#!/bin/bash
#
# Administers a device manager installation.
#
# This script is a thin wrapper on top of the deviced commands.  Its main
# purpose is to set up the installation by fetching the binaries required for a
# device manager installation from a few possible sources and setting up the
# setuid helper.

set -e

usage() {
  echo "usage:"
  echo
  echo "Install device manager:"
  echo "VANADIUM_DEVICE_DIR=<installation dir> ./devicex install [<binary source>] [ args for installer... ] [ -- args for device manager...]"
  echo "  Possible values for <binary source>:"
  echo "     unspecified: get binaries from local repository"
  echo "     /path/to/binaries: get binaries from local filesystem"
  echo "     http://host/path: get binaries from HTTP server"
  echo
  echo "Uninstall device manager:"
  echo "VANADIUM_DEVICE_DIR=<installation dir> ./devicex uninstall"
  echo
  echo "Start device manager:"
  echo "VANADIUM_DEVICE_DIR=<installation dir> ./devicex start"
  echo
  echo "Stop device manager:"
  echo "VANADIUM_DEVICE_DIR=<installation dir> ./devicex stop"
  echo "VANADIUM_DEVICE_DIR should be 0711 when running in multi-user"
  echo "mode and all of its parents directories need to be at least"
  echo "0511."
}

###############################################################################
# Wrapper around chown that works differently on Mac and Linux
# Arguments:
#   arguments to chown command
# Returns:
#   None
###############################################################################
portable_chown() {
  case "$(uname)" in
    "Darwin")
      sudo /usr/sbin/chown "$@"
      ;;
    "Linux")
      sudo chown "$@"
      ;;
  esac
}

###############################################################################
# Sets up the target to be owned by root with the suid bit on.
# Arguments:
#   path to target
# Returns:
#   None
###############################################################################
make_suid() {
  local -r target="$1"
  local root_group="root"
  if [[ "$(uname)" == "Darwin" ]]; then
    # Group root not available on Darwin.
    root_group="wheel"
  fi
  portable_chown "root:${root_group}" "${target}"
  sudo chmod 4551 "${target}"
}

###############################################################################
# Runs a command as the device manager user.  Assumes VANADIUM_DEVICE_DIR exists
# and gets the device manager user from the owner of that directory.
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   command to run and its arguments
# Returns:
#   None
###############################################################################
run() {
  local -r devmgr_user=$(getdevowner)
  if [[ "${devmgr_user}" == $(whoami) ]]; then
    "$@"
  else
    sudo -u "${devmgr_user}" \
      NAMESPACE_ROOT="${NAMESPACE_ROOT}" \
      VANADIUM_DEVICE_DIR="${VANADIUM_DEVICE_DIR}" \
      "$@"
  fi
}

readonly BIN_NAMES=(deviced suidhelper agentd inithelper)

###############################################################################
# Copies one binary from source to destination.
# Arguments:
#   name of the binary
#   source dir of binary
#   destination dir of binary
# Returns:
#   None
###############################################################################
copy_binary() {
  local -r BIN_NAME="$1"
  local -r BIN_SRC_DIR="$2"
  local -r BIN_DEST_DIR="$3"
  local -r SOURCE="${BIN_SRC_DIR}/${BIN_NAME}"
  if [[ -x "${SOURCE}" ]]; then
    local -r DESTINATION="${BIN_DEST_DIR}/${BIN_NAME}"
    cp "${SOURCE}" "${DESTINATION}"
    chmod 700 "${DESTINATION}"
  else
    echo "couldn't find ${SOURCE}"
    exit 1
  fi
}

###############################################################################
# Fetches binaries needed by device manager installation.
# Globals:
#   BIN_NAMES
#   VANADIUM_ROOT
# Arguments:
#   destination for binaries
#   source of binaries
# Returns:
#   None
###############################################################################
get_binaries() {
  local -r BIN_INSTALL="$1"
  local -r BIN_SOURCE="$2"

  local bin_names_str=""
  for bin_name in "${BIN_NAMES[@]}"; do
    bin_names_str+=" ${bin_name}"
  done

  # If source is not specified, try to look for it in the repository.
  if [[ -z "${BIN_SOURCE}" ]]; then
    if [[ -z "${VANADIUM_ROOT}" ]]; then
      echo 'ERROR: binary source not specified and no local repository available'
      exit 1
    fi
    local -r REPO_BIN_DIR="${VANADIUM_ROOT}/release/go/bin"
    echo "Fetching binaries:${bin_names_str} from build repository: ${REPO_BIN_DIR} ..."
    for bin_name in "${BIN_NAMES[@]}"; do
      copy_binary "${bin_name}" "${REPO_BIN_DIR}" "${BIN_INSTALL}"
    done
    return
  fi

