using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Text;

namespace ln.http
{
    public abstract class HttpConnection
    {
        public Listener Listener { get; }
        public IPEndPoint LocalEndpoint => Listener.LocalEndpoint;
        public IPEndPoint RemoteEndpoint { get; }
        public Stream ConnectionStream { get; }
        public string Method { get; }
        //public Uri RequestUri { get; }
        public HttpVersion HttpVersion { get; }

        public string RequestUriLine { get; set; }
        
        public HttpConnection(Listener listener, IPEndPoint remoteEndpoint, Stream connectionStream, string method,
            String requestUriLine, HttpVersion httpVersion)
        {
            Listener = listener;
            RemoteEndpoint = remoteEndpoint;
            ConnectionStream = connectionStream;

            Method = method;
            RequestUriLine = requestUriLine;
            HttpVersion = httpVersion;
        }

        public abstract void Run();

        public static string ReadLine(Stream stream) => ReadLine(stream, Encoding.ASCII);

        public static string ReadLine(Stream stream, Encoding encoding)
        {
            if (!stream.CanRead)
                return null;

            byte[] line = new byte[1024];
            int n = 0;
            int ch;
            while ((ch = stream.ReadByte()) != -1)
            {
                switch (ch)
                {
                    case '\r':
                        break;
                    case '\n':
                        return encoding.GetString(line, 0, n);
                    default:
                        line[n++] = (byte)ch;
                        break;
                }
            }

            if (n > 0)
                return encoding.GetString(line, 0, n);

            return null;
        }

        public static bool ReadRequestLine(Stream stream, out string method, out string requestUri,
            out HttpVersion httpVersion)
        {
            string requestLine = ReadLine(stream);
            if (requestLine is null)
            {
                method = null;
                requestUri = null;
                httpVersion = HttpVersion.None;
                return false;
            }

            int idxSpace1 = requestLine.IndexOf(' ');
            int idxSpace2 = requestLine.IndexOf(' ', idxSpace1 + 1);

            if ((idxSpace1 > 0) && (idxSpace2 > 0))
            {
                method = requestLine.Substring(0, idxSpace1);
                requestUri = requestLine.Substring(idxSpace1 + 1, (idxSpace2 - idxSpace1 - 1));
                string protocol = requestLine.Substring(idxSpace2 + 1);
                httpVersion = HttpVersion.None;

                if ("PRI".Equals(method) && Http2PrefaceUri.Equals(requestUri) && "HTTP/2.0".Equals(protocol))
                    httpVersion = HttpVersion.HTTP2;
                else if ("HTTP/1.0".Equals(protocol))
                    httpVersion = HttpVersion.HTTP10;
                else if ("HTTP/1.1".Equals(protocol))
                    httpVersion = HttpVersion.HTTP11;

                return true;
            }

            method = null;
            requestUri = null;
            httpVersion = HttpVersion.None;
            return false;
        }

        public abstract void SendResponse(HttpRequestContext requestContext);

        private static string Http2PrefaceUri = "*";
    }
}