# Copyright 2016 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

""" Set of functions for detaling with spam reports.
"""
from __future__ import print_function
from __future__ import division
from __future__ import absolute_import

import collections
import logging
import settings
import time

from collections import defaultdict
from framework import sql
from infra_libs import ts_mon
from services import ml_helpers


SPAMREPORT_TABLE_NAME = 'SpamReport'
SPAMVERDICT_TABLE_NAME = 'SpamVerdict'
ISSUE_TABLE = 'Issue'

REASON_MANUAL = 'manual'
REASON_THRESHOLD = 'threshold'
REASON_CLASSIFIER = 'classifier'
REASON_FAIL_OPEN = 'fail_open'
SPAM_CLASS_LABEL = '1'

SPAMREPORT_ISSUE_COLS = ['issue_id', 'reported_user_id', 'user_id']
SPAMVERDICT_ISSUE_COL = ['created', 'content_created', 'user_id',
                         'reported_user_id', 'comment_id', 'issue_id']
MANUALVERDICT_ISSUE_COLS = ['user_id', 'issue_id', 'is_spam', 'reason',
    'project_id']
THRESHVERDICT_ISSUE_COLS = ['issue_id', 'is_spam', 'reason', 'project_id']

SPAMREPORT_COMMENT_COLS = ['comment_id', 'reported_user_id', 'user_id']
MANUALVERDICT_COMMENT_COLS = ['user_id', 'comment_id', 'is_spam', 'reason',
    'project_id']
THRESHVERDICT_COMMENT_COLS = ['comment_id', 'is_spam', 'reason', 'project_id']


class SpamService(object):
  """The persistence layer for spam reports."""
  issue_actions = ts_mon.CounterMetric(
      'monorail/spam_svc/issue', 'Count of things that happen to issues.', [
          ts_mon.StringField('type'),
          ts_mon.StringField('reporter_id'),
          ts_mon.StringField('issue')
      ])
  comment_actions = ts_mon.CounterMetric(
      'monorail/spam_svc/comment', 'Count of things that happen to comments.', [
          ts_mon.StringField('type'),
          ts_mon.StringField('reporter_id'),
          ts_mon.StringField('issue'),
          ts_mon.StringField('comment_id')
      ])
  ml_engine_failures = ts_mon.CounterMetric(
      'monorail/spam_svc/ml_engine_failure',
      'Failures calling the ML Engine API',
      None)

  def __init__(self):
    self.report_tbl = sql.SQLTableManager(SPAMREPORT_TABLE_NAME)
    self.verdict_tbl = sql.SQLTableManager(SPAMVERDICT_TABLE_NAME)
    self.issue_tbl = sql.SQLTableManager(ISSUE_TABLE)

    # ML Engine library is lazy loaded below.
    self.ml_engine = None

  def LookupIssuesFlaggers(self, cnxn, issue_ids):
    """Returns users who've reported the issues or their comments as spam.

    Returns a dictionary {issue_id: (issue_reporters, comment_reporters)}
    issue_reportes is a list of users who flagged the issue;
    comment_reporters element is a dictionary {comment_id: [user_ids]} where
    user_ids are the users who flagged that comment.
    """
    rows = self.report_tbl.Select(
        cnxn, cols=['issue_id', 'user_id', 'comment_id'],
        issue_id=issue_ids)

    reporters = collections.defaultdict(
        # Return a tuple of (issue_reporters, comment_reporters) as described
        # above.
        lambda: ([], collections.defaultdict(list)))

    for row in rows:
      issue_id = int(row[0])
      user_id = row[1]
      if row[2]:
        comment_id = row[2]
        reporters[issue_id][1][comment_id].append(user_id)
      else:
        reporters[issue_id][0].append(user_id)

    return reporters

  def LookupIssueFlaggers(self, cnxn, issue_id):
    """Returns users who've reported the issue or its comments as spam.

    Returns a tuple. First element is a list of users who flagged the issue;
    second element is a dictionary of comment id to a list of users who flagged
    that comment.
    """
    return self.LookupIssuesFlaggers(cnxn, [issue_id])[issue_id]

  def _LookupIssueFlagCounts(self, cnxn, issue_ids):
    """Returns a map of issue_id to flag counts"""
    rows = self.report_tbl.Select(cnxn, cols=['issue_id', 'COUNT(*)'],
                                  issue_id=issue_ids, group_by=['issue_id'])
    counts = {}
    for row in rows:
      counts[int(row[0])] = row[1]
    return counts

