Refactor formatter (#17828)

* Refactor formatter

* Move custom emoji pre-rendering logic to view helpers

* Move more methods out of Formatter

* Fix code style issues

* Remove Formatter

* Add inline poll options to RSS feeds

* Remove unused helper method

* Fix code style issues

* Various fixes and improvements

* Fix test

app/lib/emoji_formatter.rb

@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+class EmojiFormatter
+  include RoutingHelper
+
+  DISALLOWED_BOUNDING_REGEX = /[[:alnum:]:]/.freeze
+
+  attr_reader :html, :custom_emojis, :options
+
+  # @param [ActiveSupport::SafeBuffer] html
+  # @param [Array<CustomEmoji>] custom_emojis
+  # @param [Hash] options
+  # @option options [Boolean] :animate
+  def initialize(html, custom_emojis, options = {})
+    raise ArgumentError unless html.html_safe?
+
+    @html = html
+    @custom_emojis = custom_emojis
+    @options = options
+  end
+
+  def to_s
+    return html if custom_emojis.empty? || html.blank?
+
+    i                     = -1
+    tag_open_index        = nil
+    inside_shortname      = false
+    shortname_start_index = -1
+    invisible_depth       = 0
+    last_index            = 0
+    result                = ''.dup
+
+    while i + 1 < html.size
+      i += 1
+
+      if invisible_depth.zero? && inside_shortname && html[i] == ':'
+        inside_shortname = false
+        shortcode = html[shortname_start_index + 1..i - 1]
+        char_after = html[i + 1]
+
+        next unless (char_after.nil? || !DISALLOWED_BOUNDING_REGEX.match?(char_after)) && (emoji = emoji_map[shortcode])
+
+        result << html[last_index..shortname_start_index - 1] if shortname_start_index.positive?
+        result << image_for_emoji(shortcode, emoji)
+        last_index = i + 1
+      elsif tag_open_index && html[i] == '>'
+        tag = html[tag_open_index..i]
+        tag_open_index = nil
+
+        if invisible_depth.positive?
+          invisible_depth += count_tag_nesting(tag)
+        elsif tag == '<span class="invisible">'
+          invisible_depth = 1
+        end
+      elsif html[i] == '<'
+        tag_open_index = i
+        inside_shortname = false
+      elsif !tag_open_index && html[i] == ':' && (i.zero? || !DISALLOWED_BOUNDING_REGEX.match?(html[i - 1]))
+        inside_shortname = true
+        shortname_start_index = i
+      end
+    end
+
+    result << html[last_index..-1]
+
+    result.html_safe # rubocop:disable Rails/OutputSafety
+  end
+
+  private
+
+  def emoji_map
+    @emoji_map ||= custom_emojis.each_with_object({}) { |e, h| h[e.shortcode] = [full_asset_url(e.image.url), full_asset_url(e.image.url(:static))] }
+  end
+
+  def count_tag_nesting(tag)
+    if tag[1] == '/'
+      -1
+    elsif tag[-2] == '/'
+      0
+    else
+      1
+    end
+  end
+
+  def image_for_emoji(shortcode, emoji)
+    original_url, static_url = emoji
+
+    if animate?
+      image_tag(original_url, draggable: false, class: 'emojione', alt: ":#{shortcode}:", title: ":#{shortcode}:")
+    else
+      image_tag(original_url, draggable: false, class: 'emojione custom-emoji', alt: ":#{shortcode}:", title: ":#{shortcode}:", data: { original: original_url, static: static_url })
+    end
+  end
+
+  def animate?
+    @options[:animate]
+  end
+end