package auth

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"time"

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

type Claims struct {
	UserID   uint   `json:"user_id"`
	Username string `json:"username"`
	Timezone string `json:"timezone"`
	Type     string `json:"type"`
	jwt.RegisteredClaims
}

type TokenManager struct {
	secret           []byte
	accessTTLMinutes int
	refreshTTLHours  int
}

func (tm *TokenManager) RefreshMaxAgeSeconds() int {
	return tm.refreshTTLHours * 3600
}

func NewTokenManager(secret string, accessTTLMinutes, refreshTTLHours int) *TokenManager {
	return &TokenManager{
		secret:           []byte(secret),
		accessTTLMinutes: accessTTLMinutes,
		refreshTTLHours:  refreshTTLHours,
	}
}

func (tm *TokenManager) GenerateAccessToken(userID uint, username, timezone string) (string, error) {
	now := time.Now().UTC()
	claims := Claims{
		UserID:   userID,
		Username: username,
		Timezone: timezone,
		Type:     "access",
		RegisteredClaims: jwt.RegisteredClaims{
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(time.Duration(tm.accessTTLMinutes) * time.Minute)),
			Subject:   username,
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(tm.secret)
}

func (tm *TokenManager) GenerateRefreshToken(userID uint, username, timezone string) (string, string, time.Time, error) {
	now := time.Now().UTC()
	expiresAt := now.Add(time.Duration(tm.refreshTTLHours) * time.Hour)
	jti, err := randomJTI()
	if err != nil {
		return "", "", time.Time{}, err
	}
	claims := Claims{
		UserID:   userID,
		Username: username,
		Timezone: timezone,
		Type:     "refresh",
		RegisteredClaims: jwt.RegisteredClaims{
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(expiresAt),
			Subject:   username,
			ID:        jti,
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenStr, err := token.SignedString(tm.secret)
	if err != nil {
		return "", "", time.Time{}, err
	}
	return tokenStr, jti, expiresAt, nil
}

func (tm *TokenManager) ParseAndValidate(tokenStr string, expectedType string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return tm.secret, nil
	})
	if err != nil {
		return nil, err
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, errors.New("invalid token")
	}
	if claims.Type != expectedType {
		return nil, errors.New("invalid token type")
	}
	return claims, nil
}

func randomJTI() (string, error) {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return hex.EncodeToString(b), nil
}