using Appccelerate.StateMachine;
using Appccelerate.StateMachine.Machine;
using RobotNet10.Script;
using RobotNet10.ScriptEngine.Shared;
using System.Diagnostics;
using System.Threading;

namespace RobotNet10.ScriptEngine.Models;

/// <summary>
/// Represents a periodic task with state machine management.
/// </summary>
public class ScriptTask : IDisposable
{
    private readonly PassiveStateMachine<ScriptTaskState, TaskTrigger> _stateMachine;
    private readonly ScriptTaskModel _model;
    private readonly ScriptGlobals _globals;
    private readonly ILogger _logger;
    private Thread? _timerThread;
    private volatile bool _timerThreadRunning;
    private bool _isExecuting;
    private bool _isPaused;
    private bool _disposed;
    private Exception? _lastError;
    private readonly object _lockObject = new();
    private ScriptTaskState _currentState;
    private long _executionCount;

    /// <summary>
    /// Task triggers for state machine transitions.
    /// </summary>
    public enum TaskTrigger
    {
        Start,
        Pause,
        Resume,
        Stop,
        PausingCompleted,
        ResumingCompleted,
        StoppingCompleted,
        ErrorOccurred,
    }

    /// <summary>
    /// Gets the name of the task.
    /// </summary>
    public string Name => _model.Name;

    /// <summary>
    /// Gets the interval in seconds between task executions.
    /// </summary>
    public int Interval => _model.Interval;

    /// <summary>
    /// Gets whether the task should auto-start when engine starts.
    /// </summary>
    public bool AutoStart => _model.AutoStart;

    /// <summary>
    /// Gets the current state of the task.
    /// </summary>
    public ScriptTaskState State => _currentState;

    /// <summary>
    /// Gets the last error that occurred during task execution.
    /// </summary>
    public Exception? LastError => _lastError;

    /// <summary>
    /// Gets whether the task is currently executing.
    /// </summary>
    public bool IsExecuting => _isExecuting;

    /// <summary>
    /// Gets the number of times the task has been executed.
    /// </summary>
    public long ExecutionCount => _executionCount;

    /// <summary>
    /// Initializes a new instance of the ScriptTask class.
    /// </summary>
    /// <param name="model">The task model containing task metadata and runner.</param>
    /// <param name="globals">The script globals dictionary.</param>
    public ScriptTask(
        ScriptTaskModel model,
        ScriptGlobals globals)
    {
        _model = model ?? throw new ArgumentNullException(nameof(model));
        _globals = globals ?? throw new ArgumentNullException(nameof(globals));

        // Get logger from globals.ScriptRobotNet
        if (_globals.RobotNet.TryGetValue("get_Logger", out object? getLogger) &&
            getLogger is Func<ILogger> getLoggerFunc)
        {
            _logger = getLoggerFunc.Invoke();
        }
        else
        {
            throw new InvalidOperationException($"Failed to get Logger from ScriptRobotNet globals for task '{model.Name}'");
        }

        var builder = new StateMachineDefinitionBuilder<ScriptTaskState, TaskTrigger>();

        // Configure state machine transitions according to StateMachine_Design.md
        ConfigureStateMachine(builder);

        _stateMachine = builder
            .WithInitialState(ScriptTaskState.Idle)
            .Build()
            .CreatePassiveStateMachine();

        _currentState = ScriptTaskState.Idle;
        _stateMachine.Start();
    }

    private void ConfigureStateMachine(StateMachineDefinitionBuilder<ScriptTaskState, TaskTrigger> builder)
    {
        // Idle state
        builder.In(ScriptTaskState.Idle)
            .On(TaskTrigger.Start)
            .Goto(ScriptTaskState.Running);

