using System;
using System.Collections.Generic;
using System.Net;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Laservall.Solidworks.Server
{
    internal sealed class RequestRouter
    {
        public delegate Task RouteHandler(HttpListenerContext context, CancellationToken ct);

        private readonly List<RouteEntry> _routes = new List<RouteEntry>();

        public void Map(string method, string path, RouteHandler handler)
        {
            _routes.Add(new RouteEntry
            {
                Method = method?.ToUpperInvariant(),
                Path = path,
                Handler = handler
            });
        }

        public void Get(string path, RouteHandler handler)
        {
            Map("GET", path, handler);
        }

        public void Post(string path, RouteHandler handler)
        {
            Map("POST", path, handler);
        }

        public async Task RouteAsync(HttpListenerContext context, CancellationToken ct)
        {
            string requestPath = context.Request.Url.AbsolutePath.TrimEnd('/');
            if (string.IsNullOrEmpty(requestPath))
            {
                requestPath = "/";
            }

            string method = context.Request.HttpMethod.ToUpperInvariant();

            foreach (var route in _routes)
            {
                bool methodMatch = route.Method == null || route.Method == method;
                bool pathMatch = string.Equals(route.Path, requestPath, StringComparison.OrdinalIgnoreCase);

                if (methodMatch && pathMatch)
                {
                    await route.Handler(context, ct);
                    return;
                }
            }

            await SendNotFound(context.Response);
        }

        private static async Task SendNotFound(HttpListenerResponse response)
        {
            response.StatusCode = 404;
            response.ContentType = "application/json; charset=utf-8";
            byte[] body = Encoding.UTF8.GetBytes("{\"error\":\"Not Found\"}");
            response.ContentLength64 = body.Length;
            await response.OutputStream.WriteAsync(body, 0, body.Length);
            response.Close();
        }

        private struct RouteEntry
        {
            public string Method;
            public string Path;
            public RouteHandler Handler;
        }
    }
}