gaemstone/src/gaemstone/ECS/Module+Components.cs

using System;

namespace gaemstone.ECS;

/// <summary> Use a custom name or path for this entity instead of the type's name. </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct
              | AttributeTargets.Enum  | AttributeTargets.Method)]
public class PathAttribute : Attribute
{
	public string Value { get; }
	public PathAttribute(string value) => Value = value;
}

[AttributeUsage(AttributeTargets.Struct)]
public class EntityAttribute : Attribute {  }

// On types marked as [Relation], this has an effect on the relation's behavior.
// Otherwise this has the same behavior as [Entity], but informs people
[AttributeUsage(AttributeTargets.Struct)]
public class TagAttribute : Attribute {  }

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum)]
public class ComponentAttribute : Attribute {  }

/// <summary>
/// A singleton is a single instance of a [Component] that can be retrieved
/// without explicitly specifying an entity in a query, where it is equivalent
/// to <see cref="SourceAttribute{}"/> with itself as the generic type parameter.
/// </summary>
public class SingletonAttribute : ComponentAttribute {  }

/// <summary>
/// Marked entity represents a relationship type.
/// It may be used as the "relation" in a pair.
/// </summary>
/// <remarks>
/// The relationship may have component data associated with
/// it when added to an entity under these circumstances:
/// <list type="bullet">
///   <item>If marked as a <see cref="TagAttribute"/>, does not carry data.</item>
///   <item>If marked as a <see cref="ComponentAttribute"/>, carries the relation's data.</item>
///   <item>If marked with neither, will carry the target's data, if it's a component.</item>
/// </list>
/// </remarks>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum)]
public class RelationAttribute : Attribute {  }