[Misc] External link favicons (now without a spritesheet) (#610)

* [Misc] Add favicons to some external links

* RuboCop changes from master

* Use packs for favicon images

This works better with caching.
If the file changes, the url changes

* Add favicons to an artists domain list

* Fix aliases

The lookup is done by strings, the keys were symbols

* Add old deviantart cdn alias

* Guard against links with that parse down to no host

http:twitter.com for example

* Tweak flow

* Add basic tests, fix some of what I probably broke

---------

Co-authored-by: Earlopain <14981592+Earlopain@users.noreply.github.com>

app/helpers/link_helper.rb

@@ -0,0 +1,173 @@
+# frozen_string_literal: true
+
+module LinkHelper
+  NONE = "empty"
+  DECORATABLE_DOMAINS = [
+    "e621.net",
+    #
+    # Aggregators
+    "linktr.ee",
+    "carrd.co",
+    #
+    # Art sites
+    "artfight.net",
+    "artstation.com",
+    "archiveofourown.com",
+    "aryion.com",
+    "derpibooru.org",
+    "deviantart.com",
+    "furaffinity.net",
+    "furrynetwork.com",
+    "furrystation.com",
+    "hentai-foundry.com",
+    "hiccears.com",
+    "imgur.com",
+    "inkbunny.net",
+    "itaku.ee",
+    "pillowfort.social",
+    "pixiv.net",
+    "skeb.jp",
+    "sofurry.com",
+    "toyhou.se",
+    "tumblr.com",
+    "newgrounds.com",
+    "weasyl.com",
+    "webtoons.com",
+    #
+    # Social media
+    "aethy.com",
+    "baraag.net",
+    "bsky.app",
+    "cohost.org",
+    "facebook.com",
+    "instagram.com",
+    "pawoo.net",
+    "plurk.com",
+    "privatter.net",
+    "reddit.com",
+    "tiktok.com",
+    "twitter.com",
+    "vk.com",
+    "weibo.com",
+    "youtube.com",
+    #
+    # Livestreams
+    "picarto.tv",
+    "piczel.tv",
+    "twitch.tv",
+    #
+    # Paysites
+    "artconomy.com",
+    "boosty.to",
+    "buymeacoffee.com",
+    "commishes.com",
+    "gumroad.com",
+    "etsy.com",
+    "fanbox.cc",
+    "itch.io",
+    "ko-fi.com",
+    "patreon.com",
+    "redbubble.com",
+    "subscribestar.adult",
+    #
+    # Bulk storage
+    "amazonaws.com",
+    "catbox.moe",
+    "drive.google.com",
+    "dropbox.com",
+    "mega.nz",
+    "onedrive.live.com",
+    #
+    # Imageboards
+    "4chan.org",
+    "danbooru.donmai.us",
+    "desuarchive.org",
+    "e-hentai.org",
+    "gelbooru.com",
+    "rule34.paheal.net",
+    "rule34.xxx",
+    "u18chan.com",
+    #
+    # Other
+    "curiouscat.me",
+    "discord.com",
+    "steamcommunity.com",
+    "t.me",
+    "trello.com",
+    "web.archive.org",
+  ].freeze
+
+  DECORATABLE_ALIASES = {
+    # alt names
+    "e926.net" => "e621.net",
+    "discord.gg" => "discord.com",
+    "pixiv.me" => "pixiv.net",
+    "x.com" => "twitter.com",
+
+    # same icon
+    "cloudfront.net" => "amazonaws.com",
+    "mastodon.art" => "baraag.net",
+    "meow.social" => "baraag.net",
+    "sta.sh" => "deviantart.com",
+
+    # image servers
+    "4cdn.org" => "4chan.org",
+    "discordapp.com" => "discord.com",
+    "derpicdn.net" => "derpibooru.org",
+    "deviantart.net" => "deviantart.com",
+    "dropboxusercontent.com" => "dropbox.com",
+    "facdn.net" => "furaffinity.net",
+    "fbcdn.net" => "facebook.com",
+    "ib.metapix.net" => "inkbunny.net",
+    "ngfiles.com" => "newgrounds.com",
+    "pximg.net" => "pixiv.net",
+    "redd.it" => "reddit.com",
+    "twimg.com" => "twitter.com",
+    "ungrounded.net" => "newgrounds.com",
+    "wixmp.com" => "deviantart.com",
+  }.freeze
+
+  def decorated_link_to(text, path, **)
+    link_to(path, class: "decorated", **) do
+      favicon_for_link(path) + text
+    end
+  end
+
+  def favicon_for_link(path)
+    hostname = hostname_for_link(path)
+    image_url = asset_pack_path("static/#{hostname}.png")
+    tag.span(
+      class: "link-decoration",
+      style: "background-image: url(#{image_url})",
+      data: {
+        hostname: hostname,
+      },
+    )
+  end
+
+  def hostname_for_link(path)
+    begin
+      uri = URI.parse(path)
+    rescue URI::InvalidURIError
+      return NONE
+    end
+    return NONE unless uri.host
+
+    hostname = uri.host.delete_prefix("www.")
+
+    # 1: direct match
+    return hostname if DECORATABLE_DOMAINS.include?(hostname)
+
+    # 2: aliases
+    return DECORATABLE_ALIASES[hostname] if DECORATABLE_ALIASES[hostname]
+
+    # 3: Try the same, this time with the leftmost subdomain removed
+    if hostname.count(".") > 1
+      _removed, remaining_hostname = hostname.split(".", 2)
+      return remaining_hostname if DECORATABLE_DOMAINS.include?(remaining_hostname)
+      return DECORATABLE_ALIASES[remaining_hostname] if DECORATABLE_ALIASES[remaining_hostname]
+    end
+
+    NONE
+  end
+end

