opus/sys/apis/jumper/core/path.lua

--- The Path class.
-- The `path` class is a structure which represents a path (ordered set of nodes) from a start location to a goal.
-- An instance from this class would be a result of a request addressed to `Pathfinder:getPath`.
--
-- This module is internally used by the library on purpose.
-- It should normally not be used explicitely, yet it remains fully accessible.
--

if (...) then

  local t_remove = table.remove

  local Path = {}
  Path.__index = Path

  function Path:new()
    return setmetatable({_nodes = {}}, Path)
  end

  --- Iterates on each single `node` along a `path`. At each step of iteration,
  -- returns the `node` plus a count value. Aliased as @{Path:nodes}
	-- @usage
	-- for node, count in p:iter() do
	--   ...
	-- end
  function Path:nodes()
    local i = 1
    return function()
      if self._nodes[i] then
        i = i+1
        return self._nodes[i-1],i-1
      end
    end
  end

  --- `Path` compression modifier. Given a `path`, eliminates useless nodes to return a lighter `path`
  -- consisting of straight moves. Does the opposite of @{Path:fill}
  -- @class function
  -- @treturn path self (the calling `path` itself, can be chained)
  -- @see Path:fill
  -- @usage p:filter()
  function Path:filter()
    local i = 2
    local xi,yi,zi,dx,dy,dz, olddx, olddy, olddz
    xi,yi,zi = self._nodes[i].x, self._nodes[i].y, self._nodes[i].z
    dx, dy,dz = xi - self._nodes[i-1].x, yi-self._nodes[i-1].y, zi-self._nodes[i-1].z
    while true do
      olddx, olddy, olddz = dx, dy, dz
      if self._nodes[i+1] then
        i = i+1
        xi, yi, zi = self._nodes[i].x, self._nodes[i].y, self._nodes[i].z
        dx, dy, dz = xi - self._nodes[i-1].x, yi - self._nodes[i-1].y, zi - self._nodes[i-1].z
        if olddx == dx and olddy == dy and olddz == dz then
          t_remove(self._nodes, i-1)
          i = i - 1
        end
      else break end
    end
    return self
  end

  return setmetatable(Path,
    {__call = function(_,...)
      return Path:new(...)
    end
  })
end