"use client";

import { AnimatePresence, motion } from "framer-motion";
import { useAppReducedMotion as useReducedMotion } from "@/lib/motion-pref";
import { useCallback, useEffect, useRef, useState, useSyncExternalStore } from "react";

import { useTheme } from "@/lib/theme";
import {
  CheckCircleIcon,
  ExternalLinkIcon,
  EyeIcon,
  EyeOffIcon,
  MoonIcon,
  QuestionIcon,
  SunIcon,
  XIcon,
} from "@/components/icons";
import { Spinner } from "@/components/ui";
import { LOCALES, useI18n } from "@/lib/i18n";
import { verifyOllamaKey } from "@/lib/client-api";
import { ProvidersSection } from "@/components/ProvidersSection";
import { PROVIDERS } from "@/lib/providers";
import { modelsFor, setGeneration, useProviders } from "@/lib/providers-client";
import { saveSettings, settingsStore } from "@/lib/settings";
import { useHealth } from "@/lib/use-health";
import { cn } from "@/lib/utils";

const KEYS_URL = "https://ollama.com/settings/keys";

type GateError = { tone: "invalid" | "offline"; message: string } | null;

/**
 * Full-screen gate shown when this browser has no Ollama API key yet (and the
 * server runs in `user-key` mode). It replaces the app shell entirely: no
 * sidebar, no header. The key is validated with a real one-token probe before
 * it is saved, and it is still stored only in this browser.
 */
export function ApiKeyGate({ children }: { children: React.ReactNode }) {
  const storedKey = useSyncExternalStore(
    settingsStore.subscribe,
    () => settingsStore.getSnapshot().apiKey,
    () => "",
  );
  const [mounted, setMounted] = useState(false);
  useEffect(() => setMounted(true), []);
  const { health } = useHealth();
  const providers = useProviders();

  // Server-key and local-daemon installs never need a browser key.
  const needsKeyMode = health?.authMode !== "local" && health?.authMode !== "server";

  // A paid provider is a valid first-run choice too. As soon as a key is saved
  // the study generation switches to that provider — Ollama stays untouched —
  // and the gate steps aside (the provider's models were listed on save).
  const firstEnabled = PROVIDERS.find((provider) => providers.keys[provider.id]);
  useEffect(() => {
    if (!firstEnabled || providers.generation) return;
    const models = modelsFor(providers, firstEnabled.id);
    if (models.length === 0) return;
    setGeneration({ provider: firstEnabled.id, textModel: models[0], visionModel: models[0] });
  }, [firstEnabled, providers]);
  const providerReady = Boolean(providers.generation && providers.keys[providers.generation.provider]);

  // Until hydration finishes, render the page as usual so a key holder never
  // sees the gate flash. After that, a missing key replaces the app.
  if (!mounted || storedKey || providerReady || !needsKeyMode) return <>{children}</>;

  return <GateScreen />;
}

/** Ghost icon button used for the two top-right controls. */
function CornerButton({
  label,
  title,
  onClick,
  children,
}: {
  label: string;
  title: string;
  onClick: () => void;
  children: React.ReactNode;
}) {
  return (
    <button
      type="button"
      onClick={onClick}
      aria-label={label}
      title={title}
      className="grid size-10 place-items-center rounded-full border border-[var(--field-border)] bg-[var(--gate-card)] text-[var(--text-muted)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
    >
      {children}
    </button>
  );
}

function GateScreen() {
  const reduceMotion = useReducedMotion();
  const { theme, toggle } = useTheme();
  const { locale, setLocale, t } = useI18n();
  const [draft, setDraft] = useState("");
  const [reveal, setReveal] = useState(false);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<GateError>(null);
  const [helpOpen, setHelpOpen] = useState(false);
  const [providersOpen, setProvidersOpen] = useState(false);
  const [keyboardOpen, setKeyboardOpen] = useState(false);
  const inputRef = useRef<HTMLInputElement>(null);
  const rootRef = useRef<HTMLDivElement>(null);
  const wrapRef = useRef<HTMLDivElement>(null);
  const submitRef = useRef<HTMLButtonElement>(null);

  useEffect(() => {
    // Don't force the on-screen keyboard open on touch devices — let the user
    // tap the field when they're ready.
    if (window.matchMedia("(pointer: fine)").matches) inputRef.current?.focus();
  }, []);

  // Keep the field and the Continue button in view while the on-screen keyboard
  // is up (the card itself is locked, so this is done by scrolling the wrapper
  // programmatically rather than by the user).
  const alignKeyboard = useCallback(() => {
    const wrap = wrapRef.current;
    const submit = submitRef.current;
    if (!wrap || !submit) return;
    const wrapBox = wrap.getBoundingClientRect();
    const btnBox = submit.getBoundingClientRect();
    const below = btnBox.bottom + 12 - wrapBox.bottom;
    const above = wrapBox.top + 12 - btnBox.top;
    if (below > 0) wrap.scrollTop += below;
    else if (above > 0) wrap.scrollTop -= above;
  }, []);

