#!/usr/bin/env python
# Copyright 2014 Google Inc.
#
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.


"""Parse a DEPS file and git checkout all of the dependencies.

Args:
  An optional list of deps_os values.

Environment Variables:
  GIT_EXECUTABLE: path to "git" binary; if unset, will look for git in
  your default path.

  GIT_SYNC_DEPS_PATH: file to get the dependency list from; if unset,
  will use the file ../DEPS relative to this script's directory.

  GIT_SYNC_DEPS_QUIET: if set to non-empty string, suppress messages.

Git Config:
  To disable syncing of a single repository:
      cd path/to/repository
      git config sync-deps.disable true

  To re-enable sync:
      cd path/to/repository
      git config --unset sync-deps.disable
"""


import os
import subprocess
import sys
import threading


def git_executable():
  """Find the git executable.

  Returns:
      A string suitable for passing to subprocess functions, or None.
  """
  envgit = os.environ.get('GIT_EXECUTABLE')
  searchlist = ['git']
  if envgit:
    searchlist.insert(0, envgit)
  with open(os.devnull, 'w') as devnull:
    for git in searchlist:
      try:
        subprocess.call([git, '--version'], stdout=devnull)
      except (OSError,):
        continue
      return git
  return None


DEFAULT_DEPS_PATH = os.path.normpath(
  os.path.join(os.path.dirname(__file__), os.pardir, 'DEPS'))


def usage(deps_file_path = None):
  sys.stderr.write(
    'Usage: run to grab dependencies, with optional platform support:\n')
  sys.stderr.write('  %s %s' % (sys.executable, __file__))
  if deps_file_path:
    parsed_deps = parse_file_to_dict(deps_file_path)
    if 'deps_os' in parsed_deps:
      for deps_os in parsed_deps['deps_os']:
        sys.stderr.write(' [%s]' % deps_os)
  sys.stderr.write('\n\n')
  sys.stderr.write(__doc__)


def git_repository_sync_is_disabled(git, directory):
  try:
    disable = subprocess.check_output(
      [git, 'config', 'sync-deps.disable'], cwd=directory)
    return disable.lower().strip() in ['true', '1', 'yes', 'on']
  except subprocess.CalledProcessError:
    return False


def is_git_toplevel(git, directory):
  """Return true iff the directory is the top level of a Git repository.

  Args:
    git (string) the git executable

    directory (string) the path into which the repository
              is expected to be checked out.
  """
  try:
    toplevel = subprocess.check_output(
      [git, 'rev-parse', '--show-toplevel'], cwd=directory).strip()
    return os.path.realpath(directory) == os.path.realpath(toplevel.decode())
  except subprocess.CalledProcessError:
    return False


def status(directory, commithash, change):
  def truncate(s, length):
    return s if len(s) <= length else s[:(length - 3)] + '...'
  dlen = 36
  directory = truncate(directory, dlen)
  commithash = truncate(commithash, 40)
  symbol = '>' if change else '@'
  sys.stdout.write('%-*s %s %s\n' % (dlen, directory, symbol, commithash))


def git_checkout_to_directory(git, repo, commithash, directory, verbose):
  """Checkout (and clone if needed) a Git repository.

  Args:
    git (string) the git executable

    repo (string) the location of the repository, suitable
         for passing to `git clone`.

    commithash (string) a commit, suitable for passing to `git checkout`

    directory (string) the path into which the repository
              should be checked out.

    verbose (boolean)

  Raises an exception if any calls to git fail.
  """
  if not os.path.isdir(directory):
    subprocess.check_call(
      [git, 'clone', '--quiet', '--no-checkout', repo, directory])
    subprocess.check_call([git, 'checkout', '--quiet', commithash],
                          cwd=directory)
    if verbose:
      status(directory, commithash, True)
    return

  if not is_git_toplevel(git, directory):
    # if the directory exists, but isn't a git repo, you will modify
    # the parent repostory, which isn't what you want.
    sys.stdout.write('%s\n  IS NOT TOP-LEVEL GIT DIRECTORY.\n' % directory)
    return

