import { useCallback, useEffect, useRef, useState } from "react";

import { ApiError, fetchAPI } from "@/lib/fetch";
import type { Message } from "@/types/type";

// Poll cadence for new messages. Staggered away from the ride-status poll
// (3s) and the call poll (2s) so the two tabs don't hammer the DB in lockstep.
const POLL_MS = 2500;

type UseChatResult = {
  messages: Message[];
  loading: boolean;
  sending: boolean;
  error: string | null;
  sendMessage: (body: string) => Promise<void>;
  reload: () => Promise<void>;
};

// Ride-scoped chat. Fetches the full history once, then polls for messages
// with id greater than the last one seen. Optimistic on send: the row the
// server returns is appended immediately, so the bubble appears before the
// next poll. `role` is the caller's role ("rider" | "driver") and is only
// used by the screen to align bubbles — the hook itself doesn't need it, but
// it takes it so the screen has one source of truth for the conversation.
export const useChat = (
  rideId: number | null,
  role: "rider" | "driver" | null,
): UseChatResult => {
  const [messages, setMessages] = useState<Message[]>([]);
  const [loading, setLoading] = useState(false);
  const [sending, setSending] = useState(false);
  const [error, setError] = useState<string | null>(null);

  // Last message id we've seen — the polling cursor. Kept in a ref so the
  // interval closure always reads the latest value without re-arming.
  const cursorRef = useRef<number>(0);

  const loadInitial = useCallback(async (id: number) => {
    setLoading(true);
    setError(null);
    try {
      const res = await fetchAPI(`/(api)/ride/${id}/messages`);
      const rows = (res.data ?? []) as Message[];
      setMessages(rows);
      cursorRef.current = rows.length ? rows[rows.length - 1].id : 0;
    } catch (err) {
      console.log("[CHAT_LOAD]: ", err);
      setError("chat.loadError");
    } finally {
      setLoading(false);
    }
  }, []);

  const poll = useCallback(async (id: number) => {
    try {
      const res = await fetchAPI(
        `/(api)/ride/${id}/messages?since=${cursorRef.current}`,
      );
      const rows = (res.data ?? []) as Message[];
      if (rows.length) {
        setMessages((prev) => [...prev, ...rows]);
        cursorRef.current = rows[rows.length - 1].id;
      }
    } catch (err) {
      // Swallow poll errors — a transient blip shouldn't wipe the list or
      // flash an error banner; the next tick will retry.
      console.log("[CHAT_POLL]: ", err);
    }
  }, []);

  // Initial load + polling lifecycle. Re-arms when the ride id changes.
  useEffect(() => {
    if (rideId === null) {
      setMessages([]);
      cursorRef.current = 0;
      return;
    }
    void loadInitial(rideId);
    const timer = setInterval(() => void poll(rideId), POLL_MS);
    return () => clearInterval(timer);
  }, [rideId, loadInitial, poll]);

  const sendMessage = useCallback(
    async (body: string) => {
      if (rideId === null) return;
      const text = body.trim();
      if (!text || sending) return;

      setSending(true);
      try {
        const res = await fetchAPI(`/(api)/ride/${rideId}/messages`, {
          method: "POST",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({ body: text }),
        });
        const message = res.data as Message;
        setMessages((prev) => [...prev, message]);
        cursorRef.current = Math.max(cursorRef.current, message.id);
      } catch (err) {
        if (err instanceof ApiError && err.status === 409) {
          // Ride no longer active — surface that specifically so the UI can
          // disable the input instead of retrying forever.
          setError("chat.cannotMessage");
        } else {
          console.log("[CHAT_SEND]: ", err);
          setError("chat.sendError");
        }
      } finally {
        setSending(false);
      }
    },
    [rideId, sending],
  );

  const reload = useCallback(async () => {
    if (rideId !== null) await loadInitial(rideId);
  }, [rideId, loadInitial]);

  // `role` is accepted for API symmetry but the hook doesn't read it; keep the
  // param so the screen's single conversation object carries the caller's role.
  void role;

  return { messages, loading, sending, error, sendMessage, reload };
};