export const validity = [
  // prevent agents from moving onto immutables
  (world, proposal) => (proposal.agent_changes || []).reduce(
    (acc, change) => {
      const {x, y} = change;
      if (x !== undefined && y !== undefined && world.lattice[y][x].type === 'immutable') {
        return false;
      } else {
        return acc;
      }
    },
    true,
  ),
];