#!/usr/bin/env python
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"""Filter out tests based on file differences compared to merge target branch"""

from __future__ import print_function

import re
import six
from subprocess import check_output


class TestSuite:
  """
  Contains label to identify job as belonging to this test suite and
  triggers to identify if changed files are relevant
  """
  def __init__(self, labels):
    """
    Build TestSuite to group tests based on labeling
    :param label: strings that should match a jobs's platform, config, language, or test group
    """
    self.triggers = []
    self.labels = labels

  def add_trigger(self, trigger):
    """
    Add a regex to list of triggers that determine if a changed file should run tests
    :param trigger: regex matching file relevant to tests
    """
    self.triggers.append(trigger)


# Create test suites
_CORE_TEST_SUITE = TestSuite(['c'])
_CPP_TEST_SUITE = TestSuite(['c++'])
_CSHARP_TEST_SUITE = TestSuite(['csharp'])
_NODE_TEST_SUITE = TestSuite(['node'])
_OBJC_TEST_SUITE = TestSuite(['objc'])
_PHP_TEST_SUITE = TestSuite(['php', 'php7'])
_PYTHON_TEST_SUITE = TestSuite(['python'])
_RUBY_TEST_SUITE = TestSuite(['ruby'])
_LINUX_TEST_SUITE = TestSuite(['linux'])
_WINDOWS_TEST_SUITE = TestSuite(['windows'])
_MACOS_TEST_SUITE = TestSuite(['macos'])
_ALL_TEST_SUITES = [_CORE_TEST_SUITE, _CPP_TEST_SUITE, _CSHARP_TEST_SUITE,
                    _NODE_TEST_SUITE, _OBJC_TEST_SUITE, _PHP_TEST_SUITE,
                    _PYTHON_TEST_SUITE, _RUBY_TEST_SUITE, _LINUX_TEST_SUITE,
                    _WINDOWS_TEST_SUITE, _MACOS_TEST_SUITE]

# Dictionary of whitelistable files where the key is a regex matching changed files
# and the value is a list of tests that should be run. An empty list means that
# the changed files should not trigger any tests. Any changed file that does not
# match any of these regexes will trigger all tests
# DO NOT CHANGE THIS UNLESS YOU KNOW WHAT YOU ARE DOING (be careful even if you do)
_WHITELIST_DICT = {
  '^doc/': [],
  '^examples/': [],
  '^include/grpc\+\+/': [_CPP_TEST_SUITE],
  '^summerofcode/': [],
  '^src/cpp/': [_CPP_TEST_SUITE],
  '^src/csharp/': [_CSHARP_TEST_SUITE],
  '^src/node/': [_NODE_TEST_SUITE],
  '^src/objective\-c/': [_OBJC_TEST_SUITE],
  '^src/php/': [_PHP_TEST_SUITE],
  '^src/python/': [_PYTHON_TEST_SUITE],
  '^src/ruby/': [_RUBY_TEST_SUITE],
  '^templates/': [],
  '^test/core/': [_CORE_TEST_SUITE],
  '^test/cpp/': [_CPP_TEST_SUITE],
  '^test/distrib/cpp/': [_CPP_TEST_SUITE],
  '^test/distrib/csharp/': [_CSHARP_TEST_SUITE],
  '^test/distrib/node/': [_NODE_TEST_SUITE],
  '^test/distrib/php/': [_PHP_TEST_SUITE],
  '^test/distrib/python/': [_PYTHON_TEST_SUITE],
  '^test/distrib/ruby/': [_RUBY_TEST_SUITE],
  '^tools/internal_ci/': [],
  '^vsprojects/': [_WINDOWS_TEST_SUITE],
  'binding\.gyp$': [_NODE_TEST_SUITE],
  'composer\.json$': [_PHP_TEST_SUITE],
  'config\.m4$': [_PHP_TEST_SUITE],
  'CONTRIBUTING\.md$': [],
  'Gemfile$': [_RUBY_TEST_SUITE],
  'grpc\.def$': [_WINDOWS_TEST_SUITE],
  'grpc\.gemspec$': [_RUBY_TEST_SUITE],
  'gRPC\.podspec$': [_OBJC_TEST_SUITE],
  'gRPC\-Core\.podspec$': [_OBJC_TEST_SUITE],
  'gRPC\-ProtoRPC\.podspec$': [_OBJC_TEST_SUITE],
  'gRPC\-RxLibrary\.podspec$': [_OBJC_TEST_SUITE],
  'INSTALL\.md$': [],
  'LICENSE$': [],
  'MANIFEST\.md$': [],
  'package\.json$': [_PHP_TEST_SUITE],
  'package\.xml$': [_PHP_TEST_SUITE],
  'PATENTS$': [],
  'PYTHON\-MANIFEST\.in$': [_PYTHON_TEST_SUITE],
  'README\.md$': [],
  'requirements\.txt$': [_PYTHON_TEST_SUITE],
  'setup\.cfg$': [_PYTHON_TEST_SUITE],
  'setup\.py$': [_PYTHON_TEST_SUITE]
}

