/**
 * Serene (simple) - A PoC lisp to collect data on Serenes concepts
 * Copyright (C) 2019-2020 Sameer Rahmani <lxsameer@gnu.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA  02110-1301, USA.
 */
package serene.simple.builtin;

import java.util.List;

import serene.simple.IDoc;
import serene.simple.IScope;
import serene.simple.ListNode;
import serene.simple.SereneException;


public class FirstFn extends AFn implements IDoc{
  public String fnName() {
    return "first";
  };

  public String getDoc() {
    return "`(first coll)`: Returns the first element of the given" +
      " COLL.";
  }

  public Object eval(IScope scope) throws SereneException{
    List<Object> args = this.arguments();

    if (args.size() == 0) {
      throw new SereneException("First of what ?");
    }

    if (args.size() > 1) {
      throw new SereneException("Too many parameters to 'first'.");
    }

    return ((ListNode<Object>) args.get(0)).first();
  }
}