#!/usr/bin/env bash
# Pkgself builds self-extracting installers
# Copyright (C) 2018  Aaron Ball <nullspoon@oper.io>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

template() {
  # Disable trace output in case it is enabled
  #set +x
  local _src="${1:-}"
  local _dest="${2:-}"
  local varname # Name of the variable, without double braces
  local delim=$'\001'

  local oldifs=${IFS}
  export IFS=$'\n'

  # Create the list of all variables referenced in the file
  local _vars=($(grep -o -h '{{ [a-Z0-9_\-]\+ }}' ${_src} | sort | uniq))

  printf "Parsing template %s -> %s\n" "${_src}" "${_dest}"
  install -D "${_src}" "${_dest}"

  for _var in ${_vars[@]}; do
    _varref="$(printf ${_var} | cut -d ' ' -f 2)"
    if [ -z "${!_varref+x}" ]; then
      printf "Template %s variable '%s' is not set. Skipping.\n" \
        "$(basename ${_src})" \
        "${_varref}"
      continue
    fi

    sed -i "s${delim}{{ ${_varref} }}${delim}${!_varref}${delim}g" "${_dest}"
  done

  export IFS=${oldifs}
  #set -x
}