# Regex that combines all keys in _WHITELIST_DICT
_ALL_TRIGGERS = "(" + ")|(".join(_WHITELIST_DICT.keys()) + ")"

# Add all triggers to their respective test suites
for trigger, test_suites in six.iteritems(_WHITELIST_DICT):
  for test_suite in test_suites:
    test_suite.add_trigger(trigger)


def _get_changed_files(base_branch):
  """
  Get list of changed files between current branch and base of target merge branch
  """
  # Get file changes between branch and merge-base of specified branch
  # Not combined to be Windows friendly
  base_commit = check_output(["git", "merge-base", base_branch, "HEAD"]).rstrip()
  return check_output(["git", "diff", base_commit, "--name-only"]).splitlines()


def _can_skip_tests(file_names, triggers):
  """
  Determines if tests are skippable based on if all files do not match list of regexes
  :param file_names: list of changed files generated by _get_changed_files()
  :param triggers: list of regexes matching file name that indicates tests should be run
  :return: safe to skip tests
  """
  for file_name in file_names:
    if any(re.match(trigger, file_name) for trigger in triggers):
      return False
  return True


def _remove_irrelevant_tests(tests, skippable_labels):
  """
  Filters out tests by config or language - will not remove sanitizer tests
  :param tests: list of all tests generated by run_tests_matrix.py
  :param skippable_labels: list of languages and platforms with skippable tests
  :return: list of relevant tests
  """
  # test.labels[0] is platform and test.labels[2] is language
  # We skip a test if both are considered safe to skip
  return [test for test in tests if test.labels[0] not in skippable_labels or \
          test.labels[2] not in skippable_labels]


def affects_c_cpp(base_branch):
  """
  Determines if a pull request's changes affect C/C++. This function exists because
  there are pull request tests that only test C/C++ code
  :param base_branch: branch that a pull request is requesting to merge into
  :return: boolean indicating whether C/C++ changes are made in pull request
  """
  changed_files = _get_changed_files(base_branch)
  # Run all tests if any changed file is not in the whitelist dictionary
  for changed_file in changed_files:
    if not re.match(_ALL_TRIGGERS, changed_file):
      return True
  return not _can_skip_tests(changed_files, _CPP_TEST_SUITE.triggers + _CORE_TEST_SUITE.triggers)


def filter_tests(tests, base_branch):
  """
  Filters out tests that are safe to ignore
  :param tests: list of all tests generated by run_tests_matrix.py
  :return: list of relevant tests
  """
  print('Finding file differences between gRPC %s branch and pull request...\n' % base_branch)
  changed_files = _get_changed_files(base_branch)
  for changed_file in changed_files:
    print('  %s' % changed_file)
  print('')

  # Run all tests if any changed file is not in the whitelist dictionary
  for changed_file in changed_files:
    if not re.match(_ALL_TRIGGERS, changed_file):
      return(tests)
  # Figure out which language and platform tests to run
  skippable_labels = []
  for test_suite in _ALL_TEST_SUITES:
    if _can_skip_tests(changed_files, test_suite.triggers):
      for label in test_suite.labels:
        print('  %s tests safe to skip' % label)
        skippable_labels.append(label)
  tests = _remove_irrelevant_tests(tests, skippable_labels)
  return tests
