#!/usr/bin/env python
# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Installs and then runs cipd.

This script installs cipd in ./tools/ and then executes it, passing through
all arguments.
"""

from __future__ import print_function

import hashlib
import httplib
import os
import platform
import subprocess
import sys
import urlparse


SCRIPT_DIR = os.path.dirname(__file__)
VERSION_FILE = os.path.join(SCRIPT_DIR, '.cipd_version')
DIGESTS_FILE = VERSION_FILE + '.digests'
# Put CIPD client in tools so that users can easily get it in their PATH.
CLIENT = os.path.join(SCRIPT_DIR, 'tools', 'cipd')
CIPD_HOST = 'chrome-infra-packages.appspot.com'


def platform_normalized():
  """Normalize platform into format expected in CIPD paths."""

  try:
    os_name = platform.system().lower()
    return {
        'linux': 'linux',
        'mac': 'mac',
        'darwin': 'mac',
        'windows': 'windows',
    }[os_name]
  except KeyError:
    raise Exception('unrecognized os: {}'.format(os_name))


def arch_normalized():
  """Normalize arch into format expected in CIPD paths."""

  machine = platform.machine()
  if machine.startswith('arm'):
    return machine
  if machine.endswith('64'):
    return 'amd64'
  if machine.endswith('86'):
    return '386'
  raise Exception('unrecognized arch: {}'.format(machine))


def user_agent():
  try:
    rev = subprocess.check_output(
        ['git', '-C', SCRIPT_DIR, 'rev-parse', 'HEAD']).strip()
  except subprocess.CalledProcessError:
    rev = '???'
  return 'fuchsia-infra/tools/{}'.format(rev)


def actual_hash(path):
  hasher = hashlib.sha256()
  with open(path, 'rb') as ins:
    hasher.update(ins.read())
  return hasher.hexdigest()


def expected_hash():
  """Pulls expected hash from digests file."""

  with open(DIGESTS_FILE, 'r') as ins:
    for line in ins:
      line = line.strip()
      if line.startswith('#') or not line:
        continue
      plat, hashtype, hashval = line.split()
      if (hashtype == 'sha256' and
          plat == '{}-{}'.format(platform_normalized(), arch_normalized())):
        return hashval
    raise Exception(
        'platform {} not in {}'.format(platform_normalized(), DIGESTS_FILE))


def client_bytes():
  """Pull down the CIPD client and return it as a bytes object.

  Often CIPD_HOST returns a 302 FOUND with a pointer to storage.googleapis.com,
  so this needs to handle redirects, but it shouldn't require the initial
  response to be a redirect either.
  """

  with open(VERSION_FILE, 'r') as ins:
    version = ins.read().strip()

  conn = httplib.HTTPSConnection(CIPD_HOST)
  path = '/client?platform={platform}-{arch}&version={version}'.format(
      platform=platform_normalized(),
      arch=arch_normalized(),
      version=version)

  for _ in range(10):
    conn.request('GET', path)
    res = conn.getresponse()
    # Have to read the response before making a new request, so make sure
    # we always read it.
    content = res.read()

    # Found client bytes.
    if res.status == httplib.OK:
      return content

    # Redirecting to another location.
    elif res.status == httplib.FOUND:
      location = res.getheader('location')
      url = urlparse.urlparse(location)
      if url.netloc != conn.host:
        conn = httplib.HTTPSConnection(url.netloc)
      path = '{}?{}'.format(url.path, url.query)

    # Some kind of error in this response.
    else:
      break

  raise Exception('failed to download client')


def bootstrap():
  """Bootstrap cipd client installation."""

  client_dir = os.path.dirname(CLIENT)
  if not os.path.isdir(client_dir):
    os.makedirs(client_dir)

  print(
      'Bootstrapping cipd client for {}-{}'.format(
          platform_normalized(), arch_normalized()))
  tmp_path = os.path.join(SCRIPT_DIR, 'tools', '.cipd')
  with open(tmp_path, 'wb') as tmp:
    tmp.write(client_bytes())

  expected = expected_hash()
  actual = actual_hash(tmp_path)

  if expected != actual:
    raise Exception('digest of downloaded CIPD client is incorrect, check that '
                    'digests file is current')

  os.chmod(tmp_path, 0755)
  os.rename(tmp_path, CLIENT)


def selfupdate():
  """Update cipd client."""

  cmd = [
      CLIENT,
      'selfupdate',
      '-version-file', VERSION_FILE,
      '-service-url', 'https://{}'.format(CIPD_HOST),
  ]
  subprocess.check_call(cmd)


def init():
  """Install/update cipd client."""

  os.environ['CIPD_HTTP_USER_AGENT_PREFIX'] = user_agent()

  try:
    if not os.path.isfile(CLIENT):
      bootstrap()

    try:
      selfupdate()
    except subprocess.CalledProcessError:
      print('CIPD selfupdate failed. Bootstrapping then retrying...',
            file=sys.stderr)
      bootstrap()
      selfupdate()

  except Exception:
    print('Failed to initialize CIPD. Run '
          '`CIPD_HTTP_USER_AGENT_PREFIX={user_agent}/manual {client} '
          "selfupdate -version-file '{version_file}'` "
          'to diagnose if this is persistent.'.format(
              user_agent=user_agent(),
              client=CLIENT,
              version_file=VERSION_FILE,
          ), file=sys.stderr)
    raise


if __name__ == '__main__':
  init()
  subprocess.check_call([CLIENT] + sys.argv[1:])