Add a spam check (#11217)
* Add a spam check * Use Nilsimsa to generate locality-sensitive hashes and compare using Levenshtein distance * Add more tests * Add exemption when the message is a reply to something that mentions the sender * Use Nilsimsa Compare Value instead of Levenshtein distance * Use MD5 for messages shorter than 10 characters * Add message to automated report, do not add non-public statuses to automated report, add trust level to accounts and make unsilencing raise the trust level to prevent repeated spam checks on that account * Expire spam check data after 3 months * Add support for local statuses, reduce expiration to 1 week, always create a report * Add content warnings to the spam check and exempt empty statuses * Change Nilsimsa threshold to 95 and make sure removed statuses are removed from the spam check * Add all matched statuses into automatic reportmain
Eugen Rochko
5 years ago
committed by
GitHub
parent
402302776c
commit
6ff67be0f6
@ -0,0 +1,169 @@
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# frozen_string_literal: true
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class SpamCheck
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include Redisable
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include ActionView::Helpers::TextHelper
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NILSIMSA_COMPARE_THRESHOLD = 95
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NILSIMSA_MIN_SIZE = 10
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EXPIRE_SET_AFTER = 1.week.seconds
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def initialize(status)
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@account = status.account
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@status = status
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end
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def skip?
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already_flagged? || trusted? || no_unsolicited_mentions? || solicited_reply?
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end
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def spam?
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if insufficient_data?
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false
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elsif nilsimsa?
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any_other_digest?('nilsimsa') { |_, other_digest| nilsimsa_compare_value(digest, other_digest) >= NILSIMSA_COMPARE_THRESHOLD }
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else
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any_other_digest?('md5') { |_, other_digest| other_digest == digest }
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end
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end
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def flag!
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auto_silence_account!
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auto_report_status!
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end
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def remember!
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# The scores in sorted sets don't actually have enough bits to hold an exact
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# value of our snowflake IDs, so we use it only for its ordering property. To
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# get the correct status ID back, we have to save it in the string value
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redis.zadd(redis_key, @status.id, digest_with_algorithm)
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redis.zremrangebyrank(redis_key, '0', '-10')
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redis.expire(redis_key, EXPIRE_SET_AFTER)
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end
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def reset!
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redis.del(redis_key)
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end
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def hashable_text
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return @hashable_text if defined?(@hashable_text)
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@hashable_text = @status.text
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@hashable_text = remove_mentions(@hashable_text)
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@hashable_text = strip_tags(@hashable_text) unless @status.local?
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@hashable_text = normalize_unicode(@status.spoiler_text + ' ' + @hashable_text)
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@hashable_text = remove_whitespace(@hashable_text)
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end
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def insufficient_data?
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hashable_text.blank?
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end
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def digest
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@digest ||= begin
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if nilsimsa?
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Nilsimsa.new(hashable_text).hexdigest
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else
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Digest::MD5.hexdigest(hashable_text)
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end
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end
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end
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def digest_with_algorithm
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if nilsimsa?
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['nilsimsa', digest, @status.id].join(':')
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else
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['md5', digest, @status.id].join(':')
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end
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end
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private
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def remove_mentions(text)
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return text.gsub(Account::MENTION_RE, '') if @status.local?
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Nokogiri::HTML.fragment(text).tap do |html|
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mentions = @status.mentions.map { |mention| ActivityPub::TagManager.instance.url_for(mention.account) }
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html.traverse do |element|
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element.unlink if element.name == 'a' && mentions.include?(element['href'])
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end
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end.to_s
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end
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def normalize_unicode(text)
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text.unicode_normalize(:nfkc).downcase
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end
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def remove_whitespace(text)
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text.gsub(/\s+/, ' ').strip
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end
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def auto_silence_account!
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@account.silence!
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end
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def auto_report_status!
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status_ids = Status.where(visibility: %i(public unlisted)).where(id: matching_status_ids).pluck(:id) + [@status.id] if @status.distributable?
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ReportService.new.call(Account.representative, @account, status_ids: status_ids, comment: I18n.t('spam_check.spam_detected_and_silenced'))
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end
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def already_flagged?
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@account.silenced?
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end
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def trusted?
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@account.trust_level > Account::TRUST_LEVELS[:untrusted]
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end
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def no_unsolicited_mentions?
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@status.mentions.all? { |mention| mention.silent? || (!@account.local? && !mention.account.local?) || mention.account.following?(@account) }
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end
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def solicited_reply?
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!@status.thread.nil? && @status.thread.mentions.where(account: @account).exists?
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end
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def nilsimsa_compare_value(first, second)
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first = [first].pack('H*')
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second = [second].pack('H*')
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bits = 0
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0.upto(31) do |i|
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bits += Nilsimsa::POPC[255 & (first[i].ord ^ second[i].ord)].ord
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end
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128 - bits # -128 <= Nilsimsa Compare Value <= 128
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end
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def nilsimsa?
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hashable_text.size > NILSIMSA_MIN_SIZE
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end
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def other_digests
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redis.zrange(redis_key, 0, -1)
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end
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def any_other_digest?(filter_algorithm)
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other_digests.any? do |record|
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algorithm, other_digest, status_id = record.split(':')
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next unless algorithm == filter_algorithm
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yield algorithm, other_digest, status_id
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end
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end
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def matching_status_ids
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if nilsimsa?
