Module:Namespace detect/data/sandbox

 --------------------------------------------------------------------------------
 -- Namespace detect data --
 -- This module holds data for [[Module:Namespace detect]] to be loaded per --
 -- page, rather than per #invoke, for performance reasons. --
 --------------------------------------------------------------------------------

 local cfg = require('Module:Namespace detect/config')

 local function addKey(t, key, defaultKey)
	if key ~= defaultKey then
		t[#t + 1] = key
	end
 end

 -- Get a table of parameters to query for each default parameter name.
 -- This allows wikis to customise parameter names in the cfg table while
 -- ensuring that default parameter names will always work. The cfg table
 -- values can be added as a string, or as an array of strings.

 local defaultKeys = {
	'main',
	'talk',
	'other',
	'subjectns',
	'demospace',
	'demopage'
 }

 local argKeys = {}
 for i, defaultKey in ipairs(defaultKeys) do
	argKeys[defaultKey] = {defaultKey}
 end

 for defaultKey, t in pairs(argKeys) do
	local cfgValue = cfg[defaultKey]
	local cfgValueType = type(cfgValue)
	if cfgValueType == 'string' then
		addKey(t, cfgValue, defaultKey)
	elseif cfgValueType == 'table' then
		for i, key in ipairs(cfgValue) do
			addKey(t, key, defaultKey)
		end
	end
	cfg[defaultKey] = nil -- Free the cfg value as we don't need it any more.
 end

 local function getParamMappings()
	--[[
 	-- Returns a table of how parameter names map to namespace names. The keys
 	-- are the actual namespace names, in lower case, and the values are the
 	-- possible parameter names for that namespace, also in lower case. The
 	-- table entries are structured like this:
 	-- {
 	-- [''] = {'main'},
 	-- ['wikipedia'] = {'wikipedia', 'project', 'wp'},
 	-- ...
 	-- }
 	--]]
	local mappings = {}
	local mainNsName = mw.site.subjectNamespaces[0].name
	mainNsName = mw.ustring.lower(mainNsName)
	mappings[mainNsName] = mw.clone(argKeys.main)
	mappings['talk'] = mw.clone(argKeys.talk)
	for nsid, ns in pairs(mw.site.subjectNamespaces) do
		if nsid ~= 0 then -- Exclude main namespace.
			local nsname = mw.ustring.lower(ns.name)
			local canonicalName = mw.ustring.lower(ns.canonicalName)
			mappings[nsname] = {nsname}
			if canonicalName ~= nsname then
				table.insert(mappings[nsname], canonicalName)
			end
			for _, alias in ipairs(ns.aliases) do
				table.insert(mappings[nsname], mw.ustring.lower(alias))
			end
		end
	end
	return mappings
 end

 return {
	argKeys = argKeys,
	cfg = cfg,
	mappings = getParamMappings()
 }