#!/bin/bash

if [ $# -gt 1 ]; then
  >&2 echo 'usage: '"$0"' host'
  exit 1
fi

cd "${0%/*}/.."

cmd='
  uname -n
  cut -d: -f1,6 \
  </etc/passwd \
  | tr ":" " " \
  | while read -r user home; do \
    [ -d "${home}/.ssh" ] \
    || continue
    [ -f "${home}/.ssh/authorized_keys" ] \
    || continue
    sed "s@^@${user} @" "${home}/.ssh/authorized_keys"
  done
'

cmd=$(
  printf '%s\n' "${cmd}" \
  | grep -vx '\s*' \
  | sed '
    :a
      N
      s/\\\n/ /
      ta
      s/;\s*\n/; /
      ta
      s/\n/; /
      ta
  '
)

{
  if [ $# -eq 1 ]; then
    ssh "${1}" -t "sudo -s bash -c '${cmd}'" \
    || ssh "${1}" -t "su -c '${cmd}'" \
    | sed 1d
  else
    bash -c "${cmd}"
  fi
} \
2>/dev/null \
| tee /dev/stderr \
| tr -d '\r' \
| {
  read -r host
  [ -z "${host}" ] && exit 1
  rm -rf --one-file-system "hosts/${host}"
  mkdir -p "hosts/${host}"
  while read user key; do
    printf '%s\n' "${key}" \
    >> "hosts/${host}/${user}"
  done
}