List<GameDecision> Out = new List<GameDecision>();

    foreach(Card SpellCard in PlayerSpellbook(Player))
    {
        List<Card> PossibleTargets = GetPossibleTargets(SpellCard);

        for(each combination of possible targets)
        {
            List<Card> Targets = new list of Card.TargetCount targets;
            Out.Add(new GameDecision() { Type = GameDecisionType.PlayCard, TheCard = SpellCard, Targets = Targets });