back-cache.sh

#!/usr/bin/env bash

set -o errexit    # always exit on error
set -o pipefail   # don't ignore exit codes when piping output
set -o nounset    # fail on unset variables
set -o xtrace     # print command traces before executing command

echo "PWD=$PWD"

#                   #
#  FRONT FUNCTIONS  #
#                   #

BACK_CACHE_SIGNATURE_FILE=./.back-cache-signature
BACK_CACHE_ARCHIVE=./.back-cache.tar.gz
BACK_CACHE_BASEDIR=/tmp/.back-cache
BACK_PIP_CACHE_DIRECTORY="${BACK_CACHE_BASEDIR}/pip"

create_back_cache_signature() {
#    echo "python=$(python --version);"
    if [[ -f "requirements.txt" ]]; then
        echo "requirementstxt=$(cat requirements.txt);" | tr -d "\n\r "
        echo ""
    fi
}

save_back_cache_signature() {
  echo -n "$(create_back_cache_signature)" > ${BACK_CACHE_SIGNATURE_FILE}
}

load_back_cache_signature() {
  if [[ -f "${BACK_CACHE_SIGNATURE_FILE}" ]]; then
    cat ${BACK_CACHE_SIGNATURE_FILE}
  else
    echo ""
  fi
}

get_back_cache_status() {
  if ! ${BACK_CACHE:-true}; then
    echo "disabled"
  elif [ "$(create_back_cache_signature)" != "$(load_back_cache_signature)" ]; then
    echo "invalid"
  else
    echo "valid"
  fi
}

restore_from_back_cache() {
  rm -rf "${BACK_CACHE_BASEDIR}"
  mkdir -p "${BACK_CACHE_BASEDIR}"
  tar -xPpzf "${BACK_CACHE_ARCHIVE}"
  pip install --no-index --find-links="${BACK_PIP_CACHE_DIRECTORY}" -r requirements.txt
  rm -rf "${BACK_CACHE_BASEDIR}"
}

save_back_cache() {
  rm -rf "${BACK_CACHE_BASEDIR}"
  mkdir -p "${BACK_PIP_CACHE_DIRECTORY}"
  pip wheel --wheel-dir="${BACK_PIP_CACHE_DIRECTORY}" -r requirements.txt
  tar -cPpzf "${BACK_CACHE_ARCHIVE}" --one-file-system "${BACK_CACHE_BASEDIR}"
  rm -rf "${BACK_CACHE_BASEDIR}"
}

clear_back_cache() {
  rm -rf "${BACK_CACHE_BASEDIR}"
  rm -f "${BACK_CACHE_ARCHIVE}"
  rm -f "${BACK_CACHE_SIGNATURE_FILE}"
}

install_used_cache() {
    back_cache_status="$(get_back_cache_status)"
    echo "BACK-CACHE-STATUS: ${back_cache_status}"

    if [ "$back_cache_status" == "valid" ]; then

        restore_from_back_cache

    else

        save_back_cache
        save_back_cache_signature
        restore_from_back_cache

    fi
}



case "$1" in
  -h | --help | help)
      echo "use: $0 (install|clean|status)"
      exit 0
      ;;
  install)
      install_used_cache
      exit 0
      ;;
  clean)
      clear_front_cache
      exit 0
      ;;
  status)
      set +x
      back_cache_status="$(get_back_cache_status)"
      echo $back_cache_status
      if [ "$back_cache_status" == "valid" ]; then
            exit 0
      else
            exit 1
      fi
      exit 0
      ;;
  save)
      clear_back_cache
      save_back_cache
      save_back_cache_signature
      exit 0
      ;;
  restore)
      restore_from_back_cache
      exit 0
      ;;
  *)  # No more options
      echo "Error: Unknown option: $1" >&2
      exit 1
      ;;
esac