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/message_mover.rb

@@ -0,0 +1,172 @@
+# frozen_string_literal: true
+
+##
+# Used to move chat messages from a chat channel to some other
+# location.
+#
+# Channel -> Channel:
+# -------------------
+#
+# Messages are sometimes misplaced and must be moved to another channel. For
+# now we only support moving messages between public channels, handling the
+# permissions and membership around moving things in and out of DMs is a little
+# much for V1.
+#
+# The original messages will be deleted, and then similar to PostMover in core,
+# all of the references associated to a chat message (e.g. reactions, bookmarks,
+# notifications, revisions, mentions, uploads) will be updated to the new
+# message IDs via a moved_chat_messages temporary table.
+class Chat::MessageMover
+  class NoMessagesFound < StandardError
+  end
+  class InvalidChannel < StandardError
+  end
+
+  def initialize(acting_user:, source_channel:, message_ids:)
+    @source_channel = source_channel
+    @acting_user = acting_user
+    @source_message_ids = message_ids
+    @source_messages = find_messages(@source_message_ids, source_channel)
+    @ordered_source_message_ids = @source_messages.map(&:id)
+  end
+
+  def move_to_channel(destination_channel)
+    if !@source_channel.public_channel? || !destination_channel.public_channel?
+      raise InvalidChannel.new(I18n.t("chat.errors.message_move_invalid_channel"))
+    end
+
+    if @ordered_source_message_ids.empty?
+      raise NoMessagesFound.new(I18n.t("chat.errors.message_move_no_messages_found"))
+    end
+
+    moved_messages = nil
+
+    ChatMessage.transaction do
+      create_temp_table
+      moved_messages =
+        find_messages(
+          create_destination_messages_in_channel(destination_channel),
+          destination_channel,
+        )
+      bulk_insert_movement_metadata
+      update_references
+      delete_source_messages
+    end
+
+    add_moved_placeholder(destination_channel, moved_messages.first)
+    moved_messages
+  end
+
+  private
+
+  def find_messages(message_ids, channel)
+    ChatMessage.where(id: message_ids, chat_channel_id: channel.id).order("created_at ASC, id ASC")
+  end
+
+  def create_temp_table
+    DB.exec("DROP TABLE IF EXISTS moved_chat_messages") if Rails.env.test?
+
+    DB.exec <<~SQL
+      CREATE TEMPORARY TABLE moved_chat_messages (
+        old_chat_message_id INTEGER,
+        new_chat_message_id INTEGER
+      ) ON COMMIT DROP;
+
+      CREATE INDEX moved_chat_messages_old_chat_message_id ON moved_chat_messages(old_chat_message_id);
+    SQL
+  end
+
+  def bulk_insert_movement_metadata
+    values_sql = @movement_metadata.map { |mm| "(#{mm[:old_id]}, #{mm[:new_id]})" }.join(",\n")
+    DB.exec(
+      "INSERT INTO moved_chat_messages(old_chat_message_id, new_chat_message_id) VALUES #{values_sql}",
+    )
+  end
+
+  ##
+  # We purposefully omit in_reply_to_id when creating the messages in the
+  # new channel, because it could be pointing to a message that has not
+  # been moved.
+  def create_destination_messages_in_channel(destination_channel)
+    query_args = {
+      message_ids: @ordered_source_message_ids,
+      destination_channel_id: destination_channel.id,
+    }
+    moved_message_ids = DB.query_single(<<~SQL, query_args)
+      INSERT INTO chat_messages(chat_channel_id, user_id, message, cooked, cooked_version, created_at, updated_at)
+      SELECT :destination_channel_id,
+             user_id,
+             message,
+             cooked,
+             cooked_version,
+             CLOCK_TIMESTAMP(),
+             CLOCK_TIMESTAMP()
+      FROM chat_messages
+      WHERE id IN (:message_ids)
+      RETURNING id
+    SQL
+
+    @movement_metadata =
+      moved_message_ids.map.with_index do |chat_message_id, idx|
+        { old_id: @ordered_source_message_ids[idx], new_id: chat_message_id }
+      end
+    moved_message_ids
+  end
+
+  def update_references
+    DB.exec(<<~SQL)
+      UPDATE chat_message_reactions cmr
+      SET chat_message_id = mm.new_chat_message_id
+      FROM moved_chat_messages mm
+      WHERE cmr.chat_message_id = mm.old_chat_message_id
+    SQL
+
+    DB.exec(<<~SQL)
+      UPDATE chat_uploads cu
+      SET chat_message_id = mm.new_chat_message_id
+      FROM moved_chat_messages mm
+      WHERE cu.chat_message_id = mm.old_chat_message_id
+    SQL
+
+    DB.exec(<<~SQL)
+      UPDATE chat_mentions cment
+      SET chat_message_id = mm.new_chat_message_id
+      FROM moved_chat_messages mm
+      WHERE cment.chat_message_id = mm.old_chat_message_id
+    SQL
+
+    DB.exec(<<~SQL)
+      UPDATE chat_message_revisions crev
+      SET chat_message_id = mm.new_chat_message_id
+      FROM moved_chat_messages mm
+      WHERE crev.chat_message_id = mm.old_chat_message_id
+    SQL
+
+    DB.exec(<<~SQL)
+      UPDATE chat_webhook_events cweb
+      SET chat_message_id = mm.new_chat_message_id
+      FROM moved_chat_messages mm
+      WHERE cweb.chat_message_id = mm.old_chat_message_id
+    SQL
+  end
+
+  def delete_source_messages
+    @source_messages.update_all(deleted_at: Time.zone.now, deleted_by_id: @acting_user.id)
+    ChatPublisher.publish_bulk_delete!(@source_channel, @source_message_ids)
+  end
+
+  def add_moved_placeholder(destination_channel, first_moved_message)
+    Chat::ChatMessageCreator.create(
+      chat_channel: @source_channel,
+      user: Discourse.system_user,
+      content:
+        I18n.t(
+          "chat.channel.messages_moved",
+          count: @source_message_ids.length,
+          acting_username: @acting_user.username,
+          channel_name: destination_channel.title(@acting_user),
+          first_moved_message_url: first_moved_message.url,
+        ),
+    )
+  end
+end