# Copyright 2018 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Returns a sequence of new innocent CLs which failed pre-cq.

Queries CIDB for sanity Pre-CQ build failures.
"""

from __future__ import print_function
from __future__ import absolute_import
from __future__ import division

import datetime
import itertools

from chromite.lib import constants
from chromite.lib import cidb
from chromite.lib import clactions
from chromite.lib import parallel
from chromite.lib import cros_logging as logging
from google.cloud import datastore  # pylint: disable=E0611,import-error
from infra_libs import ts_mon

from exonerator import checkpointlib
from exonerator import innocent_cls_cq
from exonerator import innocent_cls_precq_flake


PRECQ_PROCESSED_KEY = 'PreCQProcessed'
_SANITY_BUILD_REASON = 'sanity-pre-cq'

# Forgive failed builds up to 3 days before a sanity failure, and 1 day
# afterward.
_DAYS_LOWER_LIMIT = 3
_DAYS_UPPER_LIMIT = 1

_PRE_CQ_CL_LIMITS = {
  # Only kick off one build per tick during peak hours
  True: 1,
  # Kick off pre-CQ builds faster during non-peak hours
  False: 5,
}


_SANITY_FAILURES_EXAMINED = ts_mon.GaugeMetric(
    'chromeos/exonerator/sanity/failures_examined',
    description=('The current number of failed sanity runs being examined by '
                 'CL Exonerator.'),
    field_spec=None)


def NewInnocentCLs(conn, on_peak, checkpoint=True):
  """Finds new innocent CLs since the last run, with checkpointing.

  Looping over the results with a for loop will result in a checkpoint for
  each CL as it is processed. Do not convert the results to a list unless you
  don't care that this will checkpoint immediately during the list construction.

  Args:
    conn: The CIDBConnection to use.
    on_peak: Whether it's business hours (peak load) or off-peak.
    checkpoint: Whether to save progress after every buildMessage processed.

  Yields:
    lists of ChangeWithBuild objects, representing possibly innocent CLs that
    have Pre-CQ faliures which were associtaed with a recent sanity build
    failure.
  """
  limit = _PRE_CQ_CL_LIMITS[on_peak]
  innocents = _InnocentCLsFromSanityBuildFailuresCheckpointed(
      conn, on_peak, limit, checkpoint)

  # TODO(crbug.com/820379) add some logic here to find all the CLs which
  # participated in the build. Put them together in a batch to yield.
  # Also change docstring of limit to be "number of BUILDS to process."

  # Verify that this build was the latest run. We don't want to exonerate a
  # stale pre-cq run when there is a newer run.
  filtered = [
      innocent_cls_cq.ChangeWithBuild(change, build_id)
      for change, build_id in innocents
      if _ShouldExonerate(conn, change, build_id)]
  return [filtered] if filtered else []


def _InnocentCLsFromSanityBuildFailuresCheckpointed(conn, on_peak, limit,
                                                    checkpoint):
  """Finds Pre-CQ failures to forgive.

  Checkpoints processed builds with a PreCQForgiven row. Specifically,

    x = next(fetch)
    # x is not checkpointed yet
    y = next(fetch)  # This checkpoints that x is done

  Args:
    conn: The CIDBConnection to use.
    on_peak: Whether it's business hours (peak load) or off-peak.
    limit: The maximum number of innocent CLs to yield.
    checkpoint: Whether to save progress after every build yielded.

  Yields:
    tuples of (change, pre-cq build id) to forgive.
  """
  # The first priority is to forgive pre-CQ builds associated with a sanity
  # failure. Afterwards, we can consider pre-CQ failures due to flakey pre-CQ
  # configs.
  seq = itertools.chain(
      _InnocentCLsFromSanityBuildFailures(conn),
      innocent_cls_precq_flake.InnocentPreCQsFromFlake(conn, on_peak))

  if not checkpoint:
    return itertools.islice(seq, limit)

  ds = datastore.Client()

  def _AlreadyProcessed(item):
    change, build_id = item
    return _AlreadyForgiven(ds, change, build_id)

  def _Save(item):
    change, build_id = item
    entity = ds.get(key=ds.key(PRECQ_PROCESSED_KEY, build_id))
    if not entity:
      logging.info('Inserting Pre-CQ checkpoint row %s.', build_id)
      entity = datastore.Entity(key=ds.key(PRECQ_PROCESSED_KEY, build_id))
    else:
      logging.info('Updating Pre-CQ checkpoint row %s.', build_id)
    # A build may include more than one CL, so add a property to the entity for
    # each CL of the build that was processed.
    entity.update({str(change.gerrit_number): True})
    ds.put(entity)

  return checkpointlib.CheckpointSequence(
      _AlreadyProcessed, _Save, seq, limit=limit)


def _InnocentCLsFromSanityBuildFailures(conn):
  """Finds Pre-CQ failures to forgive.

  Args:
    conn: The CIDBConnection to use.