  def LookupIssueVerdicts(self, cnxn, issue_ids):
    """Returns a map of issue_id to most recent spam verdicts"""
    rows = self.verdict_tbl.Select(cnxn,
                                   cols=['issue_id', 'reason', 'MAX(created)'],
                                   issue_id=issue_ids, comment_id=None,
                                   group_by=['issue_id'])
    counts = {}
    for row in rows:
      counts[int(row[0])] = row[1]
    return counts

  def LookupIssueVerdictHistory(self, cnxn, issue_ids):
    """Returns a map of issue_id to most recent spam verdicts"""
    rows = self.verdict_tbl.Select(cnxn, cols=[
        'issue_id', 'reason', 'created', 'is_spam', 'classifier_confidence',
            'user_id', 'overruled'],
        issue_id=issue_ids, order_by=[('issue_id', []), ('created', [])])

    # TODO: group by issue_id, make class instead of dict for verdict.
    verdicts = []
    for row in rows:
      verdicts.append({
        'issue_id': row[0],
        'reason': row[1],
        'created': row[2],
        'is_spam': row[3],
        'classifier_confidence': row[4],
        'user_id': row[5],
        'overruled': row[6],
      })

    return verdicts

  def LookupCommentVerdictHistory(self, cnxn, comment_ids):
    """Returns a map of issue_id to most recent spam verdicts"""
    rows = self.verdict_tbl.Select(cnxn, cols=[
        'comment_id', 'reason', 'created', 'is_spam', 'classifier_confidence',
            'user_id', 'overruled'],
        comment_id=comment_ids, order_by=[('comment_id', []), ('created', [])])

    # TODO: group by comment_id, make class instead of dict for verdict.
    verdicts = []
    for row in rows:
      verdicts.append({
        'comment_id': row[0],
        'reason': row[1],
        'created': row[2],
        'is_spam': row[3],
        'classifier_confidence': row[4],
        'user_id': row[5],
        'overruled': row[6],
      })

    return verdicts

  def FlagIssues(self, cnxn, issue_service, issues, reporting_user_id,
                 flagged_spam):
    """Creates or deletes a spam report on an issue.

    This function is run when a user flags an issue as spam but does not
    have 'VerdictSpam' permission."""
    verdict_updates = []
    if flagged_spam:
      rows = [(issue.issue_id, issue.reporter_id, reporting_user_id)
          for issue in issues]
      self.report_tbl.InsertRows(cnxn, SPAMREPORT_ISSUE_COLS, rows,
          ignore=True)
    else:
      issue_ids = [issue.issue_id for issue in issues]
      self.report_tbl.Delete(
          cnxn, issue_id=issue_ids, user_id=reporting_user_id,
          comment_id=None)

    project_id = issues[0].project_id

    # Now record new verdicts and update issue.is_spam, if they've changed.
    ids = [issue.issue_id for issue in issues]
    counts = self._LookupIssueFlagCounts(cnxn, ids)
    previous_verdicts = self.LookupIssueVerdicts(cnxn, ids)

    for issue_id in counts:
      # If the flag counts changed enough to toggle the is_spam bit, need to
      # record a new verdict and update the Issue.

      # No number of user spam flags can overturn an admin's verdict.
      if previous_verdicts.get(issue_id) == REASON_MANUAL:
        continue

      # If enough spam flags come in, mark the issue as spam.
      if (flagged_spam and counts[issue_id] >= settings.spam_flag_thresh):
        verdict_updates.append(issue_id)

    if len(verdict_updates) == 0:
      return

    # Some of the issues may have exceed the flag threshold, so issue verdicts
    # and mark as spam in those cases.
    rows = [(issue_id, flagged_spam, REASON_THRESHOLD, project_id)
        for issue_id in verdict_updates]
    self.verdict_tbl.InsertRows(cnxn, THRESHVERDICT_ISSUE_COLS, rows,
        ignore=True)
    update_issues = []
    current_time = int(time.time())
    for issue in issues:
      if issue.issue_id in verdict_updates:
        issue.is_spam = flagged_spam
        issue.migration_modified_timestamp = current_time
        update_issues.append(issue)

    if flagged_spam:
      for issue in update_issues:
        issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
        self.issue_actions.increment(
            {
                'type': 'flag',
                'reporter_id': str(reporting_user_id),
                'issue': issue_ref
            })

    issue_service.UpdateIssues(
        cnxn, update_issues, update_cols=['is_spam', 'migration_modified'])

