import { useEffect, useRef, useState } from "react";
import { useMutation, useQueryClient } from "@tanstack/react-query";
import { useTranslation } from "react-i18next";

import { api, type DiagnosticsLevel } from "../lib/api";
import { levelInForce } from "../lib/diagnostics";
import { focusIsUnclaimed } from "../lib/useFocusKeeper";
import { updateMeCache, useMe } from "../lib/useMe";
import { Button } from "./ui/Button";
import SegmentedToggle from "./ui/SegmentedToggle";
import { Section, SettingRow } from "./ui/form";
import MyLogViewer from "./MyLogViewer";
import { RecorderSettings } from "./DebugRecorder";
import { formatUnit } from "../lib/format";

const LEVELS: readonly DiagnosticsLevel[] = ["INFO", "DEBUG", "TRACE"];

/** Hours and minutes until `until`, refreshed every 30 s — the status line counts down. */
function useRemaining(until: string | null): { h: number; m: number } | null {
  // The clock is read at render, and the interval only re-renders: a `now` held in state was the
  // moment the page MOUNTED, so a level raised two minutes after opening Settings read "24 h 2 m"
  // until the first tick (prod UAT 2026-09-19).
  const [, tick] = useState(0);
  useEffect(() => {
    if (!until) return;
    const id = window.setInterval(() => tick((n) => n + 1), 30_000);
    return () => window.clearInterval(id);
  }, [until]);
  if (!until) return null;
  // eslint-disable-next-line react-hooks/purity -- same as DebugRecorder's elapsed clock, and the comment above records the prod UAT finding that a state-held `now` produced: a level raised two minutes after opening Settings read "24 h 2 m" until the first tick.
  const minutes = Math.max(0, Math.ceil((Date.parse(until) - Date.now()) / 60_000));
  return { h: Math.floor(minutes / 60), m: minutes % 60 };
}

// Settings → Diagnosztika: the consented diagnostics level and the tab's own log.
//
// There is no separate on/off switch: Alap IS off. Choosing Részletes or Teljes does not change
// anything yet — it opens the consent box under the picker, which says what will be recorded, that
// the server keeps it and for how long, and that it lapses; only its button raises the level.
// Returning to Alap needs no consent and happens at once.
export default function DiagnosticsSettings() {
  const { t, i18n } = useTranslation();
  const lang = i18n.language;
  const me = useMe();
  const qc = useQueryClient();
  const state = me.diagnostics;
  const current = levelInForce(state);
  const [pending, setPending] = useState<DiagnosticsLevel | null>(null);
  const remaining = useRemaining(current === "INFO" ? null : (state?.until ?? null));

  // The consent box and the status line each go away with the button that closed them — the one
  // holding the focus. Put it back on the level picker (its chosen option) rather than let it fall
  // to <body>, where the next Tab starts over from the top of the page. Only when it did fall: a
  // user who moved on while the request was out keeps their place.
  //
  // Watched until that button is actually GONE, not for one render: a saved level arrives as two
  // updates (the `me` cache, then the closed box), and the first render still has the button in the
  // page — measured in Chrome, where a one-shot check spent itself there and the focus then fell.
  const pickerRef = useRef<HTMLDivElement>(null);
  const closedFrom = useRef<Element | null>(null);
  useEffect(() => {
    const from = closedFrom.current;
    if (!from || from.isConnected) return;
    closedFrom.current = null;
    if (!focusIsUnclaimed()) return;
    pickerRef.current?.querySelector<HTMLElement>('[aria-pressed="true"]')?.focus();
  });
  const watchFocus = () => {
    closedFrom.current = document.activeElement;
  };

  const change = useMutation({
    mutationFn: api.setDiagnosticsLevel,
    meta: { failTitle: "settings.diagnostics.failed" },
    onSuccess: (result) => {
      watchFocus();
      updateMeCache(qc, (prev) => ({ ...prev, diagnostics: result.diagnostics }));
      setPending(null);
    },
  });

  const cancel = () => {
    watchFocus();
    setPending(null);
  };

  const choose = (level: DiagnosticsLevel) => {
    if (level === "INFO") {
      setPending(null);
      if (current !== "INFO") change.mutate("INFO");
    } else {
      setPending(level === current ? null : level);
    }
  };

  const levelName = (level: DiagnosticsLevel) => t(`settings.diagnostics.levels.${level}`);

  return (
    <>
      <Section title={t("settings.diagnostics.title")}>
        <SettingRow
          label={t("settings.diagnostics.level")}
          hint={t("settings.diagnostics.levelHint")}
        >
          <div ref={pickerRef}>
            <SegmentedToggle
              size="md"
              ariaLabel={t("settings.diagnostics.level")}
              value={pending ?? current}
              onChange={choose}
              options={LEVELS.map((level) => ({ value: level, label: levelName(level) }))}
            />
          </div>
        </SettingRow>

        {pending && (
          <div
            data-testid="diagnostics-consent"
            className="mt-2 rounded-xl border border-border bg-accent/5 p-3 text-sm"
          >
            <p className="font-semibold">{t(`settings.diagnostics.consent.title.${pending}`)}</p>
            <ul className="mt-1.5 mb-3 list-disc space-y-1 pl-5 text-muted">
              <li>{t(`settings.diagnostics.consent.what.${pending}`)}</li>
              <li>
                {t("settings.diagnostics.consent.server", {
                  count: state?.retention_days ?? 7,
                })}
              </li>
              <li>{t("settings.diagnostics.consent.never")}</li>
              <li>
                {t("settings.diagnostics.consent.lapse")}{" "}
                <a
                  href="/privacy#diagnostics"
                  target="_blank"
                  rel="noreferrer"
                  className="text-accent hover:underline"
                >
                  {t("settings.diagnostics.consent.policy")}
                </a>
              </li>
            </ul>
            <div className="flex flex-wrap justify-end gap-2">
              <Button variant="ghost" size="sm" onClick={cancel}>
                {t("settings.diagnostics.consent.cancel")}
              </Button>
              <Button
                size="sm"
                data-testid="diagnostics-consent-confirm"
                loading={change.isPending}
                onClick={() => change.mutate(pending)}
              >
                {t("settings.diagnostics.consent.confirm")}
              </Button>
            </div>
          </div>
        )}

        {current !== "INFO" && !pending && remaining && (
          // Not a live region: the countdown changes every minute, and a screen reader would read
          // the whole line out again each time for as long as the page is open.
          <div
            data-testid="diagnostics-status"
            className="mt-2 flex flex-wrap items-center justify-between gap-2 rounded-xl border border-warn/40 bg-warn/10 px-3 py-2 text-sm"
          >
            <span className="inline-flex items-center gap-2">
              <span className="h-2 w-2 shrink-0 rounded-full bg-warn" aria-hidden />
              <span>
                {t("settings.diagnostics.status", {
                  level: levelName(current),
                  time:
                    remaining.h > 0
                      ? `${formatUnit(remaining.h, "hour", lang)} ${formatUnit(remaining.m, "minute", lang)}`
                      : formatUnit(remaining.m, "minute", lang),
                })}
              </span>
            </span>
            <Button variant="link" loading={change.isPending} onClick={() => change.mutate("INFO")}>
              {t("settings.diagnostics.revert")}
            </Button>
          </div>
        )}
      </Section>

      <Section title={t("recorder.settings.title")}>
        <RecorderSettings />
      </Section>

      <Section title={t("settings.myLog.title")}>
        <MyLogViewer />
      </Section>
    </>
  );
}