"""Run python unittests and dump a json report of the results to stdout.

Usage:
  python py_unittest_runner.py path/to/unittests_dir

"""
import argparse
import json
import logging
import os
from pathlib import Path
import sys
from typing import Optional

import gunittest.runner

LOGGER = logging.getLogger(__name__)

def run_tests(directory, test_file_filter_regex, timeout,
              fail_fast: bool,
              after_module: Optional[str]=None,
              multiprocessing=True, module_path_regex='.'):
  """Crawl |directory| and run all python tests.

  Args:
    directory: Path to search for python tests to run.
    test_file_filter_regex: File pattern for tests to be run.
    timeout: Test timeout (in seconds).
    multiprocessing: Use multiprocessing if True.
    module_path_regex: Regex to determine which modules to include.
    fail_fast: Fail on first encountered error.

  Returns:
    The summarized test results.
  """

  results = gunittest.runner.RunTests(
      directory,
      module_path_regex=module_path_regex,
      test_file_filter_regex=test_file_filter_regex,
      timeout=timeout,
      use_multiprocessing=multiprocessing,
      after_module=after_module,
      fail_fast=fail_fast,
  )
  summary = gunittest.runner.Summarize(results)
  return summary


def generate_review(summary):
  """Generate a Gerrit review from the test results |summary|.

  Args:
    summary: A dictionary with: errors, failures, results keys each
        containing a list of db.model.TestResult objects, summarizing the
        results of a test run.

  Returns:
    {'message': review_message, 'passing': passing}, where |review_message|
    is a string giving summary information of the test run and |passing| is a
    bool indicating if the tests all passed (no failurs, no errors).
  """
  errors = summary.get('errors', [])
  failures = summary.get('failures', [])
  all_results = summary.get('results', [])
  elapsed_secs = summary.get('elapsed_secs', 0)
  passing = len(errors) + len(failures) == 0
  passing_msg = 'Passing' if passing else 'Failing'
  message = ('Unit Test Results: {}\n'
             'Run: {}, Errors: {}, Failures: {}\n'
             'Total Run Time: {}').format(passing_msg,
                                          len(all_results),
                                          len(errors),
                                          len(failures), elapsed_secs)
  failure_msgs = [
      '{}\n\n{}\n'.format(f.GetTestName(), f.GetStack()) for f in failures
  ]
  if failure_msgs:
    message += '\n\nFailures:\n{}'.format('\n'.join(failure_msgs))

  error_msgs = [
      '{}\n\n{}\n'.format(e.GetTestName(), e.GetStack()) for e in errors
  ]
  if error_msgs:
    message += '\n\nErrors:\n{}'.format('\n'.join(error_msgs))

  LOGGER.info(message)

  return {'message': message, 'passing': passing}


def parse_cmdline_args() -> argparse.Namespace:
  """Returns the parsed command line arguments."""
  parser = argparse.ArgumentParser(
      description='Run python tests in a given directory.')
  parser.add_argument('--after-module',
                      help=("Run tests that are from modules alphabetically "
                            "after the provided term."))
  parser.add_argument(
      '--fail-fast',
      action='store_true',
      help='Fail on the first test error.')
  parser.add_argument(
      '--test_dir',
      help='the directory to search for tests to run.',
      required=True)
  parser.add_argument(
      '--output', type=Path, help='The file to output the JSON results to.', required=True)
  parser.add_argument(
      '--test_file_filter_regex',
      help='File pattern for tests to be run.',
      default='.*test.py$')
  parser.add_argument(
      '--module_path_regex',
      help='Regex to determine which modules to include.',
      default='.')
  parser.add_argument(
      '--timeout',
      help='Timeout (in seconds) for running tests.',
      type=int,
      required=True)
  parser.add_argument(
      '--single-process',
      help='Avoid using multiple processes when running tests.',
      action='store_true',
  )
  parser.add_argument(
      "--verbose",
      action="store_true",
      help="When present, show debug logs for the test runner.",
  )
  args = parser.parse_args()

  if not os.path.isdir(args.test_dir):
    parser.error(
        'test_dir "{}" does not exist.'.format(os.path.abspath(args.test_dir)))

  return args


class LoggingSetupError(Exception):
  pass


def _setup_logging(verbose: bool) -> None:
  """Set up logging.

  We want to both allow sending logs from this runner and to capture logs
  from tests that we plan to run.

  Args:
    verbose: show verbose logs
  """
  root = logging.getLogger()
  if root.handlers:
    raise LoggingSetupError(
      "Someone is modifying the logging setup at import time. This is a bad "
      "practice. This test runner refuses to fight with badly-behaved tests "
      "and will now exit.")
  root.setLevel(logging.WARNING)
  level = logging.DEBUG if verbose else logging.INFO
  LOGGER.setLevel(level)
  stream = logging.StreamHandler()
  stream.setFormatter(
    logging.Formatter(
      "%(levelname)s %(process)d:%(thread)d %(name)s %(asctime)s: %(message)s"))
  LOGGER.addHandler(stream)
  LOGGER.info("Logging handler established")
  test_runner = logging.getLogger("gunittest.runner")
  test_runner.addHandler(stream)
  test_runner.setLevel(level)


def main():
  args = parse_cmdline_args()
  try:
    _setup_logging(args.verbose)
  except LoggingSetupError as ex:
    print(ex)
    sys.exit(1)
  test_results = run_tests(
      args.test_dir,
      test_file_filter_regex=args.test_file_filter_regex,
      timeout=args.timeout,
      multiprocessing=not args.single_process,
      module_path_regex=args.module_path_regex,
      after_module=args.after_module,
      fail_fast=args.fail_fast,
  )
  review = generate_review(test_results)

  if args.output.parent:
    args.output.parent.mkdir(exist_ok=True)

  with open(args.output, 'w') as output:
    json.dump(review, output)


if __name__ == '__main__':
  main()