using System;

/*  Circular Buffer Generic Implementation
    *  By KDERazorback (http://twitter.com/kderazorback)
    *  
    *   Fast and Lightweight, Generic Circular Buffer Implementation, supports for bidirectional rotations
    *   Free to use or modify! Just keep me on the comments!
    */


/// <summary>
/// Used to store a Circular Buffer of objects with a particular size, that rotates when an item is added to the collection.
/// </summary>
class CircularBuffer<T>
{
    /// <summary>
    /// Creates a new Circular Buffer with the specified Capacity
    /// </summary>
    /// <param name="capacity">Total elements that can be stored inside the buffer before it starts discarding items</param>
    public CircularBuffer(int capacity)
    {
        plainBuffer = new T[capacity];
        _startIndex = 0;
    }

    private T[] plainBuffer;
    private int _startIndex; // Stores the start of the Circular Buffer

    /// <summary>
    /// Stores the current Capacity of this Buffer
    /// </summary>
    public int Capacity
    {
        get { return plainBuffer.Length; }
    }

    /// <summary>
    /// Returns the item that is stored on the specified Index inside the Circular Buffer
    /// </summary>
    /// <param name="index">Index of the Item to be returned</param>
    /// <returns>The object value stored on the specified index</returns>
    public T ElementAt(int index)
    {
        if ((index >= plainBuffer.Length) || (index < 0))
            throw new IndexOutOfRangeException();

        index += _startIndex;

        if (index >= plainBuffer.Length)
            index -= plainBuffer.Length;

        return plainBuffer[index];
    }

    /// <summary>
    /// Returns an array with the full content of the actual Circular Buffer
    /// </summary>
    /// <returns></returns>
    public T[] ToArray()
    {
        int i;
        T[] output = new T[plainBuffer.Length];

        for (i = 0; i < plainBuffer.Length; i++)
        {
            output[i] = ElementAt(i);
        }

        return output;
    }

    /// <summary>
    /// Inserts a new item inside the Circular Buffer and rotates the entire structure by one step forwards
    /// </summary>
    /// <param name="newItem">New item to be inserted into the Circular Buffer</param>
    public void Insert(T newItem)
    {
        if (_startIndex == 0)
            _startIndex = plainBuffer.Length - 1;
        else
            _startIndex--;

        plainBuffer[_startIndex] = newItem;
    }

    /// <summary>
    /// Inserts a new item inside the Circular Buffer and rotates the entire structure by one step backwards
    /// </summary>
    /// <param name="newItem">New item to be inserted into the Circular Buffer</param>
    public void InsertBackwards(T newItem)
    {
        plainBuffer[_startIndex] = newItem;

        if (_startIndex == plainBuffer.Length - 1)
            _startIndex = 0;
        else
            _startIndex++;
    }
}