const chooseSpawn = (roleCount) => {
  const priorityQueue = [
    'harvester',
    'miner',
    'transporter',
  ]
  let nextSpawn
  _.reduce(priorityQueue, (expectedRoleCount, role) => {
    if (!expectedRoleCount[role]) expectedRoleCount[role] = 0
    expectedRoleCount[role] += 1
    if (nextSpawn === 'undefined' && roleCount[role] < expectedRoleCount[role]) {
      nextSpawn = role
    } 
    return expectedRoleCount
  }, {})
  return nextSpawn
}