Dockerise a Ruby Gem

pixie

#!/usr/bin/env bash

GEM_NAME='pixie'

#
# Generic stuff
#

function fail {
  local MESSAGE=${1}
  local ERROR_CODE=${2}
  local RC=${3}
  [ -z "${MESSAGE}" ]    && MESSAGE='No more details'
  [ -z "${ERROR_CODE}" ] && ERROR_CODE='F00'
  [ -z "${RC}" ]         && RC=1

  echo -e "[${GEM_NAME}:${ERROR_CODE}] ${MESSAGE}"
  exit ${RC}
}

function fail_platform {
  fail "Fuck off, platform '$(uname)' is not supported"
}

function stat {
  local FILE=${1}
  case $(uname) in
    Darwin) /usr/bin/stat -f '%m' ${FILE} ;;
    Linux)  /usr/bin/stat --format '%Y' ${FILE} ;;
    *)      fail_platform ;;
  esac
}

function epoch {
  local TIME=${1}
  local TZ=${2}
  [ -z "${TZ}" ] && TZ='GMT'

  case $(uname) in
    Darwin) /bin/date -jf '%Y-%m-%dT%H:%M:%SZ%Z' ${TIME}Z${TZ} '+%s' ;;
    Linux)  /usr/bin/date '+%s' -d ${TIME}${TZ} ;;
    *)      fail_platform ;;
  esac
}

function mktemp {
  /usr/bin/mktemp "/tmp/${GEM_NAME}.XXXXX"
}

function docker_assert_supported_version {
  local VERSION=$(docker --version | awk '{print $3}')
  case ${VERSION} in
    19*) ;; # ok
    *)  fail "Assertion failed. ${VERSION} is not supported" "F01" ;;
  esac
}

function docker_assert_working {
  local OUTPUT=$(mktemp)
  docker images 1>${OUTPUT} 2>&1 \
    || fail "Assertion failed. Can't run 'docker' command\n$(cat ${OUTPUT})" "F02"
}

function docker_image_build_if_necessary {
  local IMAGE=${1}
  local FILE=${2}
  local OUTPUT=$(mktemp)

  docker inspect ${IMAGE} 1>${OUTPUT} 2>&1

  if [ "${?}" != "0" ] ||
     ( local FILE_MOD_EPOCH=$(stat ${DOCKER_FILE})
       local IMAGE_MOD_EPOCH=$(epoch $(cat ${OUTPUT} | awk '/\"LastTagTime\"/{print $2}' | awk -F. '{print $1}' | tr -d \") 'GMT')
       return $(( !(${FILE_MOD_EPOCH} - ${IMAGE_MOD_EPOCH} > 0) ))); then

    docker build --rm -f ${DOCKER_FILE} -t ${DOCKER_IMAGE} ${GEM_HOME}
  fi
}

# Assumptions

case $(uname) in
  Darwin) GEM_HOME=$(cd $(cd "$(dirname ${0})" ; pwd -P)/..; pwd -P) ;;
  Linux)  GEM_HOME=$(realpath $(dirname $(realpath ${0}))/..) ;;
  *)      fail_platform ;;
esac

GEM_VERSION=$(awk '/gem.version/{print $3}' ${GEM_HOME}/${GEM_NAME}.gemspec | tr -d \'\")
DOCKER_IMAGE="${GEM_NAME}:${GEM_VERSION}"
DOCKER_FILE="${GEM_HOME}/resource/runtime.dockerfile"

#
# Main
#

docker_assert_working
docker_assert_supported_version
docker_image_build_if_necessary ${DOCKER_IMAGE} ${DOCKER_FILE}

docker run -it --rm \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v /:/pixie/h:ro \
  -v ${GEM_HOME}:/pixie/gem:ro \
  -e RUBYOPT='-I /pixie/gem/lib' \
  ${DOCKER_IMAGE} \
  ruby -e 'require "pixie"; Pixie::CommandLine.new.parse_and_run' -- ${@}