  def FlagComment(
      self, cnxn, issue, comment_id, reported_user_id, reporting_user_id,
      flagged_spam):
    """Creates or deletes a spam report on a comment."""
    # TODO(seanmccullough): Bulk comment flagging? There's no UI for that.
    if flagged_spam:
      self.report_tbl.InsertRow(
          cnxn,
          ignore=True,
          issue_id=issue.issue_id,
          comment_id=comment_id,
          reported_user_id=reported_user_id,
          user_id=reporting_user_id)
      issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
      self.comment_actions.increment(
          {
              'type': 'flag',
              'reporter_id': str(reporting_user_id),
              'issue': issue_ref,
              'comment_id': str(comment_id)
          })
    else:
      self.report_tbl.Delete(
          cnxn,
          issue_id=issue.issue_id,
          comment_id=comment_id,
          user_id=reporting_user_id)

  def RecordClassifierIssueVerdict(self, cnxn, issue, is_spam, confidence,
        fail_open):
    """Records a judgment call on whether a new issue is spam.

    Only run when an issue is newly filed. If the issue is determined to be
    likely spam, the code increments a counter."""
    reason = REASON_FAIL_OPEN if fail_open else REASON_CLASSIFIER
    self.verdict_tbl.InsertRow(
        cnxn,
        issue_id=issue.issue_id,
        is_spam=is_spam,
        reason=reason,
        classifier_confidence=confidence,
        project_id=issue.project_id,
        overruled=False)
    if is_spam:
      issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
      self.issue_actions.increment(
          {
              'type': 'classifier',
              'reporter_id': 'classifier',
              'issue': issue_ref
          })
    # This is called at issue creation time, so there's nothing else to do here.

  def RecordManualIssueVerdicts(self, cnxn, issue_service, issues, user_id,
                                is_spam):
    """Bypasses the classifier to manually classify an issue as spam.

    This code can only be run by users with the 'VerdictSpam' permission."""
    rows = [(user_id, issue.issue_id, is_spam, REASON_MANUAL, issue.project_id)
        for issue in issues]
    issue_ids = [issue.issue_id for issue in issues]

    # Overrule all previous verdicts.
    self.verdict_tbl.Update(cnxn, {'overruled': True}, [
        ('issue_id IN (%s)' % sql.PlaceHolders(issue_ids), issue_ids)
        ], commit=False)

    self.verdict_tbl.InsertRows(cnxn, MANUALVERDICT_ISSUE_COLS, rows,
        ignore=True)

    current_time = int(time.time())
    for issue in issues:
      issue.is_spam = is_spam
      issue.migration_modified_timestamp = current_time

    if is_spam:
      for issue in issues:
        issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
      self.issue_actions.increment(
          {
              'type': 'manual',
              'reporter_id': str(user_id),
              'issue': issue_ref
          })
    else:
      issue_service.AllocateNewLocalIDs(cnxn, issues)

    # This will commit the transaction.
    issue_service.UpdateIssues(
        cnxn, issues, update_cols=['is_spam', 'migration_modified'])

  def RecordManualCommentVerdict(self, cnxn, issue_service, user_service,
        comment_id, user_id, is_spam):
    """Bypasses the classifier to manually classify a comment as spam.

    This code can only be run by users with the 'VerdictSpam' permission."""
    # TODO(seanmccullough): Bulk comment verdicts? There's no UI for that.
    self.verdict_tbl.InsertRow(cnxn, ignore=True,
      user_id=user_id, comment_id=comment_id, is_spam=is_spam,
      reason=REASON_MANUAL)
    comment = issue_service.GetComment(cnxn, comment_id)
    comment.is_spam = is_spam
    issue = issue_service.GetIssue(cnxn, comment.issue_id, use_cache=False)
    issue_service.SoftDeleteComment(
        cnxn, issue, comment, user_id, user_service, is_spam, True, is_spam)
    if is_spam:
      issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
      self.comment_actions.increment(
          {
              'type': 'manual',
              'reporter_id': str(user_id),
              'issue': issue_ref,
              'comment_id': str(comment_id)
          })

  def RecordClassifierCommentVerdict(
      self, cnxn, issue_service, comment, is_spam, confidence, fail_open):
    reason = REASON_FAIL_OPEN if fail_open else REASON_CLASSIFIER
    self.verdict_tbl.InsertRow(cnxn, comment_id=comment.id, is_spam=is_spam,
        reason=reason, classifier_confidence=confidence,
        project_id=comment.project_id)
    if is_spam:
      issue = issue_service.GetIssue(cnxn, comment.issue_id, use_cache=False)
      issue_ref = '%s:%s' % (issue.project_name, issue.local_id)
      self.comment_actions.increment(
          {
              'type': 'classifier',
              'reporter_id': 'classifier',
              'issue': issue_ref,
              'comment_id': str(comment.id)
          })

  def _predict(self, instance):
    """Requests a prediction from the ML Engine API.

