package service

import (
	"errors"
	"time"

	"github.com/golang-jwt/jwt/v5"
	"golang.org/x/crypto/bcrypt"

	"github.com/daniil/homelab-api/internal/model"
	"github.com/daniil/homelab-api/internal/repository"
)

var (
	ErrInvalidCredentials = errors.New("invalid credentials")
	ErrInvalidToken       = errors.New("invalid token")
	ErrWeakPassword       = errors.New("password must be at least 8 characters")
	ErrEmailNotVerified   = errors.New("email not verified")
)

type AuthService struct {
	userRepo       *repository.UserRepository
	emailTokenRepo *repository.EmailTokenRepository
	emailService   *EmailService
	jwtSecret      string
}

func NewAuthService(
	userRepo *repository.UserRepository,
	emailTokenRepo *repository.EmailTokenRepository,
	emailService *EmailService,
	jwtSecret string,
) *AuthService {
	return &AuthService{
		userRepo:       userRepo,
		emailTokenRepo: emailTokenRepo,
		emailService:   emailService,
		jwtSecret:      jwtSecret,
	}
}

func (s *AuthService) Register(req *model.RegisterRequest) (*model.AuthResponse, error) {
	if len(req.Password) < 8 {
		return nil, ErrWeakPassword
	}

	hash, err := bcrypt.GenerateFromPassword([]byte(req.Password), bcrypt.DefaultCost)
	if err != nil {
		return nil, err
	}

	user := &model.User{
		Email:         req.Email,
		Username:      req.Username,
		PasswordHash:  string(hash),
		EmailVerified: false,
	}

	if err := s.userRepo.Create(user); err != nil {
		return nil, err
	}

	// Send verification email
	if err := s.sendVerificationEmail(user); err != nil {
		// Log error but don't fail registration
		_ = err
	}

	return s.generateAuthResponse(user)
}

func (s *AuthService) Login(req *model.LoginRequest) (*model.AuthResponse, error) {
	user, err := s.userRepo.GetByEmail(req.Email)
	if err != nil {
		if errors.Is(err, repository.ErrUserNotFound) {
			return nil, ErrInvalidCredentials
		}
		return nil, err
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.Password)); err != nil {
		return nil, ErrInvalidCredentials
	}

	return s.generateAuthResponse(user)
}

func (s *AuthService) Refresh(refreshToken string) (*model.AuthResponse, error) {
	claims, err := s.validateToken(refreshToken, "refresh")
	if err != nil {
		return nil, err
	}

	userID, ok := claims["user_id"].(float64)
	if !ok {
		return nil, ErrInvalidToken
	}

	user, err := s.userRepo.GetByID(int64(userID))
	if err != nil {
		return nil, err
	}

	return s.generateAuthResponse(user)
}

func (s *AuthService) GetUser(userID int64) (*model.User, error) {
	user, err := s.userRepo.GetByID(userID)
	if err != nil {
		return nil, err
	}
	user.ProcessForJSON()
	return user, nil
}

func (s *AuthService) UpdateProfile(userID int64, req *model.UpdateProfileRequest) (*model.User, error) {
	user, err := s.userRepo.GetByID(userID)
	if err != nil {
		return nil, err
	}

	if req.Username != nil && *req.Username != "" {
		user.Username = *req.Username
	}

	if err := s.userRepo.Update(user); err != nil {
		return nil, err
	}

	user.ProcessForJSON()
	return user, nil
}

func (s *AuthService) ChangePassword(userID int64, req *model.ChangePasswordRequest) error {
	if len(req.NewPassword) < 8 {
		return ErrWeakPassword
	}

	user, err := s.userRepo.GetByID(userID)
	if err != nil {
		return err
	}

	if err := bcrypt.CompareHashAndPassword([]byte(user.PasswordHash), []byte(req.OldPassword)); err != nil {
		return ErrInvalidCredentials
	}

	hash, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		return err
	}

	return s.userRepo.UpdatePassword(userID, string(hash))
}

// Email verification

func (s *AuthService) sendVerificationEmail(user *model.User) error {
	// Delete any existing verification tokens
	s.emailTokenRepo.DeleteByUserAndType(user.ID, "verification")

