# Script for automating cleanup PR creation for deprecated runtime features
#
# sh tools/deprecate_version/deprecate_version.sh
#
# Direct usage (not recommended):
#
# python tools/deprecate_version/deprecate_version.py
#
# e.g
#
#  python tools/deprecate_version/deprecate_version.py
#
# A GitHub access token must be set in GITHUB_TOKEN. To create one, go to
# Settings -> Developer settings -> Personal access tokens in GitHub and create
# a token with public_repo scope. Keep this safe, it's broader than it needs to
# be thanks to GH permission model
# (https://github.com/dear-github/dear-github/issues/113).
#
# Known issues:
# - Minor fixup PRs (e.g. fixing a typo) will result in the creation of spurious
#   issues.

from __future__ import print_function

import datetime
from datetime import date
from collections import defaultdict
import os
import re
import subprocess
import sys

import github
from git import Repo

try:
  input = raw_input  # Python 2
except NameError:
  pass  # Python 3

# Tag issues created with these labels.
LABELS = ['deprecation', 'tech debt', 'no stalebot']


# Errors that happen during issue creation.
class DeprecateVersionError(Exception):
  pass


def GetConfirmation():
  """Obtain stdin confirmation to create issues in GH."""
  return input('Creates issues? [yN] ').strip().lower() in ('y', 'yes')


def CreateIssues(access_token, runtime_and_pr):
  """Create issues in GitHub for code to clean up old runtime guarded features.

  Args:
    access_token: GitHub access token (see comment at top of file).
    runtime_and_pr: a list of runtime guards and the PRs and commits they were added.
  """
  git = github.Github(access_token)
  repo = git.get_repo('envoyproxy/envoy')

  # Find GitHub label objects for LABELS.
  labels = []
  for label in repo.get_labels():
    if label.name in LABELS:
      labels.append(label)
  if len(labels) != len(LABELS):
    raise DeprecateVersionError('Unknown labels (expected %s, got %s)' % (LABELS, labels))

  issues = []
  for runtime_guard, pr, commit in runtime_and_pr:
    # Who is the author?
    if pr:
      # Extract PR title, number, and author.
      pr_info = repo.get_pull(pr)
      change_title = pr_info.title
      number = ('#%d') % pr
      login = pr_info.user.login
    else:
      # Extract commit message, sha, and author.
      # Only keep commit message title (remove description), and truncate to 50 characters.
      change_title = commit.message.split('\n')[0][:50]
      number = ('commit %s') % commit.hexsha
      email = commit.author.email
      # Use the commit author's email to search through users for their login.
      search_user = git.search_users(email.split('@')[0] + " in:email")
      login = search_user[0].login if search_user else None

    title = '%s deprecation' % (runtime_guard)
    body = ('Your change %s (%s) introduced a runtime guarded feature. It has been 6 months since '
            'the new code has been exercised by default, so it\'s time to remove the old code '
            'path. This issue tracks source code cleanup so we don\'t forget.') % (number,
                                                                                   change_title)

    print(title)
    print(body)
    print('  >> Assigning to %s' % (login or email))
    search_title = '%s in:title' % title

    # TODO(htuch): Figure out how to do this without legacy and faster.
    exists = repo.legacy_search_issues('open', search_title) or repo.legacy_search_issues(
        'closed', search_title)
    if exists:
      print("Issue with %s already exists" % search_title)
      print(exists)
      print('  >> Issue already exists, not posting!')
    else:
      issues.append((title, body, login))

  if not issues:
    print('No features to deprecate in this release')
    return

  if GetConfirmation():
    print('Creating issues...')
    for title, body, login in issues:
      try:
        repo.create_issue(title, body=body, assignees=[login], labels=labels)
      except github.GithubException as e:
        try:
          if login:
            body += '\ncc @' + login
          repo.create_issue(title, body=body, labels=labels)
          print(('unable to assign issue %s to %s. Add them to the Envoy proxy org'
                 'and assign it their way.') % (title, login))
        except github.GithubException as e:
          print('GithubException while creating issue.')
          raise


def GetRuntimeAndPr():
  """Returns a list of tuples of [runtime features to deprecate, PR, commit the feature was added]
  """
  repo = Repo(os.getcwd())

  # grep source code looking for reloadable features which are true to find the
  # PR they were added.
  features_to_flip = []

  runtime_features = re.compile(r'.*"(envoy.reloadable_features..*)",.*')

  removal_date = date.today() - datetime.timedelta(days=183)
  found_test_feature_true = False

  # Walk the blame of runtime_features and look for true runtime features older than 6 months.
  for commit, lines in repo.blame('HEAD', 'source/common/runtime/runtime_features.cc'):
    for line in lines:
      match = runtime_features.match(line)
      if match:
        runtime_guard = match.group(1)
        if runtime_guard == 'envoy.reloadable_features.test_feature_false':
          print("Found end sentinel\n")
          if not found_test_feature_true:
            # The script depends on the cc file having the true runtime block
            # before the false runtime block.  Fail if one isn't found.
            print('Failed to find test_feature_true.  Script needs fixing')
            sys.exit(1)
          return features_to_flip
        if runtime_guard == 'envoy.reloadable_features.test_feature_true':
          found_test_feature_true = True
          continue
        pr_num = re.search('\(#(\d+)\)', commit.message)
        # Some commits may not come from a PR (if they are part of a security point release).
        pr = (int(pr_num.group(1))) if pr_num else None
        pr_date = date.fromtimestamp(commit.committed_date)
        removable = (pr_date < removal_date)
        # Add the runtime guard and PR to the list to file issues about.
        print('Flag ' + runtime_guard + ' added at ' + str(pr_date) + ' ' +
              (removable and 'and is safe to remove' or 'is not ready to remove'))
        if removable:
          features_to_flip.append((runtime_guard, pr, commit))
  print('Failed to find test_feature_false.  Script needs fixing')
  sys.exit(1)


if __name__ == '__main__':
  runtime_and_pr = GetRuntimeAndPr()

  if not runtime_and_pr:
    print('No code is deprecated.')
    sys.exit(0)

  access_token = os.getenv('GITHUB_TOKEN')
  if not access_token:
    print('Missing GITHUB_TOKEN: see instructions in tools/deprecate_version/deprecate_version.py')
    sys.exit(1)

  CreateIssues(access_token, runtime_and_pr)