_bc_user=bitcoin
_bc_group=bitcoin

post_install() {
  _mkuser
  # disable Copy-On-Write (btrfs directories only)
  _dir="/var/lib/bitcoind"
  mkdir -p "$_dir"
  _is_btrfs "$_dir" && _disable_cow "$_dir"
  if test ! -f /etc/bitcoin/bitcoin.conf; then
     cp /etc/bitcoin/bitcoin.conf.dist /etc/bitcoin/bitcoin.conf
  fi
  chown -R $_bc_user:$_bc_group /etc/bitcoin "$_dir"
  printf "%b\n" "$bitcoin"
}

post_upgrade() {
  _mkuser
  chown -R $_bc_user:$_bc_group /etc/bitcoin "/var/lib/bitcoind"
  printf "%b\n" "$bitcoin"
}

post_remove() {
  _rmuser
}


# ------------------------------------------------------------------------------
# helper functions for creating bitcoin user / group
# ------------------------------------------------------------------------------

_mkuser() {
  getent passwd $_bc_user &>/dev/null || {
    echo -n "Creating bitcoin user... "
    grep -E "^$_bc_group:" /etc/group >/dev/null || groupadd $_bc_group
    useradd -m -d /etc/bitcoin -g $_bc_group -s /usr/bin/nologin $_bc_user 2>/dev/null
    echo "done"
  }
}

_rmuser() {
  echo -n "Removing bitcoin user... "
  userdel $_bc_user 2>/dev/null
  echo "done"
}


# ------------------------------------------------------------------------------
# helper functions for disabling btrfs Copy-On-Write (CoW)
# https://wiki.archlinux.org/index.php/Btrfs#Copy-On-Write_.28CoW.29
# ------------------------------------------------------------------------------

# check if dir is btrfs
_is_btrfs() {
  if [[ $(findmnt --target $1 --output FSTYPE --noheadings) == 'btrfs' ]]; then
    return 0
  else
    return 1
  fi
}

# disable btrfs CoW
_chattrify() {
  # original dir, with trailing slash stripped if it exists
  _orig_dir=$( echo "$1" | sed 's@/$@@' )

  # if original dir exists, back it up
  [[ -d "$1" ]] && mv "$1" "${_orig_dir}"_old

  # re-make original dir
  mkdir -p "$1"

  # set permissions on re-made dir
  chmod "$2" "$1"

  # disable btrfs CoW on re-made dir
  chattr +C "$1"

  # recursive copy to restore backed up dir while maintaining disabled CoW
  [[ -d "${_orig_dir}"_old ]] \
    && find "${_orig_dir}"_old -mindepth 1 -maxdepth 1 -exec cp -R '{}' "$1" \;

  # set ownership on re-made dir
  chown -R $3:$4 "$1"

  # purge backed up dir
  [[ -d "${_orig_dir}"_old ]] && rm -rf "${_orig_dir}"_old
}

_disable_cow() {
  _chattrify "$1" "750" "$_bc_user" "$_bc_group"
}


read -d '' bitcoin <<'EOF'
############################################################
#                                                          #
#  Bitcoin Classic                                         #
#  ____________                                            #
#                                                          #
#  To start bitcoin-classic:                               #
#                                                          #
#      # systemctl start bitcoind                          #
#                                                          #
#  To communicate with bitcoin-classic as a normal user:   #
#                                                          #
#      $ bitcoin-cli help                                  #
#                                                          #
#  Config:        /etc/bitcoin/bitcoin.conf                #
#  Blockchain:    /var/lib/bitcoind                        #
#                                                          #
############################################################
EOF