#!/bin/bash
#
# arch-bootstrap: Bootstrap a base Arch Linux system.
#
# Dependencies: coreutils, wget, sed, gawk, tar, gzip, chroot, xz.
# Bug tracker: http://code.google.com/p/tokland/issues
# Contact: Arnau Sanchez <tokland@gmail.com>
#
# Install:
#
#   $ sudo install -m 755 arch-bootstrap.sh /usr/local/bin/arch-bootstrap
#
# Some examples:
#
#   $ sudo arch-bootstrap destination
#   $ sudo arch-bootstrap -a x86_64 -r "ftp://ftp.archlinux.org" destination-x86_64 
#
# And then you can chroot to the destination directory (default user: root/root):
#
#   $ sudo chroot destination
#

set -e -o pipefail -u

# Output to standard error
stderr() { echo "$@" >&2; }

# Output debug message to standard error
debug() { stderr "--- $@"; }

# Extract href attribute from HTML link
extract_href() { sed -n '/<a / s/^.*<a [^>]*href="\([^\"]*\)".*$/\1/p'; }

# Simple wrapper around wget
fetch() { wget -c --passive-ftp --quiet "$@"; }

# Packages needed by pacman (see get-pacman-dependencies.sh)
PACMAN_PACKAGES=(
  acl archlinux-keyring attr bzip2 curl expat glibc gpgme libarchive
  libassuan libgpg-error libssh2 lzo2 openssl pacman pacman-mirrorlist xz zlib
)
BASIC_PACKAGES=("${PACMAN_PACKAGES[@]}" filesystem)
EXTRA_PACKAGES=(coreutils bash grep gawk file tar systemd)
PACKDIR="arch-bootstrap"
DEFAULT_REPO_URL="http://mirrors.kernel.org/archlinux"
DEFAULT_ARCH=i686

configure_pacman() {
  local DEST=$1; local ARCH=$2
  cp "/etc/resolv.conf" "$DEST/etc/resolv.conf"
  echo "Server = $REPO_URL/\$repo/os/$ARCH" >> "$DEST/etc/pacman.d/mirrorlist"
}

minimal_configuration() {
  local DEST=$1
  mkdir -p "$DEST/dev"
  echo "root:x:0:0:root:/root:/bin/bash" > "$DEST/etc/passwd" 
  echo 'root:$1$GT9AUpJe$oXANVIjIzcnmOpY07iaGi/:14657::::::' > "$DEST/etc/shadow"
  touch "$DEST/etc/group"
  echo "bootstrap" > "$DEST/etc/hostname"
  test -e "$DEST/etc/mtab" || echo "rootfs / rootfs rw 0 0" > "$DEST/etc/mtab"
  test -e "$DEST/dev/null" || mknod "$DEST/dev/null" c 1 3
  test -e "$DEST/dev/random" || mknod -m 0644 "$DEST/dev/random" c 1 8
  test -e "$DEST/dev/urandom" || mknod -m 0644 "$DEST/dev/urandom" c 1 9
  sed -i "s/^[[:space:]]*\(CheckSpace\)/# \1/" "$DEST/etc/pacman.conf"
  sed -i "s/^[[:space:]]*SigLevel[[:space:]]*=.*$/SigLevel = Never/" "$DEST/etc/pacman.conf"
}

check_compressed_integrity() {
  local FILEPATH=$1
  case "$FILEPATH" in
    *.gz) gunzip -t "$FILEPATH";;
    *.xz) xz -t "$FILEPATH";;
    *) debug "Error: unknown package format: $FILEPATH"
       return 1;;
  esac
}

uncompress() {
  local FILEPATH=$1; local DEST=$2
  case "$FILEPATH" in
    *.gz) tar xzf "$FILEPATH" -C "$DEST";;
    *.xz) xz -dc "$FILEPATH" | tar x -C "$DEST";;
    *) debug "Error: unknown package format: $FILEPATH"
       return 1;;
  esac
}  

usage() {
  stderr "Usage: $(basename "$0") [-a i686 | x86_64] [-r REPO_URL] DEST"
}

main() {
  test $# -eq 0 && set -- "-h"
  local ARCH=$DEFAULT_ARCH;
  local REPO_URL=$DEFAULT_REPO_URL
  while getopts "a:r:h" ARG; do
    case "$ARG" in
    a) ARCH=$OPTARG;;
    r) REPO_URL=$OPTARG;;
    *) usage; exit 1;;
    esac
  done
  shift $(($OPTIND-1))
  test $# -eq 1 || { usage; exit 1; }
  local DEST=$1   

  local REPO="${REPO_URL%/}/core/os/$ARCH"
  debug "core repository: $REPO"
  mkdir -p "$PACKDIR"
  debug "package directory created: $PACKDIR"
  mkdir -p "$DEST"
  debug "destination directory created: $DEST"

  local LIST_HTML_FILE="$PACKDIR/core_os_$ARCH-index.html"
  if ! test -s "$LIST_HTML_FILE"; then 
    debug "fetch packages list: $REPO/"
    # Force trailing '/' needed by FTP servers.
    fetch -O "$LIST_HTML_FILE" "$REPO/" ||
      { debug "Error: cannot fetch packages list: $REPO"; exit 1; }
  fi

  debug "packages HTML index: $LIST_HTML_FILE"
  local LIST=$(< "$LIST_HTML_FILE" extract_href | awk -F"/" '{print $NF}' | sort -rn)
  test "$LIST" || { debug "Error processing list file: $LIST_HTML_FILE"; exit 1; }  

  debug "pacman package and dependencies: ${BASIC_PACKAGES[*]}"
  for PACKAGE in ${BASIC_PACKAGES[*]}; do
    local FILE=$(echo "$LIST" | grep -m1 "^$PACKAGE-[[:digit:]].*\(\.gz\|\.xz\)$")
    test "$FILE" || { debug "Error: cannot find package: $PACKAGE"; exit 1; }
    local FILEPATH="$PACKDIR/$FILE"
    
    if ! test -e "$FILEPATH" || ! check_compressed_integrity "$FILEPATH"; then
      debug "download package: $REPO/$FILE"
      fetch -O "$FILEPATH" "$REPO/$FILE"
    fi
    debug "uncompress package: $FILEPATH"
    uncompress "$FILEPATH" "$DEST"
  done

  debug "configure DNS and pacman"
  configure_pacman "$DEST" "$ARCH"

  debug "re-install basic packages and install extra packages: ${EXTRA_PACKAGES[*]}"
  minimal_configuration "$DEST"
  LC_ALL=C chroot "$DEST" /usr/bin/pacman --noconfirm --arch $ARCH \
    -Sy --force ${BASIC_PACKAGES[*]} ${EXTRA_PACKAGES[*]}

  # Pacman must be re-configured
  configure_pacman "$DEST" "$ARCH"

  echo "Done! you can now chroot to the bootstrapped system."
}

main "$@"