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

namespace Tor.Controller
{
    /// <summary>
    /// A class containing methods for interacting with a control connection for a tor application.
    /// </summary>
    internal sealed class Connection : IDisposable
    {
        private readonly static string EOL = "\r\n";
        private readonly Client client;

        private volatile bool disposed;
        private StreamReader reader;
        private Socket socket;
        private NetworkStream stream;

        /// <summary>
        /// Initializes a new instance of the <see cref="Connection"/> class.
        /// </summary>
        /// <param name="client">The client hosting the control connection.</param>
        public Connection(Client client)
        {
            this.client = client;
            this.disposed = false;
            this.reader = null;
            this.socket = null;
            this.stream = null;
        }

        /// <summary>
        /// Finalizes an instance of the <see cref="Connection"/> class.
        /// </summary>
        ~Connection()
        {
            Dispose(false);
        }

        #region System.IDisposable

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        private void Dispose(bool disposing)
        {
            if (disposed)
                return;

            if (disposing)
            {
                if (reader != null)
                {
                    reader.Dispose();
                    reader = null;
                }

                if (stream != null)
                {
                    stream.Dispose();
                    stream = null;
                }

                if (socket != null)
                {
                    if (socket.Connected)
                        socket.Shutdown(SocketShutdown.Both);

                    socket.Dispose();
                    socket = null;
                }

                disposed = true;
            }
        }

        #endregion

        /// <summary>
        /// Authenticates the connection by sending the password to the control port.
        /// </summary>
        /// <param name="password">The password used for authentication.</param>
        /// <returns><c>true</c> if the authentication succeeds; otherwise, <c>false</c>.</returns>
        public bool Authenticate(string password)
        {
            if (disposed)
                throw new ObjectDisposedException("this");

            if (password == null)
                password = "";

            if (Write("authenticate \"{0}\"", password))
            {
                ConnectionResponse response = Read();

                if (response.Success)
                    return true;
            }

            return false;
        }

        /// <summary>
        /// Connects to the control port hosted by the client.
        /// </summary>
        /// <returns><c>true</c> if the connection succeeds; otherwise, <c>false</c>.</returns>
        public bool Connect()
        {
            if (disposed)
                throw new ObjectDisposedException("this");

            try
            {
                socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                socket.Connect(client.GetClientAddress(), client.GetControlPort());

                stream = new NetworkStream(socket, false);
                stream.ReadTimeout = 2000;

                reader = new StreamReader(stream);
                
                return true;
            }
            catch
            {
                if (reader != null)
                {
                    reader.Dispose();
                    reader = null;
                }

                if (stream != null)
                {
                    stream.Dispose();
                    stream = null;
                }

                if (socket != null)
                {
                    if (socket.Connected)
                        socket.Shutdown(SocketShutdown.Both);

                    socket.Dispose();
                    socket = null;
                }

                return false;
            }
        }
        
        /// <summary>
        /// Reads a response buffer from the control connection. This method is blocking with a receive timeout of 500ms.
        /// </summary>
        /// <returns>A <see cref="ConnectionResponse"/> containing the response information.</returns>
        public ConnectionResponse Read()
        {
            if (disposed)
                throw new ObjectDisposedException("this");
            if (socket == null || stream == null || reader == null)
                return new ConnectionResponse(StatusCode.Unknown);

            try
            {
                string line = reader.ReadLine();
                
                if (line == null)
                    return new ConnectionResponse(StatusCode.Unknown);

                if (line.Length < 3)
                    return new ConnectionResponse(StatusCode.Unknown);

                int code;

                if (!int.TryParse(line.Substring(0, 3), out code))
                    return new ConnectionResponse(StatusCode.Unknown);

                line = line.Substring(3);

                if (line.Length == 0)
                    return new ConnectionResponse((StatusCode)code, new List<string>() { "" });

                if (line[0] != '+' && line[0] != '-')
                {
                    if (line[0] == ' ')
                        line = line.Substring(1);

                    return new ConnectionResponse((StatusCode)code, new List<string>() { line });
                }

                char id = line[0];

                List<string> responses = new List<string>();
                responses.Add(line.Substring(1));

                try
                {
                    for (line = reader.ReadLine(); line != null; line = reader.ReadLine())
                    {
                        string temp1 = line.Trim();
                        string temp2 = temp1;

                        if (temp1.Length == 0)
                            continue;
                        if (id == '-' && temp2.Length > 3 && temp2[3] == ' ')
                            break;

                        if (temp1.Length > 3 && id != '+')
                            temp1 = temp1.Substring(4);

                        responses.Add(temp1);

                        if (id == '+' && ".".Equals(temp1))
                            break;
                    }
                }
                catch
                {
                }

                return new ConnectionResponse((StatusCode)code, responses);
            }
            catch
            {
                return new ConnectionResponse(StatusCode.Unknown);
            }
        }

        /// <summary>
        /// Writes a command to the connection and flushes the buffer to the control port.
        /// </summary>
        /// <param name="command">The command to write to the connection.</param>
        /// <returns><c>true</c> if the command is dispatched successfully; otherwise, <c>false</c>.</returns>
        public bool Write(string command)
        {
            if (command == null)
                throw new ArgumentNullException("command");

            if (!command.EndsWith(EOL))
                command += EOL;

            return Write(Encoding.ASCII.GetBytes(command));
        }

        /// <summary>
        /// Writes a command to the connection and flushes the buffer to the control port.
        /// </summary>
        /// <param name="command">The command to write to the connection.</param>
        /// <param name="parameters">An optional collection of parameters to serialize into the command.</param>
        /// <returns><c>true</c> if the command is dispatched successfully; otherwise, <c>false</c>.</returns>
        public bool Write(string command, params object[] parameters)
        {
            if (command == null)
                throw new ArgumentNullException("command");

            command = string.Format(command, parameters);

            if (!command.EndsWith(EOL))
                command += EOL;

            return Write(Encoding.ASCII.GetBytes(command));
        }

        /// <summary>
        /// Writes a command to the connection and flushes the buffer to the control port.
        /// </summary>
        /// <param name="buffer">The buffer containing the command data.</param>
        /// <returns><c>true</c> if the command is dispatched successfully; otherwise, <c>false</c>.</returns>
        public bool Write(byte[] buffer)
        {
            if (disposed)
                throw new ObjectDisposedException("this");
            if (buffer == null || buffer.Length == 0)
                throw new ArgumentNullException("buffer");
            if (socket == null || stream == null || reader == null)
                return false;

            try
            {
                stream.Write(buffer, 0, buffer.Length);
                stream.Flush();

                return true;
            }
            catch
            {
                return false;
            }
        }
    }
}