screeps/default/link.js

module.exports = {
  tickInit () {
    for (let room of Object.values(Game.rooms)) {
      if (room.memory.controllerLink && !Game.getObjectById(room.memory.controllerLink)) {
        delete room.memory.controllerLink
      }
    }
  },
  tick (link) {
    if (link.room.memory.controllerLink === link.id) {
      return
    }
    if (link.pos.findInRange(FIND_STRUCTURES, 5, {filter: s => s.structureType === STRUCTURE_CONTROLLER}).length) {
      link.room.memory.controllerLink = link.id
      return
    }

    if (link.room.memory.controllerLink && !link.store.getFreeCapacity(RESOURCE_ENERGY)) {
      let targetLink = Game.getObjectById(link.room.memory.controllerLink)
      if (targetLink.store.getFreeCapacity(RESOURCE_ENERGY) > 770) {
        link.transferEnergy(targetLink)
      }
    }
  }
}