AssignmentExpression.cs :  » Development » Vici-Parser » Vici » Core » Parser » C# / CSharp Open Source

#region License
//=============================================================================
// Vici Core - Productivity Library for .NET 3.5 
//
// Copyright (c) 2008-2010 Philippe Leybaert
//
// Permission is hereby granted, free of charge, to any person obtaining a copy 
// of this software and associated documentation files (the "Software"), to deal 
// in the Software without restriction, including without limitation the rights 
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
// copies of the Software, and to permit persons to whom the Software is 
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.
//=============================================================================
#endregion

using System;
using System.Collections.Generic;

namespace Vici.Core.Parser{
    public class AssignmentExpression : BinaryExpression
    {
        public AssignmentExpression(TokenPosition position, Expression left, Expression right)
            : base(position, left, right)
        {
        }

        public override ValueExpression Evaluate(IParserContext context)
        {
            ValueExpression valueRight = Right.Evaluate(context);

            if (Left is VariableExpression)
            {
                if ((context.AssignmentPermissions & AssignmentPermissions.Variable) == AssignmentPermissions.None)
          throw new IllegalAssignmentException("Assignment to variable not allowed", this);

                VariableExpression varExpr = (VariableExpression)Left;

                bool exists = context.Exists(varExpr.VarName);

                if (exists && (context.AssignmentPermissions & AssignmentPermissions.ExistingVariable) == AssignmentPermissions.None)
          throw new IllegalAssignmentException("Assignment to existing variable not allowed", this);

                if (!exists && (context.AssignmentPermissions & AssignmentPermissions.NewVariable) == AssignmentPermissions.None)
          throw new IllegalAssignmentException("Assignment to new variable not allowed", this);

                context.Set(varExpr.VarName, valueRight.Value, valueRight.Type);

                return valueRight;
            }

      if (Left is FieldExpression)
      {
        if ((context.AssignmentPermissions & AssignmentPermissions.Property) == AssignmentPermissions.None)
          throw new IllegalAssignmentException("Assignment to property not allowed", this);

        return ((FieldExpression)Left).Assign(context, valueRight.Value);
      }

            throw new IllegalAssignmentException(this);
        }
    }
}