storj/private/dbutil/nulltime.go

// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package dbutil

import (
	"database/sql/driver"
	"time"

	"github.com/zeebo/errs"
)

const (
	sqliteTimeLayout           = "2006-01-02 15:04:05-07:00"
	sqliteTimeLayoutNoTimeZone = "2006-01-02 15:04:05"
	sqliteTimeLayoutDate       = "2006-01-02"
)

// ErrNullTime defines error class for NullTime.
var ErrNullTime = errs.Class("null time error")

// NullTime time helps convert nil to time.Time.
type NullTime struct {
	time.Time
	Valid bool
}

// Scan implements the Scanner interface.
func (nt *NullTime) Scan(value interface{}) error {
	if value == nil {
		return nil
	}

	// check if it's time.Time which is what postgres returns
	// for lagged time values
	if nt.Time, nt.Valid = value.(time.Time); nt.Valid {
		return nil
	}

	// try to parse time from bytes which is what sqlite returns
	date, ok := value.([]byte)
	if !ok {
		return ErrNullTime.New("sql null time: scan received unsupported value type")
	}

	times, err := parseSqliteTimeString(string(date))
	if err != nil {
		return ErrNullTime.Wrap(err)
	}

	nt.Time, nt.Valid = times, true
	return nil
}

// Value implements the driver Valuer interface.
func (nt NullTime) Value() (driver.Value, error) {
	if !nt.Valid {
		return nil, nil
	}
	return nt.Time, nil
}

// parseSqliteTimeString parses sqlite times string.
// It tries to process value as string with timezone first,
// then fallback to parsing as string without timezone and
// finally to parsing value as date.
func parseSqliteTimeString(val string) (time.Time, error) {
	var times time.Time
	var err error

	times, err = time.Parse(sqliteTimeLayout, val)
	if err == nil {
		return times, nil
	}

	times, err = time.Parse(sqliteTimeLayoutNoTimeZone, val)
	if err == nil {
		return times, nil
	}

	return time.Parse(sqliteTimeLayoutDate, val)
}