package service

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/user-management-system/internal/domain"
	"github.com/user-management-system/internal/pagination"
	apierrors "github.com/user-management-system/internal/pkg/errors"
	"github.com/user-management-system/internal/repository"
	"gorm.io/gorm"
)

type deviceRepository interface {
	Create(ctx context.Context, device *domain.Device) error
	Update(ctx context.Context, device *domain.Device) error
	Delete(ctx context.Context, id int64) error
	GetByID(ctx context.Context, id int64) (*domain.Device, error)
	GetByDeviceID(ctx context.Context, userID int64, deviceID string) (*domain.Device, error)
	Exists(ctx context.Context, userID int64, deviceID string) (bool, error)
	ListByUserID(ctx context.Context, userID int64, offset, limit int) ([]*domain.Device, int64, error)
	ListByStatus(ctx context.Context, status domain.DeviceStatus, offset, limit int) ([]*domain.Device, int64, error)
	UpdateStatus(ctx context.Context, id int64, status domain.DeviceStatus) error
	UpdateLastActiveTime(ctx context.Context, id int64) error
	TrustDevice(ctx context.Context, id int64, expiresAt *time.Time) error
	UntrustDevice(ctx context.Context, id int64) error
	DeleteAllByUserIDExcept(ctx context.Context, userID int64, exceptDeviceID int64) error
	GetTrustedDevices(ctx context.Context, userID int64) ([]*domain.Device, error)
	CountTrustedDevices(ctx context.Context, userID int64) (int64, error)
	ListAll(ctx context.Context, params *repository.ListDevicesParams) ([]*domain.Device, int64, error)
	ListAllCursor(ctx context.Context, params *repository.ListDevicesParams, limit int, cursor *pagination.Cursor) ([]*domain.Device, bool, error)
}

type deviceUserRepository interface {
	GetByID(ctx context.Context, id int64) (*domain.User, error)
}

type DeviceService struct {
	deviceRepo deviceRepository
	userRepo   deviceUserRepository
}

func NewDeviceService(deviceRepo deviceRepository, userRepo deviceUserRepository) *DeviceService {
	return &DeviceService{
		deviceRepo: deviceRepo,
		userRepo:   userRepo,
	}
}

type CreateDeviceRequest struct {
	DeviceID      string `json:"device_id" binding:"required"`
	DeviceName    string `json:"device_name"`
	DeviceType    int    `json:"device_type"`
	DeviceOS      string `json:"device_os"`
	DeviceBrowser string `json:"device_browser"`
	IP            string `json:"ip"`
	Location      string `json:"location"`
}

type UpdateDeviceRequest struct {
	DeviceName    string `json:"device_name"`
	DeviceType    int    `json:"device_type"`
	DeviceOS      string `json:"device_os"`
	DeviceBrowser string `json:"device_browser"`
	IP            string `json:"ip"`
	Location      string `json:"location"`
	Status        int    `json:"status"`
}

func (s *DeviceService) CreateDevice(ctx context.Context, userID int64, req *CreateDeviceRequest) (*domain.Device, error) {
	if _, err := s.userRepo.GetByID(ctx, userID); err != nil {
		return nil, errors.New("user not found")
	}

	exists, err := s.deviceRepo.Exists(ctx, userID, req.DeviceID)
	if err != nil {
		return nil, err
	}
	if exists {
		device, err := s.deviceRepo.GetByDeviceID(ctx, userID, req.DeviceID)
		if err != nil {
			return nil, err
		}
		device.LastActiveTime = time.Now()
		return device, s.deviceRepo.Update(ctx, device)
	}

	device := &domain.Device{
		UserID:        userID,
		DeviceID:      req.DeviceID,
		DeviceName:    req.DeviceName,
		DeviceType:    domain.DeviceType(req.DeviceType),
		DeviceOS:      req.DeviceOS,
		DeviceBrowser: req.DeviceBrowser,
		IP:            req.IP,
		Location:      req.Location,
		Status:        domain.DeviceStatusActive,
	}

	if err := s.deviceRepo.Create(ctx, device); err != nil {
		return nil, err
	}

	return device, nil
}

func isDeviceNotFoundError(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, gorm.ErrRecordNotFound) {
		return true
	}

	lowerErr := strings.ToLower(strings.TrimSpace(err.Error()))
	return strings.Contains(lowerErr, "record not found") ||
		strings.Contains(lowerErr, "device not found") ||
		strings.Contains(lowerErr, "not found")
}

func (s *DeviceService) getDeviceByID(ctx context.Context, deviceID int64) (*domain.Device, error) {
	device, err := s.deviceRepo.GetByID(ctx, deviceID)
	if err != nil {
		if isDeviceNotFoundError(err) {
			return nil, apierrors.NotFound("device_not_found", "device not found").WithCause(err)
		}
		return nil, err
	}
	return device, nil
}