  // Pin the gate to the *visual* viewport so the browser never has to pan the
  // page to reveal the focused field. While the on-screen keyboard is up the
  // card is locked (not user-scrollable).
  useEffect(() => {
    const vv = window.visualViewport;
    const root = rootRef.current;
    if (!vv || !root) return;

    const baseline = window.innerHeight;
    let frame = 0;

    const sync = () => {
      if (frame) cancelAnimationFrame(frame);
      frame = requestAnimationFrame(() => {
        root.style.height = `${vv.height}px`;
        root.style.top = `${vv.offsetTop}px`;

        const open = baseline - vv.height > 120;
        setKeyboardOpen(open);
        if (open) alignKeyboard();
      });
    };

    sync();
    vv.addEventListener("resize", sync);
    vv.addEventListener("scroll", sync);
    return () => {
      if (frame) cancelAnimationFrame(frame);
      vv.removeEventListener("resize", sync);
      vv.removeEventListener("scroll", sync);
    };
  }, [alignKeyboard]);

  // Re-align when the card grows/shrinks (e.g. an error message appears) while
  // the keyboard is open.
  useEffect(() => {
    if (!keyboardOpen) return;
    const frame = requestAnimationFrame(alignKeyboard);
    return () => cancelAnimationFrame(frame);
  }, [keyboardOpen, error, busy, alignKeyboard]);

  useEffect(() => {
    if (!helpOpen) return;
    const onKey = (event: KeyboardEvent) => {
      if (event.key === "Escape") setHelpOpen(false);
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [helpOpen]);

  const submit = async (event: React.FormEvent<HTMLFormElement>) => {
    event.preventDefault();
    const key = draft.trim();
    if (!key || busy) return;

    setBusy(true);
    setError(null);
    const check = await verifyOllamaKey(key);

    if (check.result === "valid") {
      // Saving flips the gate off and drops the user into the library.
      saveSettings({ apiKey: key });
      return;
    }
    setError({ tone: check.result === "invalid" ? "invalid" : "offline", message: check.message });
    setBusy(false);
  };

  return (
    <div
      ref={rootRef}
      className="fixed inset-0 h-dvh overflow-hidden overscroll-none"
    >
      {/* corner controls: theme + help ---------------------------------- */}
      <div
        className="absolute z-20 flex items-center gap-2"
        style={{
          top: "max(env(safe-area-inset-top), 1.25rem)",
          right: "max(env(safe-area-inset-right), 1.25rem)",
        }}
      >
        <CornerButton
          label={theme === "dark" ? t("common.switchToLight") : t("common.switchToDark")}
          title={theme === "dark" ? t("common.lightMode") : t("common.darkMode")}
          onClick={toggle}
        >
          {theme === "dark" ? <SunIcon className="size-[18px]" /> : <MoonIcon className="size-[18px]" />}
        </CornerButton>

        <CornerButton
          label={t("language.label")}
          title={t("language.label")}
          onClick={() => {
            const index = LOCALES.findIndex((entry) => entry.id === locale);
            setLocale(LOCALES[(index + 1) % LOCALES.length].id);
          }}
        >
          <span className="text-[12px] font-bold tracking-wide">
            {LOCALES.find((entry) => entry.id === locale)?.short ?? "EN"}
          </span>
        </CornerButton>

        <div className="group relative">
          <CornerButton
            label={t("gate.howGetAria")}
            title={t("gate.howGet")}
            onClick={() => setHelpOpen(true)}
          >
            <QuestionIcon className="size-[18px]" />
          </CornerButton>
          <span
            role="tooltip"
            className="pointer-events-none absolute right-0 top-full mt-2 whitespace-nowrap rounded-lg border border-[var(--hairline)] bg-[var(--gate-card)] px-2.5 py-1.5 text-[11.5px] text-[var(--text-muted)] opacity-0 shadow-[var(--shadow-card)] transition group-hover:opacity-100 group-focus-within:opacity-100"
          >
            {t("gate.howGet")}
          </span>
        </div>
      </div>

      {/* card ----------------------------------------------------------- */}
      <div
        ref={wrapRef}
        className={cn(
          "relative z-10 flex h-full justify-center px-5",
          keyboardOpen
            ? "items-start touch-none overflow-hidden py-3"
            : "items-center overflow-y-auto overscroll-contain py-10",
        )}
      >
        <motion.div
          initial={reduceMotion ? false : { opacity: 0, y: 14 }}
          animate={{ opacity: 1, y: 0 }}
          transition={{ duration: 0.45, ease: [0.22, 1, 0.36, 1] }}
          className="gate-card my-auto w-full max-w-[420px] p-6 px-7 text-center sm:p-8"
        >
          {/* eslint-disable-next-line @next/next/no-img-element -- static app icon, no optimisation needed */}
          <img
            src="/icons/icon-192.png"
            alt=""
            aria-hidden
            className="mx-auto size-14 rounded-[16px] shadow-[var(--shadow-card)]"
          />

