service.nix

{ pkgs }:

{ service-dir }:

let sd = pkgs.lib.escapeShellArg service-dir;

in pkgs.writers.writeDash "service" ''
  set -e

  CMD=''${1:?please specify command as first argument}
  case "$CMD" in

    # svscan is put in the background,
    # afterwards services can be started and stopped
    init)
      ${pkgs.s6}/bin/s6-svscan ${sd} &
      echo "started service supervisor" >&2
      exit 0
      ;;


    # stop the service manager and terminate services
    quit)
      ${pkgs.s6}/bin/s6-svscanctl -t ${sd}
      echo "stopped service supervisor and services" >&2
      exit 0
      ;;

  esac

  WHAT=''${2:?please specify which service as second argument; "all" is everything}

  ALL="docker hoogle server forest"

  case "$CMD" in

    up|start)
      case "$WHAT" in
        all)
          echo "starting services: $ALL" >&2
          for s in $ALL; do
            ${pkgs.s6}/bin/s6-svc -u ${sd}/"$s"
          done
          ;;
        *) ${pkgs.s6}/bin/s6-svc -u ${sd}/"$WHAT" ;;
      esac
    ;;

    down|stop)
      case "$WHAT" in
        all)
          echo "stopping services: $ALL" >&2
          for s in $ALL; do
            ${pkgs.s6}/bin/s6-svc -d ${sd}/"$s"
          done
          ;;
        *) ${pkgs.s6}/bin/s6-svc -d ${sd}/"$WHAT" ;;
      esac
    ;;

    restart)
      case "$WHAT" in
        all) echo "restart not implemented for \"all\"" >&2 ;;
        *) ${pkgs.s6}/bin/s6-svc -r ${sd}/"$WHAT" ;;
      esac
    ;;
    *) echo "don’t know command $CMD" >&2
    ;;
  esac
''