using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Threading;
// No System.Text.Json on net40 — persistence goes through Newtonsoft, which
// writes the same JSON shape (public fields, PascalCase; see PodRpcProtocol).
using Newtonsoft.Json;
using Tesla.Net;

namespace VPod;

/// <summary>
/// The state behind vPOD's virtual TeslaLauncher service: the installed-app
/// registry, the (simulated) launched-process table, the volume level, the
/// install-progress map and the session-key store. This is the pod-side model
/// that <see cref="LauncherRpcServer" /> dispatches the console's
/// ILauncherService calls onto — the vPOD equivalent of the real launcher's
/// Service+Agent pair. Launch/Kill simulate PIDs by default; with
/// <see cref="RealLaunch" /> set they start and terminate real processes,
/// mirroring the Agent.
///
/// Persisted state:
///   %LocalAppData%\vPOD\TeslaKeyStore.key  session key, launcher format: [1-byte len][key]
///   %LocalAppData%\vPOD\LaunchApps.json    installed apps (the wire LaunchData list, PodRpc JSON)
///   C:\Games\                              where InstallProduct zips are extracted — the
///                                          REAL games root, same as the launcher's GAMES_DIR,
///                                          so deployed products land where their catalog
///                                          launch entries point (C:\Games\...\*.exe)
/// </summary>
internal sealed class VirtualLauncher
{
	/// <summary>The launcher's GAMES_DIR. Tests override via the ctor for isolation.</summary>
	public const string DefaultGamesRoot = @"C:\Games";

	private readonly object mLock = new object();
	private readonly List<LaunchData> mInstalledApps = new List<LaunchData>();
	private readonly List<LaunchedAppData> mLaunchedApps = new List<LaunchedAppData>();
	private readonly Dictionary<int, Process> mRealProcesses = new Dictionary<int, Process>(); // pid -> live process, RealLaunch mode
	private readonly Dictionary<Guid, OutOfBandProgress> mInstallProgress = new Dictionary<Guid, OutOfBandProgress>();
	private float mVolumeLevel = 1.0f;
	private int mNextPid = 4000;

	/// <summary>When set, LaunchApp actually starts the entry's ExeFile (like the
	/// real Agent) instead of recording a simulated PID, and the Kill* commands
	/// terminate those processes. Toggled from the vPOD window; off by default.
	/// Entries launched in either mode coexist — kills handle both.</summary>
	public bool RealLaunch { get; set; }

	/// <summary>The Agent's autoRestart watchdog for real-launched apps: when a
	/// tracked process exits on its own (not via a Kill* command), relaunch it
	/// after 2 s — but only for entries whose LaunchData.AutoRestart is set,
	/// exactly like the real pod. Toggled from the vPOD window.</summary>
	public bool RealAutoRestart { get; set; } = true;

	/// <summary>When set, a packaged postinstall.bat is executed at the end of a
	/// product install (like the real Agent) before being deleted, instead of
	/// being logged and removed unrun. Toggled from the vPOD window; off by
	/// default, since it runs package script code on the host machine.</summary>
	public bool RunPostInstall { get; set; }

	// Bumped to cancel watchdog restarts pending in their 2 s delay — the pod
	// "machine" went dark (power off / reboot / reprovision), so nothing may
	// relaunch after it.
	private int mWatchdogGeneration;

	public event Action<string> Log;
	public event Action AppsChanged;                                  // installed or launched list changed
	public event Action<Guid, OutOfBandProgress> InstallProgressChanged;
	public event Action<bool> ShutdownRequested;                      // restart?
	public event Action ReprovisionRequested;                         // console cleared the store (Reconfigure)

	public string DataDirectory { get; }
	public string GamesRoot { get; }
	public string KeyFilePath => Path.Combine(DataDirectory, "TeslaKeyStore.key");
	private string LaunchAppsPath => Path.Combine(DataDirectory, "LaunchApps.json");

	public VirtualLauncher()
		: this(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData), "vPOD"))
	{
	}

	public VirtualLauncher(string dataDirectory, string gamesRoot = null)
	{
		DataDirectory = dataDirectory;
		GamesRoot = gamesRoot ?? DefaultGamesRoot;
		Directory.CreateDirectory(DataDirectory);
		LoadApps();
	}

