Module:Sandbox/Jackmcbarn

local function translatenext(invariant)
	local k, v = next(invariant.src, invariant.k)
	invariant.k = k
	if k == nil then
		return nil
	elseif type(k) ~= 'string' then
		return k, v
	end
	local from = invariant.from[k]
	if from ~= nil then
		return from, v
	elseif invariant.to[k] == nil then
		return k, v
	else
		-- skip this key. tail call
		return translatenext(invariant)
	end
end
local function translate(src, to, from)
	-- to contains English keys and translated values
	-- if the value is a table, any of that table's values are valid translations
	-- from contains translated keys and English values
	-- optional if to doesn't rely on __index
	-- src is the table being wrapped
	if not from then
		from = {}
		for k,v in pairs(to) do
			from[v] = k
		end
	end

	local mt = {}
	function mt.__index(t, k)
		if type(k) == 'string' then
			local retval = src[to[k]]
			if retval ~= nil or from[k] ~= nil then
				return retval
			end
		end
		return src[k]
	end
	function mt.__newindex(t, k, v)
		if type(k) ~= 'string' then
			src[k] = v
			return
		end
		local to = to[k]
		local falseCognate = from[k] ~= nil
		if to ~= nil then
			if v == nil and not falseCognate then
				src[k] = nil
			end
			src[to] = v
		elseif not falseCognate then
			src[k] = v
		else
			error('Attempt to write key "' .. k .. '" which has no translation and is a false cognate', 2)
		end
	end
	function mt.__pairs(t)
		return translatenext, {src = src, to = to, from = from}
	end
	function mt.__ipairs(t)
		return ipairs(src)
	end
	return setmetatable({}, mt)
end

local p = {}

function p.main(frame)
	local args = {
		eins = '#ff0000',
		zwei = '#ff7f00',
		drei = '#FFFF00',
		three = 'yellow'
	}
	local to = {
		one = 'eins',
		two = 'zwei',
		three = 'drei'
	}
	local wrapper = translate(args, to)
	return wrapper
end

return p