    Sample API response:
      {'predictions': [{
        'classes': ['0', '1'],
        'scores': [0.4986788034439087, 0.5013211965560913]
      }]}

    This hits the default model.

    Returns:
      A floating point number representing the confidence
      the instance is spam.
    """
    model_name = 'projects/%s/models/%s' % (
      settings.classifier_project_id, settings.spam_model_name)
    body = {'instances': [{"inputs": instance["word_hashes"]}]}

    if not self.ml_engine:
      self.ml_engine = ml_helpers.setup_ml_engine()

    request = self.ml_engine.projects().predict(name=model_name, body=body)
    response = request.execute()
    logging.info('ML Engine API response: %r' % response)
    prediction = response['predictions'][0]

    # Ensure the class confidence we return is for the spam, not the ham label.
    # The spam label, '1', is usually at index 1 but I'm not sure of any
    # guarantees around label order.
    if prediction['classes'][1] == SPAM_CLASS_LABEL:
      return prediction['scores'][1]
    elif prediction['classes'][0] == SPAM_CLASS_LABEL:
      return prediction['scores'][0]
    else:
      raise Exception('No predicted classes found.')

  def _IsExempt(self, author, is_project_member):
    """Return True if the user is exempt from spam checking."""
    if author.email is not None and author.email.endswith(
        settings.spam_allowlisted_suffixes):
      logging.info('%s allowlisted from spam filtering', author.email)
      return True

    if is_project_member:
      logging.info('%s is a project member, assuming ham', author.email)
      return True

    return False

  def ClassifyIssue(self, issue, firstComment, reporter, is_project_member):
    """Classify an issue as either spam or ham.

    Args:
      issue: the Issue.
      firstComment: the first Comment on issue.
      reporter: User PB for the Issue reporter.
      is_project_member: True if reporter is a member of issue's project.

    Returns a JSON dict of classifier prediction results from
    the ML Engine API.
    """
    instance = ml_helpers.GenerateFeaturesRaw(
        [issue.summary, firstComment.content],
        settings.spam_feature_hashes)
    return self._classify(instance, reporter, is_project_member)

  def ClassifyComment(self, comment_content, commenter, is_project_member=True):
    """Classify a comment as either spam or ham.

    Args:
      comment: the comment text.
      commenter: User PB for the user who authored the comment.

    Returns a JSON dict of classifier prediction results from
    the ML Engine API.
    """
    instance = ml_helpers.GenerateFeaturesRaw(
        ['', comment_content],
        settings.spam_feature_hashes)
    return self._classify(instance, commenter, is_project_member)


  def _classify(self, instance, author, is_project_member):
    # Fail-safe: not spam.
    result = self.ham_classification()

    if self._IsExempt(author, is_project_member):
      return result

    if not self.ml_engine:
      self.ml_engine = ml_helpers.setup_ml_engine()

    # If setup_ml_engine returns None, it failed to init.
    if not self.ml_engine:
      logging.error("ML Engine not initialized.")
      self.ml_engine_failures.increment()
      result['failed_open'] = True
      return result

    remaining_retries = 3
    while remaining_retries > 0:
      try:
        result['confidence_is_spam'] = self._predict(instance)
        result['failed_open'] = False
        return result
      except Exception as ex:
        remaining_retries = remaining_retries - 1
        self.ml_engine_failures.increment()
        logging.error('Error calling ML Engine API: %s' % ex)

      result['failed_open'] = True
    return result

  def ham_classification(self):
    return {'confidence_is_spam': 0.0,
            'failed_open': False}

  def GetIssueFlagQueue(
      self, cnxn, _issue_service, project_id, offset=0, limit=10):
    """Returns list of recent issues that have been flagged by users"""
    issue_flags = self.report_tbl.Select(
        cnxn,
        cols=[
            "Issue.project_id", "Report.issue_id", "count(*) as count",
            "max(Report.created) as latest",
            "count(distinct Report.user_id) as users"
        ],
        left_joins=["Issue ON Issue.id = Report.issue_id"],
        where=[
            ('Report.issue_id IS NOT NULL', []),
            ("Issue.project_id == %v", [project_id])
        ],
        order_by=[('count DESC', [])],
        group_by=['Report.issue_id'],
        offset=offset,
        limit=limit)
    ret = []
    for row in issue_flags:
      ret.append(
          ModerationItem(
              project_id=row[0],
              issue_id=row[1],
              count=row[2],
              latest_report=row[3],
              num_users=row[4],
          ))

