using MediatR;
using TakeoutSaaS.Application.App.QuotaPackages.Commands;
using TakeoutSaaS.Application.App.QuotaPackages.Dto;
using TakeoutSaaS.Domain.Tenants.Entities;
using TakeoutSaaS.Domain.Tenants.Enums;
using TakeoutSaaS.Domain.Tenants.Repositories;
using TakeoutSaaS.Shared.Abstractions.Ids;

namespace TakeoutSaaS.Application.App.QuotaPackages.Handlers;

/// <summary>
/// 购买配额包命令处理器。
/// </summary>
public sealed class PurchaseQuotaPackageCommandHandler(
    IQuotaPackageRepository quotaPackageRepository,
    ITenantQuotaUsageHistoryRepository quotaUsageHistoryRepository,
    IIdGenerator idGenerator)
    : IRequestHandler<PurchaseQuotaPackageCommand, TenantQuotaPurchaseDto>
{
    /// <inheritdoc />
    public async Task<TenantQuotaPurchaseDto> Handle(PurchaseQuotaPackageCommand request, CancellationToken cancellationToken)
    {
        // 1. 查找配额包
        var quotaPackage = await quotaPackageRepository.FindByIdAsync(request.QuotaPackageId, cancellationToken);

        if (quotaPackage == null)
        {
            throw new InvalidOperationException("配额包不存在");
        }

        // 2. 创建购买记录
        var purchase = new TenantQuotaPackagePurchase
        {
            Id = idGenerator.NextId(),
            TenantId = request.TenantId,
            QuotaPackageId = request.QuotaPackageId,
            QuotaValue = quotaPackage.QuotaValue,
            Price = quotaPackage.Price,
            PurchasedAt = DateTime.UtcNow,
            ExpiredAt = request.ExpiredAt,
            Notes = request.Notes,
            CreatedAt = DateTime.UtcNow
        };

        // 3. 保存购买记录
        await quotaPackageRepository.AddPurchaseAsync(purchase, cancellationToken);

        // 4. 更新租户配额（根据配额类型更新对应配额）
        var quotaUsage = await quotaPackageRepository.FindUsageAsync(request.TenantId, quotaPackage.QuotaType, cancellationToken);

        if (quotaUsage != null)
        {
            var beforeLimit = quotaUsage.LimitValue;
            quotaUsage.LimitValue += quotaPackage.QuotaValue;
            await quotaPackageRepository.UpdateUsageAsync(quotaUsage, cancellationToken);

            // 4.1 记录配额变更历史（购买配额包视为“剩余增加”）
            await quotaUsageHistoryRepository.AddAsync(new TenantQuotaUsageHistory
            {
                TenantId = request.TenantId,
                QuotaType = quotaPackage.QuotaType,
                UsedValue = quotaUsage.UsedValue,
                LimitValue = quotaUsage.LimitValue,
                RecordedAt = DateTime.UtcNow,
                ChangeType = TenantQuotaUsageHistoryChangeType.Increase,
                ChangeAmount = quotaUsage.LimitValue - beforeLimit,
                ChangeReason = $"购买配额包：{quotaPackage.Name}"
            }, cancellationToken);
        }

        await quotaPackageRepository.SaveChangesAsync(cancellationToken);

        // 5. 返回 DTO
        return new TenantQuotaPurchaseDto
        {
            Id = purchase.Id,
            TenantId = purchase.TenantId,
            QuotaPackageId = purchase.QuotaPackageId,
            QuotaPackageName = quotaPackage.Name,
            QuotaType = quotaPackage.QuotaType,
            QuotaValue = purchase.QuotaValue,
            Price = purchase.Price,
            PurchasedAt = purchase.PurchasedAt,
            ExpiredAt = purchase.ExpiredAt,
            Notes = purchase.Notes
        };
    }
}