Sentry ECS - a simple public domain entity component system

AbstractComponent.cs

public abstract class AbstractComponent : IComponent
{
    [NonSerialized]
    protected readonly Entity _owner;

    public AbstractComponent(Entity owner)
    {
        _owner = owner;
        ID = Guid.NewGuid().ToString("n");
    }

    public virtual void OnDestroy() { }

    public abstract Type ObjectType { get; }
    public abstract ComponentTypes ComponentType { get; }

    public T Clone<T>() where T : AbstractComponent
    {
        return (T) MemberwiseClone();
    }

    public Entity Owner
    {
        get { return _owner; }
    }

    public string ID { get; private set; }
}

AbstractEditorWindow.cs

public abstract class AbstractEditorWindow : EditorWindow
{
    private float _nextUpdate = 1;

    // refreshes the display every second
    protected virtual void Update()
    {
        _nextUpdate -= Time.deltaTime;
        if (_nextUpdate > 0) return;
        Repaint();
        _nextUpdate = 1;
    }

    protected void DrawDoubleLabel(string label, string value1, string separator, string value2)
    {
        GUILayout.BeginHorizontal();
        GUILayout.Label(label, EditorStyles.miniBoldLabel);
        GUILayout.Box(value1, GUILayout.Width(100));
        GUILayout.Label(separator, GUILayout.Width(50));
        GUILayout.Box(value2, GUILayout.Width(100));
        GUILayout.EndHorizontal();
    }

    protected void DrawLabel(string label, string value, int width = 200, bool isBox = true)
    {
        GUILayout.BeginHorizontal();
        GUILayout.Label(label, EditorStyles.miniBoldLabel);
        if (isBox)
        {
            GUILayout.Box(value, GUILayout.Width(width));
        }
        else
        {
            GUILayout.Label(value, GUILayout.Width(width));
        }
        GUILayout.EndHorizontal();
    }
}

AbstractSystem.cs

public abstract class AbstractSystem : ISystem
{
    public abstract Type ObjectType { get; }
    public virtual int ExecutionPriority { get { return 100; } }

    public abstract void Init();
    public abstract void Update();
}

ComponentFactory.cs

public static class ComponentFactory
{
    public static readonly Dictionary<ComponentTypes, Type> ComponentLookup = new Dictionary<ComponentTypes, Type>
    {
        {ComponentTypes.SampleComponent, typeof(SampleComponent)}
    };

    public static IComponent Create(ComponentTypes type, Entity entity)
    {
        if (!ComponentLookup.ContainsKey(type)) return null;
        return (IComponent) Activator.CreateInstance(ComponentLookup[type], entity);
    }
}

Entity.cs

public class Entity
{
    private readonly Dictionary<Type, IComponent> _components = new Dictionary<Type, IComponent>();

    protected Entity(IEnumerable<ComponentTypes> componentTypes)
    {
        foreach (var ctype in componentTypes)
        {
            AddComponent(ctype);
        }
    }

    public virtual void OnDestroy()
    {
    }

    public bool HasComponent(ComponentTypes type)
    {
        return _components.ContainsKey(ComponentFactory.ComponentLookup[type]);
    }

    public T GetComponent<T>() where T : IComponent
    {
        var t = typeof(T);
        if (!_components.ContainsKey(t))
            throw new KeyNotFoundException(string.Format("Unable to find component {0} on {1}", t, GetType()));
        return (T) _components[t];
    }

    protected void AddComponent(ComponentTypes ctype)
    {
        var comp = ComponentFactory.Create(ctype, this);
        AddComponent(comp);
    }

    protected void AddComponent(IComponent component)
    {
        _components.Add(component.ObjectType, component);
        EntityPool.AddComponent(component);
    }

    public IEnumerable<IComponent> Components
    {
        get
        {
            return _components.Values;
        }
    }
}

EntityPool.cs

public static class EntityPool
{
    /// <summary>
    /// A list of components sorted by their type, allowing O(1) lookup for components
    /// </summary>
    private static readonly Dictionary<ComponentTypes, List<IComponent>> ComponentPools =
        new Dictionary<ComponentTypes, List<IComponent>>(Enum.GetNames(typeof(ComponentTypes)).Length);

    /// <summary>
    /// A list of systems on the game
    /// </summary>
    private static readonly List<ISystem> SystemPools = new List<ISystem>();

