-- This module provides easy processing of arguments passed to Scribunto from -- #invoke. It is intended for use by other Lua modules, and should not be -- called from #invoke directly.  local libraryUtil = require('libraryUtil') local checkType = libraryUtil.checkType  local arguments = {}  -- Generate four different tidyVal functions, so that we don't have to check the -- options every time we call it.  local function tidyValDefault(key, val)  if type(val) == 'string' then  val = val:match('^%s*(.-)%s*$')  if val == '' then  return nil  else  return val  end  else  return val  end end  local function tidyValTrimOnly(key, val)  if type(val) == 'string' then  return val:match('^%s*(.-)%s*$')  else  return val  end end  local function tidyValRemoveBlanksOnly(key, val)  if type(val) == 'string' then  if val:find('%S') then  return val  else  return nil  end  else  return val  end end  local function tidyValNoChange(key, val)  return val end  local function matchesTitle(given, title)  local tp = type( given )  return (tp == 'string' or tp == 'number') and mw.title.new( given ).prefixedText == title end  local translate_mt = { __index = function(t, k) return k end }  function arguments.getArgs(frame, options)  checkType('getArgs', 1, frame, 'table', true)  checkType('getArgs', 2, options, 'table', true)  frame = frame or {}  options = options or {}   --[[  -- Set up argument translation.  --]]  options.translate = options.translate or {}  if getmetatable(options.translate) == nil then  setmetatable(options.translate, translate_mt)  end  if options.backtranslate == nil then  options.backtranslate = {}  for k,v in pairs(options.translate) do  options.backtranslate[v] = k  end  end  if options.backtranslate and getmetatable(options.backtranslate) == nil then  setmetatable(options.backtranslate, {  __index = function(t, k)  if options.translate[k] ~= k then  return nil  else  return k  end  end  })  end   --[[  -- Get the argument tables. If we were passed a valid frame object, get the  -- frame arguments (fargs) and the parent frame arguments (pargs), depending  -- on the options set and on the parent frame's availability. If we weren't  -- passed a valid frame object, we are being called from another Lua module  -- or from the debug console, so assume that we were passed a table of args  -- directly, and assign it to a new variable (luaArgs).  --]]  local fargs, pargs, luaArgs  if type(frame.args) == 'table' and type(frame.getParent) == 'function' then  if options.wrappers then  --[[  -- The wrappers option makes Module:Arguments look up arguments in  -- either the frame argument table or the parent argument table, but  -- not both. This means that users can use either the #invoke syntax  -- or a wrapper template without the loss of performance associated  -- with looking arguments up in both the frame and the parent frame.  -- Module:Arguments will look up arguments in the parent frame  -- if it finds the parent frame's title in options.wrapper;  -- otherwise it will look up arguments in the frame object passed  -- to getArgs.  --]]  local parent = frame:getParent()  if not parent then  fargs = frame.args  else  local title = parent:getTitle():gsub('/sandbox$', '')  local found = false  if matchesTitle(options.wrappers, title) then  found = true  elseif type(options.wrappers) == 'table' then  for _,v in pairs(options.wrappers) do  if matchesTitle(v, title) then  found = true  break  end  end  end   -- We test for false specifically here so that nil (the default) acts like true.  if found or options.frameOnly == false then  pargs = parent.args  end  if not found or options.parentOnly == false then  fargs = frame.args  end  end  else  -- options.wrapper isn't set, so check the other options.  if not options.parentOnly then  fargs = frame.args  end  if not options.frameOnly then  local parent = frame:getParent()  pargs = parent and parent.args or nil  end  end  if options.parentFirst then  fargs, pargs = pargs, fargs  end  else  luaArgs = frame  end   -- Set the order of precedence of the argument tables. If the variables are  -- nil, nothing will be added to the table, which is how we avoid clashes  -- between the frame/parent args and the Lua args.  local argTables = {fargs}  argTables[#argTables + 1] = pargs  argTables[#argTables + 1] = luaArgs   --[[  -- Generate the tidyVal function. If it has been specified by the user, we  -- use that; if not, we choose one of four functions depending on the  -- options chosen. This is so that we don't have to call the options table  -- every time the function is called.  --]]  local tidyVal = options.valueFunc  if tidyVal then  if type(tidyVal) ~= 'function' then  error(  "bad value assigned to option 'valueFunc'"  .. '(function expected, got '  .. type(tidyVal)  .. ')',  2  )  end  elseif options.trim ~= false then  if options.removeBlanks ~= false then  tidyVal = tidyValDefault  else  tidyVal = tidyValTrimOnly  end  else  if options.removeBlanks ~= false then  tidyVal = tidyValRemoveBlanksOnly  else  tidyVal = tidyValNoChange  end  end   --[[  -- Set up the args, metaArgs and nilArgs tables. args will be the one  -- accessed from functions, and metaArgs will hold the actual arguments. Nil  -- arguments are memoized in nilArgs, and the metatable connects all of them  -- together.  --]]  local args, metaArgs, nilArgs, metatable = {}, {}, {}, {}  setmetatable(args, metatable)   local function mergeArgs(tables)  --[[  -- Accepts multiple tables as input and merges their keys and values  -- into one table. If a value is already present it is not overwritten;  -- tables listed earlier have precedence. We are also memoizing nil  -- values, which can be overwritten if they are 's' (soft).  --]]  for _, t in ipairs(tables) do  for key, val in pairs(t) do  if metaArgs[key] == nil and nilArgs[key] ~= 'h' then  local tidiedVal = tidyVal(key, val)  if tidiedVal == nil then  nilArgs[key] = 's'  else  metaArgs[key] = tidiedVal  end  end  end  end  end   --[[  -- Define metatable behaviour. Arguments are memoized in the metaArgs table,  -- and are only fetched from the argument tables once. Fetching arguments  -- from the argument tables is the most resource-intensive step in this  -- module, so we try and avoid it where possible. For this reason, nil  -- arguments are also memoized, in the nilArgs table. Also, we keep a record  -- in the metatable of when pairs and ipairs have been called, so we do not  -- run pairs and ipairs on the argument tables more than once. We also do  -- not run ipairs on fargs and pargs if pairs has already been run, as all  -- the arguments will already have been copied over.  --]]   metatable.__index = function (t, key)  --[[  -- Fetches an argument when the args table is indexed. First we check  -- to see if the value is memoized, and if not we try and fetch it from  -- the argument tables. When we check memoization, we need to check  -- metaArgs before nilArgs, as both can be non-nil at the same time.  -- If the argument is not present in metaArgs, we also check whether  -- pairs has been run yet. If pairs has already been run, we return nil.  -- This is because all the arguments will have already been copied into  -- metaArgs by the mergeArgs function, meaning that any other arguments  -- must be nil.  --]]  if type(key) == 'string' then  key = options.translate[key]  end  local val = metaArgs[key]  if val ~= nil then  return val  elseif metatable.donePairs or nilArgs[key] then  return nil  end  for _, argTable in ipairs(argTables) do  local argTableVal = tidyVal(key, argTable[key])  if argTableVal ~= nil then  metaArgs[key] = argTableVal  return argTableVal  end  end  nilArgs[key] = 'h'  return nil  end   metatable.__newindex = function (t, key, val)  -- This function is called when a module tries to add a new value to the  -- args table, or tries to change an existing value.  if type(key) == 'string' then  key = options.translate[key]  end  if options.readOnly then  error(  'could not write to argument table key "'  .. tostring(key)  .. '"; the table is read-only',  2  )  elseif options.noOverwrite and args[key] ~= nil then  error(  'could not write to argument table key "'  .. tostring(key)  .. '"; overwriting existing arguments is not permitted',  2  )  elseif val == nil then  --[[  -- If the argument is to be overwritten with nil, we need to erase  -- the value in metaArgs, so that __index, __pairs and __ipairs do  -- not use a previous existing value, if present; and we also need  -- to memoize the nil in nilArgs, so that the value isn't looked  -- up in the argument tables if it is accessed again.  --]]  metaArgs[key] = nil  nilArgs[key] = 'h'  else  metaArgs[key] = val  end  end   local function translatenext(invariant)  local k, v = next(invariant.t, invariant.k)  invariant.k = k  if k == nil then  return nil  elseif type(k) ~= 'string' or not options.backtranslate then  return k, v  else  local backtranslate = options.backtranslate[k]  if backtranslate == nil then  -- Skip this one. This is a tail call, so this won't cause stack overflow  return translatenext(invariant)  else  return backtranslate, v  end  end  end   metatable.__pairs = function ()  -- Called when pairs is run on the args table.  if not metatable.donePairs then  mergeArgs(argTables)  metatable.donePairs = true  end  return translatenext, { t = metaArgs }  end   local function inext(t, i)  -- This uses our __index metamethod  local v = t[i + 1]  if v ~= nil then  return i + 1, v  end  end   metatable.__ipairs = function (t)  -- Called when ipairs is run on the args table.  return inext, t, 0  end   return args end  return arguments