# shellcheck disable=SC2059 # $1 and $2 can contain the printf modifiers
out() { printf "$1 $2\n" "${@:3}"; }
error() { out "==> ERROR:" "$@"; } >&2
warning() { out "==> WARNING:" "$@"; } >&2
msg() { out "==>" "$@"; }
die() { error "$@"; exit 1; }

ignore_error() {
  "$@" 2>/dev/null
  return 0
}

chroot_add_mount() {
  mount "$@" && CHROOT_ACTIVE_MOUNTS=("$2" "${CHROOT_ACTIVE_MOUNTS[@]}")
}

chroot_maybe_add_mount() {
  local cond=$1; shift
  if eval "$cond"; then
    chroot_add_mount "$@"
  fi
}

chroot_setup() {
  CHROOT_ACTIVE_MOUNTS=()
  [[ $(trap -p EXIT) ]] && die '(BUG): attempting to overwrite existing EXIT trap'
  trap 'chroot_teardown' EXIT

  chroot_add_mount proc "$1/proc" -t proc -o nosuid,noexec,nodev &&
  chroot_add_mount sys "$1/sys" -t sysfs -o nosuid,noexec,nodev,ro &&
  ignore_error chroot_maybe_add_mount "[[ -d '$1/sys/firmware/efi/efivars' ]]" \
      efivarfs "$1/sys/firmware/efi/efivars" -t efivarfs -o nosuid,noexec,nodev &&
  chroot_add_mount udev "$1/dev" -t devtmpfs -o mode=0755,nosuid &&
  chroot_add_mount devpts "$1/dev/pts" -t devpts -o mode=0620,gid=5,nosuid,noexec &&
  chroot_add_mount shm "$1/dev/shm" -t tmpfs -o mode=1777,nosuid,nodev &&
  chroot_add_mount /run "$1/run" --bind --make-private &&
  chroot_add_mount tmp "$1/tmp" -t tmpfs -o mode=1777,strictatime,nodev,nosuid
}

chroot_teardown() {
  if (( ${#CHROOT_ACTIVE_MOUNTS[@]} )); then
    umount "${CHROOT_ACTIVE_MOUNTS[@]}"
  fi
  unset CHROOT_ACTIVE_MOUNTS
}

chroot_add_mount_lazy() {
  mount "$@" && CHROOT_ACTIVE_LAZY=("$2" "${CHROOT_ACTIVE_LAZY[@]}")
}

chroot_bind_device() {
  touch "$2" && CHROOT_ACTIVE_FILES=("$2" "${CHROOT_ACTIVE_FILES[@]}")
  chroot_add_mount "$1" "$2" --bind
}

chroot_add_link() {
  ln -sf "$1" "$2" && CHROOT_ACTIVE_FILES=("$2" "${CHROOT_ACTIVE_FILES[@]}")
}

unshare_setup() {
  CHROOT_ACTIVE_MOUNTS=()
  CHROOT_ACTIVE_LAZY=()
  CHROOT_ACTIVE_FILES=()
  [[ $(trap -p EXIT) ]] && die '(BUG): attempting to overwrite existing EXIT trap'
  trap 'unshare_teardown' EXIT

  chroot_add_mount_lazy "$1" "$1" --bind &&
  chroot_add_mount proc "$1/proc" -t proc -o nosuid,noexec,nodev &&
  chroot_add_mount_lazy /sys "$1/sys" --rbind &&
  chroot_add_link "$1/proc/self/fd" "$1/dev/fd" &&
  chroot_add_link "$1/proc/self/fd/0" "$1/dev/stdin" &&
  chroot_add_link "$1/proc/self/fd/1" "$1/dev/stdout" &&
  chroot_add_link "$1/proc/self/fd/2" "$1/dev/stderr" &&
  chroot_bind_device /dev/full "$1/dev/full" &&
  chroot_bind_device /dev/null "$1/dev/null" &&
  chroot_bind_device /dev/random "$1/dev/random" &&
  chroot_bind_device /dev/tty "$1/dev/tty" &&
  chroot_bind_device /dev/urandom "$1/dev/urandom" &&
  chroot_bind_device /dev/zero "$1/dev/zero" &&
  chroot_add_mount run "$1/run" -t tmpfs -o nosuid,nodev,mode=0755 &&
  chroot_add_mount tmp "$1/tmp" -t tmpfs -o mode=1777,strictatime,nodev,nosuid
}

unshare_teardown() {
  chroot_teardown

  if (( ${#CHROOT_ACTIVE_LAZY[@]} )); then
    umount --lazy "${CHROOT_ACTIVE_LAZY[@]}"
  fi
  unset CHROOT_ACTIVE_LAZY

  if (( ${#CHROOT_ACTIVE_FILES[@]} )); then
    rm "${CHROOT_ACTIVE_FILES[@]}"
  fi
  unset CHROOT_ACTIVE_FILES
}

pid_unshare="unshare --fork --pid"
mount_unshare="$pid_unshare --mount --map-auto --map-root-user --setuid 0 --setgid 0"

# This outputs code for declaring all variables to stdout. For example, if
# FOO=BAR, then running
#     declare -p FOO
# will result in the output
#     declare -- FOO="bar"
# This function may be used to re-declare all currently used variables and
# functions in a new shell.
declare_all() {
  # Remove read-only variables to avoid warnings. Unfortunately, declare +r -p
  # doesn't work like it looks like it should (declaring only read-write
  # variables). However, declare -rp will print out read-only variables, which
  # we can then use to remove those definitions.
  declare -p | grep -Fvf <(declare -rp)
  # Then declare functions
  declare -pf
}