"use client";

import { useCallback, useEffect, useRef } from "react";
import { useRouter } from "next/navigation";
import { toast } from "sonner";
import { useGameTick } from "@/hooks/useGameTick";

import {
  buildReminderEntries,
  parseMissionReminders,
  readReminderDismissals,
  writeReminderDismissals,
  type Dismissals,
  type MissionReminder,
  type ReminderEntry,
} from "@/components/frontend/intelligence/missionReminderClient";

const POLL_MS = 60_000;

export function MissionReminderToasts() {
  const router = useRouter();
  const mountedRef = useRef(false);
  const fetchInFlightRef = useRef<Promise<void> | null>(null);
  const expiryTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
  const pumpScheduledRef = useRef(false);
  const pumpQueueRef = useRef<() => void>(() => undefined);
  const dismissedRef = useRef<Dismissals>({});
  const currentRef = useRef(new Map<string, ReminderEntry>());
  const queueRef = useRef<ReminderEntry[]>([]);
  const queuedKeysRef = useRef(new Set<string>());
  const shownKeysRef = useRef(new Set<string>());
  const activeToastRef = useRef<{ key: string; toastId: string } | null>(null);

  const schedulePump = useCallback(() => {
    if (!mountedRef.current || pumpScheduledRef.current) return;
    pumpScheduledRef.current = true;
    setTimeout(() => {
      pumpScheduledRef.current = false;
      pumpQueueRef.current();
    }, 0);
  }, []);

  const finishToast = useCallback(
    (key: string, toastId: string) => {
      const active = activeToastRef.current;
      if (!active || active.key !== key || active.toastId !== toastId) return;
      activeToastRef.current = null;
      schedulePump();
    },
    [schedulePump],
  );

  const scheduleExpiryCheck = useCallback(() => {
    if (expiryTimerRef.current) clearTimeout(expiryTimerRef.current);
    const now = Date.now();
    const nextExpiry = [...currentRef.current.values()]
      .map((entry) => entry.expiresAt)
      .filter((expiresAt) => expiresAt > now)
      .sort((first, second) => first - second)[0];
    if (nextExpiry === undefined) return;

    expiryTimerRef.current = setTimeout(
      () => {
        expiryTimerRef.current = null;
        const currentNow = Date.now();
        for (const [key, entry] of currentRef.current) {
          if (entry.expiresAt <= currentNow) currentRef.current.delete(key);
        }
        queueRef.current = queueRef.current.filter((entry) => {
          const current = currentRef.current.get(entry.key);
          const keep = current?.expiresAt === entry.expiresAt && entry.expiresAt > currentNow;
          if (!keep) queuedKeysRef.current.delete(entry.key);
          return keep;
        });

        const active = activeToastRef.current;
        if (active && !currentRef.current.has(active.key)) {
          activeToastRef.current = null;
          toast.dismiss(active.toastId);
        }
        scheduleExpiryCheck();
        schedulePump();
      },
      Math.max(0, nextExpiry - now + 1),
    );
  }, [schedulePump]);

  const applyReminders = useCallback(
    (reminders: readonly MissionReminder[]) => {
      const now = Date.now();
      const entries = buildReminderEntries(reminders, now);
      const next = new Map(entries.map((entry) => [entry.key, entry]));

      const active = activeToastRef.current;
      if (active && !next.has(active.key)) {
        activeToastRef.current = null;
        toast.dismiss(active.toastId);
      }

      currentRef.current = next;
      queueRef.current = queueRef.current.filter((entry) => {
        const current = next.get(entry.key);
        const keep = current?.expiresAt === entry.expiresAt;
        if (!keep) queuedKeysRef.current.delete(entry.key);
        return keep;
      });

      for (const entry of entries) {
        if (
          !shownKeysRef.current.has(entry.key) &&
          !queuedKeysRef.current.has(entry.key) &&
          dismissedRef.current[entry.key] !== undefined
        ) {
          continue;
        }
        if (!shownKeysRef.current.has(entry.key) && !queuedKeysRef.current.has(entry.key)) {
          queueRef.current.push(entry);
          queuedKeysRef.current.add(entry.key);
        }
      }

      scheduleExpiryCheck();
      schedulePump();
    },
    [scheduleExpiryCheck, schedulePump],
  );

  const fetchReminders = useCallback(async () => {
    if (fetchInFlightRef.current) return fetchInFlightRef.current;

    const request = (async () => {
      try {
        const response = await fetch("/api/mission-reminder", { cache: "no-store" });
        if (!response.ok || !mountedRef.current) return;
        const body: unknown = await response.json();
        if (mountedRef.current) applyReminders(parseMissionReminders(body));
      } catch (error) {
        if (error instanceof Error) return;
        throw error;
      }
    })();

    fetchInFlightRef.current = request;
    try {
      await request;
    } finally {
      if (fetchInFlightRef.current === request) fetchInFlightRef.current = null;
    }
  }, [applyReminders]);

  const pumpQueue = useCallback(() => {
    if (!mountedRef.current || activeToastRef.current) return;

    const now = Date.now();
    let entry: ReminderEntry | undefined;
    while (queueRef.current.length > 0) {
      const candidate = queueRef.current.shift();
      if (!candidate) break;
      queuedKeysRef.current.delete(candidate.key);
      const current = currentRef.current.get(candidate.key);
      if (
        !current ||
        current.expiresAt !== candidate.expiresAt ||
        candidate.expiresAt <= now ||
        shownKeysRef.current.has(candidate.key) ||
        dismissedRef.current[candidate.key] !== undefined
      ) {
        continue;
      }
      entry = candidate;
      break;
    }
    if (!entry) return;

    const toastId = `mission-reminder:${entry.key}`;
    const leaderName = entry.leader.displayName || entry.leader.username;
    const missionName = entry.missionName || entry.missionCodeName || "the mission";
    shownKeysRef.current.add(entry.key);
    activeToastRef.current = { key: entry.key, toastId };

    toast("Mission feedback", {
      id: toastId,
      description: `Rate ${leaderName}'s leadership on ${missionName}.`,
      action: {
        label: "Rate leader",
        onClick: () => {
          toast.dismiss(toastId);
          finishToast(entry.key, toastId);
          router.push(`/profile/${encodeURIComponent(entry.leader.username)}`);
        },
      },
      cancel: {
        label: "Dismiss reminder",
        onClick: () => {
          dismissedRef.current[entry.key] = entry.expiresAt;
          writeReminderDismissals(dismissedRef.current, Date.now());
          toast.dismiss(toastId);
          finishToast(entry.key, toastId);
        },
      },
      onAutoClose: () => finishToast(entry.key, toastId),
      onDismiss: () => finishToast(entry.key, toastId),
    });
  }, [finishToast, router]);

  pumpQueueRef.current = pumpQueue;

  useEffect(() => {
    mountedRef.current = true;
    const now = Date.now();
    dismissedRef.current = readReminderDismissals(now);
    writeReminderDismissals(dismissedRef.current, now);
    void fetchReminders();

    const interval = setInterval(() => void fetchReminders(), POLL_MS);
    return () => {
      mountedRef.current = false;
      clearInterval(interval);
      if (expiryTimerRef.current) clearTimeout(expiryTimerRef.current);
      const active = activeToastRef.current;
      activeToastRef.current = null;
      if (active) toast.dismiss(active.toastId);
      queueRef.current = [];
      queuedKeysRef.current.clear();
      currentRef.current.clear();
    };
  }, [fetchReminders]);

  useGameTick(() => {
    void fetchReminders();
  });

  return null;
}