  # Check to see if this repo is disabled.  Quick return.
  if git_repository_sync_is_disabled(git, directory):
    sys.stdout.write('%s\n  SYNC IS DISABLED.\n' % directory)
    return

  with open(os.devnull, 'w') as devnull:
    # If this fails, we will fetch before trying again.  Don't spam user
    # with error infomation.
    if 0 == subprocess.call([git, 'checkout', '--quiet', commithash],
                            cwd=directory, stderr=devnull):
      # if this succeeds, skip slow `git fetch`.
      if verbose:
        status(directory, commithash, False)  # Success.
      return

  # If the repo has changed, always force use of the correct repo.
  # If origin already points to repo, this is a quick no-op.
  subprocess.check_call(
      [git, 'remote', 'set-url', 'origin', repo], cwd=directory)

  subprocess.check_call([git, 'fetch', '--quiet'], cwd=directory)

  subprocess.check_call([git, 'checkout', '--quiet', commithash], cwd=directory)

  if verbose:
    status(directory, commithash, True)  # Success.


def parse_file_to_dict(path):
  dictionary = {}
  with open(path) as f:
    exec('def Var(x): return vars[x]\n' + f.read(), dictionary)
  return dictionary


def is_sha1_sum(s):
  """SHA1 sums are 160 bits, encoded as lowercase hexadecimal."""
  return len(s) == 40 and all(c in '0123456789abcdef' for c in s)


def git_sync_deps(deps_file_path, command_line_os_requests, verbose):
  """Grab dependencies, with optional platform support.

  Args:
    deps_file_path (string) Path to the DEPS file.

    command_line_os_requests (list of strings) Can be empty list.
        List of strings that should each be a key in the deps_os
        dictionary in the DEPS file.

  Raises git Exceptions.
  """
  git = git_executable()
  assert git

  deps_file_directory = os.path.dirname(deps_file_path)
  deps_file = parse_file_to_dict(deps_file_path)
  dependencies = deps_file['deps'].copy()
  os_specific_dependencies = deps_file.get('deps_os', dict())
  if 'all' in command_line_os_requests:
    for value in os_specific_dependencies.itervalues():
      dependencies.update(value)
  else:
    for os_name in command_line_os_requests:
      # Add OS-specific dependencies
      if os_name in os_specific_dependencies:
        dependencies.update(os_specific_dependencies[os_name])
  for directory in dependencies:
    for other_dir in dependencies:
      if directory.startswith(other_dir + '/'):
        raise Exception('%r is parent of %r' % (other_dir, directory))
  list_of_arg_lists = []
  for directory in sorted(dependencies):
    if not isinstance(dependencies[directory], str):
      if verbose:
        sys.stdout.write( 'Skipping "%s".\n' % directory)
      continue
    if '@' in dependencies[directory]:
      repo, commithash = dependencies[directory].split('@', 1)
    else:
      raise Exception("please specify commit")
    if not is_sha1_sum(commithash):
      raise Exception("poorly formed commit hash: %r" % commithash)

    relative_directory = os.path.join(deps_file_directory, directory)

    list_of_arg_lists.append(
      (git, repo, commithash, relative_directory, verbose))

  multithread(git_checkout_to_directory, list_of_arg_lists)


def multithread(function, list_of_arg_lists):
  # for args in list_of_arg_lists:
  #   function(*args)
  # return
  threads = []
  for args in list_of_arg_lists:
    thread = threading.Thread(None, function, None, args)
    thread.start()
    threads.append(thread)
  for thread in threads:
    thread.join()


def main(argv):
  deps_file_path = os.environ.get('GIT_SYNC_DEPS_PATH', DEFAULT_DEPS_PATH)
  verbose = not bool(os.environ.get('GIT_SYNC_DEPS_QUIET', False))

  if '--help' in argv or '-h' in argv:
    usage(deps_file_path)
    return 1

  git_sync_deps(deps_file_path, argv, verbose)
  subprocess.check_call(
      [sys.executable,
       os.path.join(os.path.dirname(deps_file_path), 'bin', 'fetch-gn')])
  return 0


if __name__ == '__main__':
  exit(main(sys.argv[1:]))