#!/usr/bin/env python3
# Copyright 2018 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""Prints all histogram names."""

from __future__ import print_function

import argparse
import io
import subprocess
import sys

import setup_modules  # pylint: disable=unused-import

import chromium_src.tools.metrics.histograms.histogram_paths as histogram_paths
import chromium_src.tools.metrics.histograms.histogram_utils as histogram_utils


def histogram_xml_files():
  return [open(f, encoding='utf-8') for f in histogram_paths.ALL_XMLS]


def get_histogram_diff(revision):
  """Returns the added / removed histogram names relative to git revision

  Args:
    revision: A git revision as described in
      https://git-scm.com/docs/gitrevisions
  Returns:
    A tuple of (added names, removed names), where each entry is sorted in
    ascending order.
  """

  def get_file_at_revision(path):
    """Returns a file-like object containing |path|'s content at |revision|"""
    obj = '%s:%s' % (revision, path)
    contents = subprocess.check_output(
      ('git', 'cat-file', '--textconv', obj)
    ).decode()

    # Just store the contents in memory. histograms.xml is big, but it isn't
    # _that_ big.
    return io.StringIO(contents)

  prev_files = []
  for p in histogram_paths.ALL_XMLS_RELATIVE:
    try:
      prev_files.append(get_file_at_revision(p))
    except subprocess.CalledProcessError:
      # Paths might not exist in the provided revision.
      continue

  current_histogram_names = histogram_utils.get_names(histogram_xml_files())
  prev_histogram_names = histogram_utils.get_names(prev_files)

  added_names = sorted(list(current_histogram_names - prev_histogram_names))
  removed_names = sorted(list(prev_histogram_names - current_histogram_names))
  return (added_names, removed_names)


def _print_diff_names(revision):
  added_names, removed_names = get_histogram_diff(revision)
  print('%d histograms added:' % len(added_names))
  for name in added_names:
    print(name)

  print('%d histograms removed:' % len(removed_names))
  for name in removed_names:
    print(name)


def main(argv):
  parser = argparse.ArgumentParser(description='Print histogram names.')
  parser.add_argument(
    '--diff', type=str, help='Git revision to diff against (e.g. HEAD~)'
  )
  args = parser.parse_args(argv[1:])
  if args.diff is not None:
    _print_diff_names(args.diff)
  else:
    name_set = histogram_utils.get_names(histogram_xml_files())
    for name in sorted(list(name_set)):
      print(name)


if __name__ == '__main__':
  main(sys.argv)