ApplicationBuilderExtensions.cs

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using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using System;
using System.Globalization;
using System.Net;
using Tgstation.Server.Api.Models;

namespace Tgstation.Server.Host.Extensions
{
    static class ApplicationBuilderExtensions
    {
        static ILogger GetLogger(HttpContext httpContext) => httpContext.RequestServices.GetRequiredService<ILoggerFactory>().CreateLogger(typeof(ApplicationBuilderExtensions));

        public static void UseDbConflictHandling(this IApplicationBuilder applicationBuilder)
        {
            if (applicationBuilder == null)
                throw new ArgumentNullException(nameof(applicationBuilder));
            applicationBuilder.Use(async (context, next) =>
            {
                var logger = GetLogger(context);
                try
                {
                    await next().ConfigureAwait(false);
                }
                catch (DbUpdateException e)
                {
                    if (e.InnerException is OperationCanceledException)
                    {
                        logger.LogTrace("Rethrowing DbUpdateException as OperationCanceledException: {0}", e);
                        throw e.InnerException;
                    }

                    logger.LogDebug("Database conflict: {0}", e.Message);
                    await new ConflictObjectResult(new ErrorMessage(ErrorCode.DatabaseIntegrityConflict)
                    {
                        AdditionalData = String.Format(CultureInfo.InvariantCulture, (e.InnerException ?? e).Message)
                    }).ExecuteResultAsync(new ActionContext
                    {
                        HttpContext = context
                    }).ConfigureAwait(false);
                }
            });
        }

        public static void UseCancelledRequestSuppression(this IApplicationBuilder applicationBuilder)
        {
            if (applicationBuilder == null)
                throw new ArgumentNullException(nameof(applicationBuilder));
            applicationBuilder.Use(async (context, next) =>
            {
                var logger = GetLogger(context);
                try
                {
                    await next().ConfigureAwait(false);
                }
                catch (OperationCanceledException)
                {
                    logger.LogDebug("Request cancelled!");
                }
            });
        }

        public static void UseServerErrorHandling(this IApplicationBuilder applicationBuilder)
        {
            if (applicationBuilder == null)
                throw new ArgumentNullException(nameof(applicationBuilder));
            applicationBuilder.Use(async (context, next) =>
            {
                var logger = GetLogger(context);
                try
                {
                    await next().ConfigureAwait(false);
                }
                catch (Exception e)
                {
                    logger.LogError("Failed request: {0}", e);
                    await new ObjectResult(
                        new ErrorMessage(ErrorCode.InternalServerError)
                        {
                            AdditionalData = e.ToString()
                        })
                    {
                        StatusCode = (int)HttpStatusCode.InternalServerError
                    }
                    .ExecuteResultAsync(new ActionContext
                    {
                        HttpContext = context
                    }).ConfigureAwait(false);
                }
            });
        }
    }
}