#!/bin/sh
#
# mkdep - compute dependencies for the supplied source files
#
#   Copyright © 2024 The Free Software Foundation.
#
#   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 <http://www.gnu.org/licenses/>.
#
# Author: Martin D Kealey <martin@kurahaupo.gen.nz>
#
# Modified by Chet Ramey <chet.ramey@case.edu> for inclusion in Bash
#

append_depfile=false
compiler=cc
depfile=.depend
keep_path=false
keep_output=false
m_flag=-MM
skip_o=false

debug=false

usage()
{
  echo "$PROG: usage: $PROG [-a] [-c compiler] [-f depend_file] [-k f|p] [-m M|MM] [-p] [--] [cc_flags] file ..." >&2
  exit 2
}

PROG=${0##*/}

while getopts ac:f:k:m:pD opt "$@"
do
  case $opt in
    a)
      # append to the dependency file (rather than overwriting it)
      append_depfile=true ;;

    c)
      # change compiler
      compiler=$OPTARG ;;

    f)
      # select a dependency file
      depfile=$2 ;;

    k)
      case $OPTARG in
      f)  # Keep the temporary files on failure
	  keep_output=true ;;
      p)
	  # keep PATH from environment
	  keep_path=true ;;
      *) usage ; exit 2 ;;
      esac ;;

    m)
      case $OPTARG in
      M) m_flag=-M ;;
      MM) m_flag=-MM ;;
      *) usage ; exit 2 ;;
      esac;;

    p)
      # produce “program: program.c”-style dependencies
      # (to avoid generating .o files)
      skip_o=true ;;

    D) debug=true ;;
    
    ?)
      usage ;;
  esac

done

shift $(( $OPTIND - 1 ))

if [ $# = 0 ] ; then
  usage
fi

"$debug" && set -x

"$keep_path" || export PATH=/bin:/usr/bin:/usr/local/bin:/opt/bin:$PATH

output=$depfile.mkdep$$

cleanup()
{
  rm -f "$output".*
}

if "$keep_output"
then soft_cleanup() { :; }
else soft_cleanup() { cleanup ; }
fi

caught () {
  soft_cleanup
  trap 2	# SIGINT?
  kill -2 $$
}

trap caught 1 2 3 13 15

"$compiler" "$m_flag" "$@" > "$output.1" || {
  ex=$?
  echo >&2 "mkdep: compilation failed; exit status $ex."
  soft_cleanup
  exit "$ex"
}

# The pathnames here don't work for every system (e.g., macOS), but the -MM
# option (the default) usually does the right thing
{
  if "$append_depfile"
  then
    cat "$depfile"
  fi

  if "$skip_o"
  then
    sed '
	s@ \./@ @g
	s@ /usr/include[^ ]*@@g
	s@ /usr/lib/gcc[^ ]*@@g

	s@\.o @ @

        :a
        / \\$/ {
          N
          s/[[:space:]]*\\\n[[:space:]]*/ /
          ta
          s/\\$//
        }

        s/  *$//
	/^[^ ]*:$/d

        :b
        /^[^ :][^ :]*:/ {
          s@^\([^ :][^ :]*: \)\([^ ][^ ]*\) @\1\2\n\1@
          /: \/usr\/include/bd
          /: \/usr\/lib/bd
          P
          :d
          D
          tb
        }
      '
  else
    sed '
	s@ \./@ @g;
	s@ /usr/include[^ ]*@@g;
	s@ /usr/lib/gcc[^ ]*@@g;

        :a
        / \\$/ {
          N
          s/[[:space:]]*\\\n[[:space:]]*/ /
          ta
          s/\\$//
        }

        s/  *$//
	/^[^ ]*:$/d

        :b
        /^[^ :][^ :]*:/ {
          s@^\([^ :][^ :]*: \)\([^ ][^ ]*\) @\1\2\n\1@
          /: \/usr\/include/bd
          /: \/usr\/lib/bd
          P
          :d
          D
          tb
        }
      '
  fi < "$output.1"
} |
sort -o "$output.2"

mv "$output.2" "$depfile"

cleanup
exit 0