TF-EssentialsX/Essentials/src/com/earth2me/essentials/signs/SignBuy.java

package com.earth2me.essentials.signs;

import com.earth2me.essentials.ChargeException;
import com.earth2me.essentials.Trade;
import com.earth2me.essentials.User;
import net.ess3.api.IEssentials;
import net.ess3.api.MaxMoneyException;


public class SignBuy extends EssentialsSign {
    public SignBuy() {
        super("Buy");
    }

    @Override
    protected boolean onSignCreate(final ISign sign, final User player, final String username, final IEssentials ess) throws SignException {
        validateTrade(sign, 1, 2, player, ess);
        validateTrade(sign, 3, ess);
        return true;
    }

    @Override
    protected boolean onSignInteract(final ISign sign, final User player, final String username, final IEssentials ess) throws SignException, ChargeException, MaxMoneyException {
        final Trade items = getTrade(sign, 1, 2, player, ess);
        final Trade charge = getTrade(sign, 3, ess);
        charge.isAffordableFor(player);
        if (!items.pay(player)) {
            throw new ChargeException("Inventory full"); //TODO: TL
        }
        charge.charge(player);
        Trade.log("Sign", "Buy", "Interact", username, charge, username, items, sign.getBlock().getLocation(), ess);
        return true;
    }
}