          <h1 className="mt-6 text-[24px] font-semibold leading-tight tracking-[-0.02em] text-[var(--text)] sm:text-[28px]">
            {t("gate.title")}
          </h1>
          <p className="mx-auto mt-1.5 max-w-[300px] text-balance text-[15px] leading-relaxed text-[var(--text-subtle)]">
            {t("gate.subtitle")}
          </p>

          <div className="mt-6 flex items-center justify-center gap-2">
            <span className="text-[13px] font-semibold text-[var(--text)]">{t("gate.ollamaLabel")}</span>
            <span className="rounded-full bg-emerald-500/15 px-2 py-0.5 text-[10px] font-bold uppercase tracking-wide text-emerald-700 dark:text-emerald-300">
              {t("gate.free")}
            </span>
          </div>

          <form className="mt-2.5" onSubmit={submit} noValidate>
            <div className="relative">
              <label className="sr-only" htmlFor="gate-api-key">
                {t("gate.apiKeyLabel")}
              </label>
              <input
                ref={inputRef}
                id="gate-api-key"
                type={reveal ? "text" : "password"}
                value={draft}
                onChange={(event) => {
                  setDraft(event.target.value);
                  if (error) setError(null);
                }}
                placeholder={t("gate.placeholder")}
                autoComplete="off"
                autoCapitalize="off"
                spellCheck={false}
                disabled={busy}
                aria-invalid={error?.tone === "invalid" || undefined}
                aria-describedby={error ? "gate-api-key-error" : undefined}
                className="h-12 w-full rounded-[13px] border border-[var(--field-border)] bg-[var(--field)] pl-3.5 pr-12 text-left text-[14px] text-[var(--text)] outline-none transition placeholder:text-[var(--text-subtle)] focus:border-[var(--text-subtle)] disabled:opacity-60"
              />
              <button
                type="button"
                onClick={() => setReveal((value) => !value)}
                aria-label={reveal ? t("gate.hide") : t("gate.show")}
                aria-pressed={reveal}
                className="absolute right-1.5 top-1/2 grid size-9 -translate-y-1/2 place-items-center rounded-[10px] text-[var(--text-subtle)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
              >
                {reveal ? <EyeOffIcon className="size-[18px]" /> : <EyeIcon className="size-[18px]" />}
              </button>
            </div>

            {error ? (
              <p
                id="gate-api-key-error"
                role="alert"
                className={cn(
                  "mt-2.5 text-[12.5px] leading-relaxed",
                  error.tone === "invalid"
                    ? "text-rose-700 dark:text-rose-300"
                    : "text-amber-700 dark:text-amber-300",
                )}
              >
                {error.message}
              </p>
            ) : null}

            <button
              type="submit"
              ref={submitRef}
              disabled={!draft.trim() || busy}
              className={cn(
                "btn-primary mt-3 h-12 w-full rounded-[13px] text-[14.5px] font-medium",
                !draft.trim() && "cursor-not-allowed opacity-45",
              )}
            >
              {busy ? (
                <>
                  <Spinner className="size-4" /> {t("gate.checking")}
                </>
              ) : (
                t("gate.continue")
              )}
            </button>
          </form>

          <div className="mt-4 text-center">
            <button
              type="button"
              onClick={() => setHelpOpen(true)}
              className="inline-flex items-center gap-1.5 text-[12.5px] font-medium text-[var(--text-muted)] transition hover:text-[var(--text)] hover:underline"
            >
              <QuestionIcon className="size-3.5" />
              {t("gate.howGet")}
            </button>
          </div>

          <div className="mt-5 flex items-center gap-3" aria-hidden>
            <span className="h-px flex-1 bg-[var(--hairline-soft)]" />
            <span className="text-[11px] font-medium uppercase tracking-wide text-[var(--text-subtle)]">{t("gate.or")}</span>
            <span className="h-px flex-1 bg-[var(--hairline-soft)]" />
          </div>

          <button
            type="button"
            onClick={() => setProvidersOpen((open) => !open)}
            aria-expanded={providersOpen}
            className="btn-secondary mt-3 h-11 w-full rounded-[13px] text-[13.5px]"
          >
            {t("gate.paidOption")}
          </button>

          {providersOpen ? (
            <div className="mt-3 space-y-2 text-left">
              <p className="text-[11.5px] leading-snug text-[var(--text-subtle)]">{t("gate.paidNote")}</p>
              <ProvidersSection />
            </div>
          ) : null}

