namespace OECS;

/// <summary>
/// Describes a query over the ECS world.
/// Composed of a set of required component types ("with") and
/// a set of excluded component types ("without").
/// </summary>
public class QueryDescriptor
{
    /// <summary>
    /// Component types that must be present on matching entities.
    /// </summary>
    public IReadOnlySet<Type> With { get; }

    /// <summary>
    /// Component types that must NOT be present on matching entities.
    /// </summary>
    public IReadOnlySet<Type> Without { get; }

    internal QueryDescriptor(HashSet<Type> with, HashSet<Type> without)
    {
        With = with;
        Without = without;
    }

    /// <summary>
    /// Returns true if this query has no "with" components (matches nothing).
    /// </summary>
    internal bool IsEmpty => With.Count == 0;
}