DTLib/DTLib.Web/Routes/SimpleRouter.cs

namespace DTLib.Web.Routes;

public class SimpleRouter : IRouter
{
    /// route for any url that doesn't have its own handler
    public record RouteWithMethod(HttpMethod method, IRouteHandler routeHandler)
    {
        public bool CheckMethod(HttpMethod requestMethod) => (requestMethod & method) != 0;

        public bool CheckMethod(string requestMethodStr)
            => Enum.TryParse<HttpMethod>(requestMethodStr, out var requestMethod)
               && CheckMethod(requestMethod);
    }

    private readonly Dictionary<string, RouteWithMethod> _routes = new();
    private readonly ILogger _logger;

    public RouteWithMethod? DefaultRoute { get; set; }

    public SimpleRouter(ILogger logger)
    {
        _logger = new ContextLogger(nameof(SimpleRouter), logger);
    }

    public void MapRoute(string url, HttpMethod method, IRouteHandler route)
        => _routes.Add(url, new RouteWithMethod(method, route));

    public void MapRoute(string url, HttpMethod method,
        Func<HttpListenerContext, ContextLogger, Task<HttpStatusCode>> route)
        => MapRoute(url, method, new DelegateRouteHandler(route));

    public async Task Resolve(HttpListenerContext ctx, ContextLogger requestLogger)
    {
        HttpStatusCode status = HttpStatusCode.InternalServerError;
        try
        {
            string? requestPath = ctx.Request.Url?.AbsolutePath;
            if (string.IsNullOrEmpty(requestPath))
                requestPath = "/";
            
            if(!_routes.TryGetValue(requestPath!, out var routeWithMethod))
                routeWithMethod = DefaultRoute;

            if (routeWithMethod is null)
            {
                _logger.LogWarn(nameof(SimpleRouter),
                    $"couldn't resolve request path {ctx.Request.HttpMethod} {requestPath}");
                status = HttpStatusCode.NotFound;
            }
            else if (!routeWithMethod.CheckMethod(ctx.Request.HttpMethod))
            {
                _logger.LogWarn(nameof(SimpleRouter),
                    $"received request with invalid method {ctx.Request.HttpMethod} {requestPath}");
                status = HttpStatusCode.MethodNotAllowed;
            }
            else status = await routeWithMethod.routeHandler.HandleRequest(ctx, requestLogger);
        }
        finally
        {
            ctx.Response.StatusCode = (int)status;
            await ctx.Response.OutputStream.FlushAsync();
            ctx.Response.OutputStream.Close();
        }
    }
}