FIX: BBCode to Markdown conversion in phpBB3 importer was broken

This fixes the conversion for quotes, code blocks and lists (except for nested lists). It also discourages the usage of the ruby-bbcode-to-md gem.

script/import_scripts/phpbb3/support/text_processor.rb

@@ -27,6 +27,7 @@ module ImportScripts::PhpBB3
       process_links(text)
       process_lists(text)
       process_code(text)
+      fix_markdown(text)
       text
     end
 
@@ -114,11 +115,13 @@ module ImportScripts::PhpBB3
       # convert list tags to ul and list=1 tags to ol
       # list=a is not supported, so handle it like list=1
       # list=9 and list=x have the same result as list=1 and list=a
-      text.gsub!(/\[list\](.*?)\[\/list:u\]/mi, '[ul]\1[/ul]')
-      text.gsub!(/\[list=.*?\](.*?)\[\/list:o\]/mi, '[ol]\1[/ol]')
+      text.gsub!(/\[list\](.*?)\[\/list:u\]/mi) do
+        $1.gsub(/\[\*\](.*?)\[\/\*:m\]\n*/mi) { "* #{$1}\n" }
+      end
 
-      # convert *-tags to li-tags so bbcode-to-md can do its magic on phpBB's lists:
-      text.gsub!(/\[\*\](.*?)\[\/\*:m\]/mi, '[li]\1[/li]')
+      text.gsub!(/\[list=.*?\](.*?)\[\/list:o\]/mi) do
+        $1.gsub(/\[\*\](.*?)\[\/\*:m\]\n*/mi) { "1. #{$1}\n" }
+      end
     end
 
     # This replaces existing [attachment] BBCodes with the corresponding HTML tags for Discourse.
@@ -149,9 +152,14 @@ module ImportScripts::PhpBB3
 
     def process_code(text)
       text.gsub!(/<span class="syntax.*?>(.*?)<\/span>/) { "#{$1}" }
-      text.gsub!(/\[code(=[a-z]*)?\](.*?)\[\/code\]/i) { "[code]#{@he.decode($2)}[/code]" }
+      text.gsub!(/\[code(=[a-z]*)?\](.*?)\[\/code\]/i) { "[code]\n#{@he.decode($2)}\n[/code]" }
       text.gsub!(/<br \/>/, "\n")
       text
     end
+
+    def fix_markdown(text)
+      text.gsub!(/(\n*\[\/?quote.*?\]\n*)/mi) { |q| "\n#{q.strip}\n" }
+      text
+    end
   end
 end