, with the first two bytes encoding the type of the entity.
package pulid

import (
	"crypto/rand"
	"database/sql/driver"
	"fmt"
	"io"
	"strconv"
	"time"

	"github.com/oklog/ulid/v2"
)

// ID implements a PULID - a prefixed ULID.
type ID string

// The default entropy source.
var defaultEntropySource *ulid.MonotonicEntropy

func init() {
	// Seed the default entropy source.
	// TODO: To improve testability, this package should allow control of entropy sources and the time.Now implementation.
	defaultEntropySource = ulid.Monotonic(rand.Reader, 0)
}

// newULID returns a new ULID for time.Now() using the default entropy source.
func newULID() ulid.ULID {
	return ulid.MustNew(ulid.Timestamp(time.Now()), defaultEntropySource)
}

// MustNew returns a new PULID for time.Now() given a prefix. This uses the default entropy source.
func MustNew(prefix string) ID { return ID(prefix + fmt.Sprint(newULID())) }

// UnmarshalGQL implements the graphql.Unmarshaler interface
func (u *ID) UnmarshalGQL(v interface{}) error {
	return u.Scan(v)
}

// MarshalGQL implements the graphql.Marshaler interface
func (u ID) MarshalGQL(w io.Writer) {
	_, _ = io.WriteString(w, strconv.Quote(string(u)))
}

// Scan implements the Scanner interface.
func (u *ID) Scan(src interface{}) error {
	if src == nil {
		return fmt.Errorf("pulid: expected a value")
	}
	s, ok := src.(string)
	if !ok {
		return fmt.Errorf("pulid: expected a string")
	}
	*u = ID(s)
	return nil
}

// Value implements the driver Valuer interface.
func (u ID) Value() (driver.Value, error) {
	return string(u), nil
}