From c41494ee5351a742bf5b8acb545d45d3f6bd4161 Mon Sep 17 00:00:00 2001
From: Ion Dormenco <idormenco@gmail.com>
Date: Sat, 14 Oct 2023 18:33:47 +0300
Subject: [PATCH] Add global exception handler

---
 .../Extensions/ExceptionHandler.cs            | 59 +++++++++++++++++++
 src/api/VoteMonitor.Api/Program.cs            |  4 +-
 2 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 src/api/VoteMonitor.Api/Extensions/ExceptionHandler.cs

diff --git a/src/api/VoteMonitor.Api/Extensions/ExceptionHandler.cs b/src/api/VoteMonitor.Api/Extensions/ExceptionHandler.cs
new file mode 100644
index 00000000..028aeda9
--- /dev/null
+++ b/src/api/VoteMonitor.Api/Extensions/ExceptionHandler.cs
@@ -0,0 +1,59 @@
+using Microsoft.AspNetCore.Diagnostics;
+using Microsoft.AspNetCore.Mvc;
+using Serilog;
+using System;
+using System.Net;
+
+namespace VoteMonitor.Api.Extensions;
+
+/// <summary>
+/// extensions for global exception handling
+/// </summary>
+public static class ExceptionHandlerExtensions
+{
+    /// <summary>
+    /// registers the default global exception handler which will log the exceptions on the server and return a user-friendly json response to the client when unhandled exceptions occur.
+    /// TIP: when using this exception handler, you may want to turn off the asp.net core exception middleware logging to avoid duplication like so:
+    /// <code>
+    /// "Logging": { "LogLevel": { "Default": "Warning", "Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware": "None" } }
+    /// </code>
+    /// </summary>
+    public static IApplicationBuilder UseDefaultExceptionHandler(this IApplicationBuilder app)
+    {
+        app.UseExceptionHandler(errApp =>
+        {
+            errApp.Run(async ctx =>
+            {
+                var exHandlerFeature = ctx.Features.Get<IExceptionHandlerFeature>();
+                if (exHandlerFeature is not null)
+                {
+
+                    var http = exHandlerFeature.Endpoint?.DisplayName?.Split(" => ")[0];
+                    var type = exHandlerFeature.Error.GetType().Name;
+                    var error = exHandlerFeature.Error.Message;
+                    var msg =
+$@"================================= 
+{http} 
+TYPE: {type} 
+REASON: {error} 
+--------------------------------- 
+{exHandlerFeature.Error.StackTrace}";
+
+                    Log.Error("{@http}{@type}{@reason}{@exception}", http, type, error, exHandlerFeature.Error);
+
+                    ctx.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
+                    ctx.Response.ContentType = "application/problem+json";
+                    await ctx.Response.WriteAsJsonAsync(new ProblemDetails
+                    {
+                        Title = "An error occurred",
+                        Detail = error,
+                        Type = type,
+                        Status = (int)HttpStatusCode.BadRequest
+                    });
+                }
+            });
+        });
+
+        return app;
+    }
+}
diff --git a/src/api/VoteMonitor.Api/Program.cs b/src/api/VoteMonitor.Api/Program.cs
index a668da8e..dca768aa 100644
--- a/src/api/VoteMonitor.Api/Program.cs
+++ b/src/api/VoteMonitor.Api/Program.cs
@@ -42,9 +42,10 @@
         .AllowAnyHeader();
 }));
 
-
 var app = builder.Build();
+app.UseDefaultExceptionHandler();
 app.UseSerilogRequestLogging();
+
 app.UseStaticFiles();
 if (builder.Environment.IsDevelopment())
 {
@@ -58,7 +59,6 @@
 
 app.UseSwaggerAndUi();
 app.UseCors(CorsPolicyName);
-
 app.MapControllers();
 app.MapHealthChecks("/health", new HealthCheckOptions
 {