Module:Human readable duration

local p = {}

-- reproduced from Module:Convert
local scale = {
	second = 1,
	seconds = 1,
	minute = 60,
	minutes = 60,
	hour = 3600,
	hours = 3600,
	day = 86400,
	days = 86400,
	month = 2629800,
	months = 2629800,
	year = 31557600,
	years = 31557600
}

function p.main(frame)
	local args = frame:getParent().args

	local time = tonumber(args[1])

	if time == nil or time < 0 then
		return
		"<strong class='error'>Human readable duration error: First argument must be a positive number ([[Template:Human readable duration|help]])</strong>"
	end

	local unit = string.lower(args[2] or "")

	if scale[unit] == nil then
		return
		"<strong class='error'>Human readable duration error: Second argument must be a valid time unit ([[Template:Human readable duration|help]])</strong>"
	end

	local timeseconds = time * scale[unit]

	if timeseconds < 59.75 then -- rounds to 59.5 seconds or less
		local converted = math.floor(timeseconds * 2 + 0.5) / 2
		return converted .. " second" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 3585 then -- rounds to 59.5 minutes or less
		local converted = math.floor(timeseconds / scale.minute * 2 + 0.5) / 2
		return converted .. " minute" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 258300 and timeseconds ~= 86400 and timeseconds ~= 172800 then -- rounds to 71.5 hours or less, excluding 24 and 48 hours exactly
		local converted = math.floor(timeseconds / scale.hour * 2 + 0.5) / 2
		return converted .. " hour" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 4341600 then -- rounds to 50 days or less
		local converted = math.floor(timeseconds / scale.day * 2 + 0.5) / 2
		return converted .. " day" .. (converted ~= 1 and "s" or "")
	elseif timeseconds < 48651300 then -- rounds to 18 months or less (rounds to nearest integer instead of 0.5)
		local converted = math.floor(timeseconds / scale.month + 0.5)
		return converted .. " month" .. (converted ~= 1 and "s" or "")
	else -- anything over 18 months rounds to nearest 0.5 years
		local converted = math.floor(timeseconds / scale.year * 2 + 0.5) / 2
		return converted .. " year" .. (converted ~= 1 and "s" or "")
	end
end

return p