#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Copyright 2020 The ChromiumOS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Checks for new reverts in LLVM on a nightly basis.

If any reverts are found that were previously unknown, this cherry-picks them or
fires off an email. All LLVM SHAs to monitor are autodetected.
"""

from __future__ import print_function

import argparse
import io
import json
import logging
import os
import pprint
import subprocess
import sys
import typing as t

import cros_utils.email_sender as email_sender
import cros_utils.tiny_render as tiny_render

import get_llvm_hash
import get_upstream_patch
import git_llvm_rev
import revert_checker

State = t.Any


def _find_interesting_android_shas(android_llvm_toolchain_dir: str
                                   ) -> t.List[t.Tuple[str, str]]:
  llvm_project = os.path.join(android_llvm_toolchain_dir,
                              'toolchain/llvm-project')

  def get_llvm_merge_base(branch: str) -> str:
    head_sha = subprocess.check_output(
        ['git', 'rev-parse', branch],
        cwd=llvm_project,
        encoding='utf-8',
    ).strip()
    merge_base = subprocess.check_output(
        ['git', 'merge-base', branch, 'aosp/upstream-main'],
        cwd=llvm_project,
        encoding='utf-8',
    ).strip()
    logging.info('Merge-base for %s (HEAD == %s) and upstream-main is %s',
                 branch, head_sha, merge_base)
    return merge_base

  main_legacy = get_llvm_merge_base('aosp/master-legacy')  # nocheck
  testing_upstream = get_llvm_merge_base('aosp/testing-upstream')
  result = [('main-legacy', main_legacy)]

  # If these are the same SHA, there's no point in tracking both.
  if main_legacy != testing_upstream:
    result.append(('testing-upstream', testing_upstream))
  else:
    logging.info('main-legacy and testing-upstream are identical; ignoring '
                 'the latter.')
  return result


def _parse_llvm_ebuild_for_shas(ebuild_file: io.TextIOWrapper
                                ) -> t.List[t.Tuple[str, str]]:
  def parse_ebuild_assignment(line: str) -> str:
    no_comments = line.split('#')[0]
    no_assign = no_comments.split('=', 1)[1].strip()
    assert no_assign.startswith('"') and no_assign.endswith('"'), no_assign
    return no_assign[1:-1]

  llvm_hash, llvm_next_hash = None, None
  for line in ebuild_file:
    if line.startswith('LLVM_HASH='):
      llvm_hash = parse_ebuild_assignment(line)
      if llvm_next_hash:
        break
    if line.startswith('LLVM_NEXT_HASH'):
      llvm_next_hash = parse_ebuild_assignment(line)
      if llvm_hash:
        break
  if not llvm_next_hash or not llvm_hash:
    raise ValueError('Failed to detect SHAs for llvm/llvm_next. Got: '
                     'llvm=%s; llvm_next=%s' % (llvm_hash, llvm_next_hash))

  results = [('llvm', llvm_hash)]
  if llvm_next_hash != llvm_hash:
    results.append(('llvm-next', llvm_next_hash))
  return results


def _find_interesting_chromeos_shas(chromeos_base: str
                                    ) -> t.List[t.Tuple[str, str]]:
  llvm_dir = os.path.join(chromeos_base,
                          'src/third_party/chromiumos-overlay/sys-devel/llvm')
  candidate_ebuilds = [
      os.path.join(llvm_dir, x) for x in os.listdir(llvm_dir)
      if '_pre' in x and not os.path.islink(os.path.join(llvm_dir, x))
  ]

  if len(candidate_ebuilds) != 1:
    raise ValueError('Expected exactly one llvm ebuild candidate; got %s' %
                     pprint.pformat(candidate_ebuilds))

  with open(candidate_ebuilds[0], encoding='utf-8') as f:
    return _parse_llvm_ebuild_for_shas(f)


_Email = t.NamedTuple('_Email', [
    ('subject', str),
    ('body', tiny_render.Piece),
])


def _generate_revert_email(
    repository_name: str, friendly_name: str, sha: str,
    prettify_sha: t.Callable[[str], tiny_render.Piece],
    get_sha_description: t.Callable[[str], tiny_render.Piece],
    new_reverts: t.List[revert_checker.Revert]) -> _Email:
  email_pieces = [
      'It looks like there may be %s across %s (' % (
          'a new revert' if len(new_reverts) == 1 else 'new reverts',
          friendly_name,
      ),
      prettify_sha(sha),
      ').',
      tiny_render.line_break,
      tiny_render.line_break,
      'That is:' if len(new_reverts) == 1 else 'These are:',
  ]

  revert_listing = []
  for revert in sorted(new_reverts, key=lambda r: r.sha):
    revert_listing.append([
        prettify_sha(revert.sha),
        ' (appears to revert ',
        prettify_sha(revert.reverted_sha),
        '): ',
        get_sha_description(revert.sha),
    ])

  email_pieces.append(tiny_render.UnorderedList(items=revert_listing))
  email_pieces += [
      tiny_render.line_break,
      'PTAL and consider reverting them locally.',
  ]
  return _Email(
      subject='[revert-checker/%s] new %s discovered across %s' % (
          repository_name,
          'revert' if len(new_reverts) == 1 else 'reverts',
          friendly_name,
      ),
      body=email_pieces,
  )


