#!/bin/sh

# gzip-like CLI wrapper for p7zip

# version 3.0

#

# History

#  2.0 :

#    - support for -filename, "file name"

#    - p7zip file1 file2 ...

#  3.0 :  (robert@debian.org, March 2016)

#    - use 7za or 7zr, whichever one is available

#    - refactor the script for better readability

#    - remove `"$?" != 0 ' checks that do not work with `set -e'

#    - use stderr for error reporting

#    - add support for -c, -f, -k options

set -e

# detect 7z program to use

prg7z="`which 7za 2>/dev/null`" || \

  prg7z="`which 7zr 2>/dev/null`" || \

    { echo "$0: cannot find neither 7za nor 7zr command" >&2; exit 1; }

# global options

f_compress=true

f_keep=false

f_force=false

f_tostdout=false

usage()

{

  echo "Usage: $0 [options] [--] [ name ... ]"

  echo ""

  echo "Options:"

  echo "    -c --stdout --to-stdout      output data to stdout"

  echo "    -d --decompress --uncompress decompress file"

  echo "    -f --force                   do not ask questions"

  echo "    -k --keep                    keep original file"

  echo "    -h --help                    print this help"

  echo "    --                           treat subsequent arguments as file"

  echo "                                 names, even if they start with a dash"

  echo ""

  exit 0

}

has_7z_suffix()

{

  case "$1" in

    *.7z)

      return 0

      ;;

    *)

      return 1

      ;;

  esac;

}

make_tmp_file()

{

  P7ZIPTMP="${TMP:-/tmp}"

  mktemp "${P7ZIPTMP}/p7zip.XXXXXXXX"

}

check_not_a_tty()

{

  if ! ${f_force} && ${f_compress} && tty <&1 >/dev/null ; then

    echo "$0: compressed data not written to a terminal." >&2

    echo "For help, type: $0 -h" >&2

    exit 1

  fi

}

compress_file()

{

  file="$1"

  if ! ${f_force} && has_7z_suffix "${file}"; then

    echo "$0: $file already has the 7z suffix" >&2

    exit 1

  fi

  # compress to stdout via temporary file

  if ${f_tostdout}; then

    check_not_a_tty

    tmp="`make_tmp_file`"

    trap "rm -f -- ${tmp}" 0

    rm -f -- "${tmp}"

    "${prg7z}" a -si -- "${tmp}" < "${file}" >/dev/null && cat "${tmp}" || \

      { echo "$0: failed to compress data to temporary file" >&2;  exit 1; }

    rm -f -- "${tmp}"

    return 0

  fi

  # compress to a file

  if ! ${f_force} && [ -e "${file}.7z" ]; then

    echo "$0: destination file ${file}.7z already exists" >&2

    exit 1

  fi

  rm -f -- "${file}.7z"

  flags=""

  ${f_keep} || flags="$flags -sdel"

  ! ${f_force} || flags="$flags -y"

  "${prg7z}" a $flags -- "${file}.7z" "${file}" || {  rm -f -- "${file}.7z"; exit 1; }

}

decompress_file()

{

  file="$1"

  has_7z_suffix "${file}" || { echo "$0: ${file}: unknown suffix" >&2; exit 1; }

  # decompress to stdout

  if ${f_tostdout}; then

    # The following `| cat' pipe shouldn't be needed, however it is here to

    # trick 7z not to complain about writing data to terminal.

    "${prg7z}" x -so -- "${file}" | cat || exit 1

    return 0;

  fi

  flags=""

  ! ${f_force} || flags="$flags -y"

  "${prg7z}" x $flags -- "${file}" || exit 1

  # remove original file unless the archive contains more than one file

  if ! ${f_keep} && "${prg7z}" l --  "${file}" 2>/dev/null | grep -q '^1 file,' 2>/dev/null; then

    rm -f -- "${file}"

  fi

}

process_file()

{

  file="$1"

  # check if file exists and is readable

  [ -r "${file}" ] || { echo "$0: cannot read ${file}" >&2; exit 1; }

  if ${f_compress}; then

    compress_file "${file}"

  else

    decompress_file "${file}"

  fi

}

process_stdin()

{

  check_not_a_tty

  tmp="`make_tmp_file`"

  trap "rm -f -- ${tmp}" 0

  if ${f_compress}; then

    rm -f -- "${tmp}"

    "${prg7z}" a -si -- "${tmp}" >/dev/null && cat -- "${tmp}" || exit 1

  else # decompress

    cat > "${tmp}"

    # The following `| cat' pipe shouldn't be needed, however it is here to

    # trick 7z not to complain about writing data to terminal.

    "${prg7z}" x -so -- "${tmp}" | cat || exit 1

  fi

  rm -f -- "${tmp}"

}

## MAIN

# files and flags

while [ "$#" != "0" ] ; do

  case "$1" in

    -c|--stdout|--to-stdout)

      f_tostdout=true

      ;;

    -d|--decompress|--uncompress)

      f_compress=false # decompressing

      ;;

    -f|--force)

      f_force=true

      ;;

    -h|--help)

      usage

      ;;

    -k|--keep)

      f_keep=true

      ;;

    --)

      shift

      break

      ;;

    -*)

      echo "$0: ignoring unknown option $1" >&2

      ;;

    *)

      break

      ;;

  esac

  shift

done

# make sure they're present, before we screw up

for i in mktemp rm cat tty grep; do

  if ! which $i >/dev/null ; then

    echo "$0: $i: command not found" >&2

    exit 1

  fi

done

if [ "$#" = 0 ]; then

  # compressing/decompressing using standard I/O

  process_stdin

  exit 0

fi

# only files now

while [ "$#" != "0" ] ; do

  process_file  "$1"

  shift

done

exit 0