module 'autoupdater.version'


-- version comparison is based on dpkg code
local function isdigit(s, i)
	local c = s:sub(i, i)
	return c and c:match('^%d$')
end

local function char_value(s, i)
	return s:byte(i, i) or 0
end

local function char_order(s, i)
	local c = s:sub(i, i)

	if c == '' or c:match('^%d$') then
		return 0
	elseif c:match('^%a$') then
		return c:byte()
	elseif c == '~' then
		return -1
	else
		return c:byte() + 256
	end
end

-- returns true when a is a higher version number than b
function newer_than(a, b)
	local apos = 1
	local bpos = 1

	while apos <= a:len() or bpos <= b:len() do
		local first_diff = 0

		while (apos <= a:len() and not isdigit(a, apos)) or (bpos <= b:len() and not isdigit(b, bpos)) do
			local ac = char_order(a, apos)
			local bc = char_order(b, bpos)

			if ac ~= bc then
				return ac > bc
			end

			apos = apos + 1
			bpos = bpos + 1
		end

		while a:sub(apos, apos) == '0' do
			apos = apos + 1
		end

		while b:sub(bpos, bpos) == '0' do
			bpos = bpos + 1
		end

		while isdigit(a, apos) and isdigit(b, bpos) do
			if first_diff == 0 then
				first_diff = char_value(a, apos) - char_value(b, bpos)
			end

			apos = apos + 1
			bpos = bpos + 1
		end

		if isdigit(a, apos) then
			return true
		end

		if isdigit(b, bpos) then
			return false
		end

		if first_diff ~= 0 then
			return first_diff > 0
		end
	end

	return false
end