package catalog

import (
	"context"
	"errors"
	"fmt"
	"net/mail"
	"strings"
	"time"

	"bookra/apps/backend/internal/bookings"
	"bookra/apps/backend/internal/db"
	"bookra/apps/backend/internal/domain"
	"bookra/apps/backend/internal/notifications"

	"github.com/jackc/pgx/v5"
)

var (
	ErrLocationNotFound      = errors.New("location not found")
	ErrBlockedDayNotFound    = errors.New("blocked day not found")
	ErrCustomerNotFound      = errors.New("customer not found")
	ErrBookingNotFound       = errors.New("booking not found")
	ErrServiceNotFound       = errors.New("service not found")
	ErrStaffNotFound         = errors.New("staff member not found")
	ErrInvalidInput          = errors.New("invalid request")
	ErrInvalidBooking        = errors.New("invalid booking request")
	ErrBookingConflict       = errors.New("booking conflicts with an existing reservation")
	ErrTenantNotFound        = errors.New("tenant not found")
	ErrTenantMembership      = errors.New("tenant membership not found")
	ErrPlanLimitReached      = errors.New("plan limit reached")
	ErrClassTemplateNotFound = errors.New("class template not found")
	ErrClassSessionNotFound  = errors.New("class session not found")
)

type Service struct {
	repo           db.Repository
	billingService interface {
		GetEntitlements(ctx context.Context, tenantID string) (domain.PlanEntitlements, error)
	}
	notificationService interface {
		SendUsageWarning(ctx context.Context, tenantID string, locationCount, locationLimit, usagePercent int) error
		SendBookingConfirmation(ctx context.Context, data notifications.BookingEmailData) error
		SendBookingCancellation(ctx context.Context, data notifications.BookingEmailData) error
	}
}

func NewService(repo db.Repository, billingService interface {
	GetEntitlements(ctx context.Context, tenantID string) (domain.PlanEntitlements, error)
}, notificationService interface {
	SendUsageWarning(ctx context.Context, tenantID string, locationCount, locationLimit, usagePercent int) error
	SendBookingConfirmation(ctx context.Context, data notifications.BookingEmailData) error
	SendBookingCancellation(ctx context.Context, data notifications.BookingEmailData) error
}) *Service {
	return &Service{repo: repo, billingService: billingService, notificationService: notificationService}
}

// ============================================
// LOCATION / ZONE MANAGEMENT
// ============================================

func (s *Service) ListLocations(ctx context.Context, principal domain.Principal) ([]domain.Location, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListLocationsByTenant(ctx, membership.Tenant.ID)
	if err != nil {
		return nil, err
	}

	locations := make([]domain.Location, len(records))
	for i, rec := range records {
		locations[i] = locationToDomain(rec)
	}
	return locations, nil
}

func locationToDomain(rec db.LocationRecord) domain.Location {
	return domain.Location{
		ID:        rec.ID,
		TenantID:  rec.TenantID,
		Name:      rec.Name,
		Type:      rec.Type,
		Capacity:  rec.Capacity,
		Timezone:  rec.Timezone,
		CreatedAt: rec.CreatedAt,
	}
}

func (s *Service) CreateLocation(ctx context.Context, principal domain.Principal, req domain.CreateLocationRequest) (domain.Location, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Location{}, ErrTenantMembership
	}

	// Check plan entitlements for location limit
	if s.billingService != nil {
		entitlements, err := s.billingService.GetEntitlements(ctx, membership.Tenant.ID)
		if err == nil && entitlements.MaxLocations > 0 {
			// Count existing locations
			locations, err := s.repo.ListLocationsByTenant(ctx, membership.Tenant.ID)
			if err == nil && len(locations) >= entitlements.MaxLocations {
				return domain.Location{}, fmt.Errorf("%w: location limit reached (%d/%d). Upgrade your plan to add more locations.", ErrPlanLimitReached, len(locations), entitlements.MaxLocations)
			}
		}
	}

	locationType := strings.TrimSpace(req.Type)
	if locationType == "" {
		locationType = "room"
	}
	capacity := req.Capacity
	if capacity <= 0 {
		capacity = 1
	}

	params := db.CreateLocationParams{
		TenantID: membership.Tenant.ID,
		Name:     req.Name,
		Type:     locationType,
		Capacity: capacity,
		Timezone: membership.Tenant.Timezone,
	}

	rec, err := s.repo.CreateLocation(ctx, params)
	if err != nil {
		return domain.Location{}, err
	}

	// Send usage warning if at 80%+ of limit
	if s.notificationService != nil && s.billingService != nil {
		entitlements, err := s.billingService.GetEntitlements(ctx, membership.Tenant.ID)
		if err == nil && entitlements.MaxLocations > 0 {
			locations, _ := s.repo.ListLocationsByTenant(ctx, membership.Tenant.ID)
			usagePercent := (len(locations) * 100) / entitlements.MaxLocations
			if usagePercent >= 80 {
				_ = s.notificationService.SendUsageWarning(ctx, membership.Tenant.ID, len(locations), entitlements.MaxLocations, usagePercent)
			}
		}
	}

	return locationToDomain(rec), nil
}

func (s *Service) UpdateLocation(ctx context.Context, principal domain.Principal, locationID string, req domain.UpdateLocationRequest) (domain.Location, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Location{}, ErrTenantMembership
	}