	// ---- session key store (launcher's TeslaKeyStore.key format) ----

	/// <summary>The provisioned session key, or null when unprovisioned.</summary>
	public byte[] LoadKey()
	{
		try
		{
			if (!File.Exists(KeyFilePath))
			{
				return null;
			}
			byte[] raw = File.ReadAllBytes(KeyFilePath);
			if (raw.Length < 2 || raw.Length != raw[0] + 1)
			{
				return null;
			}
			byte[] key = new byte[raw[0]];
			Buffer.BlockCopy(raw, 1, key, 0, key.Length);
			return key;
		}
		catch
		{
			return null;
		}
	}

	public void SaveKey(byte[] key)
	{
		byte[] raw = new byte[key.Length + 1];
		raw[0] = (byte)key.Length;
		key.CopyTo(raw, 1);
		File.WriteAllBytes(KeyFilePath, raw);
	}

	public void DeleteKey()
	{
		try { File.Delete(KeyFilePath); } catch { }
	}

	// ---- ILauncherService state ----

	public DateTime Ping(DateTime now)
	{
		return now;
	}

	public float VolumeLevel
	{
		get { lock (mLock) { return mVolumeLevel; } }
		set
		{
			lock (mLock) { mVolumeLevel = value; }
			Log?.Invoke($"Volume set to {value:P0}.");
		}
	}

	public LaunchData[] GetInstalledApps()
	{
		lock (mLock) { return mInstalledApps.ToArray(); }
	}

	public LaunchPair[] GetLaunchableApps()
	{
		lock (mLock)
		{
			LaunchPair[] pairs = new LaunchPair[mInstalledApps.Count];
			for (int i = 0; i < mInstalledApps.Count; i++)
			{
				pairs[i] = mInstalledApps[i].LaunchPair;
			}
			return pairs;
		}
	}

	public LaunchedAppData[] GetLaunchedApps()
	{
		lock (mLock) { return mLaunchedApps.ToArray(); }
	}

	public FullUpdateData FullUpdate()
	{
		lock (mLock)
		{
			return new FullUpdateData
			{
				InstalledApps = mInstalledApps.ToArray(),
				LaunchedApps = mLaunchedApps.ToArray(),
				VolumeLevel = mVolumeLevel
			};
		}
	}

	/// <summary>Registers a launch entry (upsert by LaunchKey) — the per-entry call
	/// the console makes after a product install, and the write behind LaunchApps.json.</summary>
	public void InstallApp(LaunchData data)
	{
		lock (mLock)
		{
			int existing = mInstalledApps.FindIndex(a => a.LaunchPair.LaunchKey == data.LaunchPair.LaunchKey);
			if (existing >= 0)
			{
				mInstalledApps[existing] = data;
			}
			else
			{
				mInstalledApps.Add(data);
			}
			SaveApps();
		}
		Log?.Invoke($"InstallApp: \"{data.LaunchPair.DisplayName}\" -> {data.ExeFile} {data.Arguments}");
		AppsChanged?.Invoke();
	}

	public void UninstallApp(Guid launchKey)
	{
		string cleanupDir = null;
		string name = null;
		lock (mLock)
		{
			int index = mInstalledApps.FindIndex(a => a.LaunchPair.LaunchKey == launchKey);
			if (index < 0)
			{
				return;
			}
			LaunchData app = mInstalledApps[index];
			name = app.LaunchPair.DisplayName;
			mInstalledApps.RemoveAt(index);
			SaveApps();
			// Like the real Agent's CleanupDir: remove the product folder, but only
			// when it's inside our games root and no other app still uses it.
			string dir = app.WorkingDirectory;
			if (!string.IsNullOrEmpty(dir)
				&& IsUnderGamesRoot(dir)
				&& !mInstalledApps.Exists(a => string.Equals(a.WorkingDirectory, dir, StringComparison.OrdinalIgnoreCase)))
			{
				cleanupDir = dir;
			}
		}
		// Kill (real or simulated) BEFORE deleting the product directory, like the
		// real Agent — a still-running process would hold its files locked.
		KillRealProcesses(RemoveLaunched(l => l.LaunchKey == launchKey));
		if (cleanupDir != null)
		{
			try
			{
				if (Directory.Exists(cleanupDir))
				{
					Directory.Delete(cleanupDir, recursive: true);
					Log?.Invoke($"UninstallApp: removed product directory {cleanupDir}");
				}
			}
			catch (Exception ex)
			{
				Log?.Invoke($"UninstallApp: could not remove {cleanupDir}: {ex.Message}");
			}
		}
		Log?.Invoke($"UninstallApp: \"{name}\" removed.");
		AppsChanged?.Invoke();
	}

