package auth

import (
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"time"

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

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

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

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

func (m *TokenManager) AccessTTL() time.Duration  { return m.accessTTL }
func (m *TokenManager) RefreshTTL() time.Duration { return m.refreshTTL }

func (m *TokenManager) GenerateAccess(userID, email string) (string, error) {
	now := time.Now()
	claims := Claims{
		UserID: userID,
		Email:  email,
		RegisteredClaims: jwt.RegisteredClaims{
			Subject:   userID,
			IssuedAt:  jwt.NewNumericDate(now),
			ExpiresAt: jwt.NewNumericDate(now.Add(m.accessTTL)),
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString(m.secret)
}

func (m *TokenManager) ParseAccess(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, err
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, fmt.Errorf("invalid token")
	}
	return claims, nil
}

func NewRefreshToken() (raw string, hash string, err error) {
	buf := make([]byte, 32)
	if _, err = rand.Read(buf); err != nil {
		return "", "", err
	}
	raw = base64.RawURLEncoding.EncodeToString(buf)
	return raw, HashRefreshToken(raw), nil
}

func HashRefreshToken(raw string) string {
	sum := sha256.Sum256([]byte(raw))
	return hex.EncodeToString(sum[:])
}

func NewID() string {
	return uuid.NewString()
}