CSharpHttpServer/SimpleHttpServer/HttpServer.cs

using System.Net;
using System.Reflection;

namespace SimpleHttpServer;

public sealed class HttpServer {

    private Thread? _listenerThread;
    private HttpListener _listener;
    private readonly Dictionary<(string path, HttpRequestType rType), HttpEndpointHandler> _plainEndpoints = new();
    private readonly Dictionary<(string path, HttpRequestType rType), HttpEndpointHandler> _pparamEndpoints = new();

    public string Url { get; private set; }
    public Func<HttpListenerContext, HttpResponseBuilder> Default404 { get; private set; }

    public static HttpServer Create(int port, string url, params Type[] apiDefinitions) => Create(Console.Error, port, url, false, apiDefinitions);

    public static HttpServer Create(TextWriter error, int port, string url, bool throwOnInvalidEndpoint, params Type[] apiDefinitions) {
        var epDict = new Dictionary<(string, HttpRequestType), HttpEndpointHandler>();

        foreach (var definition in apiDefinitions) {
            foreach (var endpoint in definition.GetMethods()) {
                var attrib = endpoint.GetCustomAttributes()
                    .Where(x => x.GetType().IsAssignableTo(typeof(HttpEndpoint<>)))
                    .Select(x => (HttpEndpoint<IAuthorizer>) x)
                    .SingleOrDefault();

                if (attrib == null) {
                    continue;
                }

                // sanity checks
                if (!endpoint.IsStatic) {
                    PrintErrorOrThrow(error, endpoint, throwOnInvalidEndpoint, "HttpEndpointAttribute is only valid on static methods!");
                    continue;
                }
                var myParams = endpoint.GetParameters();
                if (myParams.Length <= 0 || !myParams[0].GetType().IsAssignableFrom(typeof(HttpListenerContext))) {
                    PrintErrorOrThrow(error, endpoint, throwOnInvalidEndpoint, $"{GetFancyMethodName(endpoint)} needs to have a HttpListenerContext as its first argument!");
                    continue;
                }
                if (!endpoint.ReturnParameter.ParameterType.IsAssignableTo(typeof(HttpResponseBuilder))) {
                    PrintErrorOrThrow(error, endpoint, throwOnInvalidEndpoint, $"{GetFancyMethodName(endpoint)} needs to have a HttpResponseBuilder as the return type!");
                }

                var path = attrib.Location;
                int idx = path.IndexOf('{');
                if (idx >= 0) {
                    // this path contains path parameters
                    throw new NotImplementedException("Implement path parameters!");
                }
                var qparams = new List<(string, Type)>();
            }
        }
        return null!;
    }


    public void Shutdown() {
        Shutdown(-1);
    }

    public bool Shutdown(int timeout) {
        if (_listenerThread == null) {
            throw new InvalidOperationException("Cannot shutdown HttpServer that has not been started");
        }
        _listenerThread.Interrupt();
        bool exited = true;
        if (timeout < 0) {
            _listenerThread.Join();
        } else {
            exited = _listenerThread.Join(timeout);
        }
        _listenerThread = null;
        _listener.Stop();
        return exited;
    }

    public void Start() {
        _listenerThread = new Thread(RunServer);
        _listener.Start();
        _listenerThread.Start();
    }


    private void RunServer() {
        try {
            for (; ; ) {
                var ctx = _listener.GetContext();

                ThreadPool.QueueUserWorkItem((localCtx) => {
                    HttpRequestType type;
                    if (!Enum.TryParse(localCtx.Request.HttpMethod, out type)) {
                        Default404(localCtx).SendResponse(localCtx.Response);
                        return;
                    }
                    var path = localCtx.Request.Url!.LocalPath.Replace('\\', '/');
                    HttpEndpointHandler? ep = null;
                    if (!_plainEndpoints.TryGetValue((path, type), out ep)) {
                        // not found among plain endpoints
                        foreach (var epk in _pparamEndpoints.Keys) {
                            if (epk.rType == type && path.StartsWith(epk.path)) {
                                ep = _pparamEndpoints[epk];
                                break;
                            }
                        }
                        if (ep == null) {
                            Default404(localCtx).SendResponse(localCtx.Response);
                            return;
                        }
                    }
                    ep.Handle(localCtx);
                }, ctx, false);
            }
        } catch (ThreadInterruptedException) {
            // this can only be reached when listener.GetContext is interrupted
            // safely exit main loop
        }
    }

    private static void PrintErrorOrThrow(TextWriter error, MethodInfo method, bool forceThrow, string msg) {
        if (forceThrow) {
            throw new Exception(msg);
        } else {
            error.WriteLine($"> {msg}\n  skipping {GetFancyMethodName(method)} ...");
        }
    }

    private static string GetFancyMethodName(MethodInfo method) => method.DeclaringType!.Name + "#" + method.Name;
}