using Syntriax.Engine.Core.Abstract;

namespace Syntriax.Engine.Core;

[System.Diagnostics.DebuggerDisplay("{GetType().Name, nq}, Priority: {Priority}, Initialized: {Initialized}")]
public abstract class BehaviourBase : BaseEntity, IBehaviour
{
    public event IHasBehaviourController.BehaviourControllerAssignedEventHandler? OnBehaviourControllerAssigned = null;
    public event IBehaviour.PriorityChangedEventHandler? OnPriorityChanged = null;
    public event IActive.ActiveChangedEventHandler? OnActiveChanged = null;

    private IBehaviourController _behaviourController = null!;
    public IBehaviourController BehaviourController => _behaviourController;

    private int _priority = 0;
    public int Priority
    {
        get => _priority;
        set
        {
            if (value == _priority)
                return;

            int previousPriority = _priority;
            _priority = value;
            OnPriorityChanged?.InvokeSafe(this, previousPriority);
        }
    }

    private bool _isActive = false;
    public bool IsActive => _isActive;

    protected virtual void OnAssign(IBehaviourController behaviourController) { }
    public bool Assign(IBehaviourController behaviourController)
    {
        if (IsInitialized)
            return false;

        _behaviourController = behaviourController;
        OnAssign(behaviourController);
        behaviourController.OnUniverseObjectAssigned += OnUniverseObjectAssigned;
        if (behaviourController.UniverseObject is not null)
            OnUniverseObjectAssigned(behaviourController);
        OnBehaviourControllerAssigned?.InvokeSafe(this);
        return true;
    }

    private void OnUniverseObjectAssigned(IHasUniverseObject sender)
    {
        sender.UniverseObject.OnActiveChanged += OnUniverseObjectActiveChanged;
        UpdateActive();
    }

    protected override void OnAssign(IStateEnable stateEnable)
    {
        base.OnAssign(stateEnable);

        stateEnable.OnEnabledChanged += OnStateEnabledChanged;
    }

    protected override void UnassignInternal()
    {
        StateEnable.OnEnabledChanged -= OnStateEnabledChanged;
        BehaviourController.OnUniverseObjectAssigned -= OnUniverseObjectAssigned;
        base.UnassignInternal();
        _behaviourController = null!;
    }

    protected override void InitializeInternal()
    {
        Debug.AssertHelpers.AssertBehaviourControllerAssigned(this);
        Debug.AssertHelpers.AssertStateEnableAssigned(this);
    }

    private void OnStateEnabledChanged(IStateEnable sender, bool previousState) => UpdateActive();
    private void OnUniverseObjectActiveChanged(IActive sender, bool previousState) => UpdateActive();

    private void UpdateActive()
    {
        bool previousActive = IsActive;
        _isActive = StateEnable.Enabled && _behaviourController.UniverseObject.IsActive;

        if (previousActive != IsActive)
            OnActiveChanged?.InvokeSafe(this, previousActive);
    }
}