	// Verify location belongs to tenant
	loc, err := s.repo.GetLocationByID(ctx, locationID)
	if err != nil {
		return domain.Location{}, ErrLocationNotFound
	}
	if loc.TenantID != membership.Tenant.ID {
		return domain.Location{}, ErrLocationNotFound
	}

	params := db.UpdateLocationParams{}
	if req.Name != "" {
		params.Name = &req.Name
	}
	if req.Type != "" {
		params.Type = &req.Type
	}
	if req.Capacity > 0 {
		params.Capacity = &req.Capacity
	}

	rec, err := s.repo.UpdateLocation(ctx, locationID, params)
	if err != nil {
		return domain.Location{}, err
	}

	return locationToDomain(rec), nil
}

func (s *Service) DeleteLocation(ctx context.Context, principal domain.Principal, locationID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	loc, err := s.repo.GetLocationByID(ctx, locationID)
	if err != nil {
		return ErrLocationNotFound
	}
	if loc.TenantID != membership.Tenant.ID {
		return ErrLocationNotFound
	}

	return s.repo.DeleteLocation(ctx, locationID)
}

// ============================================
// SERVICE CATALOG MANAGEMENT
// ============================================

func serviceToDomain(rec db.ServiceRecord) domain.Service {
	return domain.Service{
		ID:                  rec.ID,
		TenantID:            rec.TenantID,
		Name:                rec.Name,
		DurationMinutes:     rec.DurationMinutes,
		BufferBeforeMinutes: rec.BufferBeforeMinutes,
		BufferAfterMinutes:  rec.BufferAfterMinutes,
		PriceCents:          rec.PriceCents,
		CreatedAt:           rec.CreatedAt,
	}
}

func validateServiceValues(name string, duration, bufferBefore, bufferAfter, priceCents int) error {
	if trimmed := len(strings.TrimSpace(name)); trimmed < 1 || trimmed > 120 {
		return fmt.Errorf("%w: name must be between 1 and 120 characters", ErrInvalidInput)
	}
	if duration <= 0 || duration > 24*60 {
		return fmt.Errorf("%w: durationMinutes must be between 1 and 1440", ErrInvalidInput)
	}
	if bufferBefore < 0 || bufferBefore > 480 {
		return fmt.Errorf("%w: bufferBeforeMinutes must be between 0 and 480", ErrInvalidInput)
	}
	if bufferAfter < 0 || bufferAfter > 480 {
		return fmt.Errorf("%w: bufferAfterMinutes must be between 0 and 480", ErrInvalidInput)
	}
	if priceCents < 0 {
		return fmt.Errorf("%w: priceCents cannot be negative", ErrInvalidInput)
	}
	return nil
}

func (s *Service) ListServices(ctx context.Context, principal domain.Principal) ([]domain.Service, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListServicesByTenant(ctx, membership.Tenant.ID)
	if err != nil {
		return nil, err
	}

	services := make([]domain.Service, len(records))
	for i, rec := range records {
		services[i] = serviceToDomain(rec)
	}
	return services, nil
}

func (s *Service) CreateService(ctx context.Context, principal domain.Principal, req domain.CreateServiceRequest) (domain.Service, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Service{}, ErrTenantMembership
	}

	name := strings.TrimSpace(req.Name)
	if err := validateServiceValues(name, req.DurationMinutes, req.BufferBeforeMinutes, req.BufferAfterMinutes, req.PriceCents); err != nil {
		return domain.Service{}, err
	}

	rec, err := s.repo.CreateService(ctx, db.CreateServiceParams{
		TenantID:            membership.Tenant.ID,
		Name:                name,
		DurationMinutes:     req.DurationMinutes,
		BufferBeforeMinutes: req.BufferBeforeMinutes,
		BufferAfterMinutes:  req.BufferAfterMinutes,
		PriceCents:          req.PriceCents,
	})
	if err != nil {
		return domain.Service{}, err
	}
	return serviceToDomain(rec), nil
}

func (s *Service) UpdateService(ctx context.Context, principal domain.Principal, serviceID string, req domain.UpdateServiceRequest) (domain.Service, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Service{}, ErrTenantMembership
	}

	existing, err := s.repo.GetServiceByID(ctx, serviceID)
	if err != nil || existing.TenantID != membership.Tenant.ID {
		return domain.Service{}, ErrServiceNotFound
	}

	params := db.UpdateServiceParams{}
	if req.Name != nil {
		name := strings.TrimSpace(*req.Name)
		params.Name = &name
	}
	if req.DurationMinutes != nil {
		params.DurationMinutes = req.DurationMinutes
	}
	if req.BufferBeforeMinutes != nil {
		params.BufferBeforeMinutes = req.BufferBeforeMinutes
	}
	if req.BufferAfterMinutes != nil {
		params.BufferAfterMinutes = req.BufferAfterMinutes
	}
	if req.PriceCents != nil {
		params.PriceCents = req.PriceCents
	}

	// Validate against the merged result so partial updates cannot produce an
	// invalid record (e.g. setting duration to 0 while keeping the name).
	merged := existing
	if params.Name != nil {
		merged.Name = *params.Name
	}
	if params.DurationMinutes != nil {
		merged.DurationMinutes = *params.DurationMinutes
	}
	if params.BufferBeforeMinutes != nil {
		merged.BufferBeforeMinutes = *params.BufferBeforeMinutes
	}
	if params.BufferAfterMinutes != nil {
		merged.BufferAfterMinutes = *params.BufferAfterMinutes
	}
	if params.PriceCents != nil {
		merged.PriceCents = *params.PriceCents
	}
	if err := validateServiceValues(merged.Name, merged.DurationMinutes, merged.BufferBeforeMinutes, merged.BufferAfterMinutes, merged.PriceCents); err != nil {
		return domain.Service{}, err
	}

	rec, err := s.repo.UpdateService(ctx, serviceID, params)
	if err != nil {
		return domain.Service{}, err
	}
	return serviceToDomain(rec), nil
}

