SqlArray.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 System.Collections;
using System.Collections.Generic;

using Deveel.Data.Sql.Expressions;

namespace Deveel.Data.Sql.Objects {
    public sealed class SqlArray : ISqlObject, IEnumerable<SqlExpression> {
        private readonly SqlExpression[] expressions;

        public static readonly SqlArray Null = new SqlArray(null);

        public SqlArray(SqlExpression[] expressions) {
            if (expressions == null) {
                this.expressions = null;
                IsNull = true;
            } else {
                this.expressions = new SqlExpression[expressions.Length];
                Array.Copy(expressions, this.expressions, expressions.Length);
            }
        }

        int IComparable.CompareTo(object obj) {
            throw new NotSupportedException();
        }

        int IComparable<ISqlObject>.CompareTo(ISqlObject other) {
            throw new NotSupportedException();
        }

        public bool IsNull { get; private set; }

        public int Length {
            get {
                AssertNotNull();
                return expressions.Length;
            }
        }

        bool ISqlObject.IsComparableTo(ISqlObject other) {
            return false;
        }

        private void AssertNotNull() {
            if (IsNull)
                throw new NullReferenceException("The array is null");
        }

        public SqlExpression this[int index] {
            get { return GetValue(index); }
        }

        public SqlExpression GetValue(int index) {
            AssertNotNull();

            if (index < 0 || index >= Length)
                throw new ArgumentOutOfRangeException("index");

            return expressions[index];
        }

        public IEnumerator<SqlExpression> GetEnumerator() {
            AssertNotNull();
            return new Enumerator(this);
        }

        IEnumerator IEnumerable.GetEnumerator() {
            return GetEnumerator();
        }

        #region Enumerator

        class Enumerator : IEnumerator<SqlExpression> {
            private int index;
            private int length;
            private readonly SqlArray array;

            public Enumerator(SqlArray array) {
                this.array = array;
                length = array.Length;
                index = -1;
            }

            public void Dispose() {
            }

            public bool MoveNext() {
                array.AssertNotNull();
                return ++index < length;
            }

            public void Reset() {
                array.AssertNotNull();

                index = -1;
                length = array.Length;
            }

            public SqlExpression Current {
                get {
                    array.AssertNotNull();
                    return array.GetValue(index);
                }
            }

            object IEnumerator.Current {
                get { return Current; }
            }
        }

        #endregion
    }
}