using MAX.Framework.Commons;
using MAX.Framework.Mediation;
using MediatR;
using Store.Users.Entities;

namespace Store.Users.Behaviors;

/// <summary>锁定积分账户并检查消费额度，不依赖商铺信息。</summary>
public sealed class AccountConsumptionBehavior<TRequest, TResponse>(
    UnitOfWorkExecutionContext executionContext)
    : IPipelineBehavior<TRequest, TResponse>
    where TRequest : class, IRequest<TResponse>, IAccountConsumptionRequest
{
    public async Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken,
        RequestHandlerDelegate<TResponse> next)
    {
        cancellationToken.ThrowIfCancellationRequested();
        if (string.IsNullOrWhiteSpace(request.UserName))
            throw new AppException("用户名不能为空");
        var userName = request.UserName.Trim();
        var user = await executionContext.Orm.Select<UserEntity>().Where(a => a.UserName == userName)
            .ForUpdate().FirstAsync(cancellationToken)
            ?? throw new AppException("不存在的用户");
        var quote = request.CalculateConsumption(user);
        if (quote.Amount <= 0 || quote.UnitPrice <= 0)
            throw new AppException("消费金额必须大于0");
        if (user.Points < quote.Amount)
            throw new AppException("余额不足");
        lock (request)
        {
            if (request.ConsumptionContext != null)
                throw new InvalidOperationException("同一个消费命令不能同时执行");
            request.ConsumptionContext = new AccountConsumptionContext(user, quote);
        }
        try
        {
            return await next();
        }
        finally
        {
            request.ConsumptionContext = null;
        }
    }
}