	// Create new token (24 hours)
	token, err := s.emailTokenRepo.Create(user.ID, "verification", 24*time.Hour)
	if err != nil {
		return err
	}

	return s.emailService.SendVerificationEmail(user.Email, user.Username, token.Token)
}

func (s *AuthService) VerifyEmail(req *model.VerifyEmailRequest) error {
	token, err := s.emailTokenRepo.Validate(req.Token, "verification")
	if err != nil {
		return err
	}

	if err := s.userRepo.SetEmailVerified(token.UserID); err != nil {
		return err
	}

	return s.emailTokenRepo.MarkUsed(token.ID)
}

func (s *AuthService) ResendVerification(req *model.ResendVerificationRequest) error {
	user, err := s.userRepo.GetByEmail(req.Email)
	if err != nil {
		// Don't reveal if user exists
		return nil
	}

	if user.EmailVerified {
		return nil
	}

	return s.sendVerificationEmail(user)
}

// Password reset

func (s *AuthService) ForgotPassword(req *model.ForgotPasswordRequest) error {
	user, err := s.userRepo.GetByEmail(req.Email)
	if err != nil {
		// Don't reveal if user exists
		return nil
	}

	// Delete any existing reset tokens
	s.emailTokenRepo.DeleteByUserAndType(user.ID, "reset")

	// Create new token (1 hour)
	token, err := s.emailTokenRepo.Create(user.ID, "reset", 1*time.Hour)
	if err != nil {
		return err
	}

	return s.emailService.SendPasswordResetEmail(user.Email, user.Username, token.Token)
}

func (s *AuthService) ResetPassword(req *model.ResetPasswordRequest) error {
	if len(req.NewPassword) < 8 {
		return ErrWeakPassword
	}

	token, err := s.emailTokenRepo.Validate(req.Token, "reset")
	if err != nil {
		return err
	}

	hash, err := bcrypt.GenerateFromPassword([]byte(req.NewPassword), bcrypt.DefaultCost)
	if err != nil {
		return err
	}

	if err := s.userRepo.UpdatePassword(token.UserID, string(hash)); err != nil {
		return err
	}

	return s.emailTokenRepo.MarkUsed(token.ID)
}

func (s *AuthService) generateAuthResponse(user *model.User) (*model.AuthResponse, error) {
	accessToken, err := s.generateToken(user.ID, "access", 15*time.Minute)
	if err != nil {
		return nil, err
	}

	refreshToken, err := s.generateToken(user.ID, "refresh", 365*24*time.Hour)
	if err != nil {
		return nil, err
	}

	user.ProcessForJSON()

	return &model.AuthResponse{
		User:         user,
		AccessToken:  accessToken,
		RefreshToken: refreshToken,
	}, nil
}

func (s *AuthService) generateToken(userID int64, tokenType string, expiry time.Duration) (string, error) {
	claims := jwt.MapClaims{
		"user_id": userID,
		"type":    tokenType,
		"exp":     time.Now().Add(expiry).Unix(),
		"iat":     time.Now().Unix(),
	}

	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(s.jwtSecret))
}

func (s *AuthService) validateToken(tokenString, expectedType string) (jwt.MapClaims, error) {
	token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
		if _, ok := token.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, ErrInvalidToken
		}
		return []byte(s.jwtSecret), nil
	})

	if err != nil || !token.Valid {
		return nil, ErrInvalidToken
	}

	claims, ok := token.Claims.(jwt.MapClaims)
	if !ok {
		return nil, ErrInvalidToken
	}

	if tokenType, ok := claims["type"].(string); !ok || tokenType != expectedType {
		return nil, ErrInvalidToken
	}

	return claims, nil
}