using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Net;
using System.Net.Sockets;
using System.Text.Json;
using System.Threading;
using Tesla;
using Tesla.Net;

namespace VPod;

/// <summary>
/// vPOD's stand-in for the pod's TeslaLauncher service: the OFB-encrypted,
/// framed-JSON ILauncherService RPC server on TCP 53290 that the console's
/// Site Management / SitePanel talk to (client: PodManagerConnection).
/// Mirrors Launcher/TeslaLauncherService.HandleConsoleClient:
///
///   - OFB/CONF handshake on the provisioned 32-byte session key
///     (NegotiateCryptoStreams is symmetric, so the shared implementation
///     serves the pod side too).
///   - Loop: PodRpc.ReadRequest -> dispatch by method name -> WriteResponse.
///   - After answering InitiateInstallProduct, the same connection carries the
///     product zip out-of-band ([8-byte Int64 size][raw bytes]) and then closes;
///     the console polls GetOutOfBandProgress on its main connection meanwhile,
///     so multiple concurrent client connections are required.
///   - Install completion reports 99% (not 100) — the console's
///     InstallProductWorker breaks its retry loop only on 99.
///
/// All state lives in <see cref="VirtualLauncher" />; unlike the real service,
/// postinstall.bat from a package is logged but never executed.
/// </summary>
internal sealed class LauncherRpcServer
{
	public const int ManagePort = 53290;

	private readonly VirtualLauncher mLauncher;
	private readonly int mPort;
	private byte[] mSessionKey;
	private TcpListener mListener;
	private Thread mAcceptThread;
	private volatile bool mRunning;

	private readonly object mClientsLock = new object();
	private readonly List<TcpClient> mClients = new List<TcpClient>();

	public event Action<string> Log;
	public event Action<int> ConnectionsChanged; // number of active console sessions

	public bool IsListening => mRunning;

	public LauncherRpcServer(VirtualLauncher launcher, int port = ManagePort)
	{
		mLauncher = launcher;
		mPort = port;
	}

	/// <summary>Starts listening with the given provisioned session key. Throws if
	/// the port cannot be bound (e.g. a real TeslaLauncher on the same machine).</summary>
	public void Start(byte[] sessionKey)
	{
		if (mRunning)
		{
			return;
		}
		mSessionKey = sessionKey;
		mListener = new TcpListener(IPAddress.Any, mPort);
		mListener.Start();
		mRunning = true;
		mAcceptThread = new Thread(AcceptLoop) { IsBackground = true, Name = "vPOD-launcher-accept" };
		mAcceptThread.Start();
		Log?.Invoke($"Launcher RPC listening on TCP {mPort}.");
	}

	public void Stop()
	{
		if (!mRunning)
		{
			return;
		}
		mRunning = false;
		try { mListener?.Stop(); } catch { }
		lock (mClientsLock)
		{
			foreach (TcpClient client in mClients)
			{
				try { client.Close(); } catch { }
			}
			mClients.Clear();
		}
		ConnectionsChanged?.Invoke(0);
		Log?.Invoke("Launcher RPC stopped.");
	}

	private void AcceptLoop()
	{
		while (mRunning)
		{
			TcpClient client;
			try
			{
				client = mListener.AcceptTcpClient();
			}
			catch
			{
				break; // listener stopped
			}
			// Unlike the Munga side, the console legitimately opens several
			// concurrent connections (main session + out-of-band installs).
			Thread worker = new Thread(() => HandleClient(client)) { IsBackground = true, Name = "vPOD-launcher-session" };
			worker.Start();
		}
	}

	private void HandleClient(TcpClient client)
	{
		string remote;
		try
		{
			remote = client.Client.RemoteEndPoint?.ToString() ?? "?";
		}
		catch
		{
			remote = "?";
		}
		lock (mClientsLock)
		{
			mClients.Add(client);
			ConnectionsChanged?.Invoke(mClients.Count);
		}
		try
		{
			using (client)
			{
				NetworkStream netStream = client.GetStream();
				// Same session timeouts as the real service: an idle console
				// connection is dropped after 30 s and the console reconnects.
				netStream.WriteTimeout = 10000;
				netStream.ReadTimeout = 30000;

