#!/usr/bin/env python2.7
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"""Filter out tests based on file differences compared to grpc:master"""

from subprocess import call, check_output

# triggers to skip c++ tests
run_cpp_starts_with_triggers = ('src/core',
			        'src/cpp',
			        'test/core',
			        'test/cpp')


def _get_changed_files():
  """
  Get list of changed files between current branch and gRPC master branch
  """
  # git fetch might need to be called on Jenkins slave
  # todo(mattkwong): remove or uncomment below after seeing if Jenkins needs this
  # call(['git', 'fetch'])
  # this also collects files that are changed in the repo but not updated in the branch
  return check_output(["git", "diff", "--name-only", "..origin/master"]).split()


def _can_skip_tests(file_names, starts_with_triggers=(), ends_with_triggers=()):
  """
  Determines if tests are skippable based on if all file names do not match
  any begin or end triggers
  :param file_names: list of changed files generated by _get_changed_files()
  :param starts_with_triggers: tuple of strings to match with beginning of file names
  :param ends_with_triggers: tuple of strings to match with end of file names
  :return: safe to skip tests
  """
  for file_name in file_names:
    if starts_with_triggers and file_name.startswith(starts_with_triggers) or \
       ends_with_triggers and file_name.endswith(ends_with_triggers):
         return False
  return True


def _remove_irrelevant_tests(tests, tag):
  """
  Filters out tests by config or language
  :param tests: list of all tests generated by run_tests_matrix.py
  :param tag: string representing language or config to filter - "_(language)_" or "_(config)"
  :return: list of relevant tests
  """
  return [test for test in tests if not tag in test.shortname]


def filter_tests(tests):
  """
  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:master repo and pull request...")
  changed_files = _get_changed_files()
  for changed_file in changed_files:
    print(changed_file)
  # C++, tsan, msan, and asan have the same filter
  if _can_skip_tests(changed_files, starts_with_triggers=run_cpp_starts_with_triggers):
    tests = _remove_irrelevant_tests(tests, '_c++_') # filter out c++ tests
    tests = _remove_irrelevant_tests(tests, '_tsan') # filter out tsan tests
    tests = _remove_irrelevant_tests(tests, '_msan') # filter out msan tests
    tests = _remove_irrelevant_tests(tests, '_asan') # filter out asan tests
  return tests