package auth

import (
	"errors"
	"os"
	"strings"
	"time"

	"github.com/golang-jwt/jwt/v5"
)

var jwtKey = []byte(os.Getenv("JWT_SECRET"))

type Claims struct {
	UserID int `json:"user_id"`
	jwt.RegisteredClaims
}

func GenerateJWT(userID int) (string, error) {
	expirationTime := time.Now().Add(5 * time.Hour)
	claims := &Claims{
		UserID: userID,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(expirationTime),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenString, err := token.SignedString(jwtKey)
	if err != nil {
		return "", err
	}
	return tokenString, nil
}

func ValidateJWT(tokenString string) (*Claims, error) {
	claims := &Claims{}
	// A token has a form `Bearer ...`
	tokenParts := strings.Split(tokenString, " ")
	if len(tokenParts) != 2 {
		return nil, errors.New("not valid JWT")
	}

	token, err := jwt.ParseWithClaims(tokenParts[1], claims, func(token *jwt.Token) (interface{}, error) {
		return jwtKey, nil
	})

	if err != nil {
		return nil, err
	}

	if !token.Valid {
		return nil, err
	}

	return claims, nil
}