using System;

using System.Collections.Generic;

​

public struct Entity {

    public int id;

    public override bool Equals(Object rhs) {

        if (rhs is Entity) {

            return id == ((Entity)rhs).id;

        }

        return false;

    }

    public override int GetHashCode() {

        return id;

    }

    public static bool operator ==(Entity a, Entity b) {

        return a.Equals(b);

    }

    public static bool operator !=(Entity a, Entity b) {

        return !(a == b);

    }

}

​

class AStorage {

}

​

class Storage<T> : AStorage {

    public Dictionary<Entity, T> m_comps = new Dictionary<Entity, T>();

}

​

struct Info {

    public string name;

}

​

public class Registry {

    Dictionary<int, AStorage> m_stores = new Dictionary<int, AStorage>();

    int m_nextEntityID = 0;

    public Entity spawn(string name) {

        Storage<Info> store = store<Info>();

        Entity entity = new Entity();

        entity.id = ++m_nextEntityID;

        Info info = attach<Info>(entity);

        info.name = name;

        return entity;

    }

    public T attach<T>(Entity entity) where T : new() {

        Storage<T> store = store<T>();

        T t = new T();

        if (!store.m_comps.ContainsKey(entity)) {

            store.m_comps.Add(entity, t);

        } else {

            store.m_comps[entity] = t;

        }

        return t;

    }

    public T find<T>(Entity entity) {

        Storage<T> store = store<T>();

        if (store.m_comps.ContainsKey(entity)) {

            return store.m_comps[entity];

        }

        return default(T);

    }

    Storage<T> store<T>() {

        int hash = typeof(T).GetHashCode();

        if (!m_stores.ContainsKey(hash)) {

            m_stores.Add(hash, new Storage<T>());

        }

        return m_stores[hash] as Storage<T>;

    }

}

​

public class Program

{

    public class Test {

        public int value = 0;

    }

    public static void Main()

    {

        Registry reg = new Registry();

        Entity e1 = reg.spawn("E1");

        Entity e2 = reg.spawn("E2");

        Test test = reg.attach<Test>(e1);

        test.value = 42;

        test = reg.attach<Test>(e2);

        test.value = -5;

        Console.WriteLine("E1: " + reg.find<Test>(e1).value + "\nE2: " + reg.find<Test>(e2).value);

    }

}