#!/usr/bin/env python3
# Copyright 2013 The Flutter Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# The return code of this script will always be 0, even if there is an error,
# unless the --fail-loudly flag is passed.


import argparse
import tarfile
import json
import os
import shutil
import subprocess
import sys

SRC_ROOT = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
FUCHSIA_SDK_DIR = os.path.join(SRC_ROOT, 'fuchsia', 'sdk')
FLUTTER_DIR = os.path.join(SRC_ROOT, 'flutter')
SDK_VERSION_INFO_FILE = os.path.join(FLUTTER_DIR, '.fuchsia_sdk_version')


# Prints to stderr.
def eprint(*args, **kwargs):
  print(*args, file=sys.stderr, **kwargs)


def FileNameForBucket(bucket):
  return bucket.split('/')[-1]


def DownloadFuchsiaSDKFromGCS(bucket, verbose):
  file = FileNameForBucket(bucket)
  url = 'https://storage.googleapis.com/{}'.format(bucket)
  dest = os.path.join(FUCHSIA_SDK_DIR, file)

  if verbose:
    print('Fuchsia SDK url: "%s"' % url)
    print('Fuchsia SDK destination path: "%s"' % dest)

  if os.path.isfile(dest):
    os.unlink(dest)

  curl_command = [
    'curl',
    '--retry', '3',
    '--continue-at', '-', '--location',
    '--output', dest,
    url,
  ]
  if verbose:
    print('Running: "%s"' % (' '.join(curl_command)))
  curl_result = subprocess.run(
    curl_command,
    stdout=subprocess.PIPE,
    stderr=subprocess.PIPE,
    universal_newlines=True,
  )
  if curl_result.returncode == 0 and verbose:
    print('curl output:stdout:\n{}\nstderr:\n{}'.format(
      curl_result.stdout, curl_result.stderr,
    ))
  elif curl_result.returncode != 0:
    eprint('Failed to download: stdout:\n{}\nstderr:\n{}'.format(
      curl_result.stdout, curl_result.stderr,
    ))
    return None

  return dest


def OnErrorRmTree(func, path, exc_info):
  """
  Error handler for ``shutil.rmtree``.

  If the error is due to an access error (read only file)
  it attempts to add write permission and then retries.
  If the error is for another reason it re-raises the error.

  Usage : ``shutil.rmtree(path, onerror=onerror)``
  """
  import stat
  # Is the error an access error?
  if not os.access(path, os.W_OK):
    os.chmod(path, stat.S_IWUSR)
    func(path)
  else:
    raise


def ExtractGzipArchive(archive, host_os, verbose):
  sdk_dest = os.path.join(FUCHSIA_SDK_DIR, host_os)
  if os.path.isdir(sdk_dest):
    shutil.rmtree(sdk_dest, onerror=OnErrorRmTree)

  extract_dest = os.path.join(FUCHSIA_SDK_DIR, 'temp')
  if os.path.isdir(extract_dest):
    shutil.rmtree(extract_dest, onerror=OnErrorRmTree)
  os.makedirs(extract_dest, exist_ok=True)

  if verbose:
    print('Extracting "%s" to "%s"' % (archive, extract_dest))

  with tarfile.open(archive, 'r') as z:
    z.extractall(extract_dest)

  shutil.move(extract_dest, sdk_dest)


# Reads the version file and returns the bucket to download
# The file is expected to live at the flutter directory and be named .fuchsia_sdk_version.
#
# The file is a JSON file which contains a single object with the following schema:
# ```
# {
#    "protocol": "gcs",
#    "identifiers": [
#      {
#        "host_os": "linux",
#        "bucket": "fuchsia-artifacts/development/8824687191341324145/sdk/linux-amd64/core.tar.gz"
#      }
#    ]
# }
# ```
def ReadVersionFile(host_os):
  with open(SDK_VERSION_INFO_FILE) as f:
    try:
      version_obj = json.loads(f.read())
      if version_obj['protocol'] != 'gcs':
        eprint('The gcs protocol is the only suppoted protocl at this time')
        return None
      for id_obj in version_obj['identifiers']:
        if id_obj['host_os'] == host_os:
          return id_obj['bucket']
    except:
      eprint('Could not read JSON version file')
      return None


def Main():
  parser = argparse.ArgumentParser()
  parser.add_argument(
    '--fail-loudly',
    action='store_true',
    default=False,
    help="Return an error code if a prebuilt couldn't be fetched and extracted")

  parser.add_argument(
    '--verbose',
    action='store_true',
    default='LUCI_CONTEXT' in os.environ,
    help='Emit verbose output')

  parser.add_argument(
    '--host-os',
    help='The host os')

  args = parser.parse_args()
  fail_loudly = 1 if args.fail_loudly else 0
  verbose = args.verbose
  host_os = args.host_os

  bucket = ReadVersionFile(host_os)

  if bucket is None:
    eprint('Unable to find bucket in version file')
    return fail_loudly

  archive = DownloadFuchsiaSDKFromGCS(bucket, verbose)
  if archive is None:
    eprint('Failed to download SDK from %s' % bucket)
    return fail_loudly

  ExtractGzipArchive(archive, host_os, verbose)

  success = True
  return 0 if success else fail_loudly


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