  Yields:
    Tuples of (change, pre-cq build) to forgive.
  """
  sanity_runs = conn.GetLatestBuildRequestsForReason(_SANITY_BUILD_REASON)
  for sanity_run in _FailedSanityRuns(conn, sanity_runs):
    for change, build_id in _InnocentPreCQsFromSanity(conn, sanity_run):
      yield change, build_id


def _FailedSanityRuns(conn, sanity_runs):
  """Filters the latest sanity runs to only the failed sanity runs.

  Args:
    conn: The CIDBConnection to use.
    sanity_runs: An iterable of sanity builds (has a .build_id).

  Returns:
    The sanity runs that failed.
  """
  # TODO(phobbs) add a JOIN buildTable in GetLatestBuildRequestsForReason
  # to avoid creating / destroying a bunch of cidb connections.
  statuses = parallel.RunTasksInProcessPool(
      conn.GetBuildStatus,
      [[run.build_id] for run in sanity_runs],
      processes=len(sanity_runs))

  faileds = [status['status'] == constants.BUILDER_STATUS_FAILED
             for status in statuses]

  _SANITY_FAILURES_EXAMINED.set(sum(map(int, faileds)))

  for sanity_run, failed in itertools.izip(sanity_runs, faileds):
    if failed:
      # TODO(crbug.com/820379) yield build ids from here.
      yield sanity_run


def _InnocentPreCQsFromSanity(conn, sanity_failure):
  """Finds forgiveable Pre-CQ failures from a sanity failure

  Args:
    conn: A CIDBConnection
    sanity_failure: A BuildRequest corresponding to a sanity build failure.

  Yields:
    (GerritChangeTuple, build_id) corresponding to pre-cq failures to forgive
  """
  lower_limit = (
      sanity_failure.timestamp - datetime.timedelta(days=_DAYS_LOWER_LIMIT))
  upper_limit = (
      sanity_failure.timestamp + datetime.timedelta(days=_DAYS_UPPER_LIMIT))
  builds = conn.GetBuildHistory(
      sanity_failure.request_build_config,
      cidb.CIDBConnection.NUM_RESULTS_NO_LIMIT,
      start_date=lower_limit.date(),
      end_date=upper_limit.date(),)

  for build in builds:
    actions = conn.GetActionsForBuild(build['id'])
    if not actions:
      continue
    if any(action.status == constants.BUILDER_STATUS_FAILED
           for action in actions):
      action = actions[0]
      change = clactions.GerritPatchTuple(
          action.change_number, action.patch_number,
          action.change_source == 'internal')
      # TODO(crbug.com/820379) yield build ids from here.
      yield change, action.build_id


def _AlreadyForgiven(ds, change, build_id):
  """Whether the given Pre-CQ build was forgiven already.

  Args:
    ds: The cloud Datastore client.
    change: A GerritPatchTuple instance.
    build_id: The CIDB build id for the pre-cq run.
  """
  entity = ds.get(key=ds.key(PRECQ_PROCESSED_KEY, build_id))
  # Each entity stores the CLs that were processed by exonerator for that
  # build. For simplicity, assume gerrit_number:change is a one-to-one mapping.
  # Technically, this is false, but it's extremely unlikely to affect the
  # behavior.
  return (entity is not None
          and entity.get(str(change.gerrit_number), False))


def _ShouldExonerate(conn, change, build_id):
  """Whether we should exonerate the patch.

  Args:
    conn: The cidb.CIDBConnection
    change: A GerritPatchTuple to possibly exonerate
    build_id: The threshold build_id.
  """
  actions = conn.GetActionsForChanges([change])
  return (
      not _ExistsNewerPreCQForCL(actions, build_id)
      and not _PatchAlreadyExonerated(actions, change))


def _ExistsNewerPreCQForCL(actions, build_id):
  """Whether there is a newer action for a given CL of a certain type.

  Args:
    actions: The CLActions for the change
    build_id: The threshold build_id.

  Returns:
    A boolean indicating whether there are any new CLActions of the given
    |action_type|.
  """
  actions_for_build = [a for a in actions if a.build_id == build_id]
  try:
    build_config = actions_for_build[0].build_config
  except IndexError:
    return False

  newer_pickup_actions_for_build_config = [
      a.build_id > build_id
      for a in actions
      if (a.build_config == build_config
          and a.action == constants.CL_ACTION_PICKED_UP)]
  return any(newer_pickup_actions_for_build_config)


def _PatchAlreadyExonerated(actions, change):
  """Whether the patch was already exonerated once.

  This prevents infinitely retrying pre-cq on a single patch.
  TODO: consider retrying more times (2 or 3?) if there is low pre-cq load.

  Args:
    actions: The CLActions for the change
    change: A GerritPatchTuple to find actions for.
  """
  exonerations_for_patch = [
      a for a in actions
      if (a.action == constants.CL_ACTION_EXONERATED
          and a.patch_number == change.patch_number)]
  return bool(exonerations_for_patch)