using System.Net.Security;
using System.Net.Sockets;
using System.Text;
using System.Text.RegularExpressions;

namespace MailFromWho
{
    internal class Imap
    {
#pragma warning disable CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.
        private static StreamWriter _sw;
        private static TcpClient _tcpc;
        private static SslStream _ssl;
#pragma warning restore CS8618 // Non-nullable field must contain a non-null value when exiting constructor. Consider declaring as nullable.

        private readonly Settings _settings;

        public Imap(Settings settings)
        {
            _settings = settings;
        }

        internal void GetAllAddresses()
        {
            try
            {
                var path = Environment.CurrentDirectory + $"{Path.DirectorySeparatorChar}{_settings.IntermediateFile}";
                var username = _settings.UserName;
                var imapServer = _settings.ImapServer;
                var sslPort = _settings.SslPort;
                var password = string.Empty;

                while (string.IsNullOrEmpty(password))
                {
                    Console.Write($"Enter password of '{username}' @ '{imapServer}': ");
                    var fgColour = Console.ForegroundColor;
                    Console.ForegroundColor = Console.BackgroundColor;
                    password = Console.ReadLine();
                    Console.ForegroundColor = fgColour;
                }

                if (System.IO.File.Exists(path))
                {
                    System.IO.File.Delete(path);
                }

                _sw = new System.IO.StreamWriter(System.IO.File.Create(path));
                // there should be no gap between the imap command and the \r\n       
                // ssl.read() -- while ssl.readbyte!= eof does not work because there is no eof from server 
                // cannot check for \r\n because in case of larger response from server ex:read email message 
                // there are lot of lines so \r \n appears at the end of each line 
                //ssl.timeout sets the underlying tcp connections timeout if the read or write 
                //time out exceeds then the undelying connection is closed 
                _tcpc = new System.Net.Sockets.TcpClient(imapServer, sslPort);

                _ssl = new System.Net.Security.SslStream(_tcpc.GetStream());
                _ssl.ReadTimeout = 200;
                _ssl.AuthenticateAsClient(imapServer);
                receiveResponse();

                sendRequest("$ LOGIN " + username + " " + password + "\r\n");
                receiveResponse();

                // Get all folders
                sendRequest("$ LIST " + "\"\"" + " \"*\"" + "\r\n");
                var foldersRaw = receiveResponse();
                var matches = Regex.Matches(foldersRaw, @"\s(INBOX.*?)\r\n");
                var folders = new List<string>();
                foreach (Match match in matches)
                {
                    folders.Add(match.Groups[1].Value.Replace("\"", ""));
                }


                foreach (var folder in folders)
                {
                    sendRequest($"$ SELECT \"{folder}\"\r\n");
                    receiveResponse();

                    sendRequest($"$ STATUS \"{folder}\" (MESSAGES)\r\n");
                    var statusRaw = receiveResponse();
                    var regex = new Regex(@"MESSAGES.(\d+)");
                    var aantalBerichten = int.Parse(regex.Match(statusRaw).Groups[1].Value);

                    var outputStr = $"FOLDER {folder} heeft {aantalBerichten} berichten";
                    WriteOutput(outputStr, true);

                    sendRequest("$ FETCH 1:* body[header.fields (from)]\r\n");
                    var fromRaw = receiveResponse();
                    // From: "flypacificblue.com" <reservations@flypacificblue.com>
                    //matches = Regex.Matches(fromRaw, "From:\\s\\\"?(.[^\"]*?)\\\"?\\<(.*)\\>\r\n");
                    matches = Regex.Matches(fromRaw, @"From:\s(.*)\r\n");
                    var froms = new List<string>();
                    foreach (Match match in matches)
                    {
                        var addressLine = match.Groups[1].Value;
                        froms.Add(addressLine);
                        WriteOutput(addressLine, true);
                    }
                    WriteOutput("", true);
                }

                receiveResponse();


                sendRequest("$ LOGOUT\r\n");
                receiveResponse();
            }
            catch (Exception ex)
            {
                Console.WriteLine("error: " + ex.Message);
            }
            finally
            {
                if (_sw != null)
                {
                    _sw.WriteLine("");
                    _sw.Close();
                    _sw.Dispose();
                }
                if (_ssl != null)
                {
                    _ssl.Close();
                    _ssl.Dispose();
                }
                if (_tcpc != null)
                {
                    _tcpc.Close();
                }
            }
        }

        private void WriteOutput(string outputStr, bool newline)
        {
            Console.Write(outputStr);
            _sw.Write(outputStr);

            if (newline)
            {
                Console.WriteLine("");
                _sw.WriteLine("");
            }
        }

        private void sendRequest(string command)
        {
            byte[] dummy;

            try
            {
                if (command != "")
                {
                    if (_tcpc.Connected)
                    {
                        dummy = Encoding.ASCII.GetBytes(command);
                        _ssl.Write(dummy, 0, dummy.Length);
                    }
                    else
                    {
                        throw new ApplicationException("TCP CONNECTION DISCONNECTED");
                    }
                }
                _ssl.Flush();
            }
            catch (Exception ex)
            {
                throw new ApplicationException(ex.Message);
            }
        }


        private string receiveResponse()
        {
            var sb = new StringBuilder();
            byte[] buffer;

            try
            {
                var bytes = 0;
                // First wait for some data, but not too long...
                var waitTime = DateTime.Now.AddMilliseconds(200);
                while (bytes <= 0 && DateTime.Now < waitTime)
                {
                    try
                    {
                        buffer = new byte[2048];
                        bytes = _ssl.Read(buffer, 0, 2048);
                        sb.Append(ReturnCleanASCII(Encoding.ASCII.GetString(buffer, 0, bytes)));
                    }
                    catch (IOException)
                    {
                        bytes = -1;
                    }
                }
                while (bytes > 0)
                {
                    try
                    {
                        buffer = new byte[2048];
                        bytes = _ssl.Read(buffer, 0, 2048);
                        sb.Append(ReturnCleanASCII(Encoding.ASCII.GetString(buffer, 0, bytes)));
                    }
                    catch (IOException)
                    {
                        bytes = -1;
                    }
                }
            }
            catch (Exception ex)
            {
                throw new ApplicationException(ex.Message);
            }
            return sb.ToString();
        }


        private string ReturnCleanASCII(string s)
        {
            StringBuilder sb = new StringBuilder(s.Length);
            foreach (char c in s)
            {
                int i = (int)c;
                if (i > 127) // you probably don't want 127 either
                    continue;
                if (i < 32 && (i != 10 && i != 13))  // I bet you don't want control characters 
                    continue;
                sb.Append(c);
            }
            return sb.ToString();
        }
    }
}