Module:Delink

-- This module de-links most wikitext.

p = {}

local function delinkReversePipeTrick(s)

   if mw.ustring.match(s, "^%[%[|.*[|\n]") then -- Check for newlines or multiple pipes.
       return s
   else
       return mw.ustring.match(s, "%[%[|(.*)%]%]")
   end

end

local function delinkPipeTrick(s)

   local linkarea, display = "", ""
   -- We need to deal with colons, brackets, and commas, per Help:Pipe trick.
   
   -- First, remove the text before the first colon, if any.
   if mw.ustring.match(s, ":") then
       s = mw.ustring.match(s, "%[%[.-:(.*)|%]%]")
   -- If there are no colons, grab all of the text apart from the square brackets and the pipe.
   else
       s = mw.ustring.match(s, "%[%[(.*)|%]%]")
   end
   
   -- Next up, brackets and commas.
   if mw.ustring.match(s, "%(.-%)$") then -- Brackets trump commas.
       s = mw.ustring.match(s, "(.-) ?%(.-%)$")
   elseif mw.ustring.match(s, ",") then -- If there are no brackets, display only the text before the first comma.
       s = mw.ustring.match(s, "(.-),.*$")
   end
   return s

end

local function delinkWikilink(s)

   local result = s
   -- Deal with the reverse pipe trick.
   if mw.ustring.match(result, "%[%[|") then
       return delinkReversePipeTrick(result)
   end
   
   result = mw.uri.decode(result, "PATH") -- decode percent-encoded entities. Leave underscores and plus signs.
   result = mw.text.decode(result, true) -- decode HTML entities.
   
   -- Check for bad titles. To do this we need to find the
   -- title area of the link, i.e. the part before any pipes.
   local titlearea
   if mw.ustring.match(result, "|") then -- Find if we're dealing with a piped link.
       titlearea = mw.ustring.match(result, "^%[%[(.-)|.*%]%]")
   else
       titlearea = mw.ustring.match(result, "^%[%[(.-)%]%]")
   end
   -- Check for bad characters.
   if mw.ustring.match(titlearea, "[%[%]<>{}%%?%c\n]") then
       return s
   end
   
   -- Check for categories, interwikis, and files.
   local colonprefix = mw.ustring.match(result, "%[%[(.-):.*%]%]") or "" -- Get the text before the first colon.
   local ns = mw.site.namespaces[colonprefix] -- see if this is a known namespace
   if mw.language.isKnownLanguageTag(colonprefix)
   or ( ns and ( ns.canonicalName == "File" or ns.canonicalName == "Category" ) ) then
       return ""
   end
   
   -- Remove the colon if the link is using the Help:Colon trick.
   if mw.ustring.match(result, "%[%[:") then
       result = "[[" .. mw.ustring.match(result, "%[%[:(.*%]%])")
   end
   
   -- Deal with links using the Help:Pipe trick.
   if mw.ustring.match(result, "^%[%[[^|]*|%]%]") then
       return delinkPipeTrick(result)
   end
   
   -- Find the display area of the wikilink
   if mw.ustring.match(result, "|") then -- Find if we're dealing with a piped link.
       result = mw.ustring.match(result, "^%[%[.-|(.+)%]%]")
       -- Remove new lines from the display of multiline piped links,
       -- where the pipe is before the first new line.
       result = mw.ustring.gsub(result, "\n", "")
   else
       result = mw.ustring.match(result, "^%[%[(.-)%]%]")
   end

   return result

end

local function delinkURL(s)

   -- Assume we have already delinked internal wikilinks, and that
   -- we have been passed some text between two square brackets [foo].
   
   -- If the text contains a line break it is not formatted as a URL, regardless of other content.
   if mw.ustring.match(s, "\n") then
       return s
   end
   
   -- Check if the text has a valid URL prefix and at least one valid URL character.
   local valid_url_prefixes = {"//", "http://", "https://", "ftp://", "gopher://", "mailto:", "news:", "irc://"} 
   local url_prefix
   for i,v in ipairs(valid_url_prefixes) do
       if mw.ustring.match(s, '^%[' .. v ..'[^"%s?].*%]' ) then
           url_prefix = v
           break
       end
   end
   
   -- Get display text
   if not url_prefix then
       return s
   end
   s = mw.ustring.match(s, "^%[" .. url_prefix .. "(.*)%]") -- Grab all of the text after the URL prefix and before the final square bracket.
   s = mw.ustring.match(s, '^.-(["<> ?].*)') or "" -- Grab all of the text after the first URL separator character ("<> ).
   s = mw.ustring.match(s, "^%s*(%S.*)$") or "" -- If the separating character was a space, trim it off.
   
   s_decoded = mw.text.decode(s, true)
   if mw.ustring.match(s_decoded, "%c") then
       return s
   else    
       return s_decoded
   end

end

local function delinkLinkClass(s, pattern, delinkFunction)

   if not type(s) == "string" then
       error("Attempt to de-link non-string input.", 2)
   end
   if not ( type(pattern) == "string" and mw.ustring.sub(pattern, 1, 1) == "^" ) then
       error('Invalid pattern detected. Patterns must begin with "^".', 2)
   end
   -- Iterate over the text string, and replace any matched text. using the 
   -- delink function. We need to iterate character by character rather 
   -- than just use gsub, otherwise nested links aren't detected properly.
   local result = ""
   while mw.ustring.len(s) > 0 do
       -- Replace text using one iteration of gsub.
       s = mw.ustring.gsub(s, pattern, delinkFunction, 1)
       -- Append the left-most character to the result string.
       result = result .. mw.ustring.sub(s, 1, 1)
       s = mw.ustring.sub(s, 2, -1)
   end
   return result

end

function p._delink(args)

   local text = args[1] or ""
   if args.refs == "yes" then
       -- Remove any Help:Strip markers representing ref tags. In most situations 
       -- this is not a good idea - only use it if you know what you are doing!
       text = mw.ustring.gsub(text, "?UNIQ%w*%-ref%-%d*%-QINU?", "")
   end
   if not (args.comments == "no") then
       text = mw.ustring.gsub(text, "<!%-%-.-%-%->", "") -- Remove html comments.
   end
   if not (args.wikilinks == "no") then
       text = delinkLinkClass(text, "^%[%[.-%]%]", delinkWikilink) -- De-link wikilinks.
   end
   if not (args.urls == "no") then
       text = delinkLinkClass(text, "^%[.-%]", delinkURL) -- De-link URLs.
   end
   if not (args.whitespace == "no") then
       -- Replace single new lines with a single space, but leave double new lines
       -- and new lines only containing spaces or tabs before a second new line.
       text = mw.ustring.gsub(text, "([^\n \t][ \t]*)\n([ \t]*[^\n \t])", "%1 %2")
       text = mw.ustring.gsub(text, "[ \t]+", " ") -- Remove extra tabs and spaces.
   end
   return text

end

function p.delink(frame)

   local args
   if frame == mw.getCurrentFrame() then
       -- We're being called via #invoke. If the invoking template passed any args, use
       -- them. Otherwise, use the args that were passed into the template.
       args = frame:getParent().args
       for k, v in pairs(frame.args) do
           args = frame.args
           break
       end
   else
       -- We're being called from another module or from the debug console, so assume
       -- the args are passed in directly.
       args = frame
   end
   return p._delink(args)

end

return p