#!/bin/bash
# SPDX-License-Identifier: GPL-2.0-only

#
# Assumptions:
#  1) User has partitioned, formatted, and mounted partitions on /mnt
#  2) Network is functional
#  3) Arguments passed to the script are valid pacman targets
#  4) A valid mirror appears in /etc/pacman.d/mirrorlist
#

shopt -s extglob

hostcache=0
copykeyring=1
initkeyring=0
copymirrorlist=1
pacman_args=()
pacmode=-Sy
unshare=0
copyconf=0
pacman_config=/etc/pacman.conf

m4_include(common)

usage() {
  cat <<EOF
usage: ${0##*/} [options] root [packages...]

  Options:
    -C <config>    Use an alternate config file for pacman
    -c             Use the package cache on the host, rather than the target
    -D             Skip pacman dependency checks
    -G             Avoid copying the host's pacman keyring to the target
    -i             Prompt for package confirmation when needed (run interactively)
    -K             Initialize an empty pacman keyring in the target (implies '-G')
    -M             Avoid copying the host's mirrorlist to the target
    -N             Run in unshare mode as a regular user
    -P             Copy the host's pacman config to the target
    -U             Use pacman -U to install packages

    -h             Print this help message

pacstrap installs packages to the specified new root directory. If no packages
are given, pacstrap defaults to the "base" group.

EOF
}

pacstrap() {
  (( EUID == 0 )) || die 'This script must be run with root privileges'

  db_dir="/var/lib/pacman/"
  gpg_dir="/etc/pacman.d/gnupg/"
  log_dir="/var/log/"

  # These can contain multiple paths. Ensure they are arrays
  cache_dirs=("/var/cache/pacman/pkg/")

  # Ensure we only override dirs if we copy the config
  if (( copyconf )); then
    db_dir="$(pacman-conf -c "$pacman_config" DBPath)"
    gpg_dir="$(pacman-conf -c "$pacman_config" GPGDir)"
    log_dir="$(dirname "$(pacman-conf -c "$pacman_config" LogFile)")"

    mapfile -t cache_dirs < <( pacman-conf -c "$pacman_config" CacheDir )
  fi

  # create obligatory directories
  msg 'Creating install root at %s' "$newroot"
  # shellcheck disable=SC2174 # permissions are perfectly fine here
  mkdir -m 0755 -p "$newroot/$db_dir" \
                   "$newroot/$log_dir" \
                   "$newroot"/etc/pacman.d

  for path in "${cache_dirs[@]}"; do
    # shellcheck disable=SC2174 # permissions are perfectly fine here
    mkdir -m 0755 -p "$newroot/$path"
  done
  # shellcheck disable=SC2174 # permissions are perfectly fine here
  mkdir -m 0555 -p "$newroot"/{run,dev,sys,proc}
  # shellcheck disable=SC2174 # permissions are perfectly fine here
  mkdir -m 1777 -p "$newroot"/tmp

  if (( ! hostcache )); then
    for path in "${cache_dirs[@]}"; do
      pacman_args+=(--cachedir="$newroot/$path")
    done
  fi

  # mount API filesystems
  chroot_init
  $setup "$newroot" || die "failed to setup chroot %s" "$newroot"

  if [[ ! -d $newroot/$gpg_dir ]]; then
    if (( initkeyring )); then
      pacman-key --gpgdir "$newroot/$gpg_dir" --init
    elif (( copykeyring )) && [[ -d $gpg_dir ]]; then
      # if there's a keyring on the host, copy it into the new root
      cp -a --no-preserve=ownership "$gpg_dir" "$newroot/$gpg_dir"
    fi
  fi

  msg 'Installing packages to %s' "$newroot"
  if ! $pid_unshare pacman -b "$newroot/$db_dir" -r "$newroot" "${pacman_args[@]}"; then
    die 'Failed to install packages to new root'
  fi

  if (( copymirrorlist )); then
    # install the host's mirrorlist onto the new root
    cp -a /etc/pacman.d/mirrorlist "$newroot/etc/pacman.d/"
  fi

  if (( copyconf )); then
    cp -a "$pacman_config" "$newroot/etc/pacman.conf"
  fi
}

if [[ -z $1 || $1 = @(-h|--help) ]]; then
  usage
  exit $(( $# ? 0 : 1 ))
fi

while getopts ':C:cDGiKMNPU' flag; do
  case $flag in
    C)
      pacman_config=$OPTARG
      ;;
    D)
      pacman_args+=(-dd)
      ;;
    c)
      hostcache=1
      ;;
    i)
      interactive=1
      ;;
    G)
      copykeyring=0
      ;;
    K)
      initkeyring=1
      ;;
    M)
      copymirrorlist=0
      ;;
    N)
      unshare=1
      ;;
    P)
      copyconf=1
      ;;
    U)
      pacmode=-U
      ;;
    :)
      die '%s: option requires an argument -- '\''%s'\' "${0##*/}" "$OPTARG"
      ;;
    ?)
      die '%s: invalid option -- '\''%s'\' "${0##*/}" "$OPTARG"
      ;;
  esac
done
shift $(( OPTIND - 1 ))

(( $# )) || die "No root directory specified"
newroot=$1
shift

[[ -d $newroot ]] || die "%s is not a directory" "$newroot"

tmpfile="$(mktemp -t pacman.conf.XXXX)"
cp "$pacman_config" "$tmpfile"
sed -i 's/^DownloadUser/#&/' "$tmpfile"

pacman_args+=("$pacmode" "${@:-base}" --config="$tmpfile" --disable-sandbox)

if (( ! interactive )); then
  pacman_args+=(--noconfirm)
fi

if (( unshare )); then
  setup=unshare_setup
  $mount_unshare bash -c "$(declare_all); pacstrap"
else
  setup=chroot_setup
  pacstrap
fi

# TODO: There is a trap check on exit. Need to rework the trap handling with
# hook-ins/callbacks to remove aux files
rm "$tmpfile"
