"use client";

import { t } from "./i18n";
import { useCallback, useEffect, useState, useSyncExternalStore } from "react";

import { fetchHealth, type Health } from "./client-api";
import { settingsStore } from "./settings";

/**
 * Health status for the current browser (re-checks whenever the API key
 * changes). Used by the settings dialog and the API-key gate.
 *
 * Every page mounts its own gate, and one probe can sit for seconds while
 * Ollama answers — so probes are deduplicated per key and cached briefly
 * instead of firing one per mount. The manual re-check always forces.
 */
const HEALTH_TTL_MS = 30_000;

let cache: { key: string; at: number; value: Health } | null = null;
let inflight: { key: string; promise: Promise<Health> } | null = null;

function loadHealth(key: string, force: boolean): Promise<Health> {
  if (!force && cache && cache.key === key && Date.now() - cache.at < HEALTH_TTL_MS) {
    return Promise.resolve(cache.value);
  }
  if (!force && inflight && inflight.key === key) return inflight.promise;

  const promise = fetchHealth()
    .then((value) => {
      cache = { key, at: Date.now(), value };
      return value;
    })
    .finally(() => {
      if (inflight?.promise === promise) inflight = null;
    });
  inflight = { key, promise };
  return promise;
}

export function useHealth() {
  const apiKey = useSyncExternalStore(
    settingsStore.subscribe,
    () => settingsStore.getSnapshot().apiKey,
    () => "",
  );
  const [health, setHealth] = useState<Health | null>(() =>
    cache && cache.key === apiKey ? cache.value : null,
  );
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [checkedAt, setCheckedAt] = useState<number | null>(() =>
    cache && cache.key === apiKey ? cache.at : null,
  );

  const run = useCallback(async (force: boolean) => {
    setLoading(true);
    setError(null);
    try {
      const key = settingsStore.getSnapshot().apiKey;
      setHealth(await loadHealth(key, force));
    } catch (loadError) {
      setError(loadError instanceof Error ? loadError.message : t("api.unreachableShort"));
    } finally {
      // Even a failed check is a check: the panel can say when it last ran.
      setCheckedAt(Date.now());
      setLoading(false);
    }
  }, []);

  useEffect(() => {
    void run(false);
  }, [run, apiKey]);

  /** The settings dialog's re-check button: always a fresh probe. */
  const refresh = useCallback(() => run(true), [run]);

  return { health, loading, error, refresh, apiKey, checkedAt };
}