"use client";

import { useCallback, useEffect, useRef, useState } from "react";
import { api } from "@/lib/trpc";
import type { ChatMessageView } from "./chat-message-list";
import { mergeChatMessages } from "./chat-utils";
import { createMutationRecovery } from "./mutation-recovery";

export function useChatMutationRecovery({ workspace, channelId, enabled }: {
  workspace: string;
  channelId?: string;
  enabled: boolean;
}) {
  const utils = api.useUtils();
  const identity = JSON.stringify([workspace, channelId, enabled]);
  const scope = useRef({ identity });
  if (scope.current.identity !== identity) scope.current = { identity };
  const token = scope.current;
  const [state, setState] = useState<{ token: typeof token; messages: ChatMessageView[]; error: unknown }>({ token, messages: [], error: null });
  const cursors = useRef(new Map<string, { after: string; through?: string }>());
  const run = useRef<(() => void) | undefined>(undefined);
  const cursorKey = JSON.stringify([workspace, channelId ?? ""]);
  const refresh = useCallback(() => { run.current?.(); }, []);

  useEffect(() => {
    if (!enabled || !channelId) return;
    let stopped = false;
    const valid = () => !stopped && scope.current === token;
    const cursorKey = JSON.stringify([workspace, channelId]);
    const recovery = createMutationRecovery(
      (cursor) => utils.chat.mutationCatchUp.fetch({ workspace, channelId, ...cursor, limit: 100 }),
      (messages) => {
        if (!valid()) return;
        setState((previous) => ({ token, messages: mergeChatMessages(previous.token === token ? previous.messages : [], messages), error: null }));
      },
      cursors.current.get(cursorKey),
      (cursor) => cursors.current.set(cursorKey, cursor),
    );
    const recover = () => {
      void recovery.run().catch((error: unknown) => {
        if (valid()) setState((previous) => ({ token, messages: previous.token === token ? previous.messages : [], error }));
      });
    };
    run.current = recover;
    recover();
    const timer = setInterval(recover, 15000);
    window.addEventListener("online", recover);
    window.addEventListener("focus", recover);
    return () => {
      stopped = true;
      recovery.stop();
      clearInterval(timer);
      window.removeEventListener("online", recover);
      window.removeEventListener("focus", recover);
      if (run.current === recover) run.current = undefined;
    };
  }, [workspace, channelId, enabled, token, utils]);

  return {
    messages: state.token === token && enabled ? state.messages : [],
    error: state.token === token && enabled ? state.error : null,
    refresh,
  };
}