func (s *Service) DeleteService(ctx context.Context, principal domain.Principal, serviceID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	existing, err := s.repo.GetServiceByID(ctx, serviceID)
	if err != nil || existing.TenantID != membership.Tenant.ID {
		return ErrServiceNotFound
	}

	return s.repo.DeleteService(ctx, serviceID)
}

// ============================================
// STAFF MANAGEMENT
// ============================================

func staffToDomain(rec db.StaffRecord) domain.StaffMember {
	return domain.StaffMember{
		ID:          rec.ID,
		TenantID:    rec.TenantID,
		LocationID:  rec.LocationID,
		DisplayName: rec.DisplayName,
		Active:      rec.Active,
		CreatedAt:   rec.CreatedAt,
	}
}

func validateStaffName(name string) error {
	if trimmed := len(strings.TrimSpace(name)); trimmed < 1 || trimmed > 120 {
		return fmt.Errorf("%w: displayName must be between 1 and 120 characters", ErrInvalidInput)
	}
	return nil
}

// validateStaffLocation returns the normalized location reference: nil when the
// input is empty, the id when it belongs to the tenant, or an error otherwise.
func (s *Service) validateStaffLocation(ctx context.Context, tenantID string, locationID *string) (*string, error) {
	if locationID == nil {
		return nil, nil
	}
	trimmed := strings.TrimSpace(*locationID)
	if trimmed == "" {
		return nil, nil
	}
	loc, err := s.repo.GetLocationByID(ctx, trimmed)
	if err != nil || loc.TenantID != tenantID {
		return nil, fmt.Errorf("%w: locationId does not belong to this tenant", ErrInvalidInput)
	}
	return &trimmed, nil
}

func (s *Service) ListStaff(ctx context.Context, principal domain.Principal) ([]domain.StaffMember, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListStaffByTenant(ctx, membership.Tenant.ID)
	if err != nil {
		return nil, err
	}

	staff := make([]domain.StaffMember, len(records))
	for i, rec := range records {
		staff[i] = staffToDomain(rec)
	}
	return staff, nil
}

func (s *Service) CreateStaff(ctx context.Context, principal domain.Principal, req domain.CreateStaffRequest) (domain.StaffMember, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.StaffMember{}, ErrTenantMembership
	}

	if s.billingService != nil {
		entitlements, err := s.billingService.GetEntitlements(ctx, membership.Tenant.ID)
		if err == nil && entitlements.MaxStaff >= 0 {
			staff, err := s.repo.ListStaffByTenant(ctx, membership.Tenant.ID)
			if err == nil && len(staff) >= entitlements.MaxStaff {
				return domain.StaffMember{}, fmt.Errorf("%w: staff limit reached (%d/%d). Upgrade your plan to add more staff.", ErrPlanLimitReached, len(staff), entitlements.MaxStaff)
			}
		}
	}

	name := strings.TrimSpace(req.DisplayName)
	if err := validateStaffName(name); err != nil {
		return domain.StaffMember{}, err
	}
	locationID, err := s.validateStaffLocation(ctx, membership.Tenant.ID, req.LocationID)
	if err != nil {
		return domain.StaffMember{}, err
	}

	active := true
	if req.Active != nil {
		active = *req.Active
	}

	rec, err := s.repo.CreateStaff(ctx, db.CreateStaffParams{
		TenantID:    membership.Tenant.ID,
		LocationID:  locationID,
		DisplayName: name,
		Active:      active,
	})
	if err != nil {
		return domain.StaffMember{}, err
	}
	return staffToDomain(rec), nil
}

func (s *Service) UpdateStaff(ctx context.Context, principal domain.Principal, staffID string, req domain.UpdateStaffRequest) (domain.StaffMember, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.StaffMember{}, ErrTenantMembership
	}

	existing, err := s.repo.GetStaffByID(ctx, staffID)
	if err != nil || existing.TenantID != membership.Tenant.ID {
		return domain.StaffMember{}, ErrStaffNotFound
	}

	params := db.UpdateStaffParams{Active: req.Active}
	if req.DisplayName != nil {
		name := strings.TrimSpace(*req.DisplayName)
		if err := validateStaffName(name); err != nil {
			return domain.StaffMember{}, err
		}
		params.DisplayName = &name
	}
	if req.LocationID != nil {
		locationID, err := s.validateStaffLocation(ctx, membership.Tenant.ID, req.LocationID)
		if err != nil {
			return domain.StaffMember{}, err
		}
		// Keep the tri-state: an explicit empty string must clear the value.
		if locationID == nil {
			empty := ""
			params.LocationID = &empty
		} else {
			params.LocationID = locationID
		}
	}

	rec, err := s.repo.UpdateStaff(ctx, staffID, params)
	if err != nil {
		return domain.StaffMember{}, err
	}
	return staffToDomain(rec), nil
}

func (s *Service) DeleteStaff(ctx context.Context, principal domain.Principal, staffID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	existing, err := s.repo.GetStaffByID(ctx, staffID)
	if err != nil || existing.TenantID != membership.Tenant.ID {
		return ErrStaffNotFound
	}

	return s.repo.DeleteStaff(ctx, staffID)
}

// ============================================
// BLOCKED DAYS MANAGEMENT
// ============================================

func (s *Service) ListBlockedDays(ctx context.Context, principal domain.Principal, from time.Time, to time.Time) ([]domain.BlockedDay, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListBlockedDaysByTenant(ctx, membership.Tenant.ID, from, to)
	if err != nil {
		return nil, err
	}

