// Copyright (c) 2004, 2016, Oracle and/or its affiliates. All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License, version 2.0, as
// published by the Free Software Foundation.
//
// This program is also distributed with certain software (including
// but not limited to OpenSSL) that is licensed under separate terms,
// as designated in a particular file or component or in included license
// documentation.  The authors of MySQL hereby grant you an
// additional permission to link the program and your derivative works
// with the separately licensed software that they have included with
// MySQL.
//
// Without limiting anything contained in the foregoing, this file,
// which is part of MySQL Connector/NET, is also subject to the
// Universal FOSS Exception, version 1.0, a copy of which can be found at
// http://oss.oracle.com/licenses/universal-foss-exception.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License, version 2.0, for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

using System.Collections.Generic;

namespace MySql.Data.Common
{
    internal class Cache<TKeyType, TValueType>
    {
        private readonly int _capacity;
        private readonly Queue<TKeyType> _keyQ;
        private readonly Dictionary<TKeyType, TValueType> _contents;

        public Cache(int initialCapacity, int capacity)
        {
            this._capacity = capacity;
            this._contents = new Dictionary<TKeyType, TValueType>(initialCapacity);

            if (capacity > 0)
            {
                this._keyQ = new Queue<TKeyType>(initialCapacity);
            }
        }

        public TValueType this[TKeyType key]
        {
            get
            {
                TValueType val;
                if (this._contents.TryGetValue(key, out val))
                {
                    return val;
                }
                else
                {
                    return default(TValueType);
                }
            }
            set { this.InternalAdd(key, value); }
        }

        public void Add(TKeyType key, TValueType value)
        {
            this.InternalAdd(key, value);
        }

        private void InternalAdd(TKeyType key, TValueType value)
        {
            if (!this._contents.ContainsKey(key))
            {

                if (this._capacity > 0)
                {
                    this._keyQ.Enqueue(key);

                    if (this._keyQ.Count > this._capacity)
                    {
                        this._contents.Remove(this._keyQ.Dequeue());
                    }
                }
            }

            this._contents[key] = value;
        }
    }
}