using System.Collections.Generic;
using Godot;

namespace Babushka.scripts.CSharp.Low_Code.Events;

/// <summary>
/// Represents an event in the project space.
/// Can be called by <see cref="EventRaiser"/> and subscribed to by <see cref="EventListener"/>.
/// </summary>
[GlobalClass] [Tool]
public partial class EventResource : Resource
{
    /// <summary>
    /// Log into console when this event resource is adding or removing listeners, and when it's raised.
    /// </summary>
    [Export] private bool _showLog;

    [Export]
    public Variant Payload
    {
        get { return _payload; }
        set
        {
            if (!_payload.Equals(value))
            {
                _lastPayload = _payload;
                _payload = value;
                ValueChangeHandler();
            }
        }
    }

    private Variant _payload;
    private Variant _lastPayload;
    
    /// <summary>
    /// Raise-Button Call with Editor Export for easier debugging.
    /// Beware: This will only work with custom event listeners that register at edit-time.
    /// Standard <see cref="EventListeners"/> register and deregister during playtime.
    /// </summary>
    [ExportToolButton("Raise")] Callable _raiseAction => Callable.From(Raise);
    
    private List<EventListener> _eventListeners = new ();
    
    /// <summary>
    /// Adds an EventListener to the calling list for this event.
    /// </summary>
    /// <param name="listener"></param>
    public void RegisterListener(EventListener listener)
    {
        if(_showLog)
            GD.Print("Registering listener " + listener);
        _eventListeners.Add(listener);
    }

    /// <summary>
    /// Removes an Eventlistener from the calling list for this event.
    /// </summary>
    /// <param name="listener"></param>
    public void UnregisterListener(EventListener listener)
    {
        if(_showLog)
            GD.Print("Unregistering listener " + listener);
        _eventListeners.Remove(listener);
    }
    
    /// <summary>
    /// Raises this event on all current listeners. 
    /// </summary>
    public void Raise()
    {
        if(_showLog)
            GD.Print("Raising event: " + ResourcePath.GetFile().TrimSuffix(".tres"));
        
        foreach (var eventListener in _eventListeners)
        {
            eventListener.EventInvoked(_payload);
        }
    }

    /// <summary>
    /// Called when the Payload value changed.
    /// </summary>
    public void ValueChangeHandler()
    {
        if(_showLog)
            GD.Print($"Event payload changed from {_lastPayload} to {_payload} on event resource: " + ResourcePath.GetFile().TrimSuffix(".tres"));
        
        foreach (var eventListener in _eventListeners)
        {
            eventListener.EventPayloadChanged(_payload, _lastPayload);
        }
    }
    
}