Find a very long path in Screeps

index.js

function longPath(from, to) {
  let rooms = {};
  Game.map.findRoute(from.roomName, to.roomName).forEach(function(step, ii, route) {
    function generateCostMatrix(dir1, dir2) {
      let cm = new PathFinder.CostMatrix;
      let dir = 1 << dir1 | 1 << dir2;
      for (let ii = 0; ii < 49; ++ii) {
        if (!(dir & 1 << TOP)) {
          cm.set(ii, 0, 0xff);
        }
        if (!(dir & 1 << RIGHT)) {
          cm.set(49, ii, 0xff);
        }
        if (!(dir & 1 << BOTTOM)) {
          cm.set(ii, 49, 0xff);
        }
        if (!(dir & 1 << LEFT)) {
          cm.set(0, ii, 0xff);
        }
      }
      return cm;
    }
    if (ii === 0) {
      rooms[from.roomName] = generateCostMatrix(step.exit, 0);
    }
    rooms[step.room] = generateCostMatrix((step.exit + 3) % 8 + 1, route[ii + 1] ? route[ii + 1].exit : 0);
  });
  return PathFinder.search(
    from, to,
    {
      plainCost: 1,
      swampCost: 5,
      heuristicWeight: 1.2,
      maxOps: 8000,
      roomCallback: function(roomName) {
        return rooms[roomName];
      },
    }
  );
}