	blockedDays := make([]domain.BlockedDay, len(records))
	for i, rec := range records {
		blockedDays[i] = domain.BlockedDay{
			ID:        rec.ID,
			TenantID:  rec.TenantID,
			Date:      rec.StartsAt,
			Reason:    rec.Reason,
			Type:      rec.Kind,
			StaffID:   rec.StaffID,
			CreatedAt: rec.CreatedAt,
		}
	}
	return blockedDays, nil
}

func (s *Service) CreateBlockedDay(ctx context.Context, principal domain.Principal, req domain.CreateBlockedDayRequest) (domain.BlockedDay, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.BlockedDay{}, ErrTenantMembership
	}

	date, err := time.Parse(time.RFC3339, req.Date)
	if err != nil {
		return domain.BlockedDay{}, ErrInvalidBooking
	}

	params := db.CreateBlockedDayParams{
		TenantID: membership.Tenant.ID,
		StaffID:  req.StaffID,
		StartsAt: date,
		EndsAt:   date.Add(24 * time.Hour),
		Kind:     req.Type,
		Reason:   req.Reason,
	}

	rec, err := s.repo.CreateBlockedDay(ctx, params)
	if err != nil {
		return domain.BlockedDay{}, err
	}

	return domain.BlockedDay{
		ID:        rec.ID,
		TenantID:  rec.TenantID,
		Date:      rec.StartsAt,
		Reason:    rec.Reason,
		Type:      rec.Kind,
		StaffID:   rec.StaffID,
		CreatedAt: rec.CreatedAt,
	}, nil
}

func (s *Service) UpdateBlockedDay(ctx context.Context, principal domain.Principal, blockedDayID string, req domain.UpdateBlockedDayRequest) (domain.BlockedDay, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.BlockedDay{}, ErrTenantMembership
	}

	// Verify blocked day belongs to tenant
	bd, err := s.repo.ListBlockedDaysByTenant(ctx, membership.Tenant.ID, time.Time{}, time.Now().Add(365*24*time.Hour))
	if err != nil {
		return domain.BlockedDay{}, err
	}

	found := false
	for _, b := range bd {
		if b.ID == blockedDayID {
			found = true
			break
		}
	}
	if !found {
		return domain.BlockedDay{}, ErrBlockedDayNotFound
	}

	params := db.UpdateBlockedDayParams{}
	if req.Reason != "" {
		params.Reason = &req.Reason
	}
	if req.Type != "" {
		params.Kind = &req.Type
	}

	rec, err := s.repo.UpdateBlockedDay(ctx, blockedDayID, params)
	if err != nil {
		return domain.BlockedDay{}, err
	}

	return domain.BlockedDay{
		ID:        rec.ID,
		TenantID:  rec.TenantID,
		Date:      rec.StartsAt,
		Reason:    rec.Reason,
		Type:      rec.Kind,
		StaffID:   rec.StaffID,
		CreatedAt: rec.CreatedAt,
	}, nil
}

func (s *Service) DeleteBlockedDay(ctx context.Context, principal domain.Principal, blockedDayID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	// Verify blocked day belongs to tenant
	bd, err := s.repo.ListBlockedDaysByTenant(ctx, membership.Tenant.ID, time.Time{}, time.Now().Add(365*24*time.Hour))
	if err != nil {
		return err
	}

	found := false
	for _, b := range bd {
		if b.ID == blockedDayID {
			found = true
			break
		}
	}
	if !found {
		return ErrBlockedDayNotFound
	}

	return s.repo.DeleteBlockedDay(ctx, blockedDayID)
}

// ============================================
// CUSTOMER MANAGEMENT
// ============================================

func (s *Service) ListCustomers(ctx context.Context, principal domain.Principal, limit int, offset int) ([]domain.Customer, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListCustomersByTenant(ctx, membership.Tenant.ID, limit, offset)
	if err != nil {
		return nil, err
	}

	customers := make([]domain.Customer, len(records))
	for i, rec := range records {
		bookingsCount, _ := s.repo.GetCustomerBookingsCount(ctx, rec.ID)
		lastBooking, _ := s.repo.GetCustomerLastBooking(ctx, rec.ID)

		customers[i] = domain.Customer{
			ID:            rec.ID,
			TenantID:      rec.TenantID,
			Name:          rec.Name,
			Email:         rec.Email,
			Phone:         rec.Phone,
			Status:        rec.Status,
			BookingsCount: bookingsCount,
			LastBookingAt: lastBooking,
			CreatedAt:     rec.CreatedAt,
			Notes:         "",
		}
		if rec.Notes != nil {
			customers[i].Notes = *rec.Notes
		}
	}
	return customers, nil
}

func (s *Service) CreateCustomer(ctx context.Context, principal domain.Principal, req domain.CreateCustomerRequest) (domain.Customer, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Customer{}, ErrTenantMembership
	}

	status := req.Status
	if status == "" {
		status = "active"
	}

	params := db.CreateCustomerParams{
		TenantID: membership.Tenant.ID,
		Name:     req.Name,
		Email:    req.Email,
		Phone:    req.Phone,
		Status:   status,
		Notes:    nil,
	}

	rec, err := s.repo.CreateCustomer(ctx, params)
	if err != nil {
		return domain.Customer{}, err
	}

	return domain.Customer{
		ID:        rec.ID,
		TenantID:  rec.TenantID,
		Name:      rec.Name,
		Email:     rec.Email,
		Phone:     rec.Phone,
		Status:    rec.Status,
		CreatedAt: rec.CreatedAt,
		Notes:     "",
	}, nil
}

func (s *Service) UpdateCustomer(ctx context.Context, principal domain.Principal, customerID string, req domain.UpdateCustomerRequest) (domain.Customer, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.Customer{}, ErrTenantMembership
	}

