SqlYearToMonth.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;

namespace Deveel.Data.Sql.Objects {
    public struct SqlYearToMonth : ISqlObject, IComparable<SqlYearToMonth> {
        private int? months;

        public static readonly SqlYearToMonth Null = new SqlYearToMonth(true);

        public SqlYearToMonth(int months) 
            : this() {
            this.months = months;
        }

        public SqlYearToMonth(int years, int months)
            : this((years*12) + months) {
        }

        private SqlYearToMonth(bool isNull)
            : this() {
            if (isNull)
                months = null;
        }

        int IComparable.CompareTo(object obj) {
            return CompareTo((ISqlObject) obj);
        }

        public int CompareTo(ISqlObject other) {
            if (other is SqlYearToMonth)
                return CompareTo((SqlYearToMonth) other);

            throw new NotSupportedException();
        }

        public bool IsNull {
            get { return months == null; }
        }

        public int TotalMonths {
            get {
                if (months == null)
                    throw new NullReferenceException();

                return months.Value;
            }
        }

        public double TotalYears {
            get {
                if (months == null)
                    throw new NullReferenceException();

                return (months.Value/12);
            }
        }

        bool ISqlObject.IsComparableTo(ISqlObject other) {
            return other is SqlYearToMonth ||
                   other is SqlNumber ||
                   other is SqlDayToSecond;
        }

        public int CompareTo(SqlYearToMonth other) {
            if (other.IsNull && IsNull)
                return 0;
            if (IsNull && !other.IsNull)
                return 1;
            if (!IsNull && other.IsNull)
                return -1;

            return months.Value.CompareTo(other.months.Value);
        }
    }
}