using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace BF
{
    public class BFQueue<T>
    {
        private BFNode<T> head;
        private BFNode<T> tail;

        private BFStackPool<T> nodePool;

        private IEqualityComparer<T> comparer;

        private int count;

        public int Count { get { return count; } }

        public BFQueue(IEqualityComparer<T> comparer = null)
        {
            nodePool = new BFStackPool<T>();
            this.comparer = comparer ?? EqualityComparer<T>.Default;
        }

        public BFNode<T> Dequeue()
        {
            if (count == 0)
                return null;
            var temp = head;
            head = head.next;
            temp.next = null;
            temp.Invalidate();
            nodePool.Push(temp);
            --count;
            return temp;
        }

        public void Enqueue(T item)
        {
            var newNode = nodePool.SafePop();
            newNode.prev = null;
            newNode.next = null;
            newNode.item = item;
            if (count == 0)
            {
                head = newNode;
                tail = newNode;
            }
            else
            {
                newNode.prev = tail;
                tail.next = newNode;
                tail = newNode;
            }
            ++count;
        }

        public void Remove(T t)
        {
            var temp = head;
            while (temp != null)
            {
                if (comparer.Equals(temp.item, t))
                {
                    var prev = temp.prev;
                    var next = temp.next;

                    if (prev != null)
                    {
                        prev.next = next;
                    }
                    else
                    {
                        head = next;
                    }

                    if (next != null)
                    {
                        next.prev = prev;
                    }
                    else
                    {
                        tail = prev;
                    }

                    temp.prev = null;
                    temp.next = null;
                    temp.Invalidate();
                    nodePool.Push(temp);
                    --count;
                    break;
                }
                temp = temp.next;
            }
        }

        public void Clear()
        {
            var current = head;
            while (current != null)
            {
                var temp = current;
                current = current.next;
                temp.prev = null;
                temp.next = null;
                temp.Invalidate();
                nodePool.Push(temp);
            }
            head = null;
            tail = null;
            count = 0;
        }
    }
}