brick-framework/GameCore/ECS/World.cs

using GameCore.Config;
using GameCore.ECS.Interfaces;
using GameCore.Events;
using GameCore.Events.Interfaces;
using GameCore.Input.Interfaces;
using GameCore.Interaction;
using GameCore.Logging.Interfaces;
using GameCore.Services;
using GameCore.State;

namespace GameCore.ECS;

/// <summary>
///     The central container for the entire game state.
///     It manages all entities, components, and systems, and orchestrates the main game loop.
///     This class is the primary point of interaction for the Engine/Presentation layer.
/// </summary>
public class World
{
    private readonly Dictionary<int, List<IComponent>> _componentsByEntityId = new();
    private readonly EventBus _eventBus = new();
    private readonly List<ISystem> _systems = [];
    public readonly IAudioService AudioService;

    public readonly SimulationConfig Config;
    public readonly IGameStateService GameState;
    public readonly IInputService InputService;
    public readonly ILogger Logger;
    public readonly IParticleService ParticleService;
    public readonly IWorldQuery WorldQuery;
    private int _nextEntityId;

    public World(IInputService inputService,
        IWorldQuery worldQuery,
        SimulationConfig config,
        ILogger logger,
        IAudioService audioService,
        IParticleService particleService)
    {
        AudioService = audioService;
        Config = config;
        InputService = inputService;
        Logger = logger;
        ParticleService = particleService;
        WorldQuery = worldQuery;
        GameState = new GameStateService(this);
    }

    /// <summary>
    ///     Creates a new, unique entity.
    /// </summary>
    /// <returns>The newly created Entity.</returns>
    public Entity CreateEntity()
    {
        var id = _nextEntityId++;
        _componentsByEntityId[id] = [];
        return new Entity(id);
    }

    public void DestroyEntity(Entity entity)
    {
        _componentsByEntityId.Remove(entity.Id);
    }

    /// <summary>
    ///     Adds a component to a given entity.
    /// </summary>
    public void AddComponent(Entity entity, IComponent component)
    {
        _componentsByEntityId[entity.Id].Add(component);
    }

    public void RemoveComponent<T>(Entity entity) where T : class, IComponent
    {
        if (!_componentsByEntityId.TryGetValue(entity.Id, out var components)) return;

        var componentToRemove = components.OfType<T>().FirstOrDefault();
        if (componentToRemove != null) components.Remove(componentToRemove);
    }

    /// <summary>
    ///     Retrieves a specific type of component from an entity.
    /// </summary>
    /// <returns>The component instance, or null if the entity doesn't have it.</returns>
    public T? GetComponent<T>(Entity entity) where T : class, IComponent
    {
        return _componentsByEntityId.TryGetValue(entity.Id, out var components)
            ? components.OfType<T>().FirstOrDefault()
            : null;
    }

    /// <summary>
    ///     Finds all entities that have a specific component type.
    /// </summary>
    public IEnumerable<Entity> GetEntitiesWith<T>() where T : IComponent
    {
        return from pair in _componentsByEntityId
            where pair.Value.Any(c => c is T)
            select new Entity(pair.Key);
    }

    /// <summary>
    ///     Registers a system to be run in the game loop.
    /// </summary>
    public void RegisterSystem(ISystem system)
    {
        _systems.Add(system);
    }

    /// <summary>
    ///     Runs a single tick of the game simulation, updating all registered systems.
    /// </summary>
    public void Update(float deltaTime)
    {
        foreach (var system in _systems) system.Update(this, deltaTime);
    }

    public void PublishEvent(IEvent gameEvent)
    {
        _eventBus.Publish(gameEvent);
    }

    public void ProcessEvents()
    {
        _eventBus.ProcessEvents();
    }

    public void Subscribe<T>(Action<T> handler) where T : IEvent
    {
        _eventBus.Subscribe(handler);
    }

    public void Unsubscribe<T>(Action<T> handler) where T : IEvent
    {
        _eventBus.Unsubscribe(handler);
    }

    public Entity? FindEntityByWorldId(string worldId)
    {
        if (string.IsNullOrEmpty(worldId)) return null;

        foreach (var entity in _componentsByEntityId.Keys.Select(id => new Entity(id)))
        {
            var idComponent = GetComponent<WorldIdComponent>(entity);
            if (idComponent != null && idComponent.WorldId == worldId)
                return entity;
        }

        return null;
    }
}