package auth

import (
	"context"
	"errors"
	"time"

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

type Claims struct {
	UserID uuid.UUID `json:"uid"`
	jwt.RegisteredClaims
}

type Tokens struct {
	Access  string
	Refresh string
}

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

func NewService(secret string, accessTTL, refreshTTL time.Duration) *Service {
	return &Service{
		secret:     []byte(secret),
		accessTTL:  accessTTL,
		refreshTTL: refreshTTL,
	}
}

func (s *Service) Generate(userID uuid.UUID) (*Tokens, error) {
	now := time.Now()

	access := jwt.NewWithClaims(jwt.SigningMethodHS256, Claims{
		UserID: userID,
		RegisteredClaims: jwt.RegisteredClaims{
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(s.accessTTL)),
			Subject:   userID.String(),
		},
	})
	accessStr, err := access.SignedString(s.secret)
	if err != nil {
		return nil, err
	}

	refresh := jwt.NewWithClaims(jwt.SigningMethodHS256, Claims{
		UserID: userID,
		RegisteredClaims: jwt.RegisteredClaims{
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(s.refreshTTL)),
			Subject:   userID.String(),
		},
	})
	refreshStr, err := refresh.SignedString(s.secret)
	if err != nil {
		return nil, err
	}

	return &Tokens{Access: accessStr, Refresh: refreshStr}, nil
}

func (s *Service) Parse(ctx context.Context, tokenStr string) (*Claims, error) {
	claims := &Claims{}
	tok, err := jwt.ParseWithClaims(tokenStr, claims, func(t *jwt.Token) (interface{}, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, errors.New("unexpected signing method")
		}
		return s.secret, nil
	})
	if err != nil || !tok.Valid {
		return nil, errors.New("invalid token")
	}
	return claims, nil
}