				if (!PodConfigurationServer.NegotiateCryptoStreams(netStream, mSessionKey, out Stream outStream, out Stream inStream))
				{
					Log?.Invoke($"{remote}: CONF mismatch — session key mismatch, dropping connection.");
					return;
				}
				Log?.Invoke($"Console session started from {remote}.");
				SessionLoop(remote, inStream, outStream);
			}
		}
		catch (Exception ex)
		{
			Log?.Invoke($"{remote}: session error: {ex.Message}");
		}
		finally
		{
			lock (mClientsLock)
			{
				mClients.Remove(client);
				ConnectionsChanged?.Invoke(mClients.Count);
			}
			Log?.Invoke($"Console session from {remote} ended.");
		}
	}

	private void SessionLoop(string remote, Stream inStream, Stream outStream)
	{
		while (mRunning)
		{
			RpcRequest request;
			try
			{
				request = PodRpc.ReadRequest(inStream);
			}
			catch
			{
				return; // disconnected (EOF/IO/timeout)
			}
			if (request == null)
			{
				return;
			}

			string method = request.Method ?? "???";
			IReadOnlyList<JsonElement> args = request.Args ?? new List<JsonElement>();
			// GetOutOfBandProgress is polled 4x/second during installs — don't log it.
			if (method != "GetOutOfBandProgress" && method != "Ping")
			{
				Log?.Invoke($"<- {method}");
			}

			object result = null;
			string error = null;
			try
			{
				result = Dispatch(method, args);
			}
			catch (Exception ex)
			{
				error = ex.Message;
				Log?.Invoke($"{method} ERROR: {ex.Message}");
			}

			try
			{
				PodRpc.WriteResponse(outStream, result, error);
			}
			catch
			{
				return; // disconnected while writing
			}

			// The product zip follows the InitiateInstallProduct response on this
			// same connection, then the console closes it.
			if (method == "InitiateInstallProduct" && error == null && result is Guid installGuid)
			{
				ReceiveInstallFile(inStream, installGuid);
				return;
			}
		}
	}

	/// <summary>Maps the console's method names (dispatch-by-name, including the
	/// get_/set_ property accessors) onto the VirtualLauncher. Mirrors the real
	/// service's DispatchCommandAsync.</summary>
	private object Dispatch(string method, IReadOnlyList<JsonElement> args)
	{
		switch (method)
		{
		case "Ping":
			return args.Count > 0 && args[0].ValueKind != JsonValueKind.Null
				? mLauncher.Ping(args[0].GetDateTime())
				: DateTime.Now;

		case "GetInstalledApps":
			return mLauncher.GetInstalledApps();

		case "GetLaunchableApps":
			return mLauncher.GetLaunchableApps();

		case "GetLaunchedApps":
			return mLauncher.GetLaunchedApps();

		case "FullUpdate":
			return mLauncher.FullUpdate();

		case "GetOutOfBandProgress":
			return mLauncher.GetOutOfBandProgress(args[0].GetGuid());

		case "InitiateInstallProduct":
			return mLauncher.InitiateInstallProduct();

		case "InstallApp":
			mLauncher.InstallApp(args[0].Deserialize<LaunchData>(PodRpc.JsonOptions));
			return null;

		case "UninstallApp":
			mLauncher.UninstallApp(args[0].GetGuid());
			return null;

		case "RemoveApp":
			mLauncher.RemoveApp(args[0].GetGuid());
			return null;

		case "LaunchApp":
			return mLauncher.LaunchApp(args[0].GetGuid());

		case "KillApp":
			mLauncher.KillApp(args[0].GetGuid(), args[1].GetInt32());
			return null;

		case "KillAllOfType":
			mLauncher.KillAllOfType(args[0].GetGuid());
			return null;

		case "KillAllApps":
			mLauncher.KillAllApps();
			return null;

		case "Shutdown":
			mLauncher.Shutdown(args[0].GetBoolean());
			return null;

		case "ClearStore":
			mLauncher.ClearStore();
			return null;

		case "get_VolumeLevel":
			return mLauncher.VolumeLevel;

		case "set_VolumeLevel":
			mLauncher.VolumeLevel = args[0].GetSingle();
			return null;

		default:
			Log?.Invoke($"Unknown command \"{method}\" — answering null.");
			return null;
		}
	}

