package jwtx

import (
	"encoding/json"
	"errors"
	"time"

	"github.com/dgrijalva/jwt-go"
)

var (
	ErrTokenExpired        error = errors.New("token is expired")
	ErrTokenNotValidYet    error = errors.New("token not active yet")
	ErrTokenMalformed      error = errors.New("that's not even a token")
	ErrTokenInvalid        error = errors.New("couldn't handle this token")
	ErrTokenGenerateFailed error = errors.New("generate token failed!")
)

type jwtx struct {
	SignKey []byte
}

type Claims struct {
	UserData string `json:"user_data"`
	jwt.StandardClaims
}

func NewJWT(signKey string) *jwtx {
	return &jwtx{
		[]byte(signKey),
	}
}

// 仅解析Token
func (j *jwtx) Decode(tokenString string, userData interface{}) error {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		return j.SignKey, nil
	})
	if err != nil {
		if ve, ok := err.(*jwt.ValidationError); ok {
			if ve.Errors&jwt.ValidationErrorMalformed == jwt.ValidationErrorMalformed {
				return ErrTokenMalformed
			} else if ve.Errors&jwt.ValidationErrorExpired == jwt.ValidationErrorExpired {
				// Token is expired
				return ErrTokenExpired
			} else if ve.Errors&jwt.ValidationErrorNotValidYet == jwt.ValidationErrorNotValidYet {
				return ErrTokenNotValidYet
			} else {
				return ErrTokenInvalid
			}
		}
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return ErrTokenInvalid
	}

	return json.Unmarshal([]byte(claims.UserData), userData)

}

// 根据参数生成和设置 token
func (j *jwtx) Encode(userData interface{}, expiresTime time.Time) (string, error) {

	if expiresTime.Before(time.Now()) {
		return "", errors.New("时间无效")
	}

	db, err := json.Marshal(userData)
	if err != nil {
		return "", errors.New("json序列化失败")
	}

	claims := Claims{
		UserData: string(db),
	}

	// 设置有效时间
	claims.StandardClaims.ExpiresAt = expiresTime.Unix()
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(j.SignKey)
	if err != nil {
		return "", ErrTokenGenerateFailed
	}
	return tokenString, nil
}