package subordinate

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/hex"
	"math/big"
)

const (
	// 邀请码固定 6 位，字符集为大写字母+数字
	inviteTokenLength  = 6
	inviteTokenCharset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
)

// HashInviteToken 邀请码 SHA256 十六进制
func HashInviteToken(raw string) string {
	sum := sha256.Sum256([]byte(raw))
	return hex.EncodeToString(sum[:])
}

// GenerateInviteToken 生成随机邀请明文与存储用哈希
func GenerateInviteToken() (raw string, hash string, err error) {
	token := make([]byte, inviteTokenLength)
	charsetSize := big.NewInt(int64(len(inviteTokenCharset)))
	for i := range token {
		n, e := rand.Int(rand.Reader, charsetSize)
		if e != nil {
			return "", "", e
		}
		token[i] = inviteTokenCharset[n.Int64()]
	}
	raw = string(token)
	return raw, HashInviteToken(raw), nil
}