using MediatR;
using TakeoutSaaS.Application.App.Tenants.Dto;
using TakeoutSaaS.Application.App.Tenants.Queries;
using TakeoutSaaS.Domain.Tenants.Repositories;
using TakeoutSaaS.Shared.Abstractions.Results;

namespace TakeoutSaaS.Application.App.Tenants.Handlers;

/// <summary>
/// 通知分页查询处理器。
/// </summary>
public sealed class SearchTenantNotificationsQueryHandler(ITenantNotificationRepository notificationRepository)
    : IRequestHandler<SearchTenantNotificationsQuery, PagedResult<TenantNotificationDto>>
{
    /// <summary>
    /// 分页查询通知列表。
    /// </summary>
    /// <param name="request">查询条件。</param>
    /// <param name="cancellationToken">取消标记。</param>
    /// <returns>分页结果。</returns>
    public async Task<PagedResult<TenantNotificationDto>> Handle(SearchTenantNotificationsQuery request, CancellationToken cancellationToken)
    {
        // 1. 查询通知
        var notifications = await notificationRepository.SearchAsync(
            request.TenantId,
            request.Severity,
            request.UnreadOnly,
            null,
            null,
            cancellationToken);

        // 2. 排序与分页
        var ordered = notifications.OrderByDescending(x => x.SentAt).ToList();
        var page = request.Page <= 0 ? 1 : request.Page;
        var size = request.PageSize <= 0 ? 20 : request.PageSize;
        var items = ordered.Skip((page - 1) * size).Take(size).Select(x => x.ToDto()).ToList();

        // 3. 返回分页结果
        return new PagedResult<TenantNotificationDto>(items, page, size, ordered.Count);
    }
}
