using System;
using System.Text;
using UnityEngine;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;


/// <summary>
/// Зависимости:<br/>
///  - UnityMainThreadDispatcher<br/>
///  - ComNativeWrapper<br/>
/// </summary>
public static class ComWrapper
{
    public static event Action PaymentReceived;
    public static event Action<string> InputRecieved;

    private const string REQUEST_INPUT_COMMAND = "91";
    private const string REQUEST_ENCRYPTED_COMMAND = "666";
    private const string REQUEST_CONFIRMATION_COMMAND = "777";

    private static CancellationTokenSource _lifetimeCts;
    private static Thread _readerThread;
    private static CancellationTokenSource _readerCts;

    private static int h;
    private static ILogger logger;

    private static int _lastInputTick = 0;
    private const int INPUT_IDLE_BEFORE_PING_MS = 60_000;//1 минута


    public static void Initialize()//Добавить логгер в конструктор
    {
        if (_lifetimeCts != null) return;
        OpenPort();
        if (h <= 0)
        {
            Log("Порт не открылся при инициализации");
            return;
        }

        UnityMainThreadDispatcher.Initialize();
        _lifetimeCts = new CancellationTokenSource();

        
        StartReaderThread();
        _ = SetupBoardAsync(_lifetimeCts.Token);
    }

    public static void Send(string message)
    {
        if (h <= 0) return;
        try
        {
            int w = ComNativeWrapper.Serial_WriteStringUTF8(h, message, 1); //w-количество записаных символов в порт. можно обработать
        }
        catch { logger?.Log($"Ошибка отправки строкового сигнала. {message}"); }
    }

    private static void StartReaderThread()
    {
        StopReaderThread();

        _readerCts = new CancellationTokenSource();
        var ct = _readerCts.Token;

        _readerThread = new Thread(() =>
        {
            byte[] buffer = new byte[1024];


            while (!ct.IsCancellationRequested)
            {
                if (h <= 0) { Thread.Sleep(20); continue; }
                int read = 0;
                try
                {
                    //блок до таймаута чтения
                    read = ComNativeWrapper.Serial_ReadLineUTF8_bytes(h, buffer, buffer.Length);
                }
                catch (Exception ex)
                {
                    Log("Com reader exception: " + ex.Message);
                    Thread.Sleep(50);// пауза чтобы не уйти в спин при ошибке
                    continue;
                }

                if (ct.IsCancellationRequested) break;

                if (read > 0)
                {
                    var line = Encoding.UTF8.GetString(buffer, 0, read).Trim();
                    EnqueueLine(line);  
                }
            }
        });

        _readerThread.IsBackground = true;
        _readerThread.Start();
    }

    private static void StopReaderThread()
    {
        if(_readerCts != null)
        {
            _readerCts.Cancel();
            _readerCts.Dispose();
            _readerCts = null;
        }

        if(_readerThread != null)
        {
            _readerThread.Join(200);
            _readerThread = null;
        }
    }

    static void EnqueueLine(string line)
    {
        UnityMainThreadDispatcher.Instance.Enqueue(() => OnLine(line));
    }

    private static void ProcessComInput(string line)
    {
        Log($"COM. h={h}: {line}");

        if (line == "COIN")
            PaymentReceived?.Invoke();
        else if (line.StartsWith("INPUT"))
        {
            Volatile.Write(ref _lastInputTick, Environment.TickCount);
            InputRecieved?.Invoke(line.Substring(5));
        }
    }

    static readonly object _waitLock = new();
    static readonly List<Waiter> _waiters = new();
    sealed class Waiter
    {
        public Func<string, bool> Match;
        public TaskCompletionSource<string> Tcs;
    }
    static Task<string> WaitForAsync(Func<string, bool> match, int timeoutMs, CancellationToken ct)
    {
        var tcs = new TaskCompletionSource<string>(TaskCreationOptions.RunContinuationsAsynchronously);
        var w = new Waiter { Match = match, Tcs = tcs };

        lock (_waitLock) _waiters.Add(w);//

        //отмена
        if (ct.CanBeCanceled)//
        {
            ct.Register(() =>
            {
                lock (_waitLock) _waiters.Remove(w);
                tcs.TrySetCanceled(ct);
            });
        }

        _ = Task.Delay(timeoutMs, CancellationToken.None).ContinueWith(_ =>
        {
            //if (tcs.Task.IsCompleted) return;
            lock (_waitLock) _waiters.Remove(w);
            tcs.TrySetException(new TimeoutException($"Timeout waiting for line"));
        });

        return tcs.Task;
    }

    static Task<string> WaitForPrefixAsync(string prefix, int timeoutMs, CancellationToken ct)
        => WaitForAsync(s => s.StartsWith(prefix, StringComparison.Ordinal), timeoutMs, ct);
    static Task<string> WaitForContainsAsync(string prefix, int timeoutMs, CancellationToken ct)
        => WaitForAsync(s => s.IndexOf(prefix, StringComparison.Ordinal) >= 0, timeoutMs, ct);

    static void OnLine(string line)
    {
        if (string.IsNullOrEmpty(line))
            return;

        //1. обычная обработка
        ProcessComInput(line);

