local checkType = require('libraryUtil').checkType  local p = {}  local BODY_PARAM = '$B'  local specialParams = {  ['$params'] = 'parameter list',  ['$aliases'] = 'parameter aliases',  ['$flags'] = 'flags',  ['$B'] = 'template content' }  function p.main(frame, body)  -- If we are substing, this function returns a template invocation, and if  -- not, it returns the template body. The template body can be specified in  -- the body parameter, or in the template parameter defined in the  -- BODY_PARAM variable. This function can be called from Lua or from  -- #invoke.   -- Return the template body if we aren't substing.  if not mw.isSubsting() then  if body ~= nil then  return body  elseif frame.args[BODY_PARAM] ~= nil then  return frame.args[BODY_PARAM]  else  error(string.format(  "no template content specified (use parameter '%s' from #invoke)",  BODY_PARAM  ), 2)  end  end   -- Sanity check for the frame object.  if type(frame) ~= 'table'  or type(frame.getParent) ~= 'function'  or not frame:getParent()  then  error(  "argument #1 to 'main' must be a frame object with a parent " ..  "frame available",  2  )  end   -- Find the invocation name.  local mTemplateInvocation = require('Module:Template invocation')  local name = mTemplateInvocation.name(frame:getParent():getTitle())   -- Combine passed args with passed defaults  local args = {}  if string.find( ','..(frame.args['$flags'] or '')..',', ',%s*override%s*,' ) then  for k, v in pairs( frame:getParent().args ) do  args[k] = v  end  for k, v in pairs( frame.args ) do  if not specialParams[k] then  if v == '__DATE__' then  v = mw.getContentLanguage():formatDate( 'F Y' )  end  args[k] = v  end  end  else  for k, v in pairs( frame.args ) do  if not specialParams[k] then  if v == '__DATE__' then  v = mw.getContentLanguage():formatDate( 'F Y' )  end  args[k] = v  end  end  for k, v in pairs( frame:getParent().args ) do  args[k] = v  end  end   -- Trim parameters, if not specified otherwise  if not string.find( ','..(frame.args['$flags'] or '')..',', ',%s*keep%-whitespace%s*,' ) then  for k, v in pairs( args ) do args[k] = mw.ustring.match(v, '^%s*(.*)%s*$') or '' end  end   -- Pull information from parameter aliases  local aliases = {}  if frame.args['$aliases'] then  local list = mw.text.split( frame.args['$aliases'], '%s*,%s*' )  for k, v in ipairs( list ) do  local tmp = mw.text.split( v, '%s*>%s*' )  aliases[tonumber(mw.ustring.match(tmp[1], '^[1-9][0-9]*$')) or tmp[1]] = ((tonumber(mw.ustring.match(tmp[2], '^[1-9][0-9]*$'))) or tmp[2])  end  end  for k, v in pairs( aliases ) do  if args[k] and ( not args[v] or args[v] == '' ) then  args[v] = args[k]  end  args[k] = nil  end   -- Remove empty parameters, if specified  if string.find( ','..(frame.args['$flags'] or '')..',', ',%s*remove%-empty%s*,' ) then  local tmp = 0  for k, v in ipairs( args ) do  if v ~= '' or ( args[k+1] and args[k+1] ~= '' ) or ( args[k+2] and args[k+2] ~= '' ) then  tmp = k  else  break  end  end  for k, v in pairs( args ) do  if v == '' then  if not (type(k) == 'number' and k < tmp) then args[k] = nil end  end  end  end   -- Order parameters  if frame.args['$params'] then  local params, tmp = mw.text.split( frame.args['$params'], '%s*,%s*' ), {}  for k, v in ipairs(params) do  v = tonumber(mw.ustring.match(v, '^[1-9][0-9]*$')) or v  if args[v] then tmp[v], args[v] = args[v], nil end  end  for k, v in pairs(args) do tmp[k], args[k] = args[k], nil end  args = tmp  end   return mTemplateInvocation.invocation(name, args) end  p[''] = p.main -- For backwards compatibility  return p