Difference between revisions of "Module:Arguments"

Revision as of 23:17, 8 December 2013

-- 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 arguments = {}

function arguments.getArgs(frame, options)
	options = type(options) == 'table' and options or {}

	-- Get the arguments from the frame object if available. If the frame object is not available, we are being called
	-- from another Lua module or from the debug console, so assume arguments are passed directly in.
	local fargs, pargs
	if frame == mw.getCurrentFrame() then
		fargs = frame.args
		pargs = frame:getParent().args
	else
		fargs = type(frame) == 'table' and frame or {}
		pargs = {}
	end

	local args, metaArgs, metatable = {}, {}, {}
	setmetatable(args, metatable)

	local function tidyVal(key, val)
		-- Processes a value according to the options given to getArguments. Can trim whitespace and remove blanks.
		-- Keys are not used here, but they can be used by user-generated functions, so defining it here to avoid breakage.
		if type(val) == 'string' then
			if options.trim ~= false then
				val = mw.text.trim(val)
			end
			if options.removeBlanks == false or mw.ustring.find(val, '%S') then
				return val
			end
		else
			return val
		end
	end

	-- Use a user-generated functions to tidy the values if specified.
	local valueFunc = options.valueFunc
	if valueFunc then
		local valueFuncType = type(valueFunc)
		if valueFuncType == 'function' then
			tidyVal = valueFunc
		else
			error('type error in option "valueFunc": expected function, got ' .. valueFuncType, 2)
		end
	end

	local function mergeArgs(iterator, ...)
		-- Accepts multiple tables as input and merges their keys and values into one table using the specified iterator.
		-- If a value is already present it is not overwritten; tables listed earlier have precendence.
		local tables = {...}
		for _, t in ipairs(tables) do
			for key, val in iterator(t) do
				if metaArgs[key] == nil then
					metaArgs[key] = tidyVal(key, val)
				end
			end
		end
	end

	-- Set the order of precedence of frame args and parent args.
	local firstArgs, secondArgs = fargs, pargs
	if options.parentFirst then
		firstArgs, secondArgs = pargs, fargs
	end

	--[[
	-- Define metatable behaviour. Arguments are stored in the metaArgs table, and are only fetched from the
	-- fargs and pargs tables once. 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 fargs and pargs 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)
		local val = metaArgs[key]
		if val ~= nil then
			return val
		else
			local firstVal = tidyVal(key, firstArgs[key])
			if firstVal ~= nil then
				return firstVal
			else
				return tidyVal(key, secondArgs[key])
			end
		end
	end

	metatable.__newindex = function (t, key, val)
		if not options.readOnly and (not options.noOverwrite or args[key] == nil) then
			metaArgs[key] = val
		end
	end

	metatable.__pairs = function ()
		if not metatable.donePairs then
			mergeArgs(pairs, firstArgs, secondArgs)
			metatable.donePairs = true
			metatable.doneIpairs = true
		end
		return pairs(metaArgs)
	end

	metatable.__ipairs = function ()
		if not metatable.doneIpairs then
			mergeArgs(ipairs, firstArgs, secondArgs)
			metatable.doneIpairs = true
		end
		return ipairs(metaArgs)
	end
	
	return args
end

return arguments