app/helpers/posts_helper.rb

@@ -22,7 +22,7 @@ module PostsHelper
   def post_source_tag(source)
     # Only allow http:// and https:// links. Disallow javascript: links.
     if source =~ %r{\Ahttps?://}i
-      source_link = link_to(source.sub(%r{\Ahttps?://(?:www\.)?}i, ""), source, target: "_blank", rel: "nofollow noreferrer noopener")
+      source_link = decorated_link_to(source.sub(%r{\Ahttps?://(?:www\.)?}i, ""), source, target: "_blank", rel: "nofollow noreferrer noopener")
 
       if CurrentUser.is_janitor?
         source_link += " ".html_safe + link_to("»", posts_path(tags: "source:#{source.sub(%r{[^/]*$}, '')}"), rel: "nofollow")

app/javascript/packs/application.js

@@ -32,6 +32,8 @@ require('../src/styles/base.scss');
 
 importAll(require.context('../src/javascripts', true, /\.js(\.erb)?$/));
 
+require.context("../../../public/images/favicons", true)
+
 export { default as Artist } from '../src/javascripts/artist.js';
 export { default as Autocomplete } from '../src/javascripts/autocomplete.js.erb';
 export { default as Blacklist } from '../src/javascripts/blacklists.js';

app/javascript/src/styles/base.scss

@@ -19,6 +19,7 @@
 @import "common/forms.scss";
 @import "common/inline.scss";
 @import "common/jquery_ui_custom.scss";
+@import "common/link_decorator.scss";
 @import "common/main_layout.scss";
 @import "common/news.scss";
 @import "common/notices.scss";

app/javascript/src/styles/common/link_decorator.scss

@@ -0,0 +1,9 @@
+span.link-decoration {
+  vertical-align: sub;
+  display: inline-block;
+  width: 16px;
+  height: 16px;
+  margin-right: 4px; 
+  line-height: 0;
+  background-size: 16px 16px;
+}

app/views/artists/_summary.html.erb

@@ -19,7 +19,7 @@
     <li><strong>Domains</strong></li>
     <ul>
       <% artist.domains.each do |url, count| %>
-        <li><%= url %>: <%= count %></li>
+        <li><%= favicon_for_link("https://#{url}") %> <%= url %>: <%= count %></li>
       <% end %>
     </ul>
   <% end %>
@@ -29,7 +29,7 @@
       <% artist.sorted_urls.each do |url| %>
         <li>
           <% if url.is_active? %>
-            <%= link_to h(url.to_s), h(url) %>
+            <%= decorated_link_to(h(url.to_s), h(url)) %>
           <% else %>
             <del><%= h(url.url) %></del>
           <% end %>

test/helpers/link_helper_test.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class LinkHelperTest < ActionView::TestCase
+  test "for a non-handled url" do
+    assert_equal(LinkHelper::NONE, hostname_for_link("https://example.com"))
+  end
+
+  test "for a invalid url" do
+    assert_equal(LinkHelper::NONE, hostname_for_link("https:example.com"))
+  end
+
+  test "for a non-url" do
+    assert_equal(LinkHelper::NONE, hostname_for_link("text"))
+  end
+
+  test "for a normal domain" do
+    assert_equal("e621.net", hostname_for_link("https://e621.net"))
+    assert_equal("e621.net", hostname_for_link("https://www.e621.net"))
+
+    assert_equal("imgur.com", hostname_for_link("https://imgur.com"))
+    assert_equal("imgur.com", hostname_for_link("https://www.imgur.com"))
+  end
+
+  test "for a domain with aliases" do
+    assert_equal("discord.com", hostname_for_link("https://discordapp.com"))
+    assert_equal("furaffinity.net", hostname_for_link("https://d.facdn.net"))
+
+    assert_equal("inkbunny.net", hostname_for_link("https://ib.metapix.net"))
+    assert_equal("inkbunny.net", hostname_for_link("https://qb.ib.metapix.net"))
+  end
+
+  test "all listed images exist" do
+    favicon_folder = Rails.public_path.join("images/favicons")
+    all_domains = LinkHelper::DECORATABLE_DOMAINS + LinkHelper::DECORATABLE_ALIASES.values + [LinkHelper::NONE]
+    all_domains.each do |domain|
+      assert(favicon_folder.join("#{domain}.png").exist?, "missing #{domain}")
+    end
+    # No extraneous files
+    all_files = favicon_folder.children.map { |file| file.basename.to_s.delete_suffix(".png") }
+    assert_empty(all_files - all_domains, "unused files in favicon folder")
+  end
+end