using System.Text.Json;
using FozFc.Api.Application.Common;

namespace FozFc.Api.Api.Middleware;

/// <summary>
/// Converts <see cref="ApiException"/> into structured JSON error responses and
/// turns any unhandled exception into a 500 (logged, without leaking details).
/// </summary>
public sealed 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 Invoke(HttpContext context)
    {
        try
        {
            await _next(context);
        }
        catch (ApiException ex)
        {
            await WriteError(context, ex.StatusCode, ex.Message);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Unhandled exception processing {Method} {Path}", context.Request.Method, context.Request.Path);
            await WriteError(context, 500, "Internal server error.");
        }
    }

    private static Task WriteError(HttpContext context, int status, string message)
    {
        if (context.Response.HasStarted) return Task.CompletedTask;
        context.Response.Clear();
        context.Response.StatusCode = status;
        context.Response.ContentType = "application/json";
        return context.Response.WriteAsync(JsonSerializer.Serialize(new { error = message }));
    }
}