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other_digests.select { |record| record.start_with?('nilsimsa') && nilsimsa_compare_value(digest, record.split(':')[1]) >= NILSIMSA_COMPARE_THRESHOLD }.map { |record| record.split(':')[2] }.compact
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else
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other_digests.select { |record| record.start_with?('md5') && record.split(':')[1] == digest }.map { |record| record.split(':')[2] }.compact
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end
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end
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def redis_key
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@redis_key ||= "spam_check:#{@account.id}"
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end
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end
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@ -0,0 +1,5 @@
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class AddTrustLevelToAccounts < ActiveRecord::Migration[5.2]
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def change
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add_column :accounts, :trust_level, :integer
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end
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end
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@ -0,0 +1,160 @@
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require 'rails_helper'
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RSpec.describe SpamCheck do
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let!(:sender) { Fabricate(:account) }
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let!(:alice) { Fabricate(:account, username: 'alice') }
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let!(:bob) { Fabricate(:account, username: 'bob') }
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def status_with_html(text, options = {})
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status = PostStatusService.new.call(sender, { text: text }.merge(options))
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status.update_columns(text: Formatter.instance.format(status), local: false)
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status
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end
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describe '#hashable_text' do
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it 'removes mentions from HTML for remote statuses' do
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status = status_with_html('@alice Hello')
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expect(described_class.new(status).hashable_text).to eq 'hello'
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end
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it 'removes mentions from text for local statuses' do
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status = PostStatusService.new.call(alice, text: "Hey @#{sender.username}, how are you?")
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expect(described_class.new(status).hashable_text).to eq 'hey , how are you?'
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end
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end
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describe '#insufficient_data?' do
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it 'returns true when there is no text' do
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status = status_with_html('@alice')
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expect(described_class.new(status).insufficient_data?).to be true
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end
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it 'returns false when there is text' do
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status = status_with_html('@alice h')
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expect(described_class.new(status).insufficient_data?).to be false
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end
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end
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describe '#digest' do
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it 'returns a string' do
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status = status_with_html('@alice Hello world')
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expect(described_class.new(status).digest).to be_a String
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end
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end
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describe '#spam?' do
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it 'returns false for a unique status' do
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status = status_with_html('@alice Hello')
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expect(described_class.new(status).spam?).to be false
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end
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it 'returns false for different statuses to the same recipient' do
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status1 = status_with_html('@alice Hello')
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described_class.new(status1).remember!
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status2 = status_with_html('@alice Are you available to talk?')
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expect(described_class.new(status2).spam?).to be false
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end
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it 'returns false for statuses with different content warnings' do
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status1 = status_with_html('@alice Are you available to talk?')
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described_class.new(status1).remember!
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status2 = status_with_html('@alice Are you available to talk?', spoiler_text: 'This is a completely different matter than what I was talking about previously, I swear!')
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expect(described_class.new(status2).spam?).to be false
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end
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it 'returns false for different statuses to different recipients' do
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status1 = status_with_html('@alice How is it going?')
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described_class.new(status1).remember!
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status2 = status_with_html('@bob Are you okay?')
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expect(described_class.new(status2).spam?).to be false
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end
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it 'returns false for very short different statuses to different recipients' do
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status1 = status_with_html('@alice 🙄')
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described_class.new(status1).remember!
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status2 = status_with_html('@bob Huh?')
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expect(described_class.new(status2).spam?).to be false
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end
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it 'returns false for statuses with no text' do
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status1 = status_with_html('@alice')
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described_class.new(status1).remember!
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status2 = status_with_html('@bob')
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expect(described_class.new(status2).spam?).to be false
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end
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it 'returns true for duplicate statuses to the same recipient' do
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status1 = status_with_html('@alice Hello')
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described_class.new(status1).remember!
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status2 = status_with_html('@alice Hello')
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expect(described_class.new(status2).spam?).to be true
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end
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it 'returns true for duplicate statuses to different recipients' do
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status1 = status_with_html('@alice Hello')
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described_class.new(status1).remember!
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status2 = status_with_html('@bob Hello')
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expect(described_class.new(status2).spam?).to be true
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end
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it 'returns true for nearly identical statuses with random numbers' do
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source_text = 'Sodium, atomic number 11, was first isolated by Humphry Davy in 1807. A chemical component of salt, he named it Na in honor of the saltiest region on earth, North America.'
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status1 = status_with_html('@alice ' + source_text + ' 1234')
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described_class.new(status1).remember!
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status2 = status_with_html('@bob ' + source_text + ' 9568')
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expect(described_class.new(status2).spam?).to be true
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end
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end
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describe '#skip?' do
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it 'returns true when the sender is already silenced' do
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status = status_with_html('@alice Hello')
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sender.silence!
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expect(described_class.new(status).skip?).to be true
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end
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it 'returns true when the mentioned person follows the sender' do
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status = status_with_html('@alice Hello')
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alice.follow!(sender)
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expect(described_class.new(status).skip?).to be true
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end
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it 'returns false when even one mentioned person doesn\'t follow the sender' do
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status = status_with_html('@alice @bob Hello')
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alice.follow!(sender)
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expect(described_class.new(status).skip?).to be false
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end
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it 'returns true when the sender is replying to a status that mentions the sender' do
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parent = PostStatusService.new.call(alice, text: "Hey @#{sender.username}, how are you?")
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status = status_with_html('@alice @bob Hello', thread: parent)
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expect(described_class.new(status).skip?).to be true
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end
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end
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describe '#remember!' do
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pending
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end
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describe '#flag!' do
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let!(:status1) { status_with_html('@alice General Kenobi you are a bold one') }
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let!(:status2) { status_with_html('@alice @bob General Kenobi, you are a bold one') }
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before do
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described_class.new(status1).remember!
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described_class.new(status2).flag!
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end
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it 'silences the account' do
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expect(sender.silenced?).to be true
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end
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it 'creates a report about the account' do
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expect(sender.targeted_reports.unresolved.count).to eq 1
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end
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it 'attaches both matching statuses to the report' do
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expect(sender.targeted_reports.first.status_ids).to include(status1.id, status2.id)
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end
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end
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end
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