DEV: Move discourse-chat to the core repo. (#18776)

As part of this move, we are also renaming `discourse-chat` to `chat`.

plugins/chat/lib/chat_transcript_service.rb

@@ -0,0 +1,177 @@
+# frozen_string_literal: true
+
+##
+# Used to generate BBCode [chat] tags for the message IDs provided.
+#
+# If there is > 1 message then the channel name will be shown at
+# the top of the first message, and subsequent messages will have
+# the chained attribute, which will affect how they are displayed
+# in the UI.
+#
+# Subsequent messages from the same user will be put into the same
+# tag. Each new user in the chain of messages will have a new [chat]
+# tag created.
+#
+# A single message will have the channel name displayed to the right
+# of the username and datetime of the message.
+class ChatTranscriptService
+  CHAINED_ATTR = "chained=\"true\""
+  MULTIQUOTE_ATTR = "multiQuote=\"true\""
+  NO_LINK_ATTR = "noLink=\"true\""
+
+  class ChatTranscriptBBCode
+    attr_reader :channel, :multiquote, :chained, :no_link, :include_reactions
+
+    def initialize(
+      channel: nil,
+      acting_user: nil,
+      multiquote: false,
+      chained: false,
+      no_link: false,
+      include_reactions: false
+    )
+      @channel = channel
+      @acting_user = acting_user
+      @multiquote = multiquote
+      @chained = chained
+      @no_link = no_link
+      @include_reactions = include_reactions
+      @message_data = []
+    end
+
+    def add(message:, reactions: nil)
+      @message_data << { message: message, reactions: reactions }
+    end
+
+    def render
+      attrs = [quote_attr(@message_data.first[:message])]
+
+      if channel
+        attrs << channel_attr
+        attrs << channel_id_attr
+      end
+
+      attrs << MULTIQUOTE_ATTR if multiquote
+      attrs << CHAINED_ATTR if chained
+      attrs << NO_LINK_ATTR if no_link
+      attrs << reactions_attr if include_reactions
+
+      <<~MARKDOWN
+      [chat #{attrs.compact.join(" ")}]
+      #{@message_data.map { |msg| msg[:message].to_markdown }.join("\n\n")}
+      [/chat]
+      MARKDOWN
+    end
+
+    private
+
+    def reactions_attr
+      reaction_data =
+        @message_data.reduce([]) do |array, msg_data|
+          if msg_data[:reactions].any?
+            array << msg_data[:reactions].map { |react| "#{react.emoji}:#{react.usernames}" }
+          end
+          array
+        end
+      return if reaction_data.empty?
+      "reactions=\"#{reaction_data.join(";")}\""
+    end
+
+    def quote_attr(message)
+      "quote=\"#{message.user.username};#{message.id};#{message.created_at.iso8601}\""
+    end
+
+    def channel_attr
+      "channel=\"#{channel.title(@acting_user)}\""
+    end
+
+    def channel_id_attr
+      "channelId=\"#{channel.id}\""
+    end
+  end
+
+  def initialize(channel, acting_user, messages_or_ids: [], opts: {})
+    @channel = channel
+    @acting_user = acting_user
+
+    if messages_or_ids.all? { |m| m.is_a?(Numeric) }
+      @message_ids = messages_or_ids
+    else
+      @messages = messages_or_ids
+    end
+    @opts = opts
+  end
+
+  def generate_markdown
+    previous_message = nil
+    rendered_markdown = []
+    all_messages_same_user = messages.count(:user_id) == 1
+    open_bbcode_tag =
+      ChatTranscriptBBCode.new(
+        channel: @channel,
+        acting_user: @acting_user,
+        multiquote: messages.length > 1,
+        chained: !all_messages_same_user,
+        no_link: @opts[:no_link],
+        include_reactions: @opts[:include_reactions],
+      )
+
+    messages.each.with_index do |message, idx|
+      if previous_message.present? && previous_message.user_id != message.user_id
+        rendered_markdown << open_bbcode_tag.render
+
+        open_bbcode_tag =
+          ChatTranscriptBBCode.new(
+            acting_user: @acting_user,
+            chained: !all_messages_same_user,
+            no_link: @opts[:no_link],
+            include_reactions: @opts[:include_reactions],
+          )
+      end
+
+      if @opts[:include_reactions]
+        open_bbcode_tag.add(message: message, reactions: reactions_for_message(message))
+      else
+        open_bbcode_tag.add(message: message)
+      end
+      previous_message = message
+    end
+
+    # tie off the last open bbcode + render
+    rendered_markdown << open_bbcode_tag.render
+    rendered_markdown.join("\n")
+  end
+
+  private
+
+  def messages
+    @messages ||=
+      ChatMessage
+        .includes(:user, chat_uploads: :upload)
+        .where(id: @message_ids, chat_channel_id: @channel.id)
+        .order(:created_at)
+  end
+
+  ##
+  # Queries reactions and returns them in this format
+  #
+  # emoji   |  usernames  |  chat_message_id
+  # ----------------------------------------
+  # +1      | foo,bar,baz | 102
+  # heart   | foo         | 102
+  # sob     | bar,baz     | 103
+  def reactions
+    @reactions ||= DB.query(<<~SQL, @messages.map(&:id))
+    SELECT emoji, STRING_AGG(DISTINCT users.username, ',') AS usernames, chat_message_id
+    FROM chat_message_reactions
+    INNER JOIN users on users.id = chat_message_reactions.user_id
+    WHERE chat_message_id IN (?)
+    GROUP BY emoji, chat_message_id
+    ORDER BY chat_message_id, emoji
+    SQL
+  end
+
+  def reactions_for_message(message)
+    reactions.select { |react| react.chat_message_id == message.id }
+  end
+end