using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;

namespace NNTPReader
{
    public partial class Form1 : Form
    {
        // Used for receiving info
        byte[] downBuffer = new byte[2048];
        // Used for sending commands
        byte[] byteSendInfo = new byte[2048];
        // Used for connecting a socket to the NNTP server
        TcpClient tcpClient;
        // Used for sending and receiving information
        NetworkStream strRemote;
        // Stores various responses
        string Response;
        // Number of bytes in the buffer
        int bytesSize;
        // Stores the ID of the first message in a newsgroup
        int firstID;
        // Stores the ID of the last message in a newsgroup
        int lastID;
        // Stores chunks of the articles from the buffer
        string NewChunk;

        public Form1()
        {
            InitializeComponent();
        }

        private void btnGo_Click(object sender, EventArgs e)
        {
            // Open the socket to the server
            tcpClient = new System.Net.Sockets.TcpClient(txtNNTPServer.Text, 119);
            strRemote = tcpClient.GetStream();
            // Read the bytes
            bytesSize = strRemote.Read(downBuffer, 0, 2048);
            // Retrieve the response
            Response = System.Text.Encoding.ASCII.GetString(downBuffer, 0, bytesSize);
            // Just as in HTTP, if code 200 is not returned, something's not right
            if (Response.Substring(0, 3) != "200")
            {
                MessageBox.Show("The server returned an unexpected response.", "Connection failed", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
            // Show the response
            txtLog.Text = Response + "\n";

            // Make the request to list all newsgroups
            byteSendInfo = StringToByteArr("LIST\r\n");
            strRemote.Write(byteSendInfo, 0, byteSendInfo.Length);
            Response = "";

            // Loop to retrieve a list of newsgroups
            while ((bytesSize = strRemote.Read(downBuffer, 0, downBuffer.Length)) > 0)
            {
                // Get the chunk of string
                NewChunk = Encoding.ASCII.GetString(downBuffer, 0, bytesSize);
                Response += NewChunk;
                // If the string ends in a "\r\n.\r\n" then the list is over
                if (NewChunk.Substring(NewChunk.Length - 5, 5) == "\r\n.\r\n")
                {
                    // Remove the "\r\n.\r\n" from the end of the string
                    Response = Response.Substring(0, Response.Length - 3);
                    break;
                }
            }
            // Split lines into an array
            string[] ListLines = Response.Split('\n');
            // Loop line by line
            foreach (String ListLine in ListLines)
            {
                // If the response starts with 215, it's the line that indicates the status
                if (ListLine.Length > 3 && ListLine.Substring(0, 3) == "215")
                {
                    // Add the status response line to the log window
                    txtLog.Text += ListLine + "\r\n";
                }
                else
                {
                    // Add the newsgroup to the combobox
                    string[] Newsgroup = ListLine.Split(' ');
                    cmbNewsgroups.Items.Add(Newsgroup[0]);
                }
            }
        }

        public static byte[] StringToByteArr(string str)
        {
            System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
            return encoding.GetBytes(str);
        }

        private void btnGetNews_Click(object sender, EventArgs e)
        {
            // If a newsgroup is selected in the ComboBox
            if (cmbNewsgroups.SelectedIndex != -1)
            {
                // Request a certain newsgroup
                byteSendInfo = StringToByteArr("GROUP " + cmbNewsgroups.SelectedItem.ToString() + "\r\n");
                strRemote.Write(byteSendInfo, 0, byteSendInfo.Length);
                Response = "";
                bytesSize = strRemote.Read(downBuffer, 0, 2048);
                Response = System.Text.Encoding.ASCII.GetString(downBuffer, 0, bytesSize);
                // Split the information about the newsgroup by blank spaces
                string[] Group = System.Text.Encoding.ASCII.GetString(downBuffer, 0, bytesSize).Split(' ');
                // Show information about the newsgroup in the txtLog TextBox
                Response += Group[1] + " messages in the group (messages " + Group[2] + " through " + Group[3] + ")\r\n";
                txtLog.Text += Response;
                Response = "";
                // The ID of the first article in this newsgroup
                firstID = Convert.ToInt32(Group[2]);
                // The ID of the last article in this newsgroup
                lastID = Convert.ToInt32(Group[3]);
            }
            else
            {
                MessageBox.Show("Please connect to a server and select a newsgroup from the dropdown list first.", "Newsgroup retrieval", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        private void btnNext_Click(object sender, EventArgs e)
        {
            NextArticle();
        }

        private void NextArticle()
        {
            if (tcpClient != null && tcpClient.Connected == true && firstID >= 0)
            {
                // Get the header
                txtHead.Text = "";
                // Initialize the buffer to 2048 bytes
                downBuffer = new byte[2048];
                // Request the headers of the article
                byteSendInfo = StringToByteArr("HEAD " + firstID + "\r\n");
                // Send the request to the NNTP server
                strRemote.Write(byteSendInfo, 0, byteSendInfo.Length);
                while ((bytesSize = strRemote.Read(downBuffer, 0, downBuffer.Length)) > 0)
                {
                    NewChunk = System.Text.Encoding.ASCII.GetString(downBuffer, 0, bytesSize);
                    txtHead.Text += NewChunk;
                    // No such article in the group
                    if (NewChunk.Substring(0, 3) == "423")
                    {
                        // Ready for the next article, unless there is nothing else there...
                        if (firstID <= lastID)
                        {
                            firstID++;
                        }
                        // Next article please
                        NextArticle();
                        // End this method because it's retrieving a nonexistent article
                        return;
                    }
                    else if (NewChunk.Substring(NewChunk.Length - 5, 5) == "\r\n.\r\n")
                    {
                        // If the last thing in the buffer is "\r\n.\r\n" the message's finished
                        break;
                    }
                }

                // Get the body
                txtBody.Text = "";
                // Initialize the buffer to 2048 bytes
                downBuffer = new byte[2048];
                // Request the headers of the article
                byteSendInfo = StringToByteArr("BODY " + firstID + "\r\n");
                // Send the request to the NNTP server
                strRemote.Write(byteSendInfo, 0, byteSendInfo.Length);
                while ((bytesSize = strRemote.Read(downBuffer, 0, downBuffer.Length)) > 0)
                {
                    NewChunk = System.Text.Encoding.ASCII.GetString(downBuffer, 0, bytesSize);
                    txtBody.Text += NewChunk;
                    // If the last thing in the buffer is "\r\n.\r\n" the message's finished
                    if (NewChunk.Substring(NewChunk.Length - 5, 5) == "\r\n.\r\n")
                    {
                        break;
                    }
                }

                // Ready for the next article, unless there is nothing else there...
                if (firstID <= lastID)
                {
                    firstID++;
                }
            }
            else
            {
                MessageBox.Show("Please select a newsgroup from the dropdown list and click on 'Get News' first.", "Newsgroup retrieval", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }
    }
}