        // Running state - configure entry/exit actions separately
        builder.In(ScriptTaskState.Running)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Running; OnEnterRunning(); })
            .On(TaskTrigger.Pause)
            .Goto(ScriptTaskState.Pausing)
            .On(TaskTrigger.Stop)
            .Goto(ScriptTaskState.Stopping)
            .On(TaskTrigger.ErrorOccurred)
            .Goto(ScriptTaskState.Error)
            .Execute(() => { _currentState = ScriptTaskState.Error; OnEnterError(); });

        // Pausing state
        builder.In(ScriptTaskState.Pausing)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Pausing; OnEnterPausing(); })
            .ExecuteOnExit(() => OnExitPausing())
            .On(TaskTrigger.PausingCompleted)
            .Goto(ScriptTaskState.Paused)
            .On(TaskTrigger.ErrorOccurred)
            .Goto(ScriptTaskState.Error)
            .Execute(() => { _currentState = ScriptTaskState.Error; OnEnterError(); });

        // Paused state
        builder.In(ScriptTaskState.Paused)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Paused; OnEnterPaused(); })
            .ExecuteOnExit(() => OnExitPaused())
            .On(TaskTrigger.Resume)
            .Goto(ScriptTaskState.Resuming)
            .On(TaskTrigger.Stop)
            .Goto(ScriptTaskState.Stopping);

        // Resuming state
        builder.In(ScriptTaskState.Resuming)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Resuming; OnEnterResuming(); })
            .ExecuteOnExit(() => OnExitResuming())
            .On(TaskTrigger.ResumingCompleted)
            .Goto(ScriptTaskState.Running)
            .On(TaskTrigger.ErrorOccurred)
            .Goto(ScriptTaskState.Error)
            .Execute(() => { _currentState = ScriptTaskState.Error; OnEnterError(); });

        // Stopping state
        builder.In(ScriptTaskState.Stopping)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Stopping; OnEnterStopping(); })
            .On(TaskTrigger.StoppingCompleted)
            .Goto(ScriptTaskState.Stopped)
            .On(TaskTrigger.ErrorOccurred)
            .Goto(ScriptTaskState.Error)
            .Execute(() => { _currentState = ScriptTaskState.Error; OnEnterError(); });

        // Stopped state
        builder.In(ScriptTaskState.Stopped)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Stopped; OnEnterStopped(); })
            .On(TaskTrigger.Start)
            .Goto(ScriptTaskState.Running);

        // Error state
        builder.In(ScriptTaskState.Error)
            .ExecuteOnEntry(() => { _currentState = ScriptTaskState.Error; OnEnterError(); })
            .ExecuteOnExit(() => OnExitError())
            .On(TaskTrigger.Start)
            .Goto(ScriptTaskState.Running);
    }

    #region State Machine Event Handlers

    private void OnEnterRunning()
    {
        lock (_lockObject)
        {
            // Start high-priority thread with SpinWait
            StartTimerThread();
        }
    }

    private void StartTimerThread()
    {
        if (_timerThread == null || !_timerThread.IsAlive)
        {
            _timerThreadRunning = true;
            _timerThread = new Thread(TimerThreadProc)
            {
                IsBackground = false,
                Priority = ThreadPriority.Highest,
                Name = $"TaskTimer-{_model.Name}"
            };
            _timerThread.Start();
            _logger.LogInfo($"Task '{_model.Name}' started running with high-priority thread (interval: {_model.Interval}ms).");
        }
    }

    private void TimerThreadProc()
    {
        _isExecuting = true;
        Thread.BeginThreadAffinity();
        try
        {
            // Convert interval from seconds to milliseconds
            var intervalMs = _model.Interval;
            var intervalTicks = intervalMs * TimeSpan.TicksPerMillisecond;
            var stopwatch = Stopwatch.StartNew();
            var nextExecutionTime = stopwatch.ElapsedTicks + intervalTicks;
            var spinWait = new SpinWait();
            long currentTicks = 0;

            while (_timerThreadRunning)
            {
                currentTicks = stopwatch.ElapsedTicks;