    /// <summary>
    /// Static constructor
    /// </summary>
    static EntityPool()
    {
        Reset();
    }

    /// <summary>
    /// Resets the component and system pools to their fresh, empty state
    /// </summary>
    public static void Reset()
    {
        foreach (var componentList in ComponentPools.Values)
        {
            var tempList = new List<IComponent>(componentList);
            foreach (var component in tempList)
            {
                DestroyComponent(component);
            }
        }

        SystemPools.Clear();
        ComponentPools.Clear();

        var enumVals = Enum.GetValues(typeof(ComponentTypes));

        foreach (var ev in enumVals)
        {
            var ct = (ComponentTypes) ev;
            ComponentPools.Add(ct, new List<IComponent>());
        }
    }

    /// <summary>
    /// Adds a component to the pool
    /// </summary>
    /// <param name="component"></param>
    public static void AddComponent(IComponent component)
    {
        ComponentPools[component.ComponentType].Add(component);
    }

    /// <summary>
    /// Adds a system into the pool and sorts by execution priority
    /// </summary>
    /// <param name="system"></param>
    public static void AddSystem(ISystem system)
    {
        SystemPools.Add(system);
        system.Init();
        SystemPools.Sort((a, b) => a.ExecutionPriority.CompareTo(b.ExecutionPriority));
    }

    /// <summary>
    /// Removes all the components attached to an entity from the pool
    /// </summary>
    /// <param name="entity"></param>
    public static void DestroyEntity(Entity entity)
    {
        foreach (var component in entity.Components)
        {
            DestroyComponent(component);
        }

        entity.OnDestroy();
    }

    /// <summary>
    /// Removes the given component from the pool
    /// </summary>
    /// <param name="component"></param>
    public static void DestroyComponent(IComponent component)
    {
        component.OnDestroy();
        ComponentPools[component.ComponentType].Remove(component);
    }

    /// <summary>
    /// Runs through all the systems and updates them
    /// </summary>
     public static void Update()
    {
        //foreach (var system in SystemPools)
        //{
        //    system.Update();
        //}

	    for (int i = 0; i < SystemPools.Count; i++)
	    {
		    SystemPools[i].Update();
	    }
    }

    /// <summary>
    /// Gets the IComponents references of a given type in the system
    /// </summary>
    /// <param name="type"></param>
    /// <returns></returns>
    public static IEnumerable<IComponent> Get(ComponentTypes type)
    {
        return ComponentPools[type];
    }

    /// <summary>
    /// Gets the components of a given type in the system
    /// </summary>
    /// <param name="type"></param>
    /// <returns></returns>
    public static IEnumerable<T> Get<T>(ComponentTypes type) where T : IComponent
    {
        return ComponentPools[type].Cast<T>();
    }

    /// <summary>
    /// Gets a component type by ID
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="type"></param>
    /// <param name="id"></param>
    /// <returns></returns>
    public static T Get<T>(ComponentTypes type, string id) where T : class, IComponent
    {
        var comps = Get(type);
        return comps.FirstOrDefault(o => o.ID == id) as T;
    }
}

SampleComponent.cs

[Serializable]
public sealed class SampleComponent : AbstractComponent
{
    public float AWeirdNumber;
    
    #region AbstractComponent Implementation

    private static readonly Type _type = typeof(SampleComponent);

    public SampleComponent(Entity owner) : base(owner)
    {
    }

    public override Type ObjectType
    {
        get { return _type; }
    }

    public override ComponentTypes ComponentType
    {
        get
        {
            return ComponentTypes.SampleComponent;
        }
    }

    #endregion
}

SampleEntity.cs

public sealed class SampleEntity : Entity
{
    public SampleEntity() : base(new List<ComponentTypes>
    {
        ComponentTypes.SampleComponent
    }) { }
}

SampleSystem.cs

public class SampleSystem : AbstractSystem
{
    public override void Update()
    {
        var samples = EntityPool.Get<SampleComponent>(ComponentTypes.SampleComponent);
        
        foreach (var sample in samples) 
        {
            sample.AWeirdNumber = Random.value;
        }
    }

    #region Abstract System Implementation

    private static readonly Type _type = typeof(SampleSystem);

    public override Type ObjectType
    {
        get { return _type; }
    }

    public override void Init()
    {
    }

    #endregion
}