	// Verify customer belongs to tenant
	cust, err := s.repo.GetCustomerByID(ctx, customerID)
	if err != nil {
		return domain.Customer{}, ErrCustomerNotFound
	}
	if cust.TenantID != membership.Tenant.ID {
		return domain.Customer{}, ErrCustomerNotFound
	}

	params := db.UpdateCustomerParams{}
	if req.Name != "" {
		params.Name = &req.Name
	}
	if req.Email != "" {
		params.Email = &req.Email
	}
	if req.Phone != nil {
		params.Phone = req.Phone
	}
	if req.Status != "" {
		params.Status = &req.Status
	}
	if req.Notes != "" {
		params.Notes = &req.Notes
	}

	rec, err := s.repo.UpdateCustomer(ctx, customerID, params)
	if err != nil {
		return domain.Customer{}, err
	}

	bookingsCount, _ := s.repo.GetCustomerBookingsCount(ctx, rec.ID)
	lastBooking, _ := s.repo.GetCustomerLastBooking(ctx, rec.ID)

	return domain.Customer{
		ID:            rec.ID,
		TenantID:      rec.TenantID,
		Name:          rec.Name,
		Email:         rec.Email,
		Phone:         rec.Phone,
		Status:        rec.Status,
		BookingsCount: bookingsCount,
		LastBookingAt: lastBooking,
		CreatedAt:     rec.CreatedAt,
		Notes:         "",
	}, nil
}

func (s *Service) DeleteCustomer(ctx context.Context, principal domain.Principal, customerID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	cust, err := s.repo.GetCustomerByID(ctx, customerID)
	if err != nil {
		return ErrCustomerNotFound
	}
	if cust.TenantID != membership.Tenant.ID {
		return ErrCustomerNotFound
	}

	return s.repo.DeleteCustomer(ctx, customerID)
}

// ============================================
// WORKING HOURS MANAGEMENT
// ============================================

func (s *Service) ListWorkingHours(ctx context.Context, principal domain.Principal) ([]domain.WorkingHours, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListWorkingHoursByTenant(ctx, membership.Tenant.ID, nil)
	if err != nil {
		return nil, err
	}

	hours := make([]domain.WorkingHours, len(records))
	for i, rec := range records {
		open := hhmm(rec.StartsLocal)
		close_ := hhmm(rec.EndsLocal)
		hours[i] = domain.WorkingHours{
			DayOfWeek: rec.DayOfWeek,
			Open:      open,
			Close:     close_,
			IsOpen:    open != "" && close_ != "",
		}
	}
	return hours, nil
}

func (s *Service) UpdateWorkingHours(ctx context.Context, principal domain.Principal, dayOfWeek int, req domain.UpdateWorkingHoursRequest) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	params := db.UpdateWorkingHoursParams{IsOpen: req.IsOpen}
	if req.Open != "" {
		if _, err := time.Parse("15:04", req.Open); err != nil {
			return fmt.Errorf("%w: open must be HH:MM", ErrInvalidBooking)
		}
		params.StartsLocal = &req.Open
	}
	if req.Close != "" {
		if _, err := time.Parse("15:04", req.Close); err != nil {
			return fmt.Errorf("%w: close must be HH:MM", ErrInvalidBooking)
		}
		params.EndsLocal = &req.Close
	}

	return s.repo.UpdateWorkingHours(ctx, membership.Tenant.ID, nil, dayOfWeek, params)
}

// ListStaffWorkingHours returns the per-person schedule for a tenant-owned
// staff member.
func (s *Service) ListStaffWorkingHours(ctx context.Context, principal domain.Principal, staffID string) ([]domain.WorkingHours, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}
	if err := s.requireTenantStaff(ctx, membership.Tenant.ID, staffID); err != nil {
		return nil, err
	}

	records, err := s.repo.ListWorkingHoursByTenant(ctx, membership.Tenant.ID, &staffID)
	if err != nil {
		return nil, err
	}

	hours := make([]domain.WorkingHours, len(records))
	for i, rec := range records {
		open := hhmm(rec.StartsLocal)
		close_ := hhmm(rec.EndsLocal)
		hours[i] = domain.WorkingHours{
			DayOfWeek: rec.DayOfWeek,
			Open:      open,
			Close:     close_,
			IsOpen:    open != "" && close_ != "",
		}
	}
	return hours, nil
}

// UpdateStaffWorkingHours replaces a staff member's availability rule for one
// weekday. The rule directly drives public slot generation for that person.
func (s *Service) UpdateStaffWorkingHours(ctx context.Context, principal domain.Principal, staffID string, dayOfWeek int, req domain.UpdateWorkingHoursRequest) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}
	if err := s.requireTenantStaff(ctx, membership.Tenant.ID, staffID); err != nil {
		return err
	}

	params := db.UpdateWorkingHoursParams{IsOpen: req.IsOpen}
	if req.Open != "" {
		if _, err := time.Parse("15:04", req.Open); err != nil {
			return fmt.Errorf("%w: open must be HH:MM", ErrInvalidBooking)
		}
		params.StartsLocal = &req.Open
	}
	if req.Close != "" {
		if _, err := time.Parse("15:04", req.Close); err != nil {
			return fmt.Errorf("%w: close must be HH:MM", ErrInvalidBooking)
		}
		params.EndsLocal = &req.Close
	}

	return s.repo.UpdateWorkingHours(ctx, membership.Tenant.ID, &staffID, dayOfWeek, params)
}

// requireTenantStaff verifies the staff record exists and belongs to the
// tenant, returning a tenant-safe not-found error otherwise.
func (s *Service) requireTenantStaff(ctx context.Context, tenantID, staffID string) error {
	staff, err := s.repo.GetStaffByID(ctx, staffID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrStaffNotFound
		}
		return err
	}
	if staff.TenantID != tenantID {
		return ErrStaffNotFound
	}
	return nil
}

