/*

   Version: MPL 1.1/GPL 2.0/LGPL 2.1

   The contents of this file are subject to the Mozilla Public License Version

   1.1 (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.mozilla.org/MPL/

   Software distributed under the License is distributed on an "AS IS" basis,

   WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License

   for the specific language governing rights and limitations under the License.

   The Original Code is the Open Hardware Monitor code.

   The Initial Developer of the Original Code is 

   Michael Möller <m.moeller@gmx.ch>.

   Portions created by the Initial Developer are Copyright (C) 2011

   the Initial Developer. All Rights Reserved.

   Contributor(s):

   Alternatively, the contents of this file may be used under the terms of

   either the GNU General Public License Version 2 or later (the "GPL"), or

   the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),

   in which case the provisions of the GPL or the LGPL are applicable instead

   of those above. If you wish to allow use of your version of this file only

   under the terms of either the GPL or the LGPL, and not to allow others to

   use your version of this file under the terms of the MPL, indicate your

   decision by deleting the provisions above and replace them with the notice

   and other provisions required by the GPL or the LGPL. If you do not delete

   the provisions above, a recipient may use your version of this file under

   the terms of any one of the MPL, the GPL or the LGPL.

 */

 using System;

 using System.Collections;

 using System.Collections.Generic;

 namespace OpenHardwareMonitor.Collections {

   public class RingCollection<T> : IEnumerable<T> {

     private T[] array;

     // first item of collection

     private int head;

     // index after the last item of the collection

     private int tail;

     // number of items in the collection

     private int size;

     public RingCollection() : this(0) { }

     public RingCollection(int capacity) {

       if (capacity < 0)

         throw new ArgumentOutOfRangeException("capacity");

       this.array = new T[capacity];

       this.head = 0; 

       this.tail = 0;

       this.size = 0;

     }

     public int Capacity {

       get {

         return array.Length;

       }

       set {

         T[] newArray = new T[value];

         if (size > 0) {

           if (head < tail) {

             Array.Copy(array, head, newArray, 0, size);

           } else {

             Array.Copy(array, head, newArray, 0, array.Length - head);

             Array.Copy(array, 0, newArray, array.Length - head, tail);

           }

         }

         this.array = newArray;

         this.head = 0;

         this.tail = size == value ? 0 : size;

       }

     }

     public void Clear() {

       // remove potential references 

       if (head < tail) {

         Array.Clear(array, head, size);

       } else {

         Array.Clear(array, 0, tail);

         Array.Clear(array, head, array.Length - head);

       }

       this.head = 0;

       this.tail = 0;

       this.size = 0;

     }

     public void Append(T item) {

       if (size == array.Length) {

         int newCapacity = array.Length * 3 / 2;

         if (newCapacity < array.Length + 8)

           newCapacity = array.Length + 8;

         Capacity = newCapacity;

       }

       array[tail] = item;

       tail = tail + 1 == array.Length ? 0 : tail + 1;

       size++;

     }

     public T Remove() {

       if (size == 0)

         throw new InvalidOperationException();

       T result = array[head];

       array[head] = default(T);

       head = head + 1 == array.Length ? 0 : head + 1;

       size--;

       return result;

     }

     public int Count {

       get {

         return size;

       }

     }

     public T this[int index] {

       get {

         if (index < 0 || index >= size)

           throw new IndexOutOfRangeException();

         int i = head + index;

         if (i >= array.Length)

           i -= array.Length;

         return array[i];

       }

       set {

         if (index < 0 || index >= size)

           throw new IndexOutOfRangeException();

         int i = head + index;

         if (i >= array.Length)

           i -= array.Length;

         array[i] = value;

       }

     }

     public T First {

       get {

         if (size == 0)

           throw new InvalidOperationException();

         return array[head];

       }

       set {

         if (size == 0)

           throw new InvalidOperationException();

         array[head] = value;

       }

     }

     public T Last {

       get {

         if (size == 0)

           throw new InvalidOperationException();

         return array[tail == 0 ? array.Length - 1 : tail - 1];

       }

       set {

         if (size == 0)

           throw new InvalidOperationException();

         array[tail == 0 ? array.Length - 1 : tail - 1] = value;

       }

     }

     IEnumerator<T> IEnumerable<T>.GetEnumerator() {

       return new RingCollection<T>.Enumerator(this);

     }

     IEnumerator IEnumerable.GetEnumerator() {

       return new RingCollection<T>.Enumerator(this);

     }

     private struct Enumerator : IEnumerator<T>, IEnumerator {

       private RingCollection<T> collection;

       private int index;

       public Enumerator(RingCollection<T> collection) {

         this.collection = collection;

         this.index = -1;

       }

       public void Dispose() {

         this.index = -2;

       }

       public void Reset() {

         this.index = -1;

       }

       public T Current {

         get {

           if (index < 0)

             throw new InvalidOperationException();

           return collection[index];

         }

       }

       object IEnumerator.Current {

         get {

           if (index < 0)

             throw new InvalidOperationException();

           return collection[index];

         }

       }

       public bool MoveNext() {

         if (index == -2)

           return false;

         index++;

         if (index == collection.size) {

           index = -2;

           return false;

         }

         return true;

       }

     }

   }

 }