                // Check if it's time to execute
                if (currentTicks >= nextExecutionTime)
                {
                    if (_isPaused) continue;

                    try
                    {
                        lock (_lockObject)
                        {
                            _executionCount++;
                        }

                        // Execute the script runner with globals directly
                        var result = _model.Runner(_globals).GetAwaiter().GetResult();

                        // Handle async result if needed
                        if (result is Task taskResult)
                        {
                            taskResult.GetAwaiter().GetResult();
                        }
                    }
                    catch (Exception ex)
                    {
                        _lastError = ex;
                        _logger.LogError($"Task '{_model.Name}' execution error: {ex.Message}");
                        _stateMachine.Fire(TaskTrigger.ErrorOccurred);
                        break;
                    }

                    // Calculate next execution time
                    nextExecutionTime = currentTicks + intervalTicks;
                }
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.SpinOnce();
                spinWait.Reset();
            }
        }
        finally
        {
            Thread.EndThreadAffinity();
            _isExecuting = false;
        }
    }

    private void OnEnterPausing()
    {
        // Wait for current execution to complete if running
        // Then fire PausingCompleted trigger
        Task.Run(async () =>
        {
            await WaitForExecutionComplete();
            _stateMachine.Fire(TaskTrigger.PausingCompleted);
        });
    }

    private void OnExitPausing()
    {
        // Set paused flag - timer continues but ExecuteTask will skip execution
        _isPaused = true;
    }

    private void OnEnterPaused()
    {
        _isPaused = true;
        _logger.LogInfo($"Task '{_model.Name}' paused (timer continues, execution skipped).");
    }

    private void OnExitPaused()
    {
        // Clear paused flag when exiting paused state
        _isPaused = false;
    }

    private void OnEnterResuming()
    {
        // Clear paused flag immediately
        _isPaused = false;
        // Fire ResumingCompleted immediately (no async operation needed)
        _stateMachine.Fire(TaskTrigger.ResumingCompleted);
    }

    private void OnExitResuming()
    {
        // Ensure paused flag is cleared
        _isPaused = false;
    }

    private void OnEnterStopping()
    {
        // Stop timer thread, wait for current execution to complete
        lock (_lockObject)
        {
            // Stop the timer thread loop
            _timerThreadRunning = false;
        }

        // Wait for timer thread to finish (with timeout)
        if (_timerThread != null && _timerThread.IsAlive)
        {
            if (!_timerThread.Join(TimeSpan.FromSeconds(2)))
            {
                _logger.LogWarning($"Task '{_model.Name}' timer thread did not stop within timeout. Proceeding anyway.");
            }
        }

        Task.Run(async () =>
        {
            // Wait for execution to complete, but only timeout if actually executing
            await WaitForExecutionComplete();
            
            // If still executing after timeout, it's ScriptRunner blocking
            // Otherwise, proceed even if state machine didn't transition
            _stateMachine.Fire(TaskTrigger.StoppingCompleted);
        });
    }

    private void OnEnterStopped()
    {
        _logger.LogInfo($"Task '{_model.Name}' stopped.");
    }

    private void OnEnterError()
    {
        _logger.LogError($"Task '{_model.Name}' entered error state. Last error: {_lastError?.Message}");
    }

    private void OnExitError()
    {
        _lastError = null;
    }


    #endregion

    #region Public Control Methods

    /// <summary>
    /// Starts the task (transitions from Idle/Stopped/Error to Running).
    /// </summary>
    public void Start()
    {
        try
        {
            _stateMachine.Fire(TaskTrigger.Start);
        }
        catch (Exception ex)
        {
            _logger.LogError($"Failed to start task '{_model.Name}': {ex.Message}");
            throw;
        }
    }

