const INTERVAL_MS = 1;
const RS_TOP_ADDR = 0x10000;
const PROF_DATA_ADDR = 0x58;
const PROF_DATA_IDX = PROF_DATA_ADDR / 8;

let mem_8;
let mem_64;
let sampler;

const samples = [];

function sample() {
	const data = Atomics.load(mem_64, PROF_DATA_IDX);
	const ip = Number(data & 0xffffffffn);
	const rsp = Number(data >> 32n);
	samples.push({ ip, rs_bytes: mem_8.slice(rsp, RS_TOP_ADDR) });
}

function i32(bytes) {
	return bytes[0]
		| (bytes[1] << 8)
		| (bytes[2] << 16)
		| (bytes[3] << 24);
}
function postproc({ ip, rs_bytes }) {
	const rs = [];
	for (let i = 0; i < rs_bytes.length; i += 4)
		rs.push(i32(rs_bytes.slice(i, i + 4)));
	rs.reverse();
	return { ip, rs };
}

self.onmessage = (e) => {
	switch (e.data.type) {
	case "start":
		console.log("Starting profiler");
		mem_8 = new Uint8Array(e.data.mem.buffer);
		mem_64 = new BigUint64Array(e.data.mem.buffer);
		ip = e.data.ip;
		rsp = e.data.rsp;
		sampler = setInterval(sample, INTERVAL_MS);
		break;
	case "stop":
		clearInterval(sample);
		console.log("Stopped profiler");
		self.postMessage(samples.map(postproc));
	}
};