#!/usr/bin/env lua

local function usage()
	print ([[Lua static checker
Usage: ]] .. arg[0]:match('/?([^/]+)$') .. [[ LUASOURCE

Reports globals.

Warning: it does not report false negative, but is not exhaustive either.
]])
end

if #arg < 1 then
	usage()
	os.exit()
end

local builtins = {
	assert = true,
	collectgarbage = true,
	dofile = true,
	error = true,
	_G = true,
	getfenv = true,
	getmetatable = true,
	ipairs = true,
	load = true,
	loadfile = true,
	loadstring = true,
	next = true,
	pairs = true,
	pcall = true,
	print = true,
	rawequal = true,
	rawget = true,
	rawset = true,
	select = true,
	setfenv = true,
	setmetatable = true,
	tonumber = true,
	tostring = true,
	type = true,
	unpack = true,
	_VERSION = true,
	xpcall = true,

	module = true,
	package = true,
	require = true,

	coroutine = true,
	debug = true,
	io = true,
	math = true,
	os = true,
	string = true,
	table = true,
}


for _, file in ipairs(arg) do
	local p = io.popen('luac -p -l -- ' .. file)

	local globals = {}
	for m in p:lines() do
		if m:match('ETTABUP.*_ENV') then
			local line, op, field = m:match('%[([%d]+)%].*(.)ETTABUP.*"([_%w]+)"')
			if not builtins[field] then
				if op == 'G' then
					-- Global is used.
					if not globals[field] then globals[field] = {set = false, used = false, lines={}} end
					globals[field].used = true
					globals[field].lines[#globals[field].lines+1] = tonumber(line)
				else
					-- Global is set.
					if not globals[field] then globals[field] = {set = false, used = false, lines={}} end
					globals[field].set = true
					globals[field].lines[#globals[field].lines+1] = tonumber(line)
				end
			end
		end
	end
	p:close()

	local sorted = {}
	local out = {}
	for field, v in pairs(globals) do
		if v.set and v.used then
			-- Report only first appearance.
			sorted[#sorted+1] = v.lines[1]
			if not out[v.lines[1]] then out[v.lines[1]] = {} end
			out[v.lines[1]][#out[v.lines[1]]+1] = field
		else
			for _, line in ipairs(v.lines) do
				sorted[#sorted+1] = line
				if not out[line] then out[line] = {} end
				out[line][#out[line]+1] = field
			end
		end
		-- Free some memory.
		v.lines = nil
	end
	table.sort(sorted)


	for k, line in ipairs(sorted) do
		-- Sorted can contain the same line several times.
		if k == 1 or line ~= sorted[k-1] then
			for _, field in pairs(out[line]) do
				if globals[field].set and globals[field].used then
					io.stderr:write(string.format("%s:%s: global '%s' set and used\n", file, line, field))
				elseif globals[field].set and not globals[field].used then
					io.stderr:write(string.format("%s:%s: global '%s' set but not used\n", file, line, field))
				else
					io.stderr:write(string.format("%s:%s: global '%s' used but not set\n", file, line, field))
				end
			end
		end
	end

end