func (s *DeviceService) getAuthorizedDevice(ctx context.Context, actorUserID, deviceID int64, isAdmin bool) (*domain.Device, error) {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return nil, err
	}
	if !isAdmin && device.UserID != actorUserID {
		return nil, apierrors.Forbidden("device_forbidden", "permission denied")
	}
	return device, nil
}

func (s *DeviceService) persistDeviceUpdate(ctx context.Context, device *domain.Device, req *UpdateDeviceRequest) (*domain.Device, error) {
	if req == nil {
		return device, nil
	}

	if req.DeviceName != "" {
		device.DeviceName = req.DeviceName
	}
	if req.DeviceType >= 0 {
		device.DeviceType = domain.DeviceType(req.DeviceType)
	}
	if req.DeviceOS != "" {
		device.DeviceOS = req.DeviceOS
	}
	if req.DeviceBrowser != "" {
		device.DeviceBrowser = req.DeviceBrowser
	}
	if req.IP != "" {
		device.IP = req.IP
	}
	if req.Location != "" {
		device.Location = req.Location
	}
	if req.Status >= 0 {
		device.Status = domain.DeviceStatus(req.Status)
	}

	if err := s.deviceRepo.Update(ctx, device); err != nil {
		return nil, err
	}

	return device, nil
}

// maxTrustedDevicesPerUser 每个用户最大信任设备数量（P2 安全增强）
const maxTrustedDevicesPerUser = 10

func (s *DeviceService) trustDeviceRecord(ctx context.Context, device *domain.Device, trustDuration time.Duration) error {
	// P2 安全增强：检查信任设备数量上限
	trustedCount, err := s.deviceRepo.CountTrustedDevices(ctx, device.UserID)
	if err != nil {
		return fmt.Errorf("count trusted devices failed: %w", err)
	}
	if trustedCount >= maxTrustedDevicesPerUser {
		return fmt.Errorf("trusted device limit reached (max %d), please untrust an existing device first", maxTrustedDevicesPerUser)
	}

	var trustExpiresAt *time.Time
	if trustDuration > 0 {
		expiresAt := time.Now().Add(trustDuration)
		trustExpiresAt = &expiresAt
	}
	return s.deviceRepo.TrustDevice(ctx, device.ID, trustExpiresAt)
}

func (s *DeviceService) UpdateDevice(ctx context.Context, deviceID int64, req *UpdateDeviceRequest) (*domain.Device, error) {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return nil, err
	}
	return s.persistDeviceUpdate(ctx, device, req)
}

func (s *DeviceService) DeleteDevice(ctx context.Context, deviceID int64) error {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return err
	}
	return s.deviceRepo.Delete(ctx, device.ID)
}

func (s *DeviceService) GetDevice(ctx context.Context, deviceID int64) (*domain.Device, error) {
	return s.getDeviceByID(ctx, deviceID)
}

func (s *DeviceService) GetUserDevices(ctx context.Context, userID int64, page, pageSize int) ([]*domain.Device, int64, error) {
	if page <= 0 {
		page = 1
	}
	if pageSize <= 0 {
		pageSize = 20
	}

	offset := (page - 1) * pageSize
	return s.deviceRepo.ListByUserID(ctx, userID, offset, pageSize)
}

func (s *DeviceService) GetDeviceForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool) (*domain.Device, error) {
	return s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
}

func (s *DeviceService) UpdateDeviceForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool, req *UpdateDeviceRequest) (*domain.Device, error) {
	device, err := s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
	if err != nil {
		return nil, err
	}
	return s.persistDeviceUpdate(ctx, device, req)
}

func (s *DeviceService) DeleteDeviceForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool) error {
	device, err := s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
	if err != nil {
		return err
	}
	return s.deviceRepo.Delete(ctx, device.ID)
}

func (s *DeviceService) UpdateDeviceStatus(ctx context.Context, deviceID int64, status domain.DeviceStatus) error {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return err
	}
	return s.deviceRepo.UpdateStatus(ctx, device.ID, status)
}

func (s *DeviceService) UpdateDeviceStatusForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool, status domain.DeviceStatus) error {
	device, err := s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
	if err != nil {
		return err
	}
	return s.deviceRepo.UpdateStatus(ctx, device.ID, status)
}

func (s *DeviceService) UpdateLastActiveTime(ctx context.Context, deviceID int64) error {
	return s.deviceRepo.UpdateLastActiveTime(ctx, deviceID)
}

func (s *DeviceService) GetActiveDevices(ctx context.Context, page, pageSize int) ([]*domain.Device, int64, error) {
	if page <= 0 {
		page = 1
	}
	if pageSize <= 0 {
		pageSize = 20
	}

	offset := (page - 1) * pageSize
	return s.deviceRepo.ListByStatus(ctx, domain.DeviceStatusActive, offset, pageSize)
}

