#!/bin/bash

display_help() {
  >&2 printf 'lights-out version #VERSION#\n'
  >&2 printf '\n'
  >&2 printf 'usage:\n'
  >&2 printf '  lights-out get $input: display inverted pin state of $input\n'
  >&2 printf '  lights-out help: display this help and exit\n'
  >&2 printf '  lights-out init: init gpio\n'
  >&2 printf '  lights-out name: print the name of the server\n'
  >&2 printf '  lights-out push $output $time: simulate push on $output for $time seconds\n'
  >&2 printf '  lights-out turn on: turn on machine if not yet running\n'
}

check_argument_count() {
  local count="$1"
  shift
  if [ $# -ne "${count}" ]; then
    >&2 printf 'wrong number of arguments: "%s" expects %s argument' "$1" "${count}"
    if [ "${count}" -ne 1 ]; then
      printf 's'
    fi
    printf ', but %s were given\n\n' "$#"
    display_help
    exit 1
  fi
}

if [ $# -lt 1 ]; then
  display_help
  exit 1
fi

if [ ! -r '#ETCDIR#/lights-out.conf' ]; then
  >&2 printf 'cannot read config file "#ETCDIR#/lights-out.conf"\n'
  exit 1
fi

if ! command -v gpio >/dev/null 2>&1; then
  >&2 printf 'cannot find command "gpio" - is it installed?\n'
  exit
fi

unset inputs
unset outputs
declare -A inputs
declare -A outputs

. '#ETCDIR#/lights-out.conf'

if [ -z "${inputs['power']}" ]; then
  >&2 printf 'invalid config "#ETCDIR#/lights-out.conf": no power input defined.\n'
  exit 1
fi

if [ -z "${outputs['power']}" ]; then
  >&2 printf 'invalid config "#ETCDIR#/lights-out.conf": no power output defined.\n'
  exit 1
fi

if [ -z "${server}" ]; then
  >&2 printf 'invalid config "#ETCDIR#/lights-out.conf": no server name defined.\n'
  exit 1
fi

case "$1" in
  'get')
    check_argument_count 2 "$@"
    if [ -z "${inputs["$2"]}" ]; then
      >&2 printf 'unknown input "%s"\n\n' "$2"
      display_help
      exit 1
    fi
    value=$(
      gpio read "${inputs["$2"]}"
    ) || exit $?
    echo $((1-value))
  ;;
  'help')
    display_help
  ;;
  'init')
    check_argument_count 1 "$@"
    for input in "${inputs[@]}"; do
      gpio mode "${input}" in || exit $?
      gpio mode "${input}" up || exit $?
    done
    for output in "${outputs[@]}"; do
      gpio write "${output}" 0 || exit $?
      gpio mode "${output}" out || exit $?
    done
  ;;
  'name')
    printf '%s\n' "${server}"
  ;;
  'push')
    check_argument_count 3 "$@"
    if [ -z "${outputs["$2"]}" ]; then
      >&2 printf 'unknown output "%s"\n\n' "$2"
      display_help
      exit 1
    fi
    gpio write "${outputs["$2"]}" 1 || exit $?
    sleep "$3"
    gpio write "${outputs["$2"]}" 0 || exit $?
  ;;
  'turn')
    if [ $# -ne 2 ] \
    || [ "x$2" != 'xon' ]; then
      >&2 printf 'unknown command "%s"\n\n' "$*"
      display_help
      exit 1
    fi
    value=$(
      "$0" get power
    ) || exit $?
    if [ "${value}" -eq 0 ]; then
      "$0" push power 0.1 || exit $?
    fi
  ;;
  'turn on')
    check_argument_count 1 "$@"
    "$0" 'turn' 'on' || exit $?
  ;;
  *)
    >&2 printf 'unknown command "%s"\n\n' "$1"
    display_help
    exit 1
  ;;
esac