package auth

import (
	"errors"
	"fmt"
	"time"

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

// Claims represents the JWT claims
type Claims struct {
	UserID uint   `json:"user_id"`
	Email string `json:"email"`
	jwt.RegisteredClaims
}

// GenerateToken creates a new JWT token for a user
func GenerateToken(userID uint, email, secret string, expirationTime time.Duration) (string, error) {
	// Create claims with user ID and expiration time
	claims := &Claims{
		UserID: userID,
		Email: email,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(expirationTime)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
			NotBefore: jwt.NewNumericDate(time.Now()),
			Issuer:    "gomft",
			Subject:   fmt.Sprintf("%d", userID),
		},
	}

	// Create token with claims
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)

	// Sign token with secret
	tokenString, err := token.SignedString([]byte(secret))
	if err != nil {
		return "", err
	}

	return tokenString, nil
}

// ValidateToken validates a JWT token and returns the claims
func ValidateToken(tokenString, secret string) (*Claims, error) {
	// Parse token
	token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		// Validate signing method
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", token.Header["alg"])
		}
		return []byte(secret), nil
	})

	if err != nil {
		return nil, err
	}

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

	return nil, errors.New("invalid token")
}