local math_abs = math.abs;

local math_ceil = math.ceil;

local math_floor = math.floor;

local math_log = math.log;

local math_max = math.max;

local math_min = math.min;

local unpack = table.unpack or unpack; --luacheck: ignore 113

if math_log(10, 10) ~= 1 then

	-- Lua 5.1 COMPAT

	local log10 = math.log10;

	function math_log(n, base)

		return log10(n) / log10(base);

	end

end

local large = {

	"k", 1000,

	"M", 1000000,

	"G", 1000000000,

	"T", 1000000000000,

	"P", 1000000000000000,

	"E", 1000000000000000000,

	"Z", 1000000000000000000000,

	"Y", 1000000000000000000000000,

}

local small = {

	"m", 0.001,

	"μ", 0.000001,

	"n", 0.000000001,

	"p", 0.000000000001,

	"f", 0.000000000000001,

	"a", 0.000000000000000001,

	"z", 0.000000000000000000001,

	"y", 0.000000000000000000000001,

}

local binary = {

	"Ki", 2^10,

	"Mi", 2^20,

	"Gi", 2^30,

	"Ti", 2^40,

	"Pi", 2^50,

	"Ei", 2^60,

	"Zi", 2^70,

	"Yi", 2^80,

}

local function adjusted_unit(n, b)

	local round = math_floor;

	local prefixes = large;

	local logbase = 1000;

	if b == 'b' then

		prefixes = binary;

		logbase = 1024;

	elseif n < 1 then

		prefixes = small;

		round = math_ceil;

	end

	local m = math_max(0, math_min(8, round(math_abs(math_log(math_abs(n), logbase)))));

	local prefix, multiplier = unpack(prefixes, m * 2-1, m*2);

	return multiplier or 1, prefix;

end

-- n: number, the number to format

-- unit: string, the base unit

-- b: optional enum 'b', thousands base

local function format(n, unit, b) --> string

	local fmt = "%.3g %s%s";

	if n == 0 then

		return fmt:format(n, "", unit);

	end

	local multiplier, prefix = adjusted_unit(n, b);

	return fmt:format(n / multiplier, prefix or "", unit);

end

return {

	adjust = adjusted_unit;

	format = format;

};