        //2. Разубудить ожидающих
        List<Waiter> toFire = null;

        lock (_waitLock)
        {
            for (int i = _waiters.Count - 1; i >= 0; i--)
            {
                var waiter = _waiters[i];
                if (waiter.Match(line))
                {
                    _waiters.RemoveAt(i);
                    (toFire ??= new List<Waiter>()).Add(waiter);
                }
            }
        }

        if (toFire != null)
            foreach (var w in toFire)
                w.Tcs.TrySetResult(line);
    }

    private static async Task SetupBoardAsync(CancellationToken ct)
    {
        bool auth = await BoardAuthAsync(ct);
        if (!auth)
        {
            Log("Авторизация на плате не пройдена.");
            UnityMainThreadDispatcher.Instance.Enqueue(() => Application.Quit());
            return;
        }

        _ = StartKeepAliveProcessAsync(ct);
    }




    private static void OpenPort()
    {
        Log("Инициализация порта");

        var ports = ComNativeWrapper.ListPorts();
        if (ports.Length == 0) { Log("Нет портов, завершаю"); return; }

        string port = ports[^1];
        Log("Открываю порт: " + port);

        h = ComNativeWrapper.Serial_Open(port, 115200, 8, 0, 1, 4, 10);


        Log($"handle: {h}");
        if (h <= 0)
        {
            Log("Open failed: " + ComNativeWrapper.GetLastError());
            return;
        }
        else
        {
            Log($"Открыл порт: {port}");
        }
    }

    private static async Task<bool> BoardAuthAsync(CancellationToken ct)
    {
        //Проверяем зашифрована или нет
        try
        {
            Send(REQUEST_INPUT_COMMAND);
            var inputLine = await WaitForPrefixAsync("INPUT", 1000, ct);
            return true;
        }
        catch (TimeoutException)
        {
            //Не пришел инпут
            Log("Шифрованная плата");
        }

        //Запрашиваем шифрованную строку
        string encLine;
        try
        {
            Send(REQUEST_ENCRYPTED_COMMAND);
            encLine = await WaitForPrefixAsync("ENC:", 1000, ct);
        }
        catch
        {
            Log($"Зашифрованная строка не пришла");
            return false;
        }

        //Расшифровка
        var encrypted = encLine.Substring(4);
        var decrypted = BoardUtility.DecryptSerial(encrypted);

        //Отправляем расшифрованное на подтверждение
        try
        {
            Send(REQUEST_CONFIRMATION_COMMAND + decrypted);
            await WaitForContainsAsync("OK", 1000, ct);
            return true;
        }
        catch
        {
            Log("Подтверждение не пришло");
            return false;
        }
    }

    public static void Shutdown()
    {
        _lifetimeCts?.Cancel();
        _lifetimeCts?.Dispose();
        _lifetimeCts = null;

        StopReaderThread();
        CancelAllWaiters();
        ClosePort();
    }

    private static void CancelAllWaiters()
    {
        List<Waiter> snapshot;
        lock (_waitLock)
        {
            snapshot = new List<Waiter>(_waiters);
            _waiters.Clear();
        }
        foreach (Waiter waiter in snapshot)
        {
            waiter.Tcs.TrySetCanceled();
        }
    }

    private static void ClosePort()
    {
        Log($"Отпускаю порт handle:{h}");
        if (h > 0)
        {
            ComNativeWrapper.Serial_Close(h);
            h = 0;
        }
    }


    //Сделать ожидание простоя около минуты на проверку и переподелючение.
    private static async Task StartKeepAliveProcessAsync(CancellationToken ct)
    {
        try
        {
            Log("Запуск асинхронной проверки порта");
            while (!ct.IsCancellationRequested)
            {
                if (!IsInputIdleTooLong())
                {
                    await Task.Delay(5000, ct);
                    continue;
                }

                //Пингуем плату
                if (!await CheckPortConnectionAsync(ct))
                {
                    Log("Плата отвалилась. Запускаю переподключение.");
                    await ReinitializePortAsync(ct);
                }

                await Task.Delay(10000, ct);
            }
        }
        catch (OperationCanceledException)
        {
            Log("Асинхронная проверка порта остановлена");
        }
        catch (Exception e)
        {
            Log($"Ошибка проверки порта: {e.Message}");
        }
    }


    private static async Task<bool> CheckPortConnectionAsync(CancellationToken ct)
    {
        try
        {
            Send(REQUEST_INPUT_COMMAND);
            await WaitForPrefixAsync("INPUT", 1000,  ct);
            return true;
        }
        catch
        {
            return false;
        }
    }

    //реализовать
    private static async Task ReinitializePortAsync(CancellationToken ct)
    {
        StopReaderThread();
        CancelAllWaiters();
        ClosePort();

        OpenPort();
        if (h <= 0)
        {
            Log($"Ошибка при переподключении.");
            return;
        }


        StartReaderThread();
        var auth = await BoardAuthAsync(ct);
        if (!auth) 
            UnityMainThreadDispatcher.Instance.Enqueue(() => (new GameObject()).AddComponent(typeof(VfxPrefab)));
    }

    static bool IsInputIdleTooLong()
    {
        int last = Volatile.Read(ref _lastInputTick);
        if (last == 0) return true;
        int now = Environment.TickCount;

        // переполнение TickCount тут ок: сравнение интервала < 24 дней работает корректно
        int elapsed = unchecked(now - last);
        return elapsed >= INPUT_IDLE_BEFORE_PING_MS;
    }

    private static void Log(string message) => logger?.Log($"CW{message}");
}