_EmailRecipients = t.NamedTuple(
    '_EmailRecipients',
    [
        ('well_known', t.List[str]),
        ('direct', t.List[str]),
    ],
)


def _send_revert_email(recipients: _EmailRecipients, email: _Email) -> None:
  email_sender.EmailSender().SendX20Email(
      subject=email.subject,
      identifier='revert-checker',
      well_known_recipients=recipients.well_known,
      direct_recipients=['gbiv@google.com'] + recipients.direct,
      text_body=tiny_render.render_text_pieces(email.body),
      html_body=tiny_render.render_html_pieces(email.body),
  )


def _write_state(state_file: str, new_state: State) -> None:
  try:
    tmp_file = state_file + '.new'
    with open(tmp_file, 'w', encoding='utf-8') as f:
      json.dump(new_state, f, sort_keys=True, indent=2, separators=(',', ': '))
    os.rename(tmp_file, state_file)
  except:
    try:
      os.remove(tmp_file)
    except FileNotFoundError:
      pass
    raise


def _read_state(state_file: str) -> State:
  try:
    with open(state_file) as f:
      return json.load(f)
  except FileNotFoundError:
    logging.info('No state file found at %r; starting with an empty slate',
                 state_file)
    return {}


def find_shas(llvm_dir: str, interesting_shas: t.List[t.Tuple[str, str]],
              state: State, new_state: State):
  for friendly_name, sha in interesting_shas:
    logging.info('Finding reverts across %s (%s)', friendly_name, sha)
    all_reverts = revert_checker.find_reverts(llvm_dir,
                                              sha,
                                              root='origin/' +
                                              git_llvm_rev.MAIN_BRANCH)
    logging.info('Detected the following revert(s) across %s:\n%s',
                 friendly_name, pprint.pformat(all_reverts))

    new_state[sha] = [r.sha for r in all_reverts]

    if sha not in state:
      logging.info('SHA %s is new to me', sha)
      existing_reverts = set()
    else:
      existing_reverts = set(state[sha])

    new_reverts = [r for r in all_reverts if r.sha not in existing_reverts]
    if not new_reverts:
      logging.info('...All of which have been reported.')
      continue

    yield (friendly_name, sha, new_reverts)


def do_cherrypick(chroot_path: str, llvm_dir: str,
                  interesting_shas: t.List[t.Tuple[str, str]], state: State,
                  reviewers: t.List[str], cc: t.List[str]) -> State:
  new_state: State = {}
  seen: t.Set[str] = set()
  for friendly_name, _sha, reverts in find_shas(llvm_dir, interesting_shas,
                                                state, new_state):
    if friendly_name in seen:
      continue
    seen.add(friendly_name)
    for sha, reverted_sha in reverts:
      try:
        # We upload reverts for all platforms by default, since there's no
        # real reason for them to be CrOS-specific.
        get_upstream_patch.get_from_upstream(chroot_path=chroot_path,
                                             create_cl=True,
                                             start_sha=reverted_sha,
                                             patches=[sha],
                                             reviewers=reviewers,
                                             cc=cc,
                                             platforms=())
      except get_upstream_patch.CherrypickError as e:
        logging.info('%s, skipping...', str(e))
  return new_state


def do_email(is_dry_run: bool, llvm_dir: str, repository: str,
             interesting_shas: t.List[t.Tuple[str, str]], state: State,
             recipients: _EmailRecipients) -> State:
  def prettify_sha(sha: str) -> tiny_render.Piece:
    rev = get_llvm_hash.GetVersionFrom(llvm_dir, sha)

