package carpet.utils;

/**
 * <p>Allows for getting a key by having an instance of the class this object was instantiated with.</p>
 * 
 * <p>Known working map implementations: {@link it.unimi.dsi.fastutil.objects.Object2ObjectArrayMap}. 
 * Others may not behave the same way (checking equals in existing key)</p>
 * 
 * <p>To prevent IDE warnings about unlinkely arguments types in get function, use {@link Object} as key generic.</p>
 *
 */
public class InstanceOfMapKey
{
    private final Class<?> clazz;
    
    public InstanceOfMapKey(Class<?> clazz)
    {
        this.clazz = clazz;
    }
    
    @Override
    public boolean equals(Object obj)
    {
        return clazz.isInstance(obj);
    }
    
    @Override
    public int hashCode() // May allow compat with hash implementations, but won't be useful at all
    {
        return 1;
    }
}

private static final Map<Object, Function<...>> toValueMap = new Object2ObjectArrayMap<>();
static
{
    toValueMap.put(new InstanceOfMapKey(Entity.class), e -> new EntityValue(e));
    ..
}

public static Value guess(Object o) {
   var converter = toValueMap.get(o);
   if (converter == null) throw new UnsupportedOperationException();
   return converter.apply(o);
}