#!/usr/bin/env python
# Copyright (c) 2012 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.

"""Download files from Google Storage based on SHA1 sums."""


import hashlib
import optparse
import os
import Queue
import re
import sys
import threading
import time

import subprocess2


GSUTIL_DEFAULT_PATH = os.path.join(
    os.path.dirname(os.path.abspath(__file__)),
    'third_party', 'gsutil', 'gsutil')


class FileNotFoundError(IOError):
  pass


class InvalidFileError(IOError):
  pass


# Common utilities
class Gsutil(object):
  """Call gsutil with some predefined settings.  This is a convenience object,
  and is also immutable."""
  def __init__(self, path, boto_path=None, timeout=None):
    if not os.path.exists(path):
      raise FileNotFoundError('GSUtil not found in %s' % path)
    self.path = path
    self.timeout = timeout
    self.boto_path = boto_path

  def call(self, *args):
    env = os.environ.copy()
    if self.boto_path:
      env['AWS_CREDENTIAL_FILE'] = self.boto_path
    return subprocess2.call((sys.executable, self.path) + args,
                            env=env,
                            timeout=self.timeout)

  def check_call(self, *args):
    env = os.environ.copy()
    if self.boto_path:
      env['AWS_CREDENTIAL_FILE'] = self.boto_path
    ((out, err), code) = subprocess2.communicate(
        (sys.executable, self.path) + args,
        stdout=subprocess2.PIPE,
        stderr=subprocess2.PIPE,
        env=env,
        timeout=self.timeout)

    # Parse output.
    status_code_match = re.search('status=([0-9]+)', err)
    if status_code_match:
      return (int(status_code_match.group(1)), out, err)
    if ('You are attempting to access protected data with '
          'no configured credentials.' in err):
      return (403, out, err)
    if 'No such object' in err:
      return (404, out, err)
    return (code, out, err)


def check_bucket_permissions(bucket, gsutil):
  if not bucket:
    print >> sys.stderr, 'Missing bucket %s.'
    return (None, 1)
  base_url = 'gs://%s' % bucket

  code, _, ls_err = gsutil.check_call('ls', base_url)
  if code == 403:
    code, _, _ = gsutil.call('config')
    if code != 0:
      print >> sys.stderr, 'Error while authenticating to %s.' % base_url
  elif code == 404:
    print >> sys.stderr, '%s not found.' % base_url
  elif code != 0:
    print >> sys.stderr, ls_err
  return (base_url, code)


def get_sha1(filename):
  sha1 = hashlib.sha1()
  with open(filename, 'rb') as f:
    while True:
      # Read in 1mb chunks, so it doesn't all have to be loaded into memory.
      chunk = f.read(1024*1024)
      if not chunk:
        break
      sha1.update(chunk)
  return sha1.hexdigest()


# Download-specific code starts here

def enumerate_work_queue(input_filename, work_queue, directory,
                         recursive, ignore_errors, output, sha1_file):
  if sha1_file:
    if not os.path.exists(input_filename):
      if not ignore_errors:
        raise FileNotFoundError('%s not found.' % input_filename)
      print >> sys.stderr, '%s not found.' % input_filename
    with open(input_filename, 'rb') as f:
      sha1_match = re.match('^([A-Za-z0-9]{40})$', f.read(1024).rstrip())
      if sha1_match:
        work_queue.put(
            (sha1_match.groups(1)[0], input_filename.replace('.sha1', '')))
        return 1
    if not ignore_errors:
      raise InvalidFileError('No sha1 sum found in %s.' % input_filename)
    print >> sys.stderr, 'No sha1 sum found in %s.' % input_filename
    return 0

  if not directory:
    work_queue.put((input_filename, output))
    return 1

  work_queue_size = 0
  for root, dirs, files in os.walk(input_filename):
    if not recursive:
      for item in dirs[:]:
        dirs.remove(item)
    else:
      for exclude in ['.svn', '.git']:
        if exclude in dirs:
          dirs.remove(exclude)
    for filename in files:
      full_path = os.path.join(root, filename)
      if full_path.endswith('.sha1'):
        with open(full_path, 'rb') as f:
          sha1_match = re.match('^([A-Za-z0-9]{40})$', f.read(1024).rstrip())
        if sha1_match:
          work_queue.put(
              (sha1_match.groups(1)[0], full_path.replace('.sha1', '')))
          work_queue_size += 1
        else:
          if not ignore_errors:
            raise InvalidFileError('No sha1 sum found in %s.' % filename)
          print >> sys.stderr, 'No sha1 sum found in %s.' % filename
  return work_queue_size


def _downloader_worker_thread(thread_num, q, force, base_url,
                              gsutil, out_q, ret_codes):
  while True:
    input_sha1_sum, output_filename = q.get()
    if input_sha1_sum is None:
      return
    if os.path.exists(output_filename) and not force:
      if get_sha1(output_filename) == input_sha1_sum:
        out_q.put(
            '%d> File %s exists and SHA1 matches. Skipping.' % (
                thread_num, output_filename))
        continue
    # Check if file exists.
    file_url = '%s/%s' % (base_url, input_sha1_sum)
    if gsutil.check_call('ls', file_url)[0] != 0:
      out_q.put('%d> File %s for %s does not exist, skipping.' % (
          thread_num, file_url, output_filename))
      ret_codes.put((1, 'File %s for %s does not exist.' % (
          file_url, output_filename)))
      continue
    # Fetch the file.
    out_q.put('%d> Downloading %s...' % (
        thread_num, output_filename))
    code, _, err = gsutil.check_call('cp', '-q', file_url, output_filename)
    if code != 0:
      out_q.put('%d> %s' % (thread_num, err))
      ret_codes.put((code, err))