          <p className="mx-auto mt-4 max-w-[320px] text-balance text-[12px] leading-relaxed text-[var(--text-subtle)]">
            {t("gate.stays")}
          </p>
        </motion.div>
      </div>

      <HelpDialog open={helpOpen} onClose={() => setHelpOpen(false)} />
    </div>
  );
}

/* ------------------------------------------------------------------ */
/* “How do I get a key?”                                               */
/* ------------------------------------------------------------------ */

function HelpDialog({ open, onClose }: { open: boolean; onClose: () => void }) {
  const reduceMotion = useReducedMotion();
  const { t } = useI18n();

  return (
    <AnimatePresence>
      {open ? (
        <motion.div
          className="fixed inset-0 z-50 flex items-end justify-center bg-black/40 backdrop-blur-sm sm:items-center sm:p-6"
          initial={{ opacity: 0 }}
          animate={{ opacity: 1 }}
          exit={{ opacity: 0 }}
          onClick={onClose}
        >
          <motion.div
            role="dialog"
            aria-modal="true"
            aria-labelledby="gate-help-title"
            initial={reduceMotion ? false : { y: 40, opacity: 0 }}
            animate={{ y: 0, opacity: 1 }}
            exit={reduceMotion ? { opacity: 0 } : { y: 24, opacity: 0 }}
            transition={{ type: "spring", stiffness: 340, damping: 32 }}
            onClick={(event) => event.stopPropagation()}
            className="gate-card glass-sheet thin-scroll max-h-[90dvh] w-full max-w-[480px] overflow-y-auto p-6 pb-safe sm:pb-6"
          >
            <div className="flex items-center justify-between gap-4">
              <h2
                id="gate-help-title"
                className="text-[19px] font-semibold leading-snug tracking-[-0.02em] text-[var(--text)]"
              >
                {t("gate.helpTitle")}
              </h2>
              <button
                type="button"
                onClick={onClose}
                aria-label={t("common.close")}
                className="grid size-9 shrink-0 place-items-center rounded-[10px] text-[var(--text-subtle)] transition hover:bg-[var(--hover)] hover:text-[var(--text)]"
              >
                <XIcon className="size-4" />
              </button>
            </div>

            <div className="mt-4 flex items-start gap-2.5 rounded-xl border border-[var(--gate-callout-border)] bg-[var(--gate-callout-bg)] px-3.5 py-3">
              <CheckCircleIcon className="mt-px size-[18px] shrink-0 text-[var(--text-muted)]" />
              <p className="text-[12.5px] leading-relaxed text-[var(--text-muted)]">
                {t("gate.freeTier.before")}{" "}
                <strong className="font-semibold text-[var(--text)]">{t("gate.freeTier.strong")}</strong>
                {t("gate.freeTier.after")}
              </p>
            </div>

            <ol className="mt-5 space-y-4">
              <Step index={1}>
                {t("gate.step1.before")}{" "}
                <ExternalLink href="https://ollama.com">ollama.com</ExternalLink>{" "}
                {t("gate.step1.after")}
              </Step>
              <Step index={2}>
                {t("gate.step2.before")}{" "}
                <ExternalLink href={KEYS_URL}>ollama.com/settings/keys</ExternalLink>
                {t("gate.step2.after")}
              </Step>
              <Step index={3}>
                {t("gate.step3.before")}{" "}
                <span className="font-medium text-[var(--text-muted)]">{t("gate.step3.strong")}</span>
                {t("gate.step3.after")}
              </Step>
              <Step index={4}>{t("gate.step4")}</Step>
            </ol>

            <p className="mt-5 text-[12px] leading-relaxed text-[var(--text-subtle)]">
              {t("gate.footnote")}
            </p>

            <button
              type="button"
              onClick={onClose}
              className="btn-primary mt-5 h-11 w-full rounded-[13px] text-[14px] font-medium"
            >
              {t("gate.gotIt")}
            </button>
          </motion.div>
        </motion.div>
      ) : null}
    </AnimatePresence>
  );
}

function ExternalLink({ href, children }: { href: string; children: React.ReactNode }) {
  return (
    <a
      href={href}
      target="_blank"
      rel="noreferrer"
      className="inline-flex items-center gap-1 font-medium text-[var(--text)] underline underline-offset-2"
    >
      {children}
      <ExternalLinkIcon className="size-3.5 opacity-60" />
    </a>
  );
}

function Step({ index, children }: { index: number; children: React.ReactNode }) {
  return (
    <li className="flex items-start gap-3">
      <span
        aria-hidden
        className="grid size-6 shrink-0 place-items-center rounded-full border border-[var(--hairline)] text-[11.5px] font-medium tabular-nums text-[var(--text-subtle)]"
      >
        {index}
      </span>
      <span className="text-pretty text-[13px] leading-6 text-[var(--text-muted)]">{children}</span>
    </li>
  );
}