about summary refs log tree commit diff
path: root/app/services/fetch_link_card_service.rb
blob: 640c60fd473efc1c4314fe2b1bcc842b82a63abe (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
# frozen_string_literal: true

class FetchLinkCardService < BaseService
  URL_PATTERN = %r{
    (                                                                                                 #   $1 URL
      (https?:\/\/)                                                                                   #   $2 Protocol (required)
      (#{Twitter::Regex[:valid_domain]})                                                              #   $3 Domain(s)
      (?::(#{Twitter::Regex[:valid_port_number]}))?                                                   #   $4 Port number (optional)
      (/#{Twitter::Regex[:valid_url_path]}*)?                                                         #   $5 URL Path and anchor
      (\?#{Twitter::Regex[:valid_url_query_chars]}*#{Twitter::Regex[:valid_url_query_ending_chars]})? #   $6 Query String
    )
  }iox

  def call(status)
    @status = status
    @url    = parse_urls

    return if @url.nil? || @status.preview_cards.any?

    @url = @url.to_s

    RedisLock.acquire(lock_options) do |lock|
      if lock.acquired?
        @card = PreviewCard.find_by(url: @url)
        process_url if @card.nil? || @card.updated_at <= 2.weeks.ago || @card.missing_image?
      else
        raise Mastodon::RaceConditionError
      end
    end

    attach_card if @card&.persisted?
  rescue HTTP::Error, OpenSSL::SSL::SSLError, Addressable::URI::InvalidURIError, Mastodon::HostValidationError, Mastodon::LengthValidationError => e
    Rails.logger.debug "Error fetching link #{@url}: #{e}"
    nil
  end

  private

  def process_url
    @card ||= PreviewCard.new(url: @url)

    Request.new(:get, @url).perform do |res|
      if res.code == 200 && res.mime_type == 'text/html'
        @html = res.body_with_limit
        @html_charset = res.charset
      else
        @html = nil
        @html_charset = nil
      end
    end

    return if @html.nil?

    attempt_oembed || attempt_opengraph
  end

  def attach_card
    @status.preview_cards << @card
    Rails.cache.delete(@status)
  end

  def parse_urls
    if @status.local?
      urls = @status.text.scan(URL_PATTERN).map { |array| Addressable::URI.parse(array[0]).normalize }
    else
      html  = Nokogiri::HTML(@status.text)
      links = html.css('a')
      urls  = links.map { |a| Addressable::URI.parse(a['href']).normalize unless skip_link?(a) }.compact
    end

    urls.reject { |uri| bad_url?(uri) }.first
  end

  def bad_url?(uri)
    # Avoid local instance URLs and invalid URLs
    uri.host.blank? || TagManager.instance.local_url?(uri.to_s) || !%w(http https).include?(uri.scheme)
  end

  def mention_link?(a)
    @status.mentions.any? do |mention|
      a['href'] == ActivityPub::TagManager.instance.url_for(mention.account)
    end
  end

  def skip_link?(a)
    # Avoid links for hashtags and mentions (microformats)
    a['rel']&.include?('tag') || a['class']&.match?(/u-url|h-card/) || mention_link?(a)
  end

  def attempt_oembed
    service = FetchOEmbedService.new
    embed   = service.call(@url, html: @html)
    url     = Addressable::URI.parse(service.endpoint_url)

    return false if embed.nil?

    @card.type          = embed[:type]
    @card.title         = embed[:title]         || ''
    @card.author_name   = embed[:author_name]   || ''
    @card.author_url    = embed[:author_url].present? ? (url + embed[:author_url]).to_s : ''
    @card.provider_name = embed[:provider_name] || ''
    @card.provider_url  = embed[:provider_url].present? ? (url + embed[:provider_url]).to_s : ''
    @card.width         = 0
    @card.height        = 0

    case @card.type
    when 'link'
      @card.image_remote_url = (url + embed[:thumbnail_url]).to_s if embed[:thumbnail_url].present?
    when 'photo'
      return false if embed[:url].blank?

      @card.embed_url        = (url + embed[:url]).to_s
      @card.image_remote_url = (url + embed[:url]).to_s
      @card.width            = embed[:width].presence  || 0
      @card.height           = embed[:height].presence || 0
    when 'video'
      @card.width            = embed[:width].presence  || 0
      @card.height           = embed[:height].presence || 0
      @card.html             = Formatter.instance.sanitize(embed[:html], Sanitize::Config::MASTODON_OEMBED)
      @card.image_remote_url = (url + embed[:thumbnail_url]).to_s if embed[:thumbnail_url].present?
    when 'rich'
      # Most providers rely on <script> tags, which is a no-no
      return false
    end

    @card.save_with_optional_image!
  end

  def attempt_opengraph
    detector = CharlockHolmes::EncodingDetector.new
    detector.strip_tags = true

    guess      = detector.detect(@html, @html_charset)
    encoding   = guess&.fetch(:confidence, 0).to_i > 60 ? guess&.fetch(:encoding, nil) : nil
    page       = Nokogiri::HTML(@html, nil, encoding)
    player_url = meta_property(page, 'twitter:player')

    if player_url && !bad_url?(Addressable::URI.parse(player_url))
      @card.type   = :video
      @card.width  = meta_property(page, 'twitter:player:width') || 0
      @card.height = meta_property(page, 'twitter:player:height') || 0
      @card.html   = content_tag(:iframe, nil, src: player_url,
                                               width: @card.width,
                                               height: @card.height,
                                               allowtransparency: 'true',
                                               scrolling: 'no',
                                               frameborder: '0')
    else
      @card.type = :link
    end

    @card.title            = meta_property(page, 'og:title').presence || page.at_xpath('//title')&.content || ''
    @card.description      = meta_property(page, 'og:description').presence || meta_property(page, 'description') || ''
    @card.image_remote_url = (Addressable::URI.parse(@url) + meta_property(page, 'og:image')).to_s if meta_property(page, 'og:image')

    return if @card.title.blank? && @card.html.blank?

    @card.save_with_optional_image!
  end

  def meta_property(page, property)
    page.at_xpath("//meta[contains(concat(' ', normalize-space(@property), ' '), ' #{property} ')]")&.attribute('content')&.value || page.at_xpath("//meta[@name=\"#{property}\"]")&.attribute('content')&.value
  end

  def lock_options
    { redis: Redis.current, key: "fetch:#{@url}" }
  end
end