func (s *DeviceService) TrustDevice(ctx context.Context, deviceID int64, trustDuration time.Duration) error {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return err
	}
	return s.trustDeviceRecord(ctx, device, trustDuration)
}

func (s *DeviceService) TrustDeviceForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool, trustDuration time.Duration) error {
	device, err := s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
	if err != nil {
		return err
	}
	return s.trustDeviceRecord(ctx, device, trustDuration)
}

func (s *DeviceService) TrustDeviceByDeviceID(ctx context.Context, userID int64, deviceID string, trustDuration time.Duration) error {
	device, err := s.deviceRepo.GetByDeviceID(ctx, userID, deviceID)
	if err != nil {
		if isDeviceNotFoundError(err) {
			return apierrors.NotFound("device_not_found", "device not found").WithCause(err)
		}
		return err
	}
	return s.trustDeviceRecord(ctx, device, trustDuration)
}

func (s *DeviceService) UntrustDevice(ctx context.Context, deviceID int64) error {
	device, err := s.getDeviceByID(ctx, deviceID)
	if err != nil {
		return err
	}
	return s.deviceRepo.UntrustDevice(ctx, device.ID)
}

func (s *DeviceService) UntrustDeviceForActor(ctx context.Context, actorUserID, deviceID int64, isAdmin bool) error {
	device, err := s.getAuthorizedDevice(ctx, actorUserID, deviceID, isAdmin)
	if err != nil {
		return err
	}
	return s.deviceRepo.UntrustDevice(ctx, device.ID)
}

func (s *DeviceService) LogoutAllOtherDevices(ctx context.Context, userID int64, currentDeviceID int64) error {
	return s.deviceRepo.DeleteAllByUserIDExcept(ctx, userID, currentDeviceID)
}

func (s *DeviceService) GetTrustedDevices(ctx context.Context, userID int64) ([]*domain.Device, error) {
	return s.deviceRepo.GetTrustedDevices(ctx, userID)
}

type GetAllDevicesRequest struct {
	Page      int    `form:"page"`
	PageSize  int    `form:"page_size"`
	UserID    int64  `form:"user_id"`
	Status    *int   `form:"status"`
	IsTrusted *bool  `form:"is_trusted"`
	Keyword   string `form:"keyword"`
	Cursor    string `form:"cursor"`
	Size      int    `form:"size"`
}

func (s *DeviceService) GetAllDevices(ctx context.Context, req *GetAllDevicesRequest) ([]*domain.Device, int64, error) {
	if req.Page <= 0 {
		req.Page = 1
	}
	if req.PageSize <= 0 {
		req.PageSize = 20
	}
	if req.PageSize > 100 {
		req.PageSize = 100
	}

	offset := (req.Page - 1) * req.PageSize
	params := &repository.ListDevicesParams{
		UserID:  req.UserID,
		Keyword: req.Keyword,
		Offset:  offset,
		Limit:   req.PageSize,
	}

	if req.Status != nil && (*req.Status == 0 || *req.Status == 1) {
		status := domain.DeviceStatus(*req.Status)
		params.Status = &status
	}
	if req.IsTrusted != nil {
		params.IsTrusted = req.IsTrusted
	}

	return s.deviceRepo.ListAll(ctx, params)
}

func (s *DeviceService) GetAllDevicesCursor(ctx context.Context, req *GetAllDevicesRequest) (*CursorResult, error) {
	size := pagination.ClampPageSize(req.Size)
	if req.PageSize > 0 && req.Cursor == "" {
		size = pagination.ClampPageSize(req.PageSize)
	}

	cursor, err := pagination.Decode(req.Cursor)
	if err != nil {
		return nil, fmt.Errorf("invalid cursor: %w", err)
	}

	params := &repository.ListDevicesParams{
		UserID:  req.UserID,
		Keyword: req.Keyword,
	}
	if req.Status != nil && (*req.Status == 0 || *req.Status == 1) {
		status := domain.DeviceStatus(*req.Status)
		params.Status = &status
	}
	if req.IsTrusted != nil {
		params.IsTrusted = req.IsTrusted
	}

	devices, hasMore, err := s.deviceRepo.ListAllCursor(ctx, params, size, cursor)
	if err != nil {
		return nil, err
	}

	nextCursor := ""
	if len(devices) > 0 {
		last := devices[len(devices)-1]
		nextCursor = pagination.BuildNextCursor(last.ID, last.LastActiveTime)
	}

	return &CursorResult{
		Items:      devices,
		NextCursor: nextCursor,
		HasMore:    hasMore,
		PageSize:   size,
	}, nil
}

func (s *DeviceService) GetDeviceByDeviceID(ctx context.Context, userID int64, deviceID string) (*domain.Device, error) {
	return s.deviceRepo.GetByDeviceID(ctx, userID, deviceID)
}