MikuSB/SdkServer/Utils/LoggingMiddleware.cs

using Microsoft.AspNetCore.Http;
using MikuSB.Util;
using System.Text;

namespace MikuSB.SdkServer.Utils;

public class RequestLoggingMiddleware(RequestDelegate next)
{
    private const long MaxLoggedBodyBytes = 1024 * 1024;

    private static bool ShouldSkip(string path)
        => path.StartsWith("/report") || path.Contains("/log/") || path == "/alive";

    private static bool ShouldLogBody(HttpRequest request)
    {
        if (request.ContentLength is null or 0)
            return false;

        if (request.ContentLength > MaxLoggedBodyBytes)
            return false;

        if (string.IsNullOrWhiteSpace(request.ContentType))
            return false;

        return request.ContentType.Contains("json", StringComparison.OrdinalIgnoreCase)
            || request.ContentType.Contains("text", StringComparison.OrdinalIgnoreCase)
            || request.ContentType.Contains("xml", StringComparison.OrdinalIgnoreCase)
            || request.ContentType.Contains("x-www-form-urlencoded", StringComparison.OrdinalIgnoreCase);
    }

    private static string SanitizeForLog(string value)
    {
        var builder = new StringBuilder(value.Length);
        foreach (var ch in value)
        {
            if (ch == '\r')
            {
                builder.Append(@"\r");
                continue;
            }

            if (ch == '\n')
            {
                builder.Append(@"\n");
                continue;
            }

            if (char.IsControl(ch))
            {
                builder.Append(@"\u");
                builder.Append(((int)ch).ToString("x4"));
                continue;
            }

            builder.Append(ch);
        }

        return builder.ToString();
    }

    private static async Task<string> ReadBodyAsString(HttpRequest request)
    {
        request.EnableBuffering();
        request.Body.Position = 0;

        using var reader = new StreamReader(request.Body, Encoding.UTF8, leaveOpen: true);
        var body = await reader.ReadToEndAsync();

        request.Body.Position = 0;
        return body;
    }

    public async Task InvokeAsync(HttpContext context, Logger logger)
    {
        var request = context.Request;
        var method = request.Method;
        var path = request.Path.ToString();
        var pathWithQuery = path + request.QueryString;

        if (ConfigManager.Config.HttpServer.EnableLog && !ShouldSkip(path))
        {
            var body = ShouldLogBody(request)
                ? SanitizeForLog(await ReadBodyAsString(request))
                : "<omitted>";
            logger.Info($"REQ {method} {pathWithQuery} body={body}");
        }

        await next(context);

        var statusCode = context.Response.StatusCode;

        if (ShouldSkip(path))
            return;
        if (!ConfigManager.Config.HttpServer.EnableLog) return;
        if (statusCode == 200)
        {
            logger.Info($"{method} {pathWithQuery} => {statusCode}");
        }
        else if (statusCode == 404)
        {
            logger.Warn($"{method} {pathWithQuery} => {statusCode}");
        }
        else
        {
            logger.Error($"{method} {pathWithQuery} => {statusCode}");
        }
    }
}