//Copyright 2010 Microsoft Corporation
//
//Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. 
//You may obtain a copy of the License at 
//
//http://www.apache.org/licenses/LICENSE-2.0 
//
//Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an 
//"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
//See the License for the specific language governing permissions and limitations under the License.

namespace System.Data.Services.Client
{
    #region Namespaces.

    using System.Diagnostics;
    using System.Linq.Expressions;

    #endregion Namespaces.

    internal abstract class DataServiceExpressionVisitor : ExpressionVisitor
    {
        internal override Expression Visit(Expression exp)
        {
            if (exp == null)
            {
                return null;
            }

            switch ((ResourceExpressionType)exp.NodeType)
            {
                case ResourceExpressionType.RootResourceSet:
                case ResourceExpressionType.ResourceNavigationProperty:
                    return this.VisitResourceSetExpression((ResourceSetExpression)exp);
                case ResourceExpressionType.ResourceNavigationPropertySingleton:
                    return this.VisitNavigationPropertySingletonExpression((NavigationPropertySingletonExpression)exp);
                case ResourceExpressionType.InputReference:
                    return this.VisitInputReferenceExpression((InputReferenceExpression)exp);
                default:
                    return base.Visit(exp);
            }
        }

        internal virtual Expression VisitResourceSetExpression(ResourceSetExpression rse)
        {
            Expression source = this.Visit(rse.Source);

            if (source != rse.Source)
            {
                rse = new ResourceSetExpression(rse.Type, source, rse.MemberExpression, rse.ResourceType, rse.ExpandPaths, rse.CountOption, rse.CustomQueryOptions, rse.Projection);
            }

            return rse;
        }

        internal virtual Expression VisitNavigationPropertySingletonExpression(NavigationPropertySingletonExpression npse)
        {
            Expression source = this.Visit(npse.Source);

            if (source != npse.Source)
            {
                npse = new NavigationPropertySingletonExpression(npse.Type, source, npse.MemberExpression, npse.MemberExpression.Type, npse.ExpandPaths, npse.CountOption, npse.CustomQueryOptions, npse.Projection);
            }

            return npse;
        }

        internal virtual Expression VisitInputReferenceExpression(InputReferenceExpression ire)
        {
            Debug.Assert(ire != null, "ire != null -- otherwise caller never should have visited here");
            ResourceExpression re = (ResourceExpression)this.Visit(ire.Target);
            return re.CreateReference();
        }
    }
}
