package auth

import (
	"fmt"
	"time"

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

const (
	defaultAccessTTL = 7200 * time.Second
	refreshTTL       = 30 * 24 * time.Hour
)

type JWTManager struct {
	secret        []byte
	refreshSecret []byte
	accessTTL     time.Duration
	refreshTTL    time.Duration
}

func NewJWTManager(secret, refreshSecret string) *JWTManager {
	return &JWTManager{
		secret:        []byte(secret),
		refreshSecret: []byte(refreshSecret),
		accessTTL:     defaultAccessTTL,
		refreshTTL:    refreshTTL,
	}
}

func (m *JWTManager) GenerateAccessToken(claims Claims) (string, error) {
	now := time.Now()
	claims.RegisteredClaims = jwt.RegisteredClaims{
		ExpiresAt: jwt.NewNumericDate(now.Add(m.accessTTL)),
		IssuedAt:  jwt.NewNumericDate(now),
		Subject:   claims.UserID,
	}

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

func (m *JWTManager) GenerateRefreshToken(userID string) (string, error) {
	now := time.Now()
	claims := jwt.RegisteredClaims{
		ExpiresAt: jwt.NewNumericDate(now.Add(m.refreshTTL)),
		IssuedAt:  jwt.NewNumericDate(now),
		Subject:   userID,
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(m.refreshSecret)
}

func (m *JWTManager) ParseAccessToken(tokenStr string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
		}
		return m.secret, nil
	})
	if err != nil {
		return nil, fmt.Errorf("parse access token: %w", err)
	}

	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, fmt.Errorf("invalid access token")
	}

	return claims, nil
}

func (m *JWTManager) ParseRefreshToken(tokenStr string) (string, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &jwt.RegisteredClaims{}, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
		}
		return m.refreshSecret, nil
	})
	if err != nil {
		return "", fmt.Errorf("parse refresh token: %w", err)
	}

	claims, ok := token.Claims.(*jwt.RegisteredClaims)
	if !ok || !token.Valid {
		return "", fmt.Errorf("invalid refresh token")
	}

	return claims.Subject, nil
}