// The live feed of `GET /api/messages/stream`, one `SwarmMessage` per event.
// The stream has no event id, so a reconnect sends the history again from the
// start; the list therefore empties each time the connection opens, and the
// replay refills it. Not `useSwarmTermStream`: that one keeps its rows across
// a reconnect, which here would list every message twice.
import { useEffect, useState } from "preact/hooks";
import type { SwarmMessage } from "./messages.js";
import { messagesUrl, newest } from "./messages.js";

export type ConnectionState = "connecting" | "open" | "reconnecting" | "closed";

/** The most messages the page holds; older ones drop off. */
export const MAX_MESSAGES = 2000;

export function useMessageStream(sinceMinutes: number): {
  messages: SwarmMessage[];
  connection: ConnectionState;
} {
  const [messages, setMessages] = useState<SwarmMessage[]>([]);
  const [connection, setConnection] = useState<ConnectionState>("connecting");

  useEffect(() => {
    setMessages([]);
    setConnection("connecting");
    const es = new EventSource(messagesUrl(sinceMinutes));
    es.onopen = () => {
      setMessages([]);
      setConnection("open");
    };
    es.onmessage = (e) => {
      let m: SwarmMessage;
      try {
        m = JSON.parse(e.data) as SwarmMessage;
      } catch {
        return;
      }
      setMessages((prev) => newest([...prev, m], MAX_MESSAGES));
    };
    es.onerror = () => {
      setConnection(
        es.readyState === 0 /* CONNECTING */ ? "reconnecting" : "closed",
      );
    };
    return () => es.close();
  }, [sinceMinutes]);

  return { messages, connection };
}