accounting-system/backend/src/FiscalFlow.Api/Middleware/ExceptionHandlingMiddleware.cs

using Microsoft.AspNetCore.Mvc;
using System.Net;

namespace FiscalFlow.API.Middleware;

public class ExceptionHandlingMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger<ExceptionHandlingMiddleware> _logger;

    public ExceptionHandlingMiddleware(RequestDelegate next, ILogger<ExceptionHandlingMiddleware> logger)
    {
        _next = next;
        _logger = logger;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "An unhandled exception occurred");
            await HandleExceptionAsync(context, ex);
        }
    }

    private static Task HandleExceptionAsync(HttpContext context, Exception exception)
    {
        context.Response.ContentType = "application/json";
        
        var (statusCode, errorCode, message) = exception switch
        {
            UnauthorizedAccessException _ => (
                (int)HttpStatusCode.Unauthorized, 
                "UNAUTHORIZED", 
                "Authentication required"
            ),
            InvalidOperationException _ => (
                (int)HttpStatusCode.BadRequest, 
                "INVALID_OPERATION", 
                exception.Message
            ),
            KeyNotFoundException _ => (
                (int)HttpStatusCode.NotFound, 
                "NOT_FOUND", 
                "Resource not found"
            ),
            _ => (
                (int)HttpStatusCode.InternalServerError, 
                "INTERNAL_ERROR", 
                "An unexpected error occurred"
            )
        };

        context.Response.StatusCode = statusCode;

        var response = new
        {
            success = false,
            error = new
            {
                code = errorCode,
                message
            },
            meta = new
            {
                request_id = context.TraceIdentifier,
                timestamp = DateTime.UtcNow.ToString("O")
            }
        };

        return context.Response.WriteAsJsonAsync(response);
    }
}