#!/bin/bash

# Brief: lsb_release implementation in bash

EXIT_STATUS=0
ERROR_USER=1
ERROR_PROGRAM=2

MSG_RESULT=""

Usage() {
  echo -n "
Distribution information.

Usage: lsb_release [options]

Options:
  -h, --help         show this help message and exit
  -i, --id           show distributor ID
  -d, --description  show description of this distribution
  -r, --release      show release number of this distribution
  -c, --codename     show code name of this distribution
  -a, --all          show all of the above information
  -s, --short        show requested information in short format
" >&2

  exit ${EXIT_STATUS}
}

EnhancedGetopt() {
  NB_ARG=""
  local i=

  while [ $# -gt 0 ]; do
    case "$1" in
      -a|--all) SHOW_ALL="y"; NB_ARG="y"; shift ;;
      -c|--codename) SHOW_CODENAME="y"; NB_ARG="y"; shift ;;
      -d|--description) SHOW_DESCR="y"; NB_ARG="y"; shift ;;
      -i|--id) SHOW_ID="y"; NB_ARG="y"; shift ;;
      -r|--release) SHOW_REL="y"; NB_ARG="y"; shift ;;
      -s|--short) ARG_S="y"; shift ;;
      -h|--help) Usage ;;
      --) shift; break ;;
      -[!-]*)
        for ((i = 1; i < ${#1}; i++)); do
          case "${1:i:1}" in
            a) SHOW_ALL="y"; NB_ARG="y" ;;
            c) SHOW_CODENAME="y"; NB_ARG="y" ;;
            d) SHOW_DESCR="y"; NB_ARG="y" ;;
            i) SHOW_ID="y"; NB_ARG="y" ;;
            r) SHOW_REL="y"; NB_ARG="y" ;;
            s) ARG_S="y" ;;
            h) Usage ;;
            *)
              echo "Invalid option: -${1:i:1}" >&2
              EXIT_STATUS=${ERROR_USER}; Usage ;;
          esac
        done
        shift
        ;;
      *)
        echo "Invalid option: $1" >&2
        EXIT_STATUS=${ERROR_USER}; Usage ;;
    esac
  done
}

GetLSBInfo() {
  local lsb_rel_fn="/etc/lsb-release"

  if [ ! -f "${lsb_rel_fn}" ]; then
    echo "ERROR: '${lsb_rel_fn}' does not exist ..." >&2
    exit ${ERROR_PROGRAM}
  fi

  source "${lsb_rel_fn}" || exit ${ERROR_PROGRAM}
}

GetDistribInfo() {
  local MSG_NA="n/a\n"

  [ -n "${SHOW_DESCR}" ] && [ -z "$DISTRIB_DESCRIPTION" ] && DISTRIB_DESCRIPTION="${MSG_NA}"
  [ -n "${SHOW_ID}" ] && [ -z "$DISTRIB_ID" ] && DISTRIB_ID="${MSG_NA}"
  [ -n "${SHOW_REL}" ] && [ -z "$DISTRIB_RELEASE" ] && DISTRIB_RELEASE="${MSG_NA}"
  [ -n "${SHOW_CODENAME}" ] && [ -z "$DISTRIB_CODENAME" ] && DISTRIB_CODENAME="${MSG_NA}"
}

DisplayID() {
  if [ -z "${ARG_S}" ]; then
    MSG_RESULT+="Distributor ID:\t${DISTRIB_ID}\n"
  else
    MSG_RESULT+="${DISTRIB_ID}\n"
  fi
}

DisplayDescription() {
  if [ -z "${ARG_S}" ]; then
    MSG_RESULT+="Description:\t${DISTRIB_DESCRIPTION}\n"
  else
    MSG_RESULT+="${DISTRIB_DESCRIPTION}\n"
  fi
}

DisplayRelease() {
  if [ -z "${ARG_S}" ]; then
    MSG_RESULT+="Release:\t${DISTRIB_RELEASE}\n"
  else
    MSG_RESULT+="${DISTRIB_RELEASE}\n"
  fi
}

DisplayCodename() {
  if [ -z "${ARG_S}" ]; then
    MSG_RESULT+="Codename:\t${DISTRIB_CODENAME}\n"
  else
    MSG_RESULT+="${DISTRIB_CODENAME}\n"
  fi
}

main() {
  if [ -z "$1" ]; then
    SHOW_ALL="y"
  else
    EnhancedGetopt "$@"
    if [ -n "${ARG_S}" ] && [ -z "${NB_ARG}" ]; then
      SHOW_ALL="y"
    fi
  fi

  if [ -n "${SHOW_ALL}" ]; then
    [ -z "${SHOW_CODENAME}" ] && SHOW_CODENAME="y"
    [ -z "${SHOW_DESCR}" ] && SHOW_DESCR="y"
    [ -z "${SHOW_ID}" ] && SHOW_ID="y"
    [ -z "${SHOW_REL}" ] && SHOW_REL="y"
  fi

  GetLSBInfo
  GetDistribInfo

  [ -n "${SHOW_ID}" ] && DisplayID
  [ -n "${SHOW_DESCR}" ] && DisplayDescription
  [ -n "${SHOW_REL}" ] && DisplayRelease
  [ -n "${SHOW_CODENAME}" ] && DisplayCodename

  echo -ne "${MSG_RESULT}"

  exit ${EXIT_STATUS}
}

main "$@"