	/// <summary>Receives the out-of-band product zip and extracts it into the
	/// virtual games root, reporting progress exactly like the real service:
	/// 0-50% receive, 50-95% extract, 99% "Complete" (IsCompleted).</summary>
	private void ReceiveInstallFile(Stream stream, Guid callId)
	{
		string tempZip = null;
		try
		{
			byte[] sizeBuffer = ReadExact(stream, 8);
			long fileSize = BitConverter.ToInt64(sizeBuffer, 0);
			Log?.Invoke($"Install {callId:N}: receiving {fileSize:N0} bytes...");
			mLauncher.UpdateProgress(callId, 0, "Receiving file...");

			tempZip = Path.Combine(mLauncher.DataDirectory, $"install_{callId:N}.zip");
			using (FileStream fs = File.Create(tempZip))
			{
				byte[] buffer = new byte[65536];
				long received = 0;
				while (received < fileSize)
				{
					int toRead = (int)Math.Min(buffer.Length, fileSize - received);
					int read = stream.Read(buffer, 0, toRead);
					if (read == 0)
					{
						throw new IOException("Connection closed during file transfer.");
					}
					fs.Write(buffer, 0, read);
					received += read;
					mLauncher.UpdateProgress(callId, (int)(received * 50 / fileSize), "Receiving file...");
				}
			}

			mLauncher.UpdateProgress(callId, 50, "Extracting...");
			string gamesRoot = Path.GetFullPath(mLauncher.GamesRoot);
			Directory.CreateDirectory(gamesRoot);
			using (ZipArchive zip = ZipFile.OpenRead(tempZip))
			{
				int total = zip.Entries.Count;
				int done = 0;
				foreach (ZipArchiveEntry entry in zip.Entries)
				{
					string destPath = Path.GetFullPath(Path.Combine(gamesRoot, entry.FullName));
					// Zip-slip protection, as in the real service.
					if (!destPath.StartsWith(gamesRoot + Path.DirectorySeparatorChar, StringComparison.OrdinalIgnoreCase))
					{
						continue;
					}
					if (string.IsNullOrEmpty(entry.Name))
					{
						Directory.CreateDirectory(destPath);
					}
					else
					{
						Directory.CreateDirectory(Path.GetDirectoryName(destPath));
						entry.ExtractToFile(destPath, overwrite: true);
					}
					done++;
					mLauncher.UpdateProgress(callId, 50 + done * 45 / Math.Max(total, 1), "Extracting...");
				}
			}
			Log?.Invoke($"Install {callId:N}: extracted to {gamesRoot}");

			// The real service runs (then deletes) a packaged postinstall.bat here.
			// vPOD never executes package scripts on the host machine.
			string postInstall = Path.Combine(gamesRoot, "postinstall.bat");
			if (File.Exists(postInstall))
			{
				mLauncher.UpdateProgress(callId, 96, "Skipping postinstall (vPOD)...");
				Log?.Invoke($"Install {callId:N}: postinstall.bat present — NOT executed (vPOD), removed.");
				try { File.Delete(postInstall); } catch { }
			}

			mLauncher.UpdateProgress(callId, 99, "Complete", isCompleted: true);
			Log?.Invoke($"Install {callId:N}: complete.");
		}
		catch (Exception ex)
		{
			mLauncher.UpdateProgress(callId, 0, $"Failed: {ex.Message}", isCompleted: true);
			Log?.Invoke($"Install {callId:N} FAILED: {ex.Message}");
		}
		finally
		{
			try { if (tempZip != null) File.Delete(tempZip); } catch { }
		}
	}

	private static byte[] ReadExact(Stream stream, int count)
	{
		byte[] buffer = new byte[count];
		int offset = 0;
		while (offset < count)
		{
			int read = stream.Read(buffer, offset, count - offset);
			if (read == 0)
			{
				throw new EndOfStreamException("Connection closed mid-read.");
			}
			offset += read;
		}
		return buffer;
	}
}