	public void RemoveApp(Guid launchKey)
	{
		lock (mLock)
		{
			int removed = mInstalledApps.RemoveAll(a => a.LaunchPair.LaunchKey == launchKey);
			if (removed == 0)
			{
				return;
			}
			SaveApps();
		}
		KillRealProcesses(RemoveLaunched(l => l.LaunchKey == launchKey));
		Log?.Invoke($"RemoveApp: {launchKey} unregistered.");
		AppsChanged?.Invoke();
	}

	public int LaunchApp(Guid launchKey)
	{
		LaunchData app;
		lock (mLock)
		{
			int index = mInstalledApps.FindIndex(a => a.LaunchPair.LaunchKey == launchKey);
			if (index < 0)
			{
				Log?.Invoke($"LaunchApp: unknown launch key {launchKey}.");
				return 0;
			}
			app = mInstalledApps[index];
		}
		if (RealLaunch)
		{
			return LaunchRealProcess(app);
		}
		int pid;
		lock (mLock)
		{
			pid = mNextPid++;
			mLaunchedApps.Add(new LaunchedAppData { ProcessId = pid, LaunchKey = launchKey });
		}
		Log?.Invoke($"LaunchApp: \"{app.LaunchPair.DisplayName}\" -> simulated PID {pid} (no real process).");
		AppsChanged?.Invoke();
		return pid;
	}

	/// <summary>Actually starts the launch entry, mirroring the real Agent's
	/// CmdLaunchApp: same ProcessStartInfo shape, and the same clean error when
	/// the entry is registered but its files aren't installed (the console shows
	/// the thrown message, exactly as against a real pod).</summary>
	private int LaunchRealProcess(LaunchData app)
	{
		string name = app.LaunchPair.DisplayName ?? app.LaunchPair.LaunchKey.ToString();
		if (string.IsNullOrWhiteSpace(app.ExeFile) || !File.Exists(app.ExeFile))
		{
			Log?.Invoke($"LaunchApp: \"{name}\": executable not found at '{app.ExeFile}'.");
			throw new Exception(
				$"Cannot launch '{name}': executable not found at '{app.ExeFile}'. " +
				"The product may be registered but not yet installed on this pod.");
		}
		ProcessStartInfo psi = new ProcessStartInfo
		{
			FileName = app.ExeFile,
			Arguments = app.Arguments ?? "",
			WorkingDirectory = string.IsNullOrEmpty(app.WorkingDirectory)
				? Path.GetDirectoryName(app.ExeFile)
				: app.WorkingDirectory,
			UseShellExecute = false
		};
		Process process = Process.Start(psi)
			?? throw new Exception($"Process.Start returned null for '{app.ExeFile}'");
		lock (mLock)
		{
			mLaunchedApps.Add(new LaunchedAppData { ProcessId = process.Id, LaunchKey = app.LaunchPair.LaunchKey });
			mRealProcesses[process.Id] = process;
		}
		StartWatcher(app, process, process.Id);
		Log?.Invoke($"LaunchApp: \"{name}\" -> started {app.ExeFile} (real PID {process.Id}).");
		AppsChanged?.Invoke();
		return process.Id;
	}

	/// <summary>The Agent's per-process watcher: waits for exit, and if the process
	/// is STILL TRACKED (Kill*/Uninstall remove it from the table first, so a
	/// console-ordered kill never restarts), drops it from the running list and —
	/// when the watchdog toggle and the entry's AutoRestart both apply — relaunches
	/// it after the Agent's 2 s delay.</summary>
	private void StartWatcher(LaunchData app, Process process, int pid)
	{
		string name = app.LaunchPair.DisplayName ?? app.LaunchPair.LaunchKey.ToString();
		new Thread(() =>
		{
			try { process.WaitForExit(); }
			catch { /* handle disposed by a Kill* — it is no longer tracked */ }

			bool stillTracked;
			lock (mLock)
			{
				stillTracked = mRealProcesses.TryGetValue(pid, out Process tracked) && ReferenceEquals(tracked, process);
				if (stillTracked)
				{
					mRealProcesses.Remove(pid);
					mLaunchedApps.RemoveAll(l => l.ProcessId == pid);
					process.Dispose();
				}
			}
			if (!stillTracked)
			{
				return; // killed via the console / power-off; whoever killed it cleaned up
			}
			AppsChanged?.Invoke();

