#!/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 "${BASH_SOURCE[0]}" )")
pkgdir="$basedir/pip_packages"
# base_deps are pip requirements automatically included in every
# virtualenv so we have control over which versions of bootstrap
# packages are installed.
base_deps=( setuptools==28.2.0 pip==8.1.2 )

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 "$venv_dir"
  (
    # Try to acquire a lock for 3 minutes
    if ! flock -w 180 9; then
      echo 'Failed to acquire lock on virtualenv' >&2
      exit 1
    fi
    if up_to_date "$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"
  print_reqs "$requirements" | cmp -s - "$installed"
}

mark_up_to_date() {
  local venv_dir=$1
  local requirements=$2
  local installed="$venv_dir/.installed.txt"
  print_reqs "$requirements" > "$installed"
}

print_reqs() {
  local requirements=$1

  for dep in "${base_deps[@]}"; do
    echo "$dep"
  done
  "$basedir/expand_reqs.py" <"$requirements" 2>/dev/null
}

init_venv() {
  local venv_dir=$1
  # TODO(ayatane): Ubuntu Precise ships with virtualenv 1.7, which
  # requires specifying --setuptools, else distribute is used (which
  # is deprecated).  virtualenv after 1.10 supports setuptools by
  # default.  virtualenv >1.10 accepts --setuptools but does not
  # document it.  Once we no longer have any hosts on virtualenv 1.7,
  # --setuptools can be removed.
  virtualenv "$venv_dir" --extra-search-dir="$pkgdir" --setuptools
}

install_packages_in_venv() {
  local venv_dir=$1
  local requirements=$2
  local dep
  for dep in "${base_deps[@]}"; do
    venv_pip_install "$venv_dir" "$dep"
  done
  venv_pip_install "$venv_dir" -r "$requirements"
}

venv_pip_install() {
  local venv_dir=$1
  shift 1
  "$venv_dir/bin/python" \
      -m pip install --no-index -f "file://$pkgdir" "$@"
}

main "$@"