package auth

import (
	"context"
	"fmt"
	"log"
	"time"

	"a301_server/pkg/config"
	"github.com/golang-jwt/jwt/v5"
	"github.com/redis/go-redis/v9"
	"golang.org/x/crypto/bcrypt"
)

type Claims struct {
	UserID   uint   `json:"user_id"`
	Username string `json:"username"`
	Role     string `json:"role"`
	jwt.RegisteredClaims
}

type Service struct {
	repo          *Repository
	rdb           *redis.Client
	walletCreator func(userID uint) error
}

func NewService(repo *Repository, rdb *redis.Client) *Service {
	return &Service{repo: repo, rdb: rdb}
}

// SetWalletCreator sets the callback invoked after user registration
// to create a blockchain wallet.
func (s *Service) SetWalletCreator(fn func(userID uint) error) {
	s.walletCreator = fn
}

func (s *Service) Login(username, password string) (string, *User, error) {
	user, err := s.repo.FindByUsername(username)
	if err != nil {
		return "", nil, fmt.Errorf("아이디 또는 비밀번호가 올바르지 않습니다")
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(password)); err != nil {
		return "", nil, fmt.Errorf("아이디 또는 비밀번호가 올바르지 않습니다")
	}

	expiry := time.Duration(config.C.JWTExpiryHours) * time.Hour
	claims := &Claims{
		UserID:   user.ID,
		Username: user.Username,
		Role:     string(user.Role),
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(expiry)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenStr, err := token.SignedString([]byte(config.C.JWTSecret))
	if err != nil {
		return "", nil, fmt.Errorf("토큰 생성에 실패했습니다")
	}

	// Redis에 세션 저장 (1계정 1세션)
	key := fmt.Sprintf("session:%d", user.ID)
	s.rdb.Set(context.Background(), key, tokenStr, expiry)

	return tokenStr, user, nil
}

func (s *Service) Logout(userID uint) {
	key := fmt.Sprintf("session:%d", userID)
	s.rdb.Del(context.Background(), key)
}

func (s *Service) GetAllUsers() ([]User, error) {
	return s.repo.FindAll()
}

func (s *Service) UpdateRole(id string, role Role) error {
	return s.repo.UpdateRole(id, role)
}

func (s *Service) DeleteUser(id string) error {
	return s.repo.Delete(id)
}

func (s *Service) Register(username, password string) error {
	if _, err := s.repo.FindByUsername(username); err == nil {
		return fmt.Errorf("이미 사용 중인 아이디입니다")
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return fmt.Errorf("비밀번호 처리에 실패했습니다")
	}
	user := &User{
		Username:     username,
		PasswordHash: string(hash),
		Role:         RoleUser,
	}
	if err := s.repo.Create(user); err != nil {
		return err
	}
	if s.walletCreator != nil {
		if err := s.walletCreator(user.ID); err != nil {
			log.Printf("WARNING: wallet creation failed for user %d: %v", user.ID, err)
		}
	}
	return nil
}

// VerifyToken validates a JWT and its Redis session, returning (username, error).
func (s *Service) VerifyToken(tokenStr string) (string, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (any, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, fmt.Errorf("unexpected signing method")
		}
		return []byte(config.C.JWTSecret), nil
	})
	if err != nil || !token.Valid {
		return "", fmt.Errorf("유효하지 않은 토큰입니다")
	}

	claims, ok := token.Claims.(*Claims)
	if !ok {
		return "", fmt.Errorf("토큰 파싱 실패")
	}

	key := fmt.Sprintf("session:%d", claims.UserID)
	stored, err := s.rdb.Get(context.Background(), key).Result()
	if err != nil || stored != tokenStr {
		return "", fmt.Errorf("만료되었거나 로그아웃된 세션입니다")
	}

	return claims.Username, nil
}

func (s *Service) EnsureAdmin(username, password string) error {
	if _, err := s.repo.FindByUsername(username); err == nil {
		return nil // 이미 존재하면 스킵
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return err
	}
	return s.repo.Create(&User{
		Username:     username,
		PasswordHash: string(hash),
		Role:         RoleAdmin,
	})
}