#!/usr/bin/env bash
IFS=$'\n'

readonly PROGRAM_NAME=$(basename $0)
readonly PROGRAM_LOC=$(readlink -m $(dirname $0))
readonly ARGS="$@"

readonly SSH_CONFIG_FILE=~/.ssh/config

error () {
  echo $PROGRAM_NAME: missing operand
  echo Try \'$PROGRAM_NAME --help\' for information.
  exit 0
}

usage () {
  echo usage: $PROGRAM_NAME options
  echo "Try '$PROGRAM_NAME -h' for more information."
  exit 0
}

info () {
  cat <<- EOF
  usage: $PROGRAM_NAME options

  Used to make hosts configured in a .ssh config file easily accesible.
  It pulls in the .ssh/config file from the user's home directory and
  prints it based on options.

  OPTIONS:
    -g                      List all the different groups of hosts
    -l                      List all hosts for a specific group number
    -h                      This help information

  Examples:
    List all groups
    $PROGRAM_NAME -g

    List all hosts for group 3
    $PROGRAM_NAME -l 3
EOF
  exit
}

ssh_config () {
  cat $SSH_CONFIG_FILE
}

ssh_groups () {
  ssh_config \
    | grep --regexp=^# \
    | /usr/bin/tr -d '#'
}

ssh_hosts_for_group () {
  local readonly group=$1; shift

  local readonly groups=($(ssh_groups))

  local readonly start=${groups[$group]}
  local readonly end=${groups[$group + 1]}

  ssh_config \
    | sed -n "/$start/,/$end/p" \
    | /usr/bin/head -n -1
}

show_ssh_groups () {
  local readonly groups=($(ssh_groups))

  local group
  local group_number=0
  for group in "${groups[@]}"
  do
    echo "$group_number) $group"
    group_number=$[$group_number + 1]
  done
}

show_hosts_for_ssh_group () {
  local readonly group=$1; shift

  ssh_hosts_for_group $group
}

cmdline () {
  while getopts ":gl:h" opt; do
    case "${opt}" in
      g)
        show_ssh_groups
        ;;
      l)
        show_hosts_for_ssh_group $OPTARG
        ;;
      h)
        info
        ;;
      :)
        echo "Option -$OPTARG requires an argument." >&2
        exit
        ;;
      *)
        usage
        ;;
    esac
  done

  if [ $OPTIND -eq 1 ]
  then
    usage
  fi

  shift $((OPTIND-1))
}

main () {
  cmdline $ARGS
}

main