			// Thread.VolatileRead, not Volatile.Read: the latter is net45+.
			int generation = Thread.VolatileRead(ref mWatchdogGeneration);
			if (!RealAutoRestart || !app.AutoRestart)
			{
				Log?.Invoke($"\"{name}\" (PID {pid}) exited on its own (no watchdog restart).");
				return;
			}
			Log?.Invoke($"\"{name}\" (PID {pid}) exited on its own — watchdog restarting in 2 s...");
			Thread.Sleep(2000);

			// Still wanted? The pod may have powered off/reprovisioned (generation),
			// the mode or toggle flipped, or the app been uninstalled meanwhile.
			if (generation != Thread.VolatileRead(ref mWatchdogGeneration) || !RealLaunch || !RealAutoRestart)
			{
				return;
			}
			LaunchData current;
			lock (mLock)
			{
				int index = mInstalledApps.FindIndex(a => a.LaunchPair.LaunchKey == app.LaunchPair.LaunchKey);
				if (index < 0)
				{
					return; // uninstalled during the delay
				}
				current = mInstalledApps[index];
			}
			try
			{
				LaunchRealProcess(current);
			}
			catch (Exception ex)
			{
				Log?.Invoke($"Watchdog restart of \"{name}\" failed: {ex.Message}");
			}
		})
		{ IsBackground = true, Name = $"vPOD-watchdog-{pid}" }.Start();
	}

	public void KillApp(Guid launchKey, int processId)
	{
		List<LaunchedAppData> victims = RemoveLaunched(l => l.LaunchKey == launchKey && l.ProcessId == processId);
		if (victims.Count > 0)
		{
			int real = KillRealProcesses(victims);
			Log?.Invoke($"KillApp: PID {processId} killed{(real > 0 ? "" : " (simulated)")}.");
			AppsChanged?.Invoke();
		}
	}

	public void KillAllOfType(Guid launchKey)
	{
		List<LaunchedAppData> victims = RemoveLaunched(l => l.LaunchKey == launchKey);
		if (victims.Count > 0)
		{
			int real = KillRealProcesses(victims);
			Log?.Invoke($"KillAllOfType: {victims.Count} process(es) killed ({real} real).");
			AppsChanged?.Invoke();
		}
	}

	/// <summary>Kills everything launched. <paramref name="cancelPendingRestarts" />
	/// is the pod-power path (off/reboot/exit): it also aborts watchdog restarts
	/// waiting out their 2 s delay. The console's KillAllApps RPC leaves them
	/// pending, matching the real Agent's race behavior.</summary>
	public void KillAllApps(bool cancelPendingRestarts = false)
	{
		if (cancelPendingRestarts)
		{
			Interlocked.Increment(ref mWatchdogGeneration);
		}
		List<LaunchedAppData> victims = RemoveLaunched(l => true);
		if (victims.Count > 0)
		{
			int real = KillRealProcesses(victims);
			Log?.Invoke($"KillAllApps: {victims.Count} process(es) killed ({real} real).");
			AppsChanged?.Invoke();
		}
	}

	/// <summary>Removes matching entries from the launched table and returns them,
	/// so real processes can be killed outside the lock.</summary>
	private List<LaunchedAppData> RemoveLaunched(Predicate<LaunchedAppData> match)
	{
		List<LaunchedAppData> removed = new List<LaunchedAppData>();
		lock (mLock)
		{
			for (int i = mLaunchedApps.Count - 1; i >= 0; i--)
			{
				if (match(mLaunchedApps[i]))
				{
					removed.Add(mLaunchedApps[i]);
					mLaunchedApps.RemoveAt(i);
				}
			}
		}
		return removed;
	}

