import { useRouter } from "@tanstack/react-router";
import { useEffect, useState } from "react";

const RECONNECT_MS = 3000;
const PING_MS = 30000;

type LiveMessage = { type: "changed"; actor: string } | { type: "presence"; viewers: string[] };

function parse(raw: string): LiveMessage | null {
  try {
    const value: unknown = JSON.parse(raw);
    if (typeof value !== "object" || value === null || !("type" in value)) return null;
    if (value.type === "changed" && "actor" in value && typeof value.actor === "string")
      return { type: "changed", actor: value.actor };
    if (value.type === "presence" && "viewers" in value && Array.isArray(value.viewers))
      return { type: "presence", viewers: value.viewers.filter((name): name is string => typeof name === "string") };
    return null;
  } catch {
    return null;
  }
}

/** Subscribes to the project's Durable Object room: refreshes on remote edits and reports who is viewing. */
export function useProjectLive(owner: string, number: number) {
  const router = useRouter();
  const [viewers, setViewers] = useState<string[]>([]);
  const [connected, setConnected] = useState(false);

  useEffect(() => {
    let socket: WebSocket | null = null;
    let closed = false;
    let retry: ReturnType<typeof setTimeout> | undefined;
    let ping: ReturnType<typeof setInterval> | undefined;
    const connect = () => {
      const scheme = window.location.protocol === "https:" ? "wss" : "ws";
      socket = new WebSocket(`${scheme}://${window.location.host}/projects/${owner}/${number}/live`);
      socket.onopen = () => setConnected(true);
      socket.onmessage = (event) => {
        const message = typeof event.data === "string" ? parse(event.data) : null;
        if (message?.type === "presence") setViewers(message.viewers);
        if (message?.type === "changed") void router.invalidate();
      };
      socket.onclose = () => {
        setConnected(false);
        if (!closed) retry = setTimeout(connect, RECONNECT_MS);
      };
    };
    connect();
    ping = setInterval(() => socket?.readyState === WebSocket.OPEN && socket.send("ping"), PING_MS);
    return () => {
      closed = true;
      clearTimeout(retry);
      clearInterval(ping);
      socket?.close();
    };
  }, [owner, number, router]);

  return { viewers, connected };
}