a301_server/internal/auth/service.go

package auth

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"

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

const refreshTokenExpiry = 7 * 24 * time.Hour

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}
}

func (s *Service) SetWalletCreator(fn func(userID uint) error) {
	s.walletCreator = fn
}

func (s *Service) Login(username, password string) (accessToken, refreshToken string, user *User, err 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")
	}

	accessToken, err = s.issueAccessToken(user)
	if err != nil {
		return "", "", nil, err
	}

	refreshToken, err = s.issueRefreshToken(user)
	if err != nil {
		return "", "", nil, err
	}

	return accessToken, refreshToken, user, nil
}

func (s *Service) issueAccessToken(user *User) (string, error) {
	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 "", fmt.Errorf("토큰 생성에 실패했습니다")
	}

	key := fmt.Sprintf("session:%d", user.ID)
	if err := s.rdb.Set(context.Background(), key, tokenStr, expiry).Err(); err != nil {
		return "", fmt.Errorf("세션 저장에 실패했습니다")
	}

	return tokenStr, nil
}

func (s *Service) issueRefreshToken(user *User) (string, error) {
	claims := &Claims{
		UserID:   user.ID,
		Username: user.Username,
		Role:     string(user.Role),
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(refreshTokenExpiry)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	tokenStr, err := token.SignedString([]byte(config.C.RefreshSecret))
	if err != nil {
		return "", fmt.Errorf("리프레시 토큰 생성에 실패했습니다")
	}

	key := fmt.Sprintf("refresh:%d", user.ID)
	if err := s.rdb.Set(context.Background(), key, tokenStr, refreshTokenExpiry).Err(); err != nil {
		return "", fmt.Errorf("리프레시 토큰 저장에 실패했습니다")
	}

	return tokenStr, nil
}

// Refresh validates a refresh token and issues a new access + refresh token pair (rotation).
func (s *Service) Refresh(refreshTokenStr string) (newAccessToken, newRefreshToken string, err error) {
	token, err := jwt.ParseWithClaims(refreshTokenStr, &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.RefreshSecret), nil
	})
	if err != nil || !token.Valid {
		return "", "", fmt.Errorf("유효하지 않은 리프레시 토큰입니다")
	}

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

	// Redis에서 저장된 리프레시 토큰과 비교
	key := fmt.Sprintf("refresh:%d", claims.UserID)
	stored, err := s.rdb.Get(context.Background(), key).Result()
	if err != nil || stored != refreshTokenStr {
		return "", "", fmt.Errorf("만료되었거나 유효하지 않은 리프레시 토큰입니다")
	}

	user := &User{ID: claims.UserID, Username: claims.Username, Role: Role(claims.Role)}

	newAccessToken, err = s.issueAccessToken(user)
	if err != nil {
		return "", "", err
	}

	// 리프레시 토큰 로테이션
	newRefreshToken, err = s.issueRefreshToken(user)
	if err != nil {
		return "", "", err
	}

	return newAccessToken, newRefreshToken, nil
}

func (s *Service) Logout(userID uint) error {
	ctx := context.Background()
	sessionKey := fmt.Sprintf("session:%d", userID)
	refreshKey := fmt.Sprintf("refresh:%d", userID)
	return s.rdb.Del(ctx, sessionKey, refreshKey).Err()
}

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

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

func (s *Service) DeleteUser(id uint) 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("wallet creation failed for user %d: %v — rolling back", user.ID, err)
			if delErr := s.repo.Delete(user.ID); delErr != nil {
				log.Printf("WARNING: rollback delete also failed for user %d: %v", user.ID, delErr)
			}
			return fmt.Errorf("계정 초기화에 실패했습니다. 잠시 후 다시 시도해주세요")
		}
	}
	return nil
}

// GetSSAFYLoginURL returns the SSAFY OAuth authorization URL.
func (s *Service) GetSSAFYLoginURL() string {
	params := url.Values{
		"client_id":     {config.C.SSAFYClientID},
		"redirect_uri":  {config.C.SSAFYRedirectURI},
		"response_type": {"code"},
	}
	return "https://project.ssafy.com/oauth/sso-check?" + params.Encode()
}