  # If the source is specified as an existing local filesystem path,
  # look for the binaries there.
  if [[ -d "${BIN_SOURCE}" ]]; then
      echo "Fetching binaries:${bin_names_str} locally from: ${BIN_SOURCE} ..."
      for bin_name in "${BIN_NAMES[@]}"; do
        copy_binary "${bin_name}" "${BIN_SOURCE}" "${BIN_INSTALL}"
      done
      return
  fi

  # If the source looks like a URL, use HTTP to fetch.
  local -r URL_REGEXP='^(https?|ftp|file)://'
  if [[ "${BIN_SOURCE}" =~ ${URL_REGEXP} ]]; then
    echo "Fetching binaries:${bin_names_str} remotely from: ${BIN_SOURCE} ..."
    for bin_name in "${BIN_NAMES[@]}"; do
      local DEST="${BIN_INSTALL}/${bin_name}"
      curl -f -o "${DEST}" "${BIN_SOURCE}/${bin_name}"
      chmod 700 "${DEST}"
    done
    return
  fi

  echo 'ERROR: couldn'"'"'t fetch binaries.'
  exit 1
}

###############################################################################
# Installs device manager: fetches binaries, configures suidhelper, calls the
# install command on deviced.
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   source of binaries (optional)
#   args for install command and for device manager (optional)
# Returns:
#   None
###############################################################################
install() {
  if [[ -e "${VANADIUM_DEVICE_DIR}" ]]; then
    echo "${VANADIUM_DEVICE_DIR} already exists!"
    exit 1
  fi
  mkdir -m 711 "${VANADIUM_DEVICE_DIR}"
  local -r BIN_INSTALL="${VANADIUM_DEVICE_DIR}/bin"
  mkdir -m 700 "${BIN_INSTALL}"

  # Fetch the binaries.
  if [[ $# = 0 || "$1" == --* ]]; then
    local -r BIN_SOURCE=""
  else
    local -r BIN_SOURCE="$1"
    shift
  fi
  get_binaries "${BIN_INSTALL}" "${BIN_SOURCE}"
  for bin_name in "${BIN_NAMES[@]}"; do
    local BINARY="${BIN_INSTALL}/${bin_name}"
    if [[ ! -s "${BINARY}" ]]; then
      echo "${BINARY} is empty."
      exit 1
    fi
  done
  echo "Binaries are in ${BIN_INSTALL}."

  # Set up the suidhelper.
  echo "Configuring helpers ..."
  local SINGLE_USER=false
  local INIT_MODE=false
  local DEVMGR_USER=$(whoami)
  for ARG in $*; do
    if [[ ${ARG} = "--" ]]; then
      break
    elif [[ ${ARG} = "--single_user" || ${ARG} = "--single_user=true" ]]; then
      SINGLE_USER=true
    elif [[ ${ARG} = "--init_mode" || ${ARG} = "--init_mode=true" ]]; then
      INIT_MODE=true
    elif [[ ${ARG} =~ --devuser=(.*) ]]; then
      DEVMGR_USER="${BASH_REMATCH[1]}"
    fi
  done

  if [[ ${SINGLE_USER} == false && ${DEVMGR_USER} == $(whoami) ]]; then
    echo "Running in multi-user mode requires a --devuser=<user>"
    echo "argument. This limits the following unfortunate chain of events:"
    echo "install the device manager as yourself, associate an external blessee"
    echo "with your local user name and the external blessee can invoke an app"
    echo "which, because it has the same system name as the device manager,"
    echo "can use suidhelper to give itself root priviledge."
    exit 1
  fi
  if [[ ${SINGLE_USER}} == true && ${DEVMGR_USER} != $(whoami) ]]; then
    echo "The --devuser flag is unnecessary in single-user mode because"
    echo "all processes run as $(whoami)."
    exit 1
  fi
  local -r SETUID_SCRIPT="${BIN_INSTALL}/suidhelper"
  if [[ ${SINGLE_USER} == false ]]; then
    portable_chown -R "${DEVMGR_USER}:${DEVMGR_USER}" "${VANADIUM_DEVICE_DIR}"
    make_suid "${SETUID_SCRIPT}"
  fi
  local -r INIT_SCRIPT="${BIN_INSTALL}/inithelper"
  if [[ ${INIT_MODE} == true ]]; then
    make_suid "${INIT_SCRIPT}"
  fi
  echo "Helpers configured."

