using System.Diagnostics;
using AcDream.Core.Combat;
using AcDream.Core.Physics;

namespace AcDream.Runtime.Gameplay;

public interface IRuntimeLocalPlayerControllerSource
{
    PlayerMovementController? Controller { get; }
}

public interface IRuntimeLocalPlayerMotionSource
{
    MotionInterpreter? Motion { get; }
}

/// <summary>
/// Canonical local movement lifetime and intent owner. Graphical input,
/// presentation, diagnostics, and future no-window hosts borrow this exact
/// state; they never mirror the controller or the autorun latch.
/// </summary>
public sealed class RuntimeLocalPlayerMovementState
    : IRuntimeLocalPlayerControllerSource,
      IRuntimeLocalPlayerMotionSource,
      IRuntimeMovementView,
      IDisposable
{
    private PlayerMovementController? _controller;
    private PlayerMovementController? _preparingMotionOwner;
    private bool _autoRunActive;
    private bool _hasCommandInput;
    private MovementInput _commandInput;
    private bool _disposed;
    private long _revision;

    public PlayerMovementController? Controller
    {
        get => _controller;
        set
        {
            ObjectDisposedException.ThrowIf(_disposed, this);
            if (ReferenceEquals(_controller, value))
                return;
            _controller = value;
            Interlocked.Increment(ref _revision);
        }
    }

    public bool AutoRunActive => _autoRunActive;
    public bool HasCommandInput => _hasCommandInput;
    public MovementInput CommandInput => _commandInput;
    public long Revision => Interlocked.Read(ref _revision);
    public IRuntimeMovementView View => this;

    MotionInterpreter? IRuntimeLocalPlayerMotionSource.Motion =>
        _preparingMotionOwner?.Motion ?? _controller?.Motion;

    public RuntimeMovementSnapshot Snapshot
    {
        get
        {
            PlayerMovementController? controller = _controller;
            return controller is null
                ? new RuntimeMovementSnapshot(
                    false,
                    0u,
                    default,
                    default,
                    false,
                    0d,
                    Revision,
                    _autoRunActive,
                    _hasCommandInput,
                    _commandInput)
                : new RuntimeMovementSnapshot(
                    true,
                    controller.LocalEntityId,
                    controller.CellPosition,
                    controller.BodyVelocity,
                    controller.IsAirborne,
                    controller.SimTimeSeconds,
                    Revision,
                    _autoRunActive,
                    _hasCommandInput,
                    _commandInput);
        }
    }

    /// <summary>
    /// Opens the retail construction seam where a PartArray completion can
    /// reach the candidate MotionInterpreter before the controller is
    /// published to ordinary borrowers.
    /// </summary>
    public IDisposable BeginMotionPreparation(
        PlayerMovementController controller,
        Action? drainPriorAnimationQueue = null)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        ArgumentNullException.ThrowIfNull(controller);
        if (_preparingMotionOwner is not null)
        {
            throw new InvalidOperationException(
                "A local player motion owner is already being prepared.");
        }

        drainPriorAnimationQueue?.Invoke();
        _preparingMotionOwner = controller;
        return new MotionPreparation(this, controller);
    }

    public bool Execute(RuntimeMovementCommand command)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        switch (command)
        {
            case RuntimeMovementCommand.ToggleRunLock:
                _autoRunActive = !_autoRunActive;
                Interlocked.Increment(ref _revision);
                return true;
            case RuntimeMovementCommand.Stop:
                CancelAutoRun();
                ClearCommandInput();
                return true;
            case RuntimeMovementCommand.Ready:
            case RuntimeMovementCommand.Sit:
            case RuntimeMovementCommand.Crouch:
            case RuntimeMovementCommand.Sleep:
                CancelAutoRun();
                ClearCommandInput();
                uint motion = command switch
                {
                    RuntimeMovementCommand.Ready =>
                        MotionCommand.Ready,
                    RuntimeMovementCommand.Sit =>
                        MotionCommand.Sitting,
                    RuntimeMovementCommand.Crouch =>
                        MotionCommand.Crouch,
                    RuntimeMovementCommand.Sleep =>
                        MotionCommand.Sleeping,
                    _ => throw new UnreachableException(),
                };
                return _controller?.RequestPosture(motion) == true;
            default:
                return false;
        }
    }

    public bool CancelAutoRun()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (!_autoRunActive)
            return false;
        _autoRunActive = false;
        Interlocked.Increment(ref _revision);
        return true;
    }

