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

using System;

namespace Server
{
  public class PathFollower
  {
    // Should we use pathfinding? 'false' for not
    private static bool Enabled = true;

    private static TimeSpan RepathDelay = TimeSpan.FromSeconds(2.0);

    private 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 MoveResult Move(Direction d)
    {
      if (Mover == null)
        return m_From.Move(d) ? MoveResult.Success : MoveResult.Blocked;

      return Mover(d);
    }

    public Point3D GetGoalLocation()
    {
      if (Goal is Item item)
        return item.GetWorldLocation();

      return new Point3D(Goal);
    }

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

        if (index >= 0 && index < dirs.Length)
        {
          int x = p.X, y = p.Y;

          Movement.Offset(dirs[index], ref x, ref y);

          p.X = x;
          p.Y = y;
        }
      }
    }

    public void ForceRepath()
    {
      m_Path = null;
    }

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

      Point3D goal = GetGoalLocation();

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

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

    public bool Follow(bool run, int range)
    {
      Point3D goal = GetGoalLocation();
      Direction d;

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

      bool repathed = CheckPath();

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

        if (run)
          d |= Direction.Running;

        m_From.SetDirection(d);
        Move(d);

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

      d = m_From.GetDirectionTo(m_Next);

      if (run)
        d |= Direction.Running;

      m_From.SetDirection(d);

      MoveResult res = Move(d);

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

        m_Path = null;
        CheckPath();

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

          if (run)
            d |= Direction.Running;

          m_From.SetDirection(d);
          Move(d);

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

        d = m_From.GetDirectionTo(m_Next);

        if (run)
          d |= Direction.Running;

        m_From.SetDirection(d);

        res = Move(d);

        if (res == 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);
    }
  }
}