package renewchange

import (
	"crypto/rand"
	"fmt"
	"strings"
	"time"

	"github.com/gogf/gf/v2/errors/gerror"
)

const businessNoAlphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"

// NextOrderSN returns a production order number before any INSERT is issued.
func NextOrderSN(now time.Time) (string, error) {
	suffix, err := randomBusinessNoSuffix(8)
	if err != nil {
		return "", err
	}
	return fmt.Sprintf("SO%s%s", now.Format("20060102150405"), suffix), nil
}

func randomBusinessNoSuffix(length int) (string, error) {
	if length <= 0 {
		return "", gerror.New("business number suffix length must be greater than zero")
	}
	randomBytes := make([]byte, length)
	if _, err := rand.Read(randomBytes); err != nil {
		return "", gerror.Wrap(err, "generate business number suffix failed")
	}
	buf := make([]byte, length)
	for i, value := range randomBytes {
		buf[i] = businessNoAlphabet[int(value)%len(businessNoAlphabet)]
	}
	return string(buf), nil
}

// GenerateOrderSn 形如 "yyyyMMddHHmmssfff"+6位随机后缀
func GenerateOrderSn(t *time.Time) string {
	now := time.Now()
	if t != nil {
		now = *t
	}
	return fmt.Sprintf("%s%06d", now.UTC().Format("20060102150405.000")[0:14], now.Nanosecond()/1000%1000000)
}

// GenerateSubscriptionNo 形如 "SUB" + yyyyMMddHHmmss + 6位后缀
func GenerateSubscriptionNo(prefix string) string {
	now := time.Now()
	if strings.TrimSpace(prefix) == "" {
		prefix = "SUB"
	}
	return fmt.Sprintf("%s%s%06d", prefix, now.UTC().Format("20060102150405"), now.Nanosecond()/1000%1000000)
}