def printer_worker(output_queue):
  while True:
    line = output_queue.get()
    # Its plausible we want to print empty lines.
    if line is None:
      break
    print line


def download_from_google_storage(
    input_filename, base_url, gsutil, num_threads, directory, recursive,
    force, output, ignore_errors, sha1_file):
  # Start up all the worker threads.
  all_threads = []
  download_start = time.time()
  stdout_queue = Queue.Queue()
  work_queue = Queue.Queue()
  ret_codes = Queue.Queue()
  ret_codes.put((0, None))
  for thread_num in range(num_threads):
    t = threading.Thread(
        target=_downloader_worker_thread,
        args=[thread_num, work_queue, force, base_url,
              gsutil, stdout_queue, ret_codes])
    t.daemon = True
    t.start()
    all_threads.append(t)
  printer_thread = threading.Thread(target=printer_worker, args=[stdout_queue])
  printer_thread.daemon = True
  printer_thread.start()

  # Enumerate our work queue.
  work_queue_size = enumerate_work_queue(
      input_filename, work_queue, directory, recursive,
      ignore_errors, output, sha1_file)
  for _ in all_threads:
    work_queue.put((None, None))  # Used to tell worker threads to stop.

  # Wait for all downloads to finish.
  for t in all_threads:
    t.join()
  stdout_queue.put(None)
  printer_thread.join()

  # See if we ran into any errors.
  max_ret_code = 0
  for ret_code, message in ret_codes.queue:
    max_ret_code = max(ret_code, max_ret_code)
    if message:
      print >> sys.stderr, message
  if not max_ret_code:
    print 'Success!'

  print 'Downloading %d files took %1f second(s)' % (
      work_queue_size, time.time() - download_start)
  return max_ret_code


def main(args):
  usage = ('usage: %prog [options] target\n'
           'Target must be:\n'
           '  (default) a sha1 sum ([A-Za-z0-9]{40}).\n'
           '  (-s or --sha1_file) a .sha1 file, containing a sha1 sum on '
           'the first line.\n'
           '  (-d or --directory) A directory to scan for .sha1 files.')
  parser = optparse.OptionParser(usage)
  parser.add_option('-o', '--output',
                    help='Specify the output file name. Defaults to: '
                         '(a) Given a SHA1 hash, the name is the SHA1 hash. '
                         '(b) Given a .sha1 file or directory, the name will '
                         'match (.*).sha1.')
  parser.add_option('-b', '--bucket',
                    help='Google Storage bucket to fetch from.')
  parser.add_option('-e', '--boto',
                    help='Specify a custom boto file.')
  parser.add_option('-c', '--no_resume', action='store_true',
                    help='Resume download if file is partially downloaded.')
  parser.add_option('-f', '--force', action='store_true',
                    help='Force download even if local file exists.')
  parser.add_option('-i', '--ignore_errors', action='store_true',
                    help='Don\'t throw error if we find an invalid .sha1 file.')
  parser.add_option('-r', '--recursive', action='store_true',
                    help='Scan folders recursively for .sha1 files. '
                         'Must be used with -d/--directory')
  parser.add_option('-t', '--num_threads', default=1, type='int',
                    help='Number of downloader threads to run.')
  parser.add_option('-d', '--directory', action='store_true',
                    help='The target is a directory.  '
                         'Cannot be used with -s/--sha1_file.')
  parser.add_option('-s', '--sha1_file', action='store_true',
                    help='The target is a file containing a sha1 sum.  '
                         'Cannot be used with -d/--directory.')

  (options, args) = parser.parse_args()
  if not args:
    parser.error('Missing target.')
  if len(args) > 1:
    parser.error('Too many targets.')
  if not options.bucket:
    parser.error('Missing bucket.  Specify bucket with --bucket.')
  if options.sha1_file and options.directory:
    parser.error('Both --directory and --sha1_file are specified, '
                 'can only specify one.')
  if options.recursive and not options.directory:
    parser.error('--recursive specified but --directory not specified.')
  if options.output and options.directory:
    parser.error('--directory is specified, so --output has no effect.')
  input_filename = args[0]

  # Set output filename if not specified.
  if not options.output and not options.directory:
    if not options.sha1_file:
      # Target is a sha1 sum, so output filename would also be the sha1 sum.
      options.output = input_filename
    elif options.sha1_file:
      # Target is a .sha1 file.
      if not input_filename.endswith('.sha1'):
        parser.error('--sha1_file is specified, but the input filename '
                     'does not end with .sha1, and no --output is specified. '
                     'Either make sure the input filename has a .sha1 '
                     'extension, or specify --output.')
      options.output = input_filename[:-5]
    else:
      parser.error('Unreachable state.')

  # Check if output file already exists.
  if not options.directory and not options.force and not options.no_resume:
    if os.path.exists(options.output):
      parser.error('Output file %s exists and --no_resume is specified.'
                   % options.output)

  # Make sure we can find a working instance of gsutil.
  if os.path.exists(GSUTIL_DEFAULT_PATH):
    gsutil = Gsutil(GSUTIL_DEFAULT_PATH)
  else:
    gsutil = None
    for path in os.environ["PATH"].split(os.pathsep):
      if os.path.exists(path) and 'gsutil' in os.listdir(path):
        gsutil = Gsutil(os.path.join(path, 'gsutil'))
    if not gsutil:
      parser.error('gsutil not found in %s, bad depot_tools checkout?' %
                   GSUTIL_DEFAULT_PATH)

  # Check we have a valid bucket with valid permissions.
  base_url, code = check_bucket_permissions(options.bucket, gsutil)
  if code:
    return code

  return download_from_google_storage(
      input_filename, base_url, gsutil, options.num_threads, options.directory,
      options.recursive, options.force, options.output, options.ignore_errors,
      options.sha1_file)


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