	/// <summary>Terminates any real processes behind the given (already removed)
	/// entries; simulated PIDs are ignored. Waits briefly for each exit so a
	/// following product-directory delete doesn't race the dying process.</summary>
	private int KillRealProcesses(List<LaunchedAppData> victims)
	{
		int killed = 0;
		foreach (LaunchedAppData victim in victims)
		{
			Process process;
			lock (mLock)
			{
				if (!mRealProcesses.TryGetValue(victim.ProcessId, out process))
				{
					continue;
				}
				mRealProcesses.Remove(victim.ProcessId);
			}
			try
			{
				if (!process.HasExited)
				{
					process.Kill();
					process.WaitForExit(3000);
					killed++;
				}
			}
			catch (Exception ex)
			{
				Log?.Invoke($"Kill PID {victim.ProcessId}: {ex.Message}");
			}
			finally
			{
				process.Dispose();
			}
		}
		return killed;
	}

	public void Shutdown(bool restart)
	{
		Log?.Invoke(restart ? "Shutdown(restart) — power-cycling the pod." : "Shutdown — powering the pod off.");
		ShutdownRequested?.Invoke(restart);
	}

	/// <summary>The console's Reconfigure calls this before deleting the pod from the
	/// site. Wipe the store AND drop the session key: the console no longer holds it,
	/// so re-entering provisioning (beacon mode) is what makes Reconfigure completable
	/// without the real pod's reboot-with-DHCP step.</summary>
	public void ClearStore()
	{
		WipeApps();
		Log?.Invoke("ClearStore: installed apps wiped; dropping session key to re-enter provisioning.");
		ReprovisionRequested?.Invoke();
	}

	/// <summary>Clears the installed/launched app registries (LaunchApps.json) —
	/// the store-wipe half of ClearStore, also used by the UI's Reprovision.
	/// Any real launched processes are terminated first, and pending watchdog
	/// restarts cancelled.</summary>
	public void WipeApps()
	{
		Interlocked.Increment(ref mWatchdogGeneration);
		KillRealProcesses(RemoveLaunched(l => true));
		lock (mLock)
		{
			mInstalledApps.Clear();
			SaveApps();
		}
		AppsChanged?.Invoke();
	}

	// ---- install progress (InitiateInstallProduct / GetOutOfBandProgress) ----

	public Guid InitiateInstallProduct()
	{
		Guid callId = Guid.NewGuid();
		UpdateProgress(callId, 0, "Waiting for file...");
		return callId;
	}

	public OutOfBandProgress GetOutOfBandProgress(Guid callId)
	{
		lock (mLock)
		{
			if (mInstallProgress.TryGetValue(callId, out OutOfBandProgress progress))
			{
				return progress;
			}
		}
		return new OutOfBandProgress { PercentComplete = 0, Status = "Unknown call ID", IsCompleted = true };
	}

	public void UpdateProgress(Guid callId, int percent, string status, bool isCompleted = false)
	{
		OutOfBandProgress progress = new OutOfBandProgress
		{
			PercentComplete = percent,
			Status = status,
			IsCompleted = isCompleted
		};
		lock (mLock)
		{
			mInstallProgress[callId] = progress;
		}
		InstallProgressChanged?.Invoke(callId, progress);
	}

	private bool IsUnderGamesRoot(string path)
	{
		try
		{
			string full = Path.GetFullPath(path);
			string root = Path.GetFullPath(GamesRoot) + Path.DirectorySeparatorChar;
			return full.StartsWith(root, StringComparison.OrdinalIgnoreCase);
		}
		catch
		{
			return false;
		}
	}

	// ---- persistence (PodRpc's JSON options round-trip the wire types exactly) ----

	private void LoadApps()
	{
		try
		{
			if (!File.Exists(LaunchAppsPath))
			{
				return;
			}
			LaunchData[] apps = JsonConvert.DeserializeObject<LaunchData[]>(File.ReadAllText(LaunchAppsPath));
			if (apps != null)
			{
				mInstalledApps.AddRange(apps);
			}
		}
		catch
		{
			// unreadable store: start empty, like a fresh pod
		}
	}

	private void SaveApps()
	{
		try
		{
			File.WriteAllText(LaunchAppsPath, JsonConvert.SerializeObject(mInstalledApps.ToArray()));
		}
		catch (Exception ex)
		{
			Log?.Invoke("Could not persist LaunchApps.json: " + ex.Message);
		}
	}
}