#!/usr/bin/env python
# Copyright 2014 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Run a pinned gsutil."""


import argparse
import base64
import hashlib
import json
import os
import shutil
import subprocess
import sys
import urllib2
import zipfile


GSUTIL_URL = 'https://storage.googleapis.com/pub/'
API_URL = 'https://www.googleapis.com/storage/v1/b/pub/o/'

THIS_DIR = os.path.dirname(os.path.abspath(__file__))
DEFAULT_BIN_DIR = os.path.join(THIS_DIR, 'external_bin', 'gsutil')
DEFAULT_FALLBACK_GSUTIL = os.path.join(
    THIS_DIR, 'third_party', 'gsutil', 'gsutil')


class SubprocessError(Exception):
  pass


class InvalidGsutilError(Exception):
  pass


def call(args, verbose=True, **kwargs):
  kwargs['stdout'] = subprocess.PIPE
  kwargs['stderr'] = subprocess.STDOUT
  proc = subprocess.Popen(args, **kwargs)
  out = []
  for line in proc.stdout:
    out.append(line)
    if verbose:
      sys.stdout.write(line)
  code = proc.wait()
  if code:
    raise SubprocessError('%s failed with %s' % (args, code))
  return ''.join(out)


def download_gsutil(version, target_dir):
  """Downloads gsutil into the target_dir."""
  filename = 'gsutil_%s.zip' % version
  target_filename = os.path.join(target_dir, filename)

  # Check if the target exists already.
  if os.path.exists(target_filename):
    md5_calc = hashlib.md5()
    with open(target_filename, 'rb') as f:
      while True:
        buf = f.read(4096)
        if not buf:
          break
        md5_calc.update(buf)
    local_md5 = md5_calc.hexdigest()

    metadata_url = '%s%s' % (API_URL, filename)
    metadata = json.load(urllib2.urlopen(metadata_url))
    remote_md5 = base64.b64decode(metadata['md5Hash'])

    if local_md5 == remote_md5:
      return target_filename
    os.remove(target_filename)

  # Do the download.
  url = '%s%s' % (GSUTIL_URL, filename)
  u = urllib2.urlopen(url)
  with open(target_filename, 'wb') as f:
    while True:
      buf = u.read(4096)
      if not buf:
        break
      f.write(buf)
  return target_filename


def check_gsutil(gsutil_bin):
  """Run gsutil version and make sure it runs."""
  try:
    call([sys.executable, gsutil_bin, 'version'], verbose=False)
    return True
  except SubprocessError:
    return False


def ensure_gsutil(version, target):
  bin_dir = os.path.join(target, 'gsutil_%s' % version)
  gsutil_bin = os.path.join(bin_dir, 'gsutil', 'gsutil')
  if os.path.isfile(gsutil_bin) and check_gsutil(gsutil_bin):
    # Everything is awesome! we're all done here.
    return gsutil_bin

  if os.path.isdir(bin_dir):
    # Clean up if we're redownloading a corrupted gsutil.
    shutil.rmtree(bin_dir)
  cache_dir = os.path.join(target, '.cache_dir')
  if not os.path.isdir(cache_dir):
    os.makedirs(cache_dir)
  target_zip_filename = download_gsutil(version, cache_dir)
  with zipfile.ZipFile(target_zip_filename, 'r') as target_zip:
    target_zip.extractall(bin_dir)

  # Final check that the gsutil bin is okay.  This should never fail.
  if not check_gsutil(gsutil_bin):
    raise InvalidGsutilError()

  return gsutil_bin


def run_gsutil(force_version, fallback, target, args):
  if force_version:
    gsutil_bin = ensure_gsutil(force_version, target)
  else:
    gsutil_bin = fallback
  cmd = [sys.executable, gsutil_bin] + args
  os.execv(cmd[0], cmd)


def parse_args():
  parser = argparse.ArgumentParser()
  parser.add_argument('--force-version')
  parser.add_argument('--fallback', default=DEFAULT_FALLBACK_GSUTIL)
  parser.add_argument('--target', default=DEFAULT_BIN_DIR)
  parser.add_argument('args', nargs=argparse.REMAINDER)

  args, extras = parser.parse_known_args()
  if args.args and args.args[0] == '--':
    args.args.pop(0)
  if extras:
    args.args = extras + args.args
  return args.force_version, args.fallback, args.target, args.args


def main():
  force_version, fallback, target, args = parse_args()
  run_gsutil(force_version, fallback, target, args)

if __name__ == '__main__':
  sys.exit(main())