// CreateBooking creates a manual booking from the dashboard. The service name
// is resolved against the tenant's services; when it matches nothing, the
// tenant's first service is used so the booking still carries a duration.
func (s *Service) CreateBooking(ctx context.Context, principal domain.Principal, req domain.DashboardBookingRequest) (domain.UpcomingBooking, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.UpcomingBooking{}, ErrTenantMembership
	}
	tenant := membership.Tenant

	startsAt, err := time.Parse(time.RFC3339, req.StartsAt)
	if err != nil {
		return domain.UpcomingBooking{}, fmt.Errorf("%w: startsAt must be RFC3339", ErrInvalidBooking)
	}

	customerName := strings.TrimSpace(req.CustomerName)
	customerEmail := strings.TrimSpace(req.CustomerEmail)
	if len(customerName) < 2 || len(customerName) > 120 {
		return domain.UpcomingBooking{}, fmt.Errorf("%w: customerName must be between 2 and 120 characters", ErrInvalidBooking)
	}
	if _, err := mail.ParseAddress(customerEmail); err != nil {
		return domain.UpcomingBooking{}, fmt.Errorf("%w: customerEmail must be valid", ErrInvalidBooking)
	}

	services, err := s.repo.ListServicesByTenant(ctx, tenant.ID)
	if err != nil {
		return domain.UpcomingBooking{}, err
	}
	if len(services) == 0 {
		return domain.UpcomingBooking{}, fmt.Errorf("%w: tenant has no services configured", ErrInvalidBooking)
	}

	selected := services[0]
	requested := strings.TrimSpace(req.Service)
	for _, service := range services {
		if strings.EqualFold(service.Name, requested) || service.ID == requested {
			selected = service
			break
		}
	}

	endsAt := startsAt.Add(time.Duration(selected.DurationMinutes) * time.Minute)

	// Upsert the customer record so the booking shows up under the customers page.
	customer, err := s.repo.GetCustomerByEmail(ctx, tenant.ID, customerEmail)
	if err != nil {
		customer, err = s.repo.CreateCustomer(ctx, db.CreateCustomerParams{
			TenantID: tenant.ID,
			Name:     customerName,
			Email:    customerEmail,
			Status:   "active",
		})
		if err != nil {
			return domain.UpcomingBooking{}, err
		}
	}
	customerPhone := strings.TrimSpace(req.CustomerPhone)
	if customerPhone != "" && (customer.Phone == nil || *customer.Phone != customerPhone) {
		_, _ = s.repo.UpdateCustomer(ctx, customer.ID, db.UpdateCustomerParams{Phone: &customerPhone})
	}

	existing, err := s.repo.ListBookingsByTenantBetween(ctx, tenant.ID, startsAt, endsAt)
	if err != nil {
		return domain.UpcomingBooking{}, err
	}
	for _, booking := range existing {
		if booking.Status == "cancelled" || booking.Status == "waitlisted" {
			continue
		}
		if bookings.AppointmentResourceConflict(booking, nil, nil) {
			return domain.UpcomingBooking{}, ErrBookingConflict
		}
	}

	created, err := s.repo.CreateBooking(ctx, db.CreateBookingParams{
		TenantID:      tenant.ID,
		ServiceID:     &selected.ID,
		BookingMode:   "appointment",
		CustomerName:  customerName,
		CustomerEmail: customerEmail,
		CustomerPhone: customerPhone,
		StartsAt:      startsAt.UTC(),
		EndsAt:        endsAt.UTC(),
		Status:        "confirmed",
		Reference:     db.Reference("BK", time.Now()),
		ManageToken:   bookings.GenerateManageToken(),
		Notes:         strings.TrimSpace(req.Notes),
	})
	if err != nil {
		return domain.UpcomingBooking{}, err
	}

	return domain.UpcomingBooking{
		ID:            created.ID,
		Reference:     created.Reference,
		CustomerName:  customerName,
		CustomerEmail: customerEmail,
		Service:       selected.Name,
		StartsAt:      startsAt,
		EndsAt:        endsAt,
		Status:        created.Status,
		Notes:         strings.TrimSpace(req.Notes),
	}, nil
}

// ============================================
// CLASS TEMPLATE & SESSION MANAGEMENT
// ============================================

func (s *Service) ListClassTemplates(ctx context.Context, principal domain.Principal) ([]domain.ClassTemplate, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}

	records, err := s.repo.ListClassTemplatesByTenant(ctx, membership.Tenant.ID)
	if err != nil {
		return nil, err
	}
	templates := make([]domain.ClassTemplate, len(records))
	for i, rec := range records {
		templates[i] = domain.ClassTemplate{
			ID:              rec.ID,
			TenantID:        rec.TenantID,
			Title:           rec.Title,
			DurationMinutes: rec.DurationMinutes,
			Capacity:        rec.Capacity,
			CreatedAt:       rec.CreatedAt,
		}
	}
	return templates, nil
}

func (s *Service) CreateClassTemplate(ctx context.Context, principal domain.Principal, req domain.UpsertClassTemplateRequest) (domain.ClassTemplate, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.ClassTemplate{}, ErrTenantMembership
	}

	title, err := validateClassTemplateInput(req)
	if err != nil {
		return domain.ClassTemplate{}, err
	}

	rec, err := s.repo.CreateClassTemplate(ctx, db.CreateClassTemplateParams{
		TenantID:        membership.Tenant.ID,
		Title:           title,
		DurationMinutes: req.DurationMinutes,
		Capacity:        req.Capacity,
	})
	if err != nil {
		return domain.ClassTemplate{}, err
	}
	return domain.ClassTemplate{
		ID:              rec.ID,
		TenantID:        rec.TenantID,
		Title:           rec.Title,
		DurationMinutes: rec.DurationMinutes,
		Capacity:        rec.Capacity,
		CreatedAt:       rec.CreatedAt,
	}, nil
}

func (s *Service) DeleteClassTemplate(ctx context.Context, principal domain.Principal, templateID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}
	if err := s.requireTenantClassTemplate(ctx, membership.Tenant.ID, templateID); err != nil {
		return err
	}
	return s.repo.DeleteClassTemplate(ctx, templateID)
}

