Module:Check for unknown parameters

-- This module may be used to compare the arguments passed to the parent
-- with a list of arguments, returning a specified result if an argument is
-- not on the list
local p = {}

local function trim(s)
 return s:match('^%s*(.-)%s*$')
end

local function isnotempty(s)
 return s and s:match('%S')
end

local function clean(text)
 -- Return text cleaned for display and truncated if too long.
 -- Strip markers are replaced with dummy text representing the original wikitext.
 local pos, truncated
 local function truncate(text)
  if truncated then
   return ''
  end
  if mw.ustring.len(text) > 25 then
   truncated = true
   text = mw.ustring.sub(text, 1, 25) .. '...'
  end
  return mw.text.nowiki(text)
 end
 local parts = {}
 for before, tag, remainder in text:gmatch('([^\127]*)\127[^\127]*%-(%l+)%-[^\127]*\127()') do
  pos = remainder
  table.insert(parts, truncate(before) .. '<' .. tag .. '>...</' .. tag .. '>')
 end
 table.insert(parts, truncate(text:sub(pos or 1)))
 return table.concat(parts)
end

function p._check(args, pargs)
 if type(args) ~= "table" or type(pargs) ~= "table" then
  -- TODO: error handling
  return
 end

 -- create the list of known args, regular expressions, and the return string
 local knownargs = {}
 local regexps = {}
 for k, v in pairs(args) do
  if type(k) == 'number' then
   v = trim(v)
   knownargs[v] = 1
  elseif k:find('^regexp[1-9][0-9]*$') then
   table.insert(regexps, '^' .. v .. '$')
  end
 end

 -- loop over the parent args, and make sure they are on the list
 local ignoreblank = isnotempty(args['ignoreblank'])
 local showblankpos = isnotempty(args['showblankpositional'])
 local values = {}
 for k, v in pairs(pargs) do
  if type(k) == 'string' and knownargs[k] == nil then
   local knownflag = false
   for _, regexp in ipairs(regexps) do
    if mw.ustring.match(k, regexp) then
     knownflag = true
     break
    end
   end
   if not knownflag and ( not ignoreblank or isnotempty(v) )  then
    table.insert(values, clean(k))
   end
  elseif type(k) == 'number' and knownargs[tostring(k)] == nil then
   local knownflag = false
   for _, regexp in ipairs(regexps) do
    if mw.ustring.match(tostring(k), regexp) then
     knownflag = true
     break
    end
   end
   if not knownflag and ( showblankpos or isnotempty(v) ) then
    table.insert(values, k .. ' = ' .. clean(v))
   end
  end
 end

 -- add results to the output tables
 local res = {}
 if #values > 0 then
  local unknown_text = args['unknown'] or 'Found _VALUE_, '

  if mw.getCurrentFrame():preprocess( "{{REVISIONID}}" ) == "" then
   local preview_text = args['preview']
   if isnotempty(preview_text) then
    preview_text = require('Module:If preview')._warning({preview_text})
   elseif preview == nil then
    preview_text = unknown_text
   end
   unknown_text = preview_text
  end
  for _, v in pairs(values) do
   -- Fix odd bug for | = which gets stripped to the empty string and
   -- breaks category links
   if v == '' then v = ' ' end

   -- avoid error with v = 'example%2' ("invalid capture index")
   local r = unknown_text:gsub('_VALUE_', {_VALUE_ = v})
   table.insert(res, r)
  end
 end

 return table.concat(res)
end

function p.check(frame)
 local args = frame.args
 local pargs = frame:getParent().args
 return p._check(args, pargs)
end

return p