Babushka/scripts/CSharp/Common/Fight/FighterTurn.cs

using System;
using System.Diagnostics;

namespace Babushka.scripts.CSharp.Common.Fight;

public class FighterTurn
{
    private class Node
    {
        public required Node next;
        public required FightWorld.Fighter fighter;
    }

    private Node? _currentNode;

    public FightWorld.Fighter Current => _currentNode?.fighter ?? throw new InvalidOperationException("No current fighter");

    public void Next()
    {
        Debug.Assert(_currentNode != null, "currentNode!=null");
        _currentNode = _currentNode.next;
    }

    public FightWorld.Fighter PeekNext()
    {
        Debug.Assert(_currentNode != null, "currentNode!=null");
        return _currentNode.next.fighter;
    }

    public void AddAsLast(FightWorld.Fighter value)
    {
        // if first node
        if (_currentNode == null)
        {
            _currentNode = new Node { fighter = value, next = null! };
            _currentNode.next = _currentNode;
            return;
        }

        var newNode = new Node { fighter = value, next = _currentNode };
        var node = _currentNode;
        while (node.next != _currentNode)
        {
            node = node.next;
        }

        node.next = newNode;
    }

    public void AddAsNext(FightWorld.Fighter value)
    {
        // if first node
        if (_currentNode == null)
        {
            AddAsLast(value);
            return;
        }

        var newNode = new Node { fighter = value, next = _currentNode.next };
        _currentNode.next = newNode;
    }

    public bool Remove(FightWorld.Fighter value)
    {
        if (_currentNode == null) return false;

        // if only one node
        if (_currentNode.next == _currentNode)
        {
            if (_currentNode.fighter == value)
            {
                _currentNode = null;
                return true;
            }

            return false;
        }

        var node = _currentNode;
        do
        {
            // next is the fighter to remove
            if (node.next.fighter == value)
            {
                // if removing current, keep current
                // it will be implicitly deleted by loss of reference on the next Next() call
                
                node.next = node.next.next;
                return true;
            }

            node = node.next;
        } while (node != _currentNode);

        return false;
    }
}