Module:Arguments

Documentation: https://en.wikipedia.org/wiki/Module:Arguments/doc

---

-- 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.

---@generic T
---@param key unknown
---@param val T
---@return T?
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

---@generic T
---@param key unknown
---@param val T
---@return T?
local function tidyValTrimOnly(key, val)
  if type(val) == 'string' then
    return val:match('^%s*(.-)%s*$')
  else
    return val
  end
end

---@generic T
---@param key unknown
---@param val T
---@return T?
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

---@generic T
---@param key unknown
---@param val T
---@return T
local function tidyValNoChange(key, val)
  return val
end

---@param given string | integer
---@param title string
---@overload fun(given: unknown, title: string): boolean
local function matchesTitle(given, title)
  local tp = type(given)
  return (tp == 'string' or tp == 'number') and mw.title.new(given).prefixedText == title
end

---@type metatable
local translate_mt = { __index = function(t, k) return k end }

---@class arguments.getArgs.options
---Remove whitespace around the text of positional arguments (named arguments are always trimmed).
---Incompatible with `valueFunc.`
---@field trim? boolean
---Remove arguments that are empty or consist only of whitespace. Incompatible with `valueFunc`.
---@field removeBlanks? boolean
---Function to transform values when they are read.
---The `key` argument is the key that is being accessed, `val` is the original raw value,
---and the return value is the transformed value.
---
---Supplying `valueFunc` disables `trim` and `removeBlanks`.
---@field valueFunc? fun(key: unknown, val: unknown): unknown
---Prevent writing anything to the arguments table (best practice).
---@field readOnly? boolean
---Allows writing to the arguments table, but only if there is no value already present.
---@field noOverwrite? boolean
---Only read arguments passed directly from the #invoke call and not from any other wrapping templates.
---@field frameOnly? boolean
---Prioritize arguments passed to a wrapping template over arguments passed to #invoke.
---@field parentFirst? boolean
---Only read arguments passed to a wrapping template, ignore arguments passed to #invoke.
---@field parentOnly? boolean
---List of templates that are dedicated wrappers for this module.
---This optimizes argument reading when the module is called through the wrappers.
---
---`/sandbox` subpages are automatically detected.
---@field wrappers? string | integer | (string | integer)[]
---Rename named keys before they are accessed in the frame.
---
---For example, if translate is `{ a = 'b' }`, then accessing `args.a` will return the value of the `b` parameter.
---@field translate? table<string, string>
---Rename named arguments when they are produced by pairs().
---
---Defaults to the inverse of the `translate` option.
---@field backtranslate? table<string, string>

---Easy processing of frame arguments
---
---https://en.wikipedia.org/wiki/Module:Arguments/doc
---
---@param frame frame | table | nil The frame to parse, or a table directly containing the arguments to use.
---@param options? arguments.getArgs.options
---@return table
---@nodiscard
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
          ---@diagnostic disable-next-line: param-type-mismatch
          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.
	--]]
  ---@class argsmetatable: metatable
  ---@field __pairs? fun(t):((fun(t,k,v):any,any),table)
  ---@field __ipairs? fun(t):((fun(t,k,v):any,any),table,integer) removed in lua5.3
  ---@field donePairs? boolean
  ---@type table, table, table<any, 'h' | 's'>, argsmetatable
  local args, metaArgs, nilArgs, metatable = {}, {}, {}, {}
  setmetatable(args, metatable)

  ---@param tables table[]
  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

  ---@param invariant { t: table, k: any }
  ---@return any, any
  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