# Copyright 2021 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Module for determining coverage of fuzzers."""
import logging
import sys
import json
import urllib.error
import urllib.request

# pylint: disable=wrong-import-position,import-error
sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
import utils

# The path to get project's latest report json file.
LATEST_REPORT_INFO_PATH = 'oss-fuzz-coverage/latest_report_info/'

class OSSFuzzCoverageGetter:
  def __init__(self, project_name, repo_path):
    self.project_name = project_name
    self.repo_path = _normalize_repo_path(repo_path)
    self.fuzzer_stats_url = _get_fuzzer_stats_dir_url(self.project_name)

  def get_target_coverage_report(self, target):
    """Get the coverage report for a specific fuzz target.

    Args:
      latest_cov_info: A dict containing a project's latest cov report info.
      target_name: The name of the fuzz target whose coverage is requested.

    Returns:
      The targets coverage json dict or None on failure.
    """
    target_url = utils.url_join(self.fuzzer_stats_url, target + '.json')
    return get_json_from_url(target_url)

  def get_files_covered_by_target(self, target):
    """Gets a list of source files covered by the specific fuzz target.

    Args:
      latest_cov_info: A dict containing a project's latest cov report info.
      target_name: The name of the fuzz target whose coverage is requested.
      oss_fuzz_repo_path: The location of the repo in the docker image.

    Returns:
      A list of files that the fuzzer covers or None.
    """
    target_cov = self.get_target_coverage_report(target)
    if not target_cov:
        logging.error('No coverage data for %s', target)
        return None

    coverage_per_file = target_cov['data'][0]['files']
    if not coverage_per_file:
      logging.info('No files found in coverage report.')
      return None

    affected_file_list = []
    for file in coverage_per_file:
      norm_file_path = os.path.normpath(file['filename'])
      if not norm_file_path.startswith(self.repo_path):
        continue
      if not file['summary']['regions']['count']:
        # Don't consider a file affected if code in it is never executed.
        continue

      relative_path = file['filename'].replace(self.repo_path, '')
      affected_file_list.append(relative_path)

    return affected_file_list


def _normalize_repo_path(repo_path):
  # Make sure cases like /src/curl and /src/curl/ are both handled.
  repo_path = os.path.normpath(repo_path)
  if not repo_path.endswith('/'):
    repo_path += '/'
  return repo_path



def _get_fuzzer_stats_dir_url(project_name):
  """Gets latest coverage report info for a specific OSS-Fuzz project from GCS.

  Args:
    project_name: The name of the relevant OSS-Fuzz project.

  Returns:
    The projects coverage report info in json dict or None on failure.
  """
  latest_report_info_url = utils.url_join(utils.GCS_DOMAIN_NAME,
                                          LATEST_REPORT_INFO_PATH,
                                          project_name + '.json')
  latest_cov_info = get_json_from_url(latest_report_info_url)
  if not latest_cov_info:
    logging.error('Could not get the coverage report json from url: %s.',
                  latest_report_info_url)
    return None

  fuzzer_stats_dir_gs_url = latest_cov_info['fuzzer_stats_dir']
  latest_cov_info_json = utils.gs_url_to_https(fuzzer_stats_dir_gs_url)
  return fuzzer_stats_dir_url


def get_json_from_url(url):
  """Gets a json object from a specified HTTP URL.

  Args:
    url: The url of the json to be downloaded.

  Returns:
    A dictionary deserialized from JSON or None on failure.
  """
  try:
    response = urllib.request.urlopen(url)
  except urllib.error.HTTPError:
    logging.error('HTTP error with url %s.', url)
    return None
  try:
    # read().decode() fixes compatibility issue with urllib response object.
    result_json = json.loads(response.read().decode())
  except (ValueError, TypeError, json.JSONDecodeError) as err:
    logging.error('Loading json from url %s failed with: %s.', url, str(err))
    return None
  return result_json