Dominion.PlayerState.RequestPlayerDiscardCardFromHand C# (CSharp) Method

        internal bool RequestPlayerDiscardCardFromHand(GameState gameState, CardPredicate acceptableCardsToDiscard, bool isOptional)
        {
            if (!this.hand.HasCard(acceptableCardsToDiscard))
            {
                return false;
            }

            Card cardTypeToDiscard = this.actions.GetCardFromHandToDiscard(gameState, acceptableCardsToDiscard, isOptional);
            if (cardTypeToDiscard == null)
            {
                if (isOptional)
                {
                    return false;
                }
                else
                {
                    throw new Exception("Player must choose a card to discard");
                }
            }
            else
            {
                if (gameState.GetPile(cardTypeToDiscard) != null &&  // TODO: this currently can not find ruins ... rework this method so a card is returned instead of a type.
                    !acceptableCardsToDiscard( cardTypeToDiscard))
                    throw new Exception("Card does not meet constraint: ");
            }

            this.MoveCardFromHandToDiscard(cardTypeToDiscard, gameState);

            return true;
        }

 public override void DoSpecializedAction(PlayerState currentPlayer, GameState gameState)
 {
     if (currentPlayer.RequestPlayerDiscardCardFromHand(gameState, acceptableCard => acceptableCard == Estate.card, isOptional: true))
     {
         currentPlayer.AddCoins(4);
     }
     else
     {
         currentPlayer.GainCardFromSupply(Estate.card, gameState);
     }
 }