// ListClassSessions returns upcoming sessions enriched with location names and
// live booked counts for the management UI.
func (s *Service) ListClassSessions(ctx context.Context, principal domain.Principal) ([]domain.ClassSession, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return nil, ErrTenantMembership
	}
	tenantID := membership.Tenant.ID

	now := time.Now().UTC()
	sessions, err := s.repo.ListClassSessionsByTenant(ctx, tenantID, now, 100)
	if err != nil {
		return nil, err
	}
	if len(sessions) == 0 {
		return []domain.ClassSession{}, nil
	}

	var windowEnd time.Time
	for _, session := range sessions {
		if session.EndsAt.After(windowEnd) {
			windowEnd = session.EndsAt
		}
	}
	bookings, err := s.repo.ListBookingsByTenantBetween(ctx, tenantID, now, windowEnd)
	if err != nil {
		return nil, err
	}
	locations, err := s.repo.ListLocationsByTenant(ctx, tenantID)
	if err != nil {
		return nil, err
	}
	locationNames := make(map[string]string, len(locations))
	for _, loc := range locations {
		locationNames[loc.ID] = loc.Name
	}

	out := make([]domain.ClassSession, len(sessions))
	for i, session := range sessions {
		booked := 0
		for _, booking := range bookings {
			if booking.ClassSessionID != nil && *booking.ClassSessionID == session.ID &&
				booking.Status != "cancelled" && booking.Status != "waitlisted" {
				booked++
			}
		}
		out[i] = domain.ClassSession{
			ID:            session.ID,
			TenantID:      session.TenantID,
			TemplateID:    session.TemplateID,
			TemplateTitle: session.Title,
			LocationID:    session.LocationID,
			LocationName:  locationNames[deref(session.LocationID)],
			StartsAt:      session.StartsAt,
			EndsAt:        session.EndsAt,
			Capacity:      int(session.Capacity),
			BookedCount:   booked,
		}
	}
	return out, nil
}

func (s *Service) CreateClassSession(ctx context.Context, principal domain.Principal, req domain.CreateClassSessionRequest) (domain.ClassSession, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.ClassSession{}, ErrTenantMembership
	}
	tenantID := membership.Tenant.ID

	if err := s.requireTenantClassTemplate(ctx, tenantID, req.TemplateID); err != nil {
		return domain.ClassSession{}, err
	}
	template, err := s.repo.GetClassTemplateByID(ctx, req.TemplateID)
	if err != nil {
		return domain.ClassSession{}, err
	}

	startsAt, err := time.Parse(time.RFC3339, strings.TrimSpace(req.StartsAt))
	if err != nil {
		return domain.ClassSession{}, fmt.Errorf("%w: startsAt must be RFC3339", ErrInvalidInput)
	}
	if !startsAt.After(time.Now()) {
		return domain.ClassSession{}, fmt.Errorf("%w: startsAt must be in the future", ErrInvalidInput)
	}

	if req.LocationID != nil {
		location, err := s.repo.GetLocationByID(ctx, *req.LocationID)
		if err != nil {
			if errors.Is(err, pgx.ErrNoRows) {
				return domain.ClassSession{}, ErrLocationNotFound
			}
			return domain.ClassSession{}, err
		}
		if location.TenantID != tenantID {
			return domain.ClassSession{}, ErrLocationNotFound
		}
	}

	capacity := template.Capacity
	if req.Capacity != nil {
		if *req.Capacity < 1 || *req.Capacity > 500 {
			return domain.ClassSession{}, fmt.Errorf("%w: capacity must be between 1 and 500", ErrInvalidInput)
		}
		capacity = *req.Capacity
	}
	endsAt := startsAt.Add(time.Duration(template.DurationMinutes) * time.Minute)

	rec, err := s.repo.CreateClassSession(ctx, db.CreateClassSessionParams{
		TenantID:   tenantID,
		TemplateID: req.TemplateID,
		LocationID: req.LocationID,
		StartsAt:   startsAt.UTC(),
		EndsAt:     endsAt.UTC(),
		Capacity:   int32(capacity),
	})
	if err != nil {
		return domain.ClassSession{}, err
	}
	return domain.ClassSession{
		ID:            rec.ID,
		TenantID:      rec.TenantID,
		TemplateID:    rec.TemplateID,
		TemplateTitle: rec.Title,
		LocationID:    rec.LocationID,
		StartsAt:      rec.StartsAt,
		EndsAt:        rec.EndsAt,
		Capacity:      int(rec.Capacity),
	}, nil
}

func (s *Service) DeleteClassSession(ctx context.Context, principal domain.Principal, sessionID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}
	session, err := s.repo.GetClassSessionByID(ctx, sessionID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrClassSessionNotFound
		}
		return err
	}
	if session.TenantID != membership.Tenant.ID {
		return ErrClassSessionNotFound
	}
	return s.repo.DeleteClassSession(ctx, sessionID)
}

func (s *Service) requireTenantClassTemplate(ctx context.Context, tenantID, templateID string) error {
	template, err := s.repo.GetClassTemplateByID(ctx, templateID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrClassTemplateNotFound
		}
		return err
	}
	if template.TenantID != tenantID {
		return ErrClassTemplateNotFound
	}
	return nil
}

func deref(value *string) string {
	if value == nil {
		return ""
	}
	return *value
}

