//
//  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
//  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
//  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
//  PURPOSE. IT CAN BE DISTRIBUTED FREE OF CHARGE AS LONG AS THIS HEADER 
//  REMAINS UNCHANGED.
//
//  Email:  gustavo_franco@hotmail.com
//
//  Copyright (C) 2006 Franco, Gustavo 
//
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;

namespace AStar
{
    #region Interfaces
    [Author("Franco, Gustavo")]
    public interface IPriorityQueue<T>
    {
        #region Methods
        int Push(T item);
		T Pop();
		T Peek();
		void Update(int i);
        #endregion
    }
    #endregion

    [Author("Franco, Gustavo")]
    public class PriorityQueueB<T> : IPriorityQueue<T>
    {
        #region Variables Declaration
        protected List<T>       InnerList = new List<T>();
		protected IComparer<T>  mComparer;
        #endregion

        #region Contructors
        public PriorityQueueB()
		{
			mComparer = Comparer<T>.Default;
		}

        public PriorityQueueB(IComparer<T> comparer)
		{
			mComparer = comparer;
		}

		public PriorityQueueB(IComparer<T> comparer, int capacity)
		{
			mComparer = comparer;
			InnerList.Capacity = capacity;
		}
		#endregion

        #region Methods
        protected void SwitchElements(int i, int j)
		{
			T h = InnerList[i];
			InnerList[i] = InnerList[j];
			InnerList[j] = h;
		}

        protected virtual int OnCompare(int i, int j)
        {
            return mComparer.Compare(InnerList[i],InnerList[j]);
        }

		/// <summary>
		/// Push an object onto the PQ
		/// </summary>
		/// <param name="O">The new object</param>
		/// <returns>The index in the list where the object is _now_. This will change when objects are taken from or put onto the PQ.</returns>
		public int Push(T item)
		{
			int p = InnerList.Count,p2;
			InnerList.Add(item); // E[p] = O
			do
			{
				if(p==0)
					break;
				p2 = (p-1)/2;
				if(OnCompare(p,p2)<0)
				{
					SwitchElements(p,p2);
					p = p2;
				}
				else
					break;
			}while(true);
			return p;
		}

		/// <summary>
		/// Get the smallest object and remove it.
		/// </summary>
		/// <returns>The smallest object</returns>
		public T Pop()
		{
			T result = InnerList[0];
			int p = 0,p1,p2,pn;
			InnerList[0] = InnerList[InnerList.Count-1];
			InnerList.RemoveAt(InnerList.Count-1);
			do
			{
				pn = p;
				p1 = 2*p+1;
				p2 = 2*p+2;
				if(InnerList.Count>p1 && OnCompare(p,p1)>0) // links kleiner
					p = p1;
				if(InnerList.Count>p2 && OnCompare(p,p2)>0) // rechts noch kleiner
					p = p2;
				
				if(p==pn)
					break;
				SwitchElements(p,pn);
			}while(true);

            return result;
		}

		/// <summary>
		/// Notify the PQ that the object at position i has changed
		/// and the PQ needs to restore order.
		/// Since you dont have access to any indexes (except by using the
		/// explicit IList.this) you should not call this function without knowing exactly
		/// what you do.
		/// </summary>
		/// <param name="i">The index of the changed object.</param>
		public void Update(int i)
		{
			int p = i,pn;
			int p1,p2;
			do	// aufsteigen
			{
				if(p==0)
					break;
				p2 = (p-1)/2;
				if(OnCompare(p,p2)<0)
				{
					SwitchElements(p,p2);
					p = p2;
				}
				else
					break;
			}while(true);
			if(p<i)
				return;
			do	   // absteigen
			{
				pn = p;
				p1 = 2*p+1;
				p2 = 2*p+2;
				if(InnerList.Count>p1 && OnCompare(p,p1)>0) // links kleiner
					p = p1;
				if(InnerList.Count>p2 && OnCompare(p,p2)>0) // rechts noch kleiner
					p = p2;
				
				if(p==pn)
					break;
				SwitchElements(p,pn);
			}while(true);
		}

		/// <summary>
		/// Get the smallest object without removing it.
		/// </summary>
		/// <returns>The smallest object</returns>
		public T Peek()
		{
			if(InnerList.Count>0)
				return InnerList[0];
			return default(T);
		}

		public void Clear()
		{
			InnerList.Clear();
		}

		public int Count
		{
			get{ return InnerList.Count; }
		}

        public void RemoveLocation(T item)
        {
            int index = -1;
            for(int i=0; i<InnerList.Count; i++)
            {
                
                if (mComparer.Compare(InnerList[i], item) == 0)
                    index = i;
            }

            if (index != -1)
                InnerList.RemoveAt(index);
        }

        public T this[int index]
        {
            get { return InnerList[index]; }
            set 
            { 
                InnerList[index] = value;
				Update(index);
            }
        }
		#endregion
    }
}