using System.Collections.Immutable;
using System.Runtime.CompilerServices;
using imm;

namespace exp;


abstract public record class Exp<T> : imm.Versioned<Exp<T>>
{
	protected Exp()
		:
		base()
	{

	}

	abstract public T exec();
}

public record class ConstantExp<T>( T value ) : Exp<T>
{
	public override T exec() => value;
}

public record class VarExp<T> : Exp<T>
{

	public T val = default!;

	public VarExp()
	{
	}

	public override T exec() => val;

	public VarExp<T> set( T newVal )
	{
		return this with { val = newVal };
	}
}

public ref struct RefHolder<T>
{
	public T val = default!;

	public RefHolder()
	{
	}

	public RefHolder( T initial )
	{
		val = initial;
	}
}


/*

public record class Op<T>( EntityId id, Func<Entity, T> fn,
													[CallerMemberName] string dbgMethod = "",
													[CallerFilePath] string dbgPath = "",
													[CallerLineNumber] int dbgLine = 0,
													[CallerArgumentExpression("fn")]
													string dbgExp = ""
) : Exp<T>
{
	public override T exec()
	{
		var ent = ent.Entity.Get( id );
		if( ent == null )
			throw new System.Exception( $"Op<{typeof(T).Name}>: Entity {id} not found" );

		return fn( ent );
	}
}
*/


public record class StackExp<T>( VarExp<T> BaseVal ) : Exp<T>
{
	public VarExp<T> ModValue = BaseVal;

	public ImmutableArray<Exp<T>> Adds = ImmutableArray<Exp<T>>.Empty;
	public ImmutableArray<Exp<T>> Mults = ImmutableArray<Exp<T>>.Empty;

	public override T exec()
	{
		return ModValue.exec();
	}
}






/// //