package activity

import (
	"context"
	"errors"
	"time"

	"bookra/apps/backend/internal/db"
	"bookra/apps/backend/internal/domain"
)

var ErrTenantMembership = errors.New("tenant membership not found")

const defaultLimit = 50
const maxLimit = 100

type Service struct {
	repo db.Repository
}

func NewService(repo db.Repository) *Service {
	return &Service{repo: repo}
}

// List returns the tenant's recent activity, newest first. The feed is
// tenant-scoped — every dashboard user sees the same audit trail.
func (s *Service) List(ctx context.Context, principal domain.Principal, limit int) (domain.ActivityFeedResponse, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return domain.ActivityFeedResponse{}, ErrTenantMembership
	}
	if limit <= 0 || limit > maxLimit {
		limit = defaultLimit
	}
	records, err := s.repo.ListActivityEvents(ctx, membership.Tenant.ID, limit)
	if err != nil {
		return domain.ActivityFeedResponse{}, err
	}
	readAt, err := s.repo.GetNotificationCursor(ctx, membership.Tenant.ID, principal.Subject)
	if err != nil {
		return domain.ActivityFeedResponse{}, err
	}
	unread := 0
	events := make([]domain.ActivityEvent, 0, len(records))
	for _, rec := range records {
		event := domain.ActivityEvent{
			ID:         rec.ID,
			ActorKind:  rec.ActorKind,
			ActorName:  rec.ActorName,
			Action:     rec.Action,
			EntityType: rec.EntityType,
			Summary:    rec.Summary,
			CreatedAt:  rec.CreatedAt,
		}
		if rec.EntityID != nil {
			event.EntityID = *rec.EntityID
		}
		if readAt == nil || rec.CreatedAt.After(*readAt) {
			unread++
		}
		events = append(events, event)
	}
	return domain.ActivityFeedResponse{Events: events, UnreadCount: unread, ReadAt: readAt}, nil
}

// MarkAllRead persists the user's cursor — events at or before now count as
// read for this subject on every subsequent load.
func (s *Service) MarkAllRead(ctx context.Context, principal domain.Principal) (time.Time, error) {
	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
	if err != nil {
		return time.Time{}, ErrTenantMembership
	}
	readAt := time.Now().UTC()
	if err := s.repo.SetNotificationCursor(ctx, membership.Tenant.ID, principal.Subject, readAt); err != nil {
		return time.Time{}, err
	}
	return readAt, nil
}