Variable.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;
using Deveel.Data.Types;

namespace Deveel.Data.Sql.Variables {
    public sealed class Variable : IDbObject, IEquatable<Variable> {
        public Variable(VariableInfo variableInfo) {
            if (variableInfo == null)
                throw new ArgumentNullException("variableInfo");

            VariableInfo = variableInfo;
        }

        public VariableInfo VariableInfo { get; private set; }

        public string Name {
            get { return VariableInfo.VariableName; }
        }

        public SqlType Type {
            get { return VariableInfo.Type; }
        }

        public SqlExpression Expression { get; private set; }

        public bool ValueFromExpression {
            get { return Expression != null; }
        }

        public DataObject Value { get; private set; }

        public bool IsConstant {
            get { return VariableInfo.IsConstant; }
        }

        public bool IsNotNull {
            get { return VariableInfo.IsNotNull; }
        }

        ObjectName IDbObject.FullName {
            get { return new ObjectName(VariableInfo.VariableName); }
        }

        DbObjectType IDbObject.ObjectType {
            get { return DbObjectType.Variable; }
        }

        public bool Equals(Variable other) {
            if (other == null)
                return false;

            if (!Name.Equals(other.Name) ||
                !Type.Equals(other.Type))
                return false;

            if (ValueFromExpression &&
                other.ValueFromExpression) {
                // TODO: Determine if the two expressions are equal!
                return true;
            }

            return Value.Equals(other.Value);
        }

        public void SetValue(IQuery context, SqlExpression expression) {
            if (expression == null)
                throw new ArgumentNullException("expression");

            if (IsConstant)
                throw new InvalidOperationException();

            if (!expression.IsConstant())
                throw new ArgumentException();

            Expression = expression;

            var exp = expression.Evaluate(context, null);
            if (exp.ExpressionType != SqlExpressionType.Constant)
                throw new InvalidOperationException();

            var value = ((SqlConstantExpression) exp).Value;
            SetValue(value);
        }

        public void SetValue(DataObject value) {
            if (IsConstant)
                throw new InvalidOperationException();

            if (!IsNotNull && value.IsNull)
                throw new ArgumentException();

            if (!Type.Equals(value.Type)) {
                if (!value.Type.CanCastTo(Type))
                    throw new ArgumentException();

                value = value.CastTo(Type);
            }

            Value = value;
        }
    }
}