// hhmm trims a local time value to HH:MM; PostgreSQL returns time columns as
// HH:MM:SS while the API contract uses HH:MM.
func hhmm(value string) string {
	if len(value) >= 5 {
		return value[:5]
	}
	return value
}

// ============================================
// BOOKING LIFECYCLE
// ============================================

// CancelBooking cancels a tenant-owned booking from the dashboard. Cancelling a
// class booking frees the seat and promotes the earliest waitlisted bookings.
func (s *Service) CancelBooking(ctx context.Context, principal domain.Principal, bookingID string) error {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return ErrTenantMembership
	}

	booking, err := s.repo.GetBookingByID(ctx, bookingID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ErrBookingNotFound
		}
		return err
	}
	if booking.TenantID != membership.Tenant.ID {
		return ErrBookingNotFound
	}
	if booking.Status == "cancelled" {
		return fmt.Errorf("%w: booking already cancelled", ErrInvalidInput)
	}

	if err := s.repo.UpdateBookingStatus(ctx, booking.ID, "cancelled"); err != nil {
		return err
	}
	_ = s.repo.CancelPendingReminderJobsForBooking(ctx, booking.ID)

	go s.sendBookingEmail(booking, false)

	if booking.ClassSessionID != nil {
		promoted, err := bookings.PromoteWaitlist(ctx, s.repo, booking.TenantID, *booking.ClassSessionID)
		if err != nil {
			return nil
		}
		for _, promotedBooking := range promoted {
			go s.sendBookingEmail(promotedBooking, true)
		}
	}
	return nil
}

// sendBookingEmail builds the shared payload and fires a confirmation
// (promoted=true) or cancellation notification. Failures are logged-and-done:
// email delivery must not fail the cancellation itself.
func (s *Service) sendBookingEmail(booking db.BookingRecord, promoted bool) {
	if s.notificationService == nil {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	tenant, err := s.repo.GetTenantByID(ctx, booking.TenantID)
	if err != nil {
		return
	}
	brand, _ := s.repo.GetBrandProfile(ctx, tenant.ID)
	brandColor := brand.PrimaryColor
	if brandColor == "" {
		brandColor = "#a65c3e"
	}

	var serviceName, locationName string
	if booking.ServiceID != nil {
		if service, err := s.repo.GetServiceByID(ctx, *booking.ServiceID); err == nil {
			serviceName = service.Name
		}
	}
	if booking.ClassSessionID != nil {
		if session, err := s.repo.GetClassSessionByID(ctx, *booking.ClassSessionID); err == nil {
			serviceName = session.Title
		}
	}
	if booking.LocationID != nil {
		if location, err := s.repo.GetLocationByID(ctx, *booking.LocationID); err == nil {
			locationName = location.Name
		}
	}

	data := notifications.BookingEmailData{
		TenantID:      tenant.ID,
		TenantName:    tenant.Name,
		TenantSlug:    tenant.Slug,
		BrandColor:    brandColor,
		CustomerName:  booking.CustomerName,
		CustomerEmail: booking.CustomerEmail,
		Service:       serviceName,
		Location:      locationName,
		Reference:     booking.Reference,
		StartsAt:      booking.StartsAt,
		EndsAt:        booking.EndsAt,
		Timezone:      tenant.Timezone,
		Locale:        tenant.Locale,
	}
	if promoted {
		s.notificationService.SendBookingConfirmation(ctx, data)
	} else {
		s.notificationService.SendBookingCancellation(ctx, data)
	}
}

func (s *Service) UpdateClassTemplate(ctx context.Context, principal domain.Principal, templateID string, req domain.UpsertClassTemplateRequest) (domain.ClassTemplate, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.ClassTemplate{}, ErrTenantMembership
	}
	if err := s.requireTenantClassTemplate(ctx, membership.Tenant.ID, templateID); err != nil {
		return domain.ClassTemplate{}, err
	}
	title, err := validateClassTemplateInput(req)
	if err != nil {
		return domain.ClassTemplate{}, err
	}
	rec, err := s.repo.UpdateClassTemplate(ctx, templateID, db.CreateClassTemplateParams{
		TenantID:        membership.Tenant.ID,
		Title:           title,
		DurationMinutes: req.DurationMinutes,
		Capacity:        req.Capacity,
	})
	if err != nil {
		return domain.ClassTemplate{}, err
	}
	return domain.ClassTemplate{
		ID:              rec.ID,
		TenantID:        rec.TenantID,
		Title:           rec.Title,
		DurationMinutes: rec.DurationMinutes,
		Capacity:        rec.Capacity,
		CreatedAt:       rec.CreatedAt,
	}, nil
}

func validateClassTemplateInput(req domain.UpsertClassTemplateRequest) (string, error) {
	title := strings.TrimSpace(req.Title)
	if len(title) < 1 || len(title) > 120 {
		return "", fmt.Errorf("%w: title must be between 1 and 120 characters", ErrInvalidInput)
	}
	if req.DurationMinutes < 1 || req.DurationMinutes > 1440 {
		return "", fmt.Errorf("%w: durationMinutes must be between 1 and 1440", ErrInvalidInput)
	}
	if req.Capacity < 1 || req.Capacity > 500 {
		return "", fmt.Errorf("%w: capacity must be between 1 and 500", ErrInvalidInput)
	}
	return title, nil
}