FetchContext.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    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.
//

using System;

using Deveel.Data;
using Deveel.Data.Sql.Expressions;

namespace Deveel.Data.Sql.Cursors {
    public sealed class FetchContext {
        private int offset;

        public FetchContext(IRequest request, SqlExpression reference) 
            : this(request, FetchDirection.Next, reference) {
        }

        public FetchContext(IRequest request, FetchDirection direction, SqlExpression reference) {
            if (request == null)
                throw new ArgumentNullException("request");
            if (reference == null)
                throw new ArgumentNullException("reference");

            if (reference.ExpressionType != SqlExpressionType.VariableReference &&
                reference.ExpressionType != SqlExpressionType.Reference)
                throw new ArgumentException("Invalid reference expression type.");

            Request = request;
            Direction = direction;
            Reference = reference;
        }

        public FetchDirection Direction { get; private set; }

        public SqlExpression Reference { get; set; }

        public bool IsVariableReference {
            get { return Reference.ExpressionType == SqlExpressionType.VariableReference; }
        }

        public bool IsGlobalReference {
            get { return Reference.ExpressionType == SqlExpressionType.Reference; }
        }

        public IRequest Request { get; private set; }

        public int Offset {
            get { return offset; }
            set {
                if (Direction != FetchDirection.Absolute &&
                    Direction != FetchDirection.Relative)
                    throw new ArgumentException("Cannot set offset for this direction.");

                offset = value;
            }
        }
    }
}