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 reportmaster
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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