main.lua

collectgarbage("setpause", 110);

assert(arg[1], "Please supply upstream URL");

local server = require "net.server_select";
local http = require "net.http";
local logger = require "util.logger";
events = require "util.events".new();

require "clients";

local function printf(source, level, fmt, ...) return print(source, level, fmt:format(...)); end
for _, level in ipairs{"debug", "info", "warn", "error"} do
	logger.add_level_sink(level, printf);
end

local request;

events.add_handler("have-clients", function ()
	request = http.request(arg[1], {success_on_chunk=true}, function (data, code, response)
		local boundary = response.headers["content-type"]:match("; boundary=(.+)$").."\r\n";
		if #data > #boundary and data:sub(1, #boundary) ~= boundary then
			print(string.format(("%02X "):rep(6), data:byte(1,6)));
			error("bad format");
		end
		local img_header, header_len = data:sub(#boundary-1):match("(\r\n.-\r\n)\r\n()");
		if not img_header then return; end
		local img_size = tonumber(img_header:match("\r\nContent%-Length:%s*(%d+)\r\n"));
		local start_idx, end_idx = #boundary-2+header_len, #boundary-2+header_len+img_size-1;
		if end_idx + 2 > #data then return; end
		local img = data:sub(start_idx, end_idx);
		assert(#img == img_size, "incorrect image size: actual:"..#img.." vs expected: "..img_size.." data: "..#data)
		response.body = data:sub(end_idx+3);
		events.fire_event("image-changed", { image = img });
	end);
end);

events.add_handler("no-clients", function ()
	request.conn:close();
end);

server.loop();