    # 12 is arbitrary, but should be unambiguous enough.
    short_sha = sha[:12]
    return tiny_render.Switch(
        text=f'r{rev} ({short_sha})',
        html=tiny_render.Link(href='https://reviews.llvm.org/rG' + sha,
                              inner='r' + str(rev)),
    )

  def get_sha_description(sha: str) -> tiny_render.Piece:
    return subprocess.check_output(
        ['git', 'log', '-n1', '--format=%s', sha],
        cwd=llvm_dir,
        encoding='utf-8',
    ).strip()

  new_state: State = {}
  for friendly_name, sha, new_reverts in find_shas(llvm_dir, interesting_shas,
                                                   state, new_state):
    email = _generate_revert_email(repository, friendly_name, sha,
                                   prettify_sha, get_sha_description,
                                   new_reverts)
    if is_dry_run:
      logging.info('Would send email:\nSubject: %s\nBody:\n%s\n',
                   email.subject, tiny_render.render_text_pieces(email.body))
    else:
      logging.info('Sending email with subject %r...', email.subject)
      _send_revert_email(recipients, email)
      logging.info('Email sent.')
  return new_state


def parse_args(argv: t.List[str]) -> t.Any:
  parser = argparse.ArgumentParser(
      description=__doc__,
      formatter_class=argparse.RawDescriptionHelpFormatter)
  parser.add_argument(
      'action',
      choices=['cherry-pick', 'email', 'dry-run'],
      help='Automatically cherry-pick upstream reverts, send an email, or '
      'write to stdout.')
  parser.add_argument('--state_file',
                      required=True,
                      help='File to store persistent state in.')
  parser.add_argument('--llvm_dir',
                      required=True,
                      help='Up-to-date LLVM directory to use.')
  parser.add_argument('--debug', action='store_true')
  parser.add_argument(
      '--reviewers',
      type=str,
      nargs='*',
      help='Requests reviews from REVIEWERS. All REVIEWERS must have existing '
      'accounts.')
  parser.add_argument(
      '--cc',
      type=str,
      nargs='*',
      help='CCs the CL to the recipients. All recipients must have existing '
      'accounts.')

  subparsers = parser.add_subparsers(dest='repository')
  subparsers.required = True

  chromeos_subparser = subparsers.add_parser('chromeos')
  chromeos_subparser.add_argument('--chromeos_dir',
                                  required=True,
                                  help='Up-to-date CrOS directory to use.')

  android_subparser = subparsers.add_parser('android')
  android_subparser.add_argument(
      '--android_llvm_toolchain_dir',
      required=True,
      help='Up-to-date android-llvm-toolchain directory to use.')

  return parser.parse_args(argv)


def find_chroot(opts: t.Any, reviewers: t.List[str], cc: t.List[str]
                ) -> t.Tuple[str, t.List[t.Tuple[str, str]], _EmailRecipients]:
  recipients = reviewers + cc
  if opts.repository == 'chromeos':
    chroot_path = opts.chromeos_dir
    return (chroot_path, _find_interesting_chromeos_shas(chroot_path),
            _EmailRecipients(well_known=['mage'], direct=recipients))
  elif opts.repository == 'android':
    if opts.action == 'cherry-pick':
      raise RuntimeError(
          "android doesn't currently support automatic cherry-picking.")

    chroot_path = opts.android_llvm_toolchain_dir
    return (chroot_path, _find_interesting_android_shas(chroot_path),
            _EmailRecipients(well_known=[],
                             direct=['android-llvm-dev@google.com'] +
                             recipients))
  else:
    raise ValueError(f'Unknown repository {opts.repository}')


def main(argv: t.List[str]) -> int:
  opts = parse_args(argv)

  logging.basicConfig(
      format='%(asctime)s: %(levelname)s: %(filename)s:%(lineno)d: %(message)s',
      level=logging.DEBUG if opts.debug else logging.INFO,
  )

  action = opts.action
  llvm_dir = opts.llvm_dir
  repository = opts.repository
  state_file = opts.state_file
  reviewers = opts.reviewers if opts.reviewers else []
  cc = opts.cc if opts.cc else []

  chroot_path, interesting_shas, recipients = find_chroot(opts, reviewers, cc)
  logging.info('Interesting SHAs were %r', interesting_shas)

  state = _read_state(state_file)
  logging.info('Loaded state\n%s', pprint.pformat(state))

  # We want to be as free of obvious side-effects as possible in case something
  # above breaks. Hence, action as late as possible.
  if action == 'cherry-pick':
    new_state = do_cherrypick(chroot_path=chroot_path,
                              llvm_dir=llvm_dir,
                              interesting_shas=interesting_shas,
                              state=state,
                              reviewers=reviewers,
                              cc=cc)
  else:
    new_state = do_email(is_dry_run=action == 'dry-run',
                         llvm_dir=llvm_dir,
                         repository=repository,
                         interesting_shas=interesting_shas,
                         state=state,
                         recipients=recipients)

  _write_state(state_file, new_state)
  return 0


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