// Copyright (C) 2003, 2005 Daisuke Arai <darai@users.sourceforge.jp>
// Copyright (C) 2008, 2013 panacoran <panacoran@users.sourceforge.jp>
// 
// This program is part of Protra.
//
// Protra 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 3 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, see <http://www.gnu.org/licenses/>.
// 
// $Id: ReturnStatementNode.cs 482 2013-07-08 04:36:10Z panacoran $

namespace Protra.Lib.Lang
{
    /// <summary>
    /// return文のノードを表すクラス。
    /// </summary>
    public class ReturnStatementNode : ExecutableNode
    {
        /// <summary>
        /// 式のノード
        /// </summary>
        private ExpressionNode _expNode;

        /// <summary>
        /// 構文解析する。
        /// </summary>
        /// <exception cref="Protra.Lib.Lang.ParseException">
        /// 構文解析中にエラーが発生したときにthrowされる。
        /// </exception>
        /// <return>
        /// 解析した結果のノード。
        /// </return>
        public override ExecutableNode Parse(Scanner scanner)
        {
            Token = scanner.Token;
            if (!scanner.Scan())
                throw new ParseException("';' expected", scanner.Token);
            if (scanner.Token.Value == ";")
                return this;
            _expNode = new ExpressionNode().Parse(scanner);
            if (scanner.Token.Value != ";")
                throw new ParseException("';' expected", scanner.Token);
            return this;
        }

        /// <summary>
        /// プログラムを実行する。
        /// </summary>
        /// <exception cref="Protra.Lib.Lang.RuntimeException">
        /// プログラム実行中にエラーが発生した場合にthrowされる。
        /// </exception>
        /// <param name="resource">リソース</param>
        /// <param name="at">int型@作用素の値</param>
        /// <param name="ats">string型@作用素の値</param>
        /// <returns>実行結果</returns>
        public override Result Execute(Resource resource, int at, string ats)
        {
            resource.ReturnValue = _expNode == null ? null : _expNode.Evaluate(resource, at, ats);
            resource.Token = Token;
            return Result.Return;
        }
    }
}