    count = self.verdict_tbl.SelectValue(
        cnxn,
        col='COUNT(DISTINCT Report.issue_id)',
        where=[('Issue.project_id = %s', [project_id])],
        left_joins=["Issue ON Issue.id = SpamReport.issue_id"])
    return ret, count


  def GetCommentClassifierQueue(
      self, cnxn, _issue_service, project_id, offset=0, limit=10):
    """Returns list of recent comments with spam verdicts,
     ranked in ascending order of confidence (so uncertain items are first).
     """
    # TODO(seanmccullough): Optimize pagination. This query probably gets
    # slower as the number of SpamVerdicts grows, regardless of offset
    # and limit values used here.  Using offset,limit in general may not
    # be the best way to do this.
    comment_results = self.verdict_tbl.Select(
        cnxn,
        cols=[
            'issue_id', 'is_spam', 'reason', 'classifier_confidence', 'created'
        ],
        where=[
            ('project_id = %s', [project_id]),
            (
                'classifier_confidence <= %s',
                [settings.classifier_moderation_thresh]),
            ('overruled = %s', [False]),
            ('comment_id IS NOT NULL', []),
        ],
        order_by=[
            ('classifier_confidence ASC', []),
            ('created ASC', []),
        ],
        group_by=['comment_id'],
        offset=offset,
        limit=limit,
    )

    ret = []
    for row in comment_results:
      ret.append(
          ModerationItem(
              comment_id=int(row[0]),
              is_spam=row[1] == 1,
              reason=row[2],
              classifier_confidence=row[3],
              verdict_time='%s' % row[4],
          ))

    count = self.verdict_tbl.SelectValue(
        cnxn,
        col='COUNT(*)',
        where=[
            ('project_id = %s', [project_id]),
            (
                'classifier_confidence <= %s',
                [settings.classifier_moderation_thresh]),
            ('overruled = %s', [False]),
            ('comment_id IS NOT NULL', []),
        ])

    return ret, count


  def GetTrainingIssues(self, cnxn, issue_service, since, offset=0, limit=100):
    """Returns list of recent issues with human-labeled spam/ham verdicts.
    """

    # get all of the manual verdicts in the past day.
    results = self.verdict_tbl.Select(cnxn,
        cols=['issue_id'],
        where=[
            ('overruled = %s', [False]),
            ('reason = %s', ['manual']),
            ('issue_id IS NOT NULL', []),
            ('created > %s', [since.isoformat()]),
        ],
        offset=offset,
        limit=limit,
        )

    issue_ids = [int(row[0]) for row in results if row[0]]
    issues = issue_service.GetIssues(cnxn, issue_ids)
    comments = issue_service.GetCommentsForIssues(cnxn, issue_ids)
    first_comments = {}
    for issue in issues:
      first_comments[issue.issue_id] = (comments[issue.issue_id][0].content
          if issue.issue_id in comments else "[Empty]")

    count = self.verdict_tbl.SelectValue(cnxn,
        col='COUNT(*)',
        where=[
            ('overruled = %s', [False]),
            ('reason = %s', ['manual']),
            ('issue_id IS NOT NULL', []),
            ('created > %s', [since.isoformat()]),
        ])

    return issues, first_comments, count

  def GetTrainingComments(self, cnxn, issue_service, since, offset=0,
      limit=100):
    """Returns list of recent comments with human-labeled spam/ham verdicts.
    """

    # get all of the manual verdicts in the past day.
    results = self.verdict_tbl.Select(
        cnxn,
        distinct=True,
        cols=['comment_id'],
        where=[
            ('overruled = %s', [False]),
            ('reason = %s', ['manual']),
            ('comment_id IS NOT NULL', []),
            ('created > %s', [since.isoformat()]),
        ],
        offset=offset,
        limit=limit,
        )

    comment_ids = [int(row[0]) for row in results if row[0]]
    # Don't care about sequence numbers in this context yet.
    comments = issue_service.GetCommentsByID(cnxn, comment_ids,
        defaultdict(int))
    return comments

  def ExpungeUsersInSpam(self, cnxn, user_ids):
    """Removes all references to given users from Spam DB tables.

    This method will not commit the operations. This method will
    not make changes to in-memory data.
    """
    commit = False
    self.report_tbl.Delete(cnxn, reported_user_id=user_ids, commit=commit)
    self.report_tbl.Delete(cnxn, user_id=user_ids, commit=commit)
    self.verdict_tbl.Delete(cnxn, user_id=user_ids, commit=commit)


class ModerationItem:
  def __init__(self, **kwargs):
    self.__dict__ = kwargs