EndavaTask/EndavaTask/Middleware/ExceptionHandlingMiddleware.cs

using System.Text.Json;
using EndavaTask.Exceptions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.ModelBinding;

namespace EndavaTask.Middleware;

public class ExceptionHandlingMiddleware(RequestDelegate next, ILogger<ExceptionHandlingMiddleware> logger, IHostEnvironment environment)
{
    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await next(context);
        }
        catch (Exception exception)
        {
            logger.LogError(exception, "Unhandled exception while processing {Method} {Path}", context.Request.Method, context.Request.Path);

            var details = BuildProblemDetails(context, exception);

            context.Response.StatusCode = details.Status ?? StatusCodes.Status500InternalServerError;
            context.Response.ContentType = "application/problem+json";
            details.Extensions["traceId"] = context.TraceIdentifier;

            var json = JsonSerializer.Serialize(details);
            await context.Response.WriteAsync(json);
        }
    }

    private ProblemDetails BuildProblemDetails(HttpContext context, Exception exception)
    {
        switch (exception)
        {
            case ApiValidationException validationException:
            {
                var modelState = new ModelStateDictionary();
                foreach (var error in validationException.Errors)
                {
                    foreach (var message in error.Value)
                    {
                        modelState.AddModelError(error.Key, message);
                    }
                }

                return new ValidationProblemDetails(modelState)
                {
                    Status = StatusCodes.Status400BadRequest,
                    Title = "Validation failed",
                    Detail = "One or more validation errors occurred.",
                    Instance = context.Request.Path
                };
            }
            case ApiNotFoundException:
                return new ProblemDetails
                {
                    Status = StatusCodes.Status404NotFound,
                    Title = "Resource not found",
                    Detail = exception.Message,
                    Instance = context.Request.Path
                };
            default:
                return new ProblemDetails
                {
                    Status = StatusCodes.Status500InternalServerError,
                    Title = "Unexpected server error",
                    Detail = environment.IsDevelopment() ? exception.Message : "An unexpected error occurred.",
                    Instance = context.Request.Path
                };
        }
    }
}