oecs-sharp/OECS/QueryBuilder.cs

namespace OECS;

/// <summary>
/// Fluent builder for constructing <see cref="QueryDescriptor"/> instances.
/// Returned by <see cref="World.Query"/>.
/// </summary>
public class QueryBuilder
{
    private readonly HashSet<Type> _with = new();
    private readonly HashSet<Type> _without = new();

    /// <summary>
    /// Requires entities to have a component of type <typeparamref name="T"/>.
    /// </summary>
    public QueryBuilder With<T>() where T : struct
    {
        _with.Add(typeof(T));
        return this;
    }

    /// <summary>
    /// Excludes entities that have a component of type <typeparamref name="T"/>.
    /// </summary>
    public QueryBuilder Without<T>() where T : struct
    {
        _without.Add(typeof(T));
        return this;
    }

    /// <summary>
    /// Builds the query descriptor.
    /// </summary>
    public QueryDescriptor Build()
    {
        return new QueryDescriptor(
            new HashSet<Type>(_with),
            new HashSet<Type>(_without));
    }
}