    /// <summary>
    /// Installs the persistent semantic movement level sampled by either host.
    /// The graphical input adapter and direct host both consume this exact
    /// owner; no bot-only movement latch exists.
    /// </summary>
    public void SetCommandInput(in MovementInput input)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (_hasCommandInput && _commandInput == input)
            return;
        _commandInput = input;
        _hasCommandInput = true;
        Interlocked.Increment(ref _revision);
    }

    public bool ClearCommandInput()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (!_hasCommandInput)
            return false;
        _commandInput = default;
        _hasCommandInput = false;
        Interlocked.Increment(ref _revision);
        return true;
    }

    /// <summary>
    /// Direct-host projection of the same combat readiness query used by the
    /// graphical attack adapter. A host without a constructed local movement
    /// owner is not ready; Slice K's content host must hydrate that owner
    /// before combat packets can leave.
    /// </summary>
    public bool IsReadyForAttack(CombatMode mode)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (_controller is not { } controller)
            return false;
        var motion = controller.Motion.InterpretedState;
        return CombatInputPlanner.PlayerInReadyPositionForAttack(
            mode,
            motion.CurrentStyle,
            motion.ForwardCommand);
    }

    public bool IsDualWield
    {
        get
        {
            ObjectDisposedException.ThrowIf(_disposed, this);
            return _controller?.Motion.InterpretedState.CurrentStyle
                == CombatInputPlanner.DualWieldCombatStyle;
        }
    }

    public bool PrepareForAttackRequest()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        CancelAutoRun();
        return _controller?.PrepareForAttackRequest() == true;
    }

    public void ResetInputIntent()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (!_autoRunActive && !_hasCommandInput)
            return;
        _autoRunActive = false;
        _hasCommandInput = false;
        _commandInput = default;
        Interlocked.Increment(ref _revision);
    }

    /// <summary>
    /// Retires every character-generation movement owner while keeping the
    /// process-scoped Runtime root reusable for the next session.
    /// Graphical hosts release their camera/physics projections first; direct
    /// hosts have no parallel projection to coordinate.
    /// </summary>
    public void ResetSession()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        bool changed =
            _autoRunActive
            || _hasCommandInput
            || _controller is not null
            || _preparingMotionOwner is not null;
        _autoRunActive = false;
        _hasCommandInput = false;
        _commandInput = default;
        _controller = null;
        _preparingMotionOwner = null;
        if (changed)
            Interlocked.Increment(ref _revision);
    }

    public RuntimeLocalMovementOwnershipSnapshot CaptureOwnership() =>
        new(
            _disposed,
            _controller is not null,
            _preparingMotionOwner is not null,
            _autoRunActive,
            _hasCommandInput,
            Revision);

    public void Dispose()
    {
        if (_disposed)
            return;
        _autoRunActive = false;
        _hasCommandInput = false;
        _commandInput = default;
        _controller = null;
        _preparingMotionOwner = null;
        Interlocked.Increment(ref _revision);
        _disposed = true;
    }

    private void EndMotionPreparation(PlayerMovementController controller)
    {
        // Terminal disposal clears the unpublished construction seam. A
        // caller may still unwind the already-issued lease afterward; that
        // unwind is idempotent rather than resurrecting or faulting the
        // retired runtime owner.
        if (_disposed && _preparingMotionOwner is null)
            return;

        if (!ReferenceEquals(_preparingMotionOwner, controller))
        {
            throw new InvalidOperationException(
                "The local player motion preparation owner changed unexpectedly.");
        }
        _preparingMotionOwner = null;
    }

    private sealed class MotionPreparation(
        RuntimeLocalPlayerMovementState owner,
        PlayerMovementController controller) : IDisposable
    {
        private RuntimeLocalPlayerMovementState? _owner = owner;

        public void Dispose()
        {
            RuntimeLocalPlayerMovementState? current =
                Interlocked.Exchange(ref _owner, null);
            current?.EndMotionPreparation(controller);
        }
    }
}

public readonly record struct RuntimeLocalMovementOwnershipSnapshot(
    bool IsDisposed,
    bool HasController,
    bool HasPreparingMotionOwner,
    bool AutoRunActive,
    bool HasCommandInput,
    long Revision)
{
    public bool IsConverged =>
        IsDisposed
        && !HasController
        && !HasPreparingMotionOwner
        && !AutoRunActive
        && !HasCommandInput;
}