Modül:Arguments

-- 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