  # Install the device manager.
  echo "Installing device manager under ${VANADIUM_DEVICE_DIR} ..."
  echo "VANADIUM_DEVICE_DIR=${VANADIUM_DEVICE_DIR}"
  run "${BIN_INSTALL}/deviced" install \
    --suid_helper="${SETUID_SCRIPT}" \
    --agent="${BIN_INSTALL}/agentd" \
    --init_helper="${INIT_SCRIPT}" "$@"
  echo "Device manager installed."
}

###############################################################################
# Determines the owner of the device manager
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   None
# Returns:
#  user owning the device manager
###############################################################################
getdevowner() {
  case "$(uname)" in
    "Darwin")
      ls -dl  "${VANADIUM_DEVICE_DIR}" | awk '{print $3}'
      ;;
    "Linux")
      stat -c "%U" "${VANADIUM_DEVICE_DIR}"
      ;;
  esac
}

###############################################################################
# Uninstalls device manager: calls the uninstall command of deviced and removes
# the installation.
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   None
# Returns:
#   None
###############################################################################
uninstall() {
  if [[ ! -d "${VANADIUM_DEVICE_DIR}" ]]; then
    echo "${VANADIUM_DEVICE_DIR} does not exist or is not a directory!"
    exit 1
  fi
  local -r BIN_INSTALL="${VANADIUM_DEVICE_DIR}/bin"
  local -r SETUID_SCRIPT="${BIN_INSTALL}/suidhelper"
  echo "Uninstalling device manager from ${VANADIUM_DEVICE_DIR} ..."
  run "${BIN_INSTALL}/deviced" uninstall \
    --suid_helper="${SETUID_SCRIPT}"

   echo "Device manager uninstalled."
   # Any data created underneath "${VANADIUM_DEVICE_DIR}" by the "deviced
   # install" command would have been cleaned up already by "deviced uninstall".
   # However, install() created "${VANADIUM_DEVICE_DIR}", so uninstall() needs
   # to remove it (as well as data created by install(), like bin/*).

   run rm -rf "${VANADIUM_DEVICE_DIR}/bin"
   rmdir "${VANADIUM_DEVICE_DIR}"
   echo "Removed ${VANADIUM_DEVICE_DIR}"
}

###############################################################################
# Starts device manager: calls the start command of deviced.
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   None
# Returns:
#   None
###############################################################################
start() {
  if [[ ! -d "${VANADIUM_DEVICE_DIR}" ]]; then
    echo "${VANADIUM_DEVICE_DIR} does not exist or is not a directory!"
    exit 1
  fi
  local -r BIN_INSTALL="${VANADIUM_DEVICE_DIR}/bin"
    run "${BIN_INSTALL}/deviced" start
}

###############################################################################
# Stops device manager: calls the stop command of deviced.
# Globals:
#   VANADIUM_DEVICE_DIR
# Arguments:
#   None
# Returns:
#   None
###############################################################################
stop() {
  if [[ ! -d "${VANADIUM_DEVICE_DIR}" ]]; then
    echo "${VANADIUM_DEVICE_DIR} does not exist or is not a directory!"
    exit 1
  fi
  local -r BIN_INSTALL="${VANADIUM_DEVICE_DIR}/bin"
  run "${BIN_INSTALL}/deviced" stop
}

main() {
  if [[ -z "${VANADIUM_DEVICE_DIR}" ]]; then
    echo 'No local device installation dir specified!'
    usage
    exit 1
  fi
  if [[ -e "${VANADIUM_DEVICE_DIR}" && ! -d "${VANADIUM_DEVICE_DIR}" ]]; then
    echo "${VANADIUM_DEVICE_DIR} is not a directory!"
    usage
    exit 1
  fi

  if [[ $# = 0 ]]; then
    echo 'No command specified!'
    usage
    exit 1
  fi
  local -r COMMAND="$1"
  shift
  case "${COMMAND}" in
    install)
      install "$@"
      ;;
    uninstall)
      uninstall
      ;;
    start)
      start
      ;;
    stop)
      stop
      ;;
    *)
      echo "Unrecognized command: ${COMMAND}!"
      usage
      exit 1
  esac
}

main "$@"