using MediatR;
using TakeoutSaaS.Application.App.Billings.Queries;
using TakeoutSaaS.Domain.Tenants.Repositories;
using TakeoutSaaS.Domain.Tenants.Services;
using TakeoutSaaS.Shared.Abstractions.Constants;
using TakeoutSaaS.Shared.Abstractions.Exceptions;

namespace TakeoutSaaS.Application.App.Billings.Handlers;

/// <summary>
/// 导出账单处理器。
/// </summary>
public sealed class ExportBillingsQueryHandler(
    ITenantBillingRepository billingRepository,
    IBillingExportService exportService)
    : IRequestHandler<ExportBillingsQuery, byte[]>
{
    /// <inheritdoc />
    public async Task<byte[]> Handle(ExportBillingsQuery request, CancellationToken cancellationToken)
    {
        // 1. 参数验证
        if (request.BillingIds.Length == 0)
        {
            throw new BusinessException(ErrorCodes.BadRequest, "账单 ID 列表不能为空");
        }

        // 2. 查询账单数据
        var billings = await billingRepository.GetByIdsAsync(request.BillingIds, cancellationToken);
        if (billings.Count == 0)
        {
            throw new BusinessException(ErrorCodes.NotFound, "未找到任何匹配的账单");
        }

        // 3. 根据格式导出
        var format = (request.Format ?? string.Empty).Trim().ToLowerInvariant();
        return format switch
        {
            "excel" or "xlsx" => await exportService.ExportToExcelAsync(billings, cancellationToken),
            "pdf" => await exportService.ExportToPdfAsync(billings, cancellationToken),
            "csv" => await exportService.ExportToCsvAsync(billings, cancellationToken),
            _ => throw new BusinessException(ErrorCodes.BadRequest, $"不支持的导出格式: {request.Format}")
        };
    }
}
