using System.Collections.Generic;

namespace MantisLOD
{
	internal abstract class BinaryHeap
	{
		private const int rootIndex = 1;

		private readonly List<My_Half_edge> collection;

		private int LastNodeIndex => collection.Count - 1;

		public BinaryHeap()
		{
			collection = new List<My_Half_edge>();
			collection.Add(new My_Half_edge());
		}

		public BinaryHeap(int capacity)
		{
			collection = new List<My_Half_edge>(capacity);
			collection.Add(new My_Half_edge());
		}

		public void Push(My_Half_edge item)
		{
			collection.Add(item);
			item.pqIndex = LastNodeIndex;
			BubbleUp(LastNodeIndex);
		}

		public My_Half_edge Pop()
		{
			if (LastNodeIndex == 0)
			{
				return null;
			}
			My_Half_edge result = collection[1];
			collection[1].pqIndex = -1;
			collection[1] = collection[LastNodeIndex];
			collection[1].pqIndex = 1;
			BubbleDown(1);
			collection.RemoveAt(LastNodeIndex);
			return result;
		}

		public bool Remove(int index)
		{
			if (LastNodeIndex == 0)
			{
				return false;
			}
			collection[index].pqIndex = -1;
			collection[index] = collection[LastNodeIndex];
			collection[index].pqIndex = index;
			BubbleDown(index);
			collection.RemoveAt(LastNodeIndex);
			return true;
		}

		public int Size()
		{
			return collection.Count - 1;
		}

		public My_Half_edge Top()
		{
			if (LastNodeIndex == 0)
			{
				return null;
			}
			return collection[1];
		}

		protected abstract bool Compare(My_Half_edge current, My_Half_edge other);

		private void BubbleUp(int index)
		{
			int num = index;
			int num2 = index / 2;
			My_Half_edge my_Half_edge = collection[num];
			while (num > 1 && Compare(collection[num2], my_Half_edge))
			{
				collection[num] = collection[num2];
				collection[num].pqIndex = num;
				num = num2;
				num2 /= 2;
			}
			collection[num] = my_Half_edge;
			collection[num].pqIndex = num;
		}

		private void BubbleDown(int index)
		{
			int num = index;
			int num2 = index * 2;
			My_Half_edge my_Half_edge = collection[num];
			while (num2 <= LastNodeIndex)
			{
				if (num2 < LastNodeIndex && Compare(collection[num2], collection[num2 + 1]))
				{
					num2++;
				}
				if (!Compare(my_Half_edge, collection[num2]))
				{
					break;
				}
				collection[num] = collection[num2];
				collection[num].pqIndex = num;
				num = num2;
				num2 *= 2;
			}
			collection[num] = my_Half_edge;
			collection[num].pqIndex = num;
		}
	}
}