#!/bin/sh

# Copyright 2020 Gero Treuner <gero@70t.de>

# 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/>.

if test "$#" != 3
then
  echo 'Usage: $0 PLACEHOLDER FILEINSERT FILETRANSFORM
Transforms a file by inserting a JSON string encoded file at placeholders.

Arguments
  #1 placeholder string
  #2 file what content to insert at placeholder positions
  #3 file with placeholders to transform'
  test "$1" = '-h' -o "$1" = '--help'
  exit $?
fi

exec /usr/bin/gawk -F "$1" -v insertfile="$2" -- '
BEGIN {
  savedORS = ORS
  for (i = 0; i < 32; ++i) ctrlchars[sprintf("%c", i)] = sprintf("\\u%04X", i)
}
{
  if (NF > 1) {
    ORS = ""
    print $1
    for (i = 2; i <= NF; ++i) {
      ORS = "\\n"
      while (0 < getline line < insertfile) {
        gsub(/["\\]/, "\\\\&", line)
        if (match(/[\b\t\n\f\r]/, line)) {
          gsub(/\b/, "\\b", line)
          gsub(/\t/, "\\t", line)
          gsub(/\n/, "\\n", line)
          gsub(/\f/, "\\f", line)
          gsub(/\r/, "\\r", line)
        }
        if (pos = match(line, /([\000-\037])/, a)) {
          ORS = ""
          do {
            print substr(line, 0, pos - 1)
            print ctrlchars[a[1]]
            line = substr(line, pos + 1)
          } while (pos = match(line, /([\000-\037])/, a))
          ORS = "\\n"
        }
        if (RT == "") ORS = ""
        print line
      }
      close(insertfile)
      ORS = i == NF ? savedORS : ""
      print $i
    }
  } else {
    print
  }
}
' "$3"