DEV: Improve mbox import script

* Customizable email subject prefixes to remove "Re" and "Fwd" as well as localized prefixes.
* Configuration option for prefixes like [FOO] or (BAR) which can be replaced with tags during import.
* Bugfix: Import script might have skipped some users due to missing ORDER BY.

script/import_scripts/mbox/importer.rb

@@ -30,6 +30,8 @@ module ImportScripts::Mbox
       if @settings.index_only
         @skip_updates = true
       else
+        SiteSetting.tagging_enabled = true if @settings.tags.present?
+
         import_categories
         import_users
         import_posts
@@ -142,9 +144,13 @@ module ImportScripts::Mbox
     end
 
     def map_first_post(row)
+      subject = row['subject']
+      tags = remove_tags!(subject)
+
       mapped = map_post(row)
       mapped[:category] = category_id_from_imported_category_id(row['category'])
-      mapped[:title] = row['subject'].strip[0...255]
+      mapped[:title] = subject.strip[0...255]
+      mapped[:tags] = tags if tags.present?
       mapped
     end
 
@@ -161,6 +167,37 @@ module ImportScripts::Mbox
       mapped
     end
 
+    def remove_tags!(subject)
+      tag_names = []
+      remove_prefixes!(subject)
+
+      loop do
+        old_length = subject.length
+
+        @settings.tags.each do |tag|
+          if subject.sub!(tag[:regex], "") && tag[:name].present?
+            tag_names << tag[:name]
+          end
+        end
+
+        remove_prefixes!(subject) if subject.length != old_length
+        break if subject.length == old_length
+      end
+
+      tag_names.uniq
+    end
+
+    def remove_prefixes!(subject)
+      # There could be multiple prefixes...
+      loop do
+        if subject.sub!(@settings.subject_prefix_regex, "")
+          subject.strip!
+        else
+          break
+        end
+      end
+    end
+
     def create_incoming_email(post, row)
       IncomingEmail.create(
         message_id: row['msg_id'],

script/import_scripts/mbox/settings.yml

@@ -16,3 +16,20 @@ staged: true
 index_only: false
 
 group_messages_by_subject: false
+
+# Remove prefixes like [FOO] or (BAR) from topic titles and replace them with tags.
+# You can map one or more case-insensitive prefixes to the same tag in Discourse.
+# "Tag name in Discourse": "foo"
+# "Tag name in Discourse": ["foo", "bar"]
+# You can use an empty tag name to remove prefixes without creating a tag in Discourse.
+tags:
+#  "off-topic": "ot"
+#  announcement: ["ann", "announce", "announcement"]
+#  "": ["foo", "bar"]
+
+# These prefixes will be removed from the beginning of topic titles. You can use regular expessions.
+# Prefixes are case-insensitive. You can add additional prefixes (e.g. localized prefixes from
+# https://en.wikipedia.org/wiki/List_of_email_subject_abbreviations#Abbreviations_in_other_languages).
+remove_subject_prefixes:
+  - "Re: "
+  - "Fwd?: "

script/import_scripts/mbox/support/database.rb

@@ -168,6 +168,7 @@ module ImportScripts::Mbox
         SELECT email, name, date_of_first_message
         FROM user
         WHERE email > :last_email
+        ORDER BY email
         LIMIT #{@batch_size}
       SQL
 

script/import_scripts/mbox/support/indexer.rb

@@ -204,37 +204,7 @@ module ImportScripts::Mbox
 
     def extract_subject(receiver, list_name)
       subject = receiver.subject
-      return nil if subject.blank?
-
-      # TODO: make the list name (or maybe multiple names) configurable
-      # Strip mailing list name from subject
-      subject = subject.gsub(/\[#{Regexp.escape(list_name)}\]/i, '').strip
-
-      clean_subject(subject)
-    end
-
-    # TODO: refactor and move prefixes to settings
-    def clean_subject(subject)
-      original_length = subject.length
-
-      # Strip Reply prefix from title (Standard and localized)
-      subject = subject.gsub(/^Re: */i, '')
-      subject = subject.gsub(/^R: */i, '') #Italian
-      subject = subject.gsub(/^RIF: */i, '') #Italian
-
-      # Strip Forward prefix from title (Standard and localized)
-      subject = subject.gsub(/^Fwd: */i, '')
-      subject = subject.gsub(/^I: */i, '') #Italian
-
-      subject.strip
-
-      # In case of mixed localized prefixes there could be many of them
-      # if the mail client didn't strip the localized ones
-      if original_length > subject.length
-        clean_subject(subject)
-      else
-        subject
-      end
+      subject.blank? ? nil : subject.strip
     end
 
     def ignored_file?(path, checksums)

script/import_scripts/mbox/support/settings.rb

@@ -17,6 +17,9 @@ module ImportScripts::Mbox
     attr_reader :staged
     attr_reader :index_only
     attr_reader :group_messages_by_subject
+    attr_reader :subject_prefix_regex
+    attr_reader :automatically_remove_list_name_prefix
+    attr_reader :tags
 
     def initialize(yaml)
       @data_dir = yaml['data_dir']
@@ -27,6 +30,22 @@ module ImportScripts::Mbox
       @staged = yaml['staged']
       @index_only = yaml['index_only']
       @group_messages_by_subject = yaml['group_messages_by_subject']
+
+      unless yaml['remove_subject_prefixes'].empty?
+        prefix_regexes = yaml['remove_subject_prefixes'].map { |p| Regexp.new(p) }
+        @subject_prefix_regex = /^#{Regexp.union(prefix_regexes).source}/i
+      end
+
+      @automatically_remove_list_name_prefix = yaml['automatically_remove_list_name_prefix']
+
+      @tags = []
+      yaml['tags'].each do |tag_name, value|
+        prefixes = Regexp.union(value).source
+        @tags << {
+          regex: /^(?:(?:\[(?:#{prefixes})\])|(?:\((?:#{prefixes})\)))\s*/i,
+          name: tag_name
+        }
+      end
     end
   end
 end