ModernUO/Projects/UOContent/Engines/Pathing/PathFollower.cs

using System;
using CalcMoves = Server.Movement.Movement;

namespace Server;

public class PathFollower
{
    private static bool Enabled;
    private static readonly TimeSpan RepathDelay = TimeSpan.FromSeconds(2.0);

    private readonly Mobile m_From;
    private int m_Index;
    private DateTime m_LastPathTime;
    private Point3D m_Next, m_LastGoalLoc;
    private MovementPath m_Path;

    public PathFollower(Mobile from, IPoint3D goal)
    {
        m_From = from;
        Goal = goal;
    }

    public MoveMethod Mover { get; set; }

    public IPoint3D Goal { get; }

    public static void Configure()
    {
        Enabled = ServerConfiguration.GetOrUpdateSetting("pathfinding.enable", true);
    }

    public MoveResult Move(Direction d) =>
        Mover?.Invoke(d, true) ?? (m_From.Move(d) ? MoveResult.Success : MoveResult.Blocked);

    public Point3D GetGoalLocation() => (Goal as Item)?.GetWorldLocation() ?? new Point3D(Goal);

    public void Advance(ref Point3D p, int index)
    {
        if (m_Path?.Success == true)
        {
            var dirs = m_Path.Directions;

            if (index >= 0 && index < dirs.Length)
            {
                CalcMoves.Offset(dirs[index], ref p);
            }
        }
    }

    public void ForceRepath()
    {
        m_Path = null;
    }

    public bool CheckPath()
    {
        if (!Enabled)
        {
            return false;
        }

        var goal = GetGoalLocation();

        if (m_Path != null && (m_Path.Success && goal == m_LastGoalLoc || m_LastPathTime + RepathDelay > Core.Now) &&
            !(m_Path.Success && Check(m_From.Location, m_LastGoalLoc, 0)))
        {
            return false;
        }

        m_LastPathTime = Core.Now;
        m_LastGoalLoc = goal;

        m_Path = new MovementPath(m_From, goal);

        m_Index = 0;
        m_Next = m_From.Location;

        Advance(ref m_Next, m_Index);

        return true;
    }

    public static bool Check(Point3D loc, Point3D goal, int range) =>
        Utility.InRange(loc, goal, range) && (range > 1 || (loc.Z - goal.Z).Abs() < 16);

    public bool Follow(int range)
    {
        var goal = GetGoalLocation();
        Direction d;

        if (Check(m_From.Location, goal, range))
        {
            return true;
        }

        var repathed = CheckPath();

        if (!(Enabled && m_Path.Success))
        {
            d = m_From.GetDirectionTo(goal);
            m_From.SetDirection(d);

            return Move(d) is MoveResult.Success or MoveResult.SuccessAutoTurn && Check(m_From.Location, goal, range);
        }

        d = m_From.GetDirectionTo(m_Next);
        m_From.SetDirection(d);
        var res = Move(d);

        if (res == MoveResult.Blocked)
        {
            if (repathed)
            {
                return false;
            }

            m_Path = null;
            CheckPath();

            if (!m_Path!.Success)
            {
                d = m_From.GetDirectionTo(goal);
                m_From.SetDirection(d);

                return Move(d) is MoveResult.Success or MoveResult.SuccessAutoTurn && Check(m_From.Location, goal, range);
            }

            d = m_From.GetDirectionTo(m_Next);
            m_From.SetDirection(d);

            if (Move(d) == MoveResult.Blocked)
            {
                return false;
            }
        }

        if (m_From.X == m_Next.X && m_From.Y == m_Next.Y)
        {
            if (m_From.Z == m_Next.Z)
            {
                ++m_Index;
                Advance(ref m_Next, m_Index);
            }
            else
            {
                m_Path = null;
            }
        }

        return Check(m_From.Location, goal, range);
    }
}