// ExchangeSSAFYCode exchanges an authorization code for SSAFY tokens.
func (s *Service) ExchangeSSAFYCode(code string) (*SSAFYTokenResponse, error) {
	data := url.Values{
		"grant_type":    {"authorization_code"},
		"client_id":     {config.C.SSAFYClientID},
		"client_secret": {config.C.SSAFYClientSecret},
		"redirect_uri":  {config.C.SSAFYRedirectURI},
		"code":          {code},
	}

	resp, err := http.Post(
		"https://project.ssafy.com/ssafy/oauth2/token",
		"application/x-www-form-urlencoded;charset=utf-8",
		strings.NewReader(data.Encode()),
	)
	if err != nil {
		return nil, fmt.Errorf("SSAFY 토큰 요청 실패: %v", err)
	}
	defer resp.Body.Close()

	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("SSAFY 토큰 발급 실패 (status %d): %s", resp.StatusCode, string(body))
	}

	var tokenResp SSAFYTokenResponse
	if err := json.Unmarshal(body, &tokenResp); err != nil {
		return nil, fmt.Errorf("SSAFY 토큰 응답 파싱 실패: %v", err)
	}
	return &tokenResp, nil
}

// GetSSAFYUserInfo fetches user info from SSAFY using an access token.
func (s *Service) GetSSAFYUserInfo(accessToken string) (*SSAFYUserInfo, error) {
	req, _ := http.NewRequest("GET", "https://project.ssafy.com/ssafy/resources/userInfo", nil)
	req.Header.Set("Authorization", "Bearer "+accessToken)
	req.Header.Set("Content-type", "application/x-www-form-urlencoded;charset=utf-8")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("SSAFY 사용자 정보 요청 실패: %v", err)
	}
	defer resp.Body.Close()

	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("SSAFY 사용자 정보 조회 실패 (status %d): %s", resp.StatusCode, string(body))
	}

	var userInfo SSAFYUserInfo
	if err := json.Unmarshal(body, &userInfo); err != nil {
		return nil, fmt.Errorf("SSAFY 사용자 정보 파싱 실패: %v", err)
	}
	return &userInfo, nil
}

// SSAFYLogin handles the full SSAFY OAuth callback: exchange code, get user info, find or create user, issue tokens.
func (s *Service) SSAFYLogin(code string) (accessToken, refreshToken string, user *User, err error) {
	tokenResp, err := s.ExchangeSSAFYCode(code)
	if err != nil {
		return "", "", nil, err
	}

	userInfo, err := s.GetSSAFYUserInfo(tokenResp.AccessToken)
	if err != nil {
		return "", "", nil, err
	}

	// SSAFY ID로 기존 사용자 조회
	user, err = s.repo.FindBySsafyID(userInfo.UserID)
	if err != nil {
		// 신규 사용자 자동 가입
		randomBytes := make([]byte, 16)
		rand.Read(randomBytes)
		randomPassword := hex.EncodeToString(randomBytes)

		hash, err := bcrypt.GenerateFromPassword([]byte(randomPassword), bcrypt.DefaultCost)
		if err != nil {
			return "", "", nil, fmt.Errorf("계정 생성 실패")
		}

		ssafyID := userInfo.UserID
		username := "ssafy_" + ssafyID
		user = &User{
			Username:     username,
			PasswordHash: string(hash),
			Role:         RoleUser,
			SsafyID:      &ssafyID,
		}
		if err := s.repo.Create(user); err != nil {
			return "", "", nil, fmt.Errorf("계정 생성 실패: %v", err)
		}
		if s.walletCreator != nil {
			if err := s.walletCreator(user.ID); err != nil {
				log.Printf("wallet creation failed for SSAFY user %d: %v — rolling back", user.ID, err)
				if delErr := s.repo.Delete(user.ID); delErr != nil {
					log.Printf("WARNING: rollback delete also failed for SSAFY user %d: %v", user.ID, delErr)
				}
				return "", "", nil, fmt.Errorf("계정 초기화에 실패했습니다. 잠시 후 다시 시도해주세요")
			}
		}
	}

	accessToken, err = s.issueAccessToken(user)
	if err != nil {
		return "", "", nil, err
	}

	refreshToken, err = s.issueRefreshToken(user)
	if err != nil {
		return "", "", nil, err
	}

	return accessToken, refreshToken, user, 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
	}
	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return err
	}
	user := &User{
		Username:     username,
		PasswordHash: string(hash),
		Role:         RoleAdmin,
	}
	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: admin wallet creation failed for user %d: %v", user.ID, err)
		}
	}
	return nil
}