local p = {}

-- Finds the next key key <= or >= the given i.
-- operator is ±1
local function findItemRange(data, i, operator)
    local bestIndex = nil
    i = i * operator
    for k, v in pairs(data) do
    	local kop = type(k) == 'number' and k * operator
        if kop and kop <= i and (bestIndex == nil or kop > bestIndex * operator) then
        	bestIndex = k
        end
    end
    if bestIndex then return data[bestIndex] else return nil end
end

local function load(datamodule, frame)
	local args = frame.args
    local data = mw.loadData(datamodule)
    for i = 1, 20 do
        if args[i] then data = data[tonumber(args[i]) or args[i]]
        elseif args[i .. ' lteq'] then
            data = findItemRange(data, tonumber(args[i .. ' lteq']), 1)
        elseif args[i .. ' gteq'] then
            data = findItemRange(data, tonumber(args[i .. ' gteq']), -1)
        else break end
    end
    
    if data == nil then
    	return args['if_nil'] -- not a required argument, OK to return nil here.
    end
    
    if type(data) == 'table' then
    	-- Put the table into another table because the return value of loadData
    	-- is a "fake" table that only has certain metamethods.
    	local realdata = {}
    	for k, v in pairs(data) do
    		realdata[k] = v
    	end
    	data = realdata
    else
    	data = { data }
    end
    
    if args['template'] then
    	return mw.text.unstripNoWiki(args['template']):format(unpack(data))
    elseif args['preprocess'] then
    	return frame:preprocess(mw.text.unstripNoWiki(args['preprocess']):format(unpack(data)))
    else
    	return table.concat(data)
    end
end

return setmetatable({}, {
	__index = function(t, k)
		return function(frame)
			return load('Module:' .. k, frame)
    	end
	end
})