#!/bin/bash
# Copyright 2016 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# Create or update a virtualenv.
#
# $ create_venv path/to/venv path/to/requirements.txt
set -eu

basedir=$(readlink -f "$(dirname "${BASH_SOURCE[0]}" )")
pkgdir="file://$basedir/pip_packages"

main() {
  if [[ $# -ne 2 ]]; then
    print_help >&2
    exit 1
  fi

  local venv_dir=$1
  local requirements=$2
  local lock="$venv_dir/.create_venv.lock"

  mkdir -p "$venv_dir"
  (
    # Try to acquire a lock for 90 seconds.
    if ! flock -w 90 9; then
      echo 'Failed to acquire lock on virtualenv' >&2
      exit 1
    fi
    if up_to_date "$venv_dir" "$requirements"; then
      echo "Existing virtualenv $venv_dir is already up to date"
    else
      echo "Creating or updating virtualenv in $venv_dir"
      init_venv "$venv_dir"
      install_packages_in_venv "$venv_dir" "$requirements"
      mark_up_to_date "$venv_dir" "$requirements"
    fi
  ) 9>"$lock"
}

print_help() {
  echo "Usage: $0 path/to/venv path/to/requirements.txt

Create or update a Python virtualenv."
}

up_to_date() {
  local venv_dir=$1
  local requirements=$2
  local installed="$venv_dir/.installed.txt"
  cmp -s <("$basedir/expand_reqs.py" <"$requirements" 2>/dev/null) "$installed"
}

mark_up_to_date() {
  local venv_dir=$1
  local requirements=$2
  local installed="$venv_dir/.installed.txt"
  "$basedir/expand_reqs.py" <"$requirements" >"$installed"
}

init_venv() {
  local venv_dir=$1
  virtualenv "$venv_dir" --extra-search-dir="$pkgdir"
}

install_packages_in_venv() {
  local venv_dir=$1
  local requirements=$2
  venv_command "$venv_dir" \
               pip install --no-index -f "$pkgdir" -r "$requirements"
}

venv_command() {
  "$basedir/venv_command" "$@"
}

main "$@"