package utl

import (
	"fmt"
	"github.com/dgrijalva/jwt-go"
	"time"
)

type Tokenizer struct {
	key   string        // key
	lasts time.Duration // valid period
}

func NewToken(key string, lasts time.Duration) *Tokenizer {
	return &Tokenizer{
		key:   key,
		lasts: lasts,
	}
}

func (self *Tokenizer) Gen(id uint64) (string, error) {
	clm := jwt.MapClaims{}
	clm["uid"] = id
	clm["exp"] = time.Now().Add(self.lasts)
	tok := jwt.NewWithClaims(jwt.SigningMethodHS512, clm)
	return tok.SignedString(self.key)
}

func (self *Tokenizer) Parse(tokenstr string) (uint64, error) {
	tok, err := jwt.Parse(tokenstr, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return self.key, nil
	})
	if err != nil {
		return 0, err
	}
	clm, ok := tok.Claims.(jwt.MapClaims)
	if !ok || !tok.Valid {
		return 0, err
	}
	return clm["uid"].(uint64), nil
}