    /// <summary>
    /// Pauses the task (transitions from Running to Pausing → Paused).
    /// </summary>
    public void Pause()
    {
        try
        {
            _stateMachine.Fire(TaskTrigger.Pause);
        }
        catch (Exception ex)
        {
            _logger.LogError($"Failed to pause task '{_model.Name}': {ex.Message}");
            throw;
        }
    }

    /// <summary>
    /// Resumes the task (transitions from Paused to Resuming → Running).
    /// </summary>
    public void Resume()
    {
        try
        {
            _stateMachine.Fire(TaskTrigger.Resume);
        }
        catch (Exception ex)
        {
            _logger.LogError($"Failed to resume task '{_model.Name}': {ex.Message}");
            throw;
        }
    }

    /// <summary>
    /// Stops the task (transitions from Running/Paused to Stopping → Stopped).
    /// </summary>
    public void Stop()
    {
        try
        {
            _stateMachine.Fire(TaskTrigger.Stop);
        }
        catch (Exception ex)
        {
            _logger.LogError($"Failed to stop task '{_model.Name}': {ex.Message}");
            throw;
        }
    }

    #endregion

    #region Task Execution

    private async Task WaitForExecutionComplete()
    {
        // Wait for current execution to complete (max 30 seconds)
        // Only timeout if task is actually executing (ScriptRunner running)
        var timeout = TimeSpan.FromSeconds(30);
        var startTime = DateTime.UtcNow;

        while (_isExecuting && (DateTime.UtcNow - startTime) < timeout)
        {
            await Task.Delay(100);
        }

        if (_isExecuting)
        {
            // Task is still executing - ScriptRunner is blocking
            _logger.LogWarning($"Task '{_model.Name}' execution timeout while waiting for completion. ScriptRunner may be blocking.");
        }
        // If task is not executing, it's effectively stopped (even if state machine didn't transition)
        // No need to log - proceed silently
    }

    #endregion

    #region IDisposable

    /// <summary>
    /// Disposes the task. Can be called from any state.
    /// </summary>
    public void Dispose()
    {
        if (_disposed)
        {
            return;
        }

        lock (_lockObject)
        {
            if (_disposed)
            {
                return;
            }
            _disposed = true;
        }

        // Stop the task if it's running
        try
        {
            if (_currentState == ScriptTaskState.Running ||
                _currentState == ScriptTaskState.Paused ||
                _currentState == ScriptTaskState.Pausing ||
                _currentState == ScriptTaskState.Resuming)
            {
                _stateMachine.Fire(TaskTrigger.Stop);
                // Wait a bit for stopping to complete
                var stopTimeout = TimeSpan.FromSeconds(2);
                var startTime = DateTime.UtcNow;
                while ((_currentState == ScriptTaskState.Running ||
                       _currentState == ScriptTaskState.Paused ||
                       _currentState == ScriptTaskState.Pausing ||
                       _currentState == ScriptTaskState.Resuming ||
                       _currentState == ScriptTaskState.Stopping) &&
                       (DateTime.UtcNow - startTime) < stopTimeout)
                {
                    Thread.Sleep(50);
                }
            }
        }
        catch
        {
            // Ignore errors during stop
        }

        // Ensure timer thread is stopped
        lock (_lockObject)
        {
            _timerThreadRunning = false;
        }

        // Wait for timer thread to finish (with timeout)
        if (_timerThread != null && _timerThread.IsAlive)
        {
            if (!_timerThread.Join(TimeSpan.FromSeconds(2)))
            {
                _logger.LogWarning($"Task '{_model.Name}' timer thread did not stop within timeout during dispose.");
            }
        }
        _timerThread = null;

        // Wait for execution to complete
        try
        {
            WaitForExecutionComplete().Wait(TimeSpan.FromSeconds(5));
        }
        catch
        {
            // Ignore errors
        }

        // Stop state machine
        try
        {
            _stateMachine.Stop();
        }
        catch
        {
            // Ignore errors
        }

        GC.SuppressFinalize(this);
    }

    #endregion
}