package auth

import (
	"fmt"
	"time"

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

type Claims struct {
	UserID string `json:"user_id"`
	Email  string `json:"email"`
	jwt.RegisteredClaims
}

type JWTService struct {
	secret []byte
	expiry time.Duration
}

func NewJWTService(secret string, expiryHours int) *JWTService {
	return &JWTService{
		secret: []byte(secret),
		expiry: time.Duration(expiryHours) * time.Hour,
	}
}

func (s *JWTService) GenerateToken(userID, email string) (string, error) {
	claims := Claims{
		UserID: userID,
		Email:  email,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(s.expiry)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(s.secret)
}

func (s *JWTService) ValidateToken(tokenString string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, 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 s.secret, nil
	})

	if err != nil {
		return nil, err
	}

	if claims, ok := token.Claims.(*Claims); ok && token.Valid {
		return claims, nil
	}

	return nil, fmt.Errorf("invalid token")
}