Babushka/scripts/CSharp/GameEntity/Management/EntityManager.cs

using System.Collections.Generic;
using System.Linq;
using Godot;
using Entity = Babushka.scripts.CSharp.GameEntity.Entities.Entity;
using PositionalEntity = Babushka.scripts.CSharp.GameEntity.Entities.PositionalEntity;

namespace Babushka.scripts.CSharp.GameEntity.Management;

/// <summary>
/// Manages the lifecycle and interactions of all entities within the game, including their creation, retrieval,
/// and organization. The EntityManager serves as a centralized hub for managing both standard and positional entities.
/// </summary>
public partial class EntityManager : Node
{
    public static EntityManager Instance;
    
    [Export] private EntityNodeCreator _nodeCreator = null!;
    
    private EntitySceneContainer? _currentEntitySceneContainer;
    private readonly List<Entity> _allEntities = new();
    
    public IEnumerable<Entity> AllEntities => _allEntities;
    public IEnumerable<PositionalEntity> AllPositionalEntities => _allEntities.OfType<PositionalEntity>();
    public EntitySceneContainer? CurrentEntitySceneContainer => _currentEntitySceneContainer;
    public EntityNodeCreator NodeCreator => _nodeCreator;

    public override void _EnterTree()
    {
        Instance = this;
    }

    public override void _Input(InputEvent @event)
    {
        // for debugging purposes
        if (@event.IsActionPressed("DebugEntities"))
        {
            GD.Print("Entities:");
            foreach (var entity in AllEntities)
            {
                GD.Print(entity.EntityType + " " + entity.id);
            }
        }
    }
    
    #region ENTITY MANAGEMENT

    /// <summary>
    /// Adds an entity to the list of managed entities. If the entity is a positional entity
    /// and its scene matches the current scene container, it is also instantiated in the scene.
    /// </summary>
    /// <param name="entity">The entity to be added to the manager.</param>
    public void AddEntity(Entity entity)
    {
        if (!_allEntities.Contains(entity))
            _allEntities.Add(entity);
        if(entity is PositionalEntity positionalEntity && positionalEntity.sceneName == _currentEntitySceneContainer?.sceneName)
            InstantiatePositionalEntityNode(positionalEntity);
    }

    private void InstantiatePositionalEntityNode(PositionalEntity entity)
    {
        if(_currentEntitySceneContainer == null) return;
        entity.InstantiateEntityNode(_currentEntitySceneContainer);
    }

    /// <summary>
    /// Retrieves the first entity of the specified type from the list of managed entities.
    /// If no such entity exists, creates a new instance of the specified type, adds it to the manager, and returns it.
    /// </summary>
    /// <typeparam name="T">The type of entity to retrieve or create. Must inherit from the Entity class and have a parameterless constructor.</typeparam>
    /// <returns>The first entity of the specified type or a newly created entity of that type if none were found.</returns>
    public T GetUniqueEntity<T>() where T : Entity, new()
    {
        var result = AllEntities.OfType<T>().FirstOrDefault();
        if (result == null)
        {
            var newEntity = new T();
            AddEntity(newEntity);
            result = newEntity;
        }
        return result;
    }
    
    #endregion
    
    #region SCENE CONTAINER ACCESS
    
    public void SetSceneContainer(EntitySceneContainer sceneContainer)
    {
        _currentEntitySceneContainer = sceneContainer;
    }
    
    public void UnsetSceneContainer()
    {
        _currentEntitySceneContainer = null;
    }
    
    #endregion

}