Editing Module:Infobox road/length

local p = {}

local math = require "Module:Math"

local function getLengths(args, num)
    local precision = math._precision
    local round = math._round
    local format = math._precision_format
    local lengths = {}
    local km = args["length_km" .. num] or ''
    local mi = args["length_mi" .. num] or ''
    local prec = tonumber(args["length_round" .. num])
    if '' == km then
        local n = tonumber(mi)
        prec = prec or precision(mi)
        if n then
            lengths.km = format(tostring(n * 1.609344), tostring(prec))
        else
            lengths.km = '0'
        end
    else
        prec = prec or precision(km)
        lengths.km = format(km, tostring(prec))
        lengths.orig = "km"
        lengths.comp = "mi"
    end
    if '' == mi then
        local n = tonumber(km)
        prec = prec or precision(km)
        if n then
            lengths.mi = format(tostring(n / 1.609344), tostring(prec))
        else
            lengths.mi = '0'
        end
    else
        prec = prec or precision(mi)
        lengths.mi = format(mi, tostring(prec))
        lengths.orig = "mi"
        lengths.comp = "km"
    end
    return lengths
end

function p._length(num, args)
    local ref = args["length_ref" .. num] or ''
    local notes = args["length_notes" .. num] or ''
    local lengths = getLengths(args, num)
     
    local first, second
    if lengths.orig == "mi" then
        first = lengths.mi
        second = lengths.km
    else
        first = lengths.km
        second = lengths.mi
    end
    if first == '0' and second == '0' then
        return
    end
    local text = {first, "&nbsp;", lengths.orig, ref, " (", second, "&nbsp;", lengths.comp, ")", }
    if notes ~= '' then
        table.insert(text, "<br><small>" .. notes .. "</small>")
    end
    return table.concat(text)
end

function p.length(frame)
    local pframe = frame:getParent()
    local config = frame.args -- the arguments passed BY the template, in the wikitext of the template itself
    local args = pframe.args -- the arguments passed TO the template, in the wikitext that transcludes the template
    
    local num = config.num or ''
    return p._length(num, args)
end

return p