#! /bin/sh
#
# Copyright (C) 2001-2023 Free Software Foundation, Inc.
#
# 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/>.
#

# This program creates a program's manual from the .x skeleton and its --help
# output.
#
# Usage: x-to-1 [OPTIONS] PERL HELP2MAN [HELP2MAN-OPTIONS] EXECUTABLE PROGRAM.x PROGRAM.1
# where
#
#   PERL        The file name of the perl program.
#   HELP2MAN    Either the file name of the help2man perl script, or a complete
#               command such as "$PERL -w -- help2man".
#   HELP2MAN-OPTIONS  Options to pass to the help2man perl script.
#   EXECUTABLE  The file name of the program to invoke with --help.
#   PROGRAM     The name of the program.
#   PROGRAM.x   The .x skeleton is a file containing manual page text that is
#               not part of the --help output. It is passed to help2man via
#               its --include option. Its format is described in the help2man
#               documentation.
#   PROGRAM.1   The output file, a manual page in mandoc format.
#
# Options:
#   --update    Don't overwrite the output if nothing would change.
#
# Configure-time prerequisites:
#
#   PERL        Can be set through
#                 ac_aux_dir_abs=`cd $ac_aux_dir && pwd`
#                 AC_PATH_PROG([PERL], [perl], [$ac_aux_dir_abs/missing perl])
#               or, alternatively, by the Gnulib 'perl' module.
#
#   CROSS_COMPILING  Can be set through
#                      CROSS_COMPILING=$cross_compiling
#                      AC_SUBST([CROSS_COMPILING])
#                    The variable 'cross_compiling' is set by AC_PROG_CC.

update=
while true; do
  case "$1" in
    --update) update=yes; shift;;
    *) break;;
  esac
done

if test $# -lt 5; then
  echo "Usage: x-to-1 [OPTIONS] PERL HELP2MAN [HELP2MAN-OPTIONS] executable program.x program.1" 1>&2
  exit 1
fi

# In order to construct a command that invokes HELP2MAN [HELP2MAN-OPTIONS] ...
# we need 'eval'.
command_for_print=
command_for_eval=
# Protecting special characters, hiding them from 'eval':
# Double each backslash.
sed_protect_1='s/\\/\\\\/g'
# Escape each dollar, backquote, double-quote.
sed_protect_2a='s/\$/\\$/g'
sed_protect_2b='s/`/\\`/g'
sed_protect_2c='s/"/\\"/g'
# Add double-quotes at the beginning and end of the word.
sed_protect_3a='1s/^/"/'
sed_protect_3b='$s/$/"/'
func_add_word_to_command ()
{
  command_for_print="${command_for_print:+$command_for_print }$1"
  word_protected=`echo "$1" | sed -e "$sed_protect_1" -e "$sed_protect_2a" -e "$sed_protect_2b" -e "$sed_protect_2c" -e "$sed_protect_3a" -e "$sed_protect_3b"`
  command_for_eval="${command_for_eval:+$command_for_eval }$word_protected"
}

PERL="$1"; shift
HELP2MAN="$1"; shift

# Accommodate both possible forms of the HELP2MAN argument.
case "$HELP2MAN" in
  "$PERL "*) ;;
  *) HELP2MAN="$PERL $HELP2MAN" ;;
esac

# Do word-splitting of $HELP2MAN, but carefully.
for word in $HELP2MAN; do
  func_add_word_to_command "$word"
done

# Now grok the HELP2MAN-OPTIONS.
while test $# -gt 3; do
  arg="$1"; shift
  func_add_word_to_command "$arg"
done

# Grok the final arguments.
executable="$1"
aux="$2"
output="$3"

progname=`basename $aux .x`
# configure determined whether perl exists.
case "$PERL" in
  *"/missing perl")
    perlok=no
    ;;
  *)
    # Determine whether all the perl modules that help2man needs are installed.
    if $HELP2MAN --help >/dev/null 2>/dev/null; then
      perlok=yes
    else
      perlok=no
    fi
    ;;
esac
if test @CROSS_COMPILING@ = no && test -f $executable && test $perlok = yes; then
  echo "Updating man page $output"
  func_add_word_to_command "--include=$aux"
  func_add_word_to_command "$executable"
  echo "$command_for_print > $output"
  rm -f t-$progname.1
  eval "$command_for_eval" > t-$progname.1 || exit 1
  if test -n "$update"; then
    # In --update mode, don't overwrite the output if nothing would change.
    if cmp t-$progname.1 $output >/dev/null 2>&1; then
      rm -f t-$progname.1
    else
      mv t-$progname.1 $output
    fi
  else
    mv t-$progname.1 $output
  fi
else
  echo "WARNING: The man page $output cannot be updated yet."
fi
