import { useEffect, useId, useRef } from "react";
import { Trans, useTranslation } from "react-i18next";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { qk } from "../lib/queryKeys";
import { AlertTriangle, Check, Loader2, RefreshCw, ShieldCheck, X, Youtube } from "lucide-react";
import { api, type Me } from "../lib/api";
import { beginGrant, endOnboarding } from "../lib/onboarding";
import { Button } from "./ui/Button";
import Overlay from "./ui/Overlay";
import Toaster from "./ui/Toaster";
import { useOverlayOrder } from "./ui/overlayOrder";
import { useLayer } from "../lib/layerStack";
import { trapTab, useDialogChrome } from "./ui/dialogFocus";
import { IconButton } from "./ui/IconButton";
import { SURFACE } from "./ui/surfaces";

// A first-login wizard that walks the user through granting YouTube access one scope at a
// time, each with a plain explanation and an up-front heads-up about Google's "unverified
// app" screen. Sign-in itself only asks for name/email (no warning); YouTube access is
// always an explicit, informed opt-in here.
//
// The visible step is derived from what's already granted, so the wizard resumes correctly
// after each redirect: no read -> "read", read but no write -> "write", both -> "done".
// Right after read is granted, it auto-imports the user's subscriptions so they land on a
// populated feed (channels already in the shared catalog appear instantly).

// A small reusable heads-up so the Google consent warning never feels like a surprise.
function ConsentHeadsUp() {
  return (
    <div className="flex gap-2.5 rounded-xl border border-warn/30 bg-warn/5 p-3 text-left">
      <AlertTriangle className="w-4 h-4 shrink-0 mt-0.5 text-warn" />
      <p className="text-xs leading-relaxed text-fg/80">
        <Trans
          i18nKey="onboarding.consent"
          components={[
            <span className="font-medium" />,
            <span className="font-medium" />,
            <span className="font-medium" />,
            <a
              href="https://myaccount.google.com/permissions"
              target="_blank"
              rel="noreferrer"
              className="text-accent hover:underline"
            />,
          ]}
        />
      </p>
    </div>
  );
}

function Dots({ index, total }: { index: number; total: number }) {
  return (
    <div className="flex justify-center gap-1.5">
      {Array.from({ length: total }).map((_, i) => (
        <span
          key={i}
          className={`h-1.5 rounded-full transition-all ${
            i === index ? "w-5 bg-accent" : "w-1.5 bg-border"
          }`}
        />
      ))}
    </div>
  );
}

export default function OnboardingWizard({ me, onClose }: { me: Me; onClose: () => void }) {
  const { t } = useTranslation();
  const qc = useQueryClient();
  const importTriggered = useRef(false);

  // Once we have read access, find out whether any subscriptions are imported yet.
  const myStatus = useQuery({
    queryKey: qk.myStatus(),
    queryFn: api.myStatus,
    enabled: me.can_read,
  });

  const importSubs = useMutation({
    mutationFn: () => api.syncSubscriptions(),
    onSuccess: () => {
      // Feed/channels/status now have content — refresh the app behind the wizard.
      qc.invalidateQueries({ queryKey: qk.feed() });
      qc.invalidateQueries({ queryKey: qk.feedSummary() });
      qc.invalidateQueries({ queryKey: qk.channels() });
      qc.invalidateQueries({ queryKey: qk.myStatus() });
    },
    // The step itself says the import failed and offers a retry button — no toast on top.
    meta: { errorShownInline: true },
  });

  const { mutate: startImport } = importSubs;
  // First time we see read access with zero imported channels, pull the user's
  // subscriptions automatically so they don't have to hunt for a button.
  useEffect(() => {
    if (
      me.can_read &&
      myStatus.data &&
      myStatus.data.channels_total === 0 &&
      !importTriggered.current
    ) {
      importTriggered.current = true;
      startImport();
    }
    // `mutate` is stable (react-query memoises it) while the mutation object around it is not, so
    // the effect can name what it calls. The ref keeps it to once regardless.
  }, [me.can_read, myStatus.data, startImport]);

  // Closing without finishing the essential read step suppresses future auto-popups
  // (it stays reachable from Settings). Once read is granted, closing is just "done".
  const close = () => {
    endOnboarding(!me.can_read);
    onClose();
  };
  const overlayOrder = useOverlayOrder(); // this overlay's toast-host rank (see ui/Toaster)

  // A layer in the shared stack, so Escape closes the wizard only when it is on top: a raw document
  // listener ran BEFORE the error dialog's (a sync that failed inside the wizard opens one), and one
  // Esc closed the error AND ended onboarding, skipping the write-scope step (deep-review round 4).
  const layer = useLayer(true, close);

  // The rest of the dialog contract. This is a modal overlay in every way that matters to a user, but
  // it renders its own shell (it is not a titled dialog with a header row), so Escape ordering was all
  // it had: focus started on <body>, nothing announced a dialog, and Tab past the last control walked
  // into the app behind the scrim — where the focus ring is invisible (deep-review round 5). The trap
  // and the roles come from the same place `ui/Modal` gets them, not from a second hand-written copy.
  const panelRef = useRef<HTMLDivElement>(null);
  const rootRef = useRef<HTMLDivElement>(null);
  const titleId = useId();
  useDialogChrome(panelRef, rootRef);
  useEffect(() => {
    const onKey = (e: KeyboardEvent) => {
      // Only while nothing that owns the keyboard is above us: an error dialog opened from inside the
      // wizard owns the Tab, a hover card under the pointer does not.
      if (e.key !== "Tab" || layer.blockingAbove()) return;
      const panel = panelRef.current;
      // The SAME three arguments `ui/Modal` passes, for the same two reasons — and this call had
      // neither of them (round 6, on the commit that extracted the helper so the two shells could
      // not disagree). Scope is the whole dialog, so the toast host beside the panel stays in the
      // Tab cycle (a sticky connection notice's ✕ was unreachable from the keyboard); `container`
      // is the tabIndex=-1 panel, because `panel.contains(panel)` is true, so focus sitting ON the
      // panel — where a click on its dead space puts it — matched no branch at all and a Shift+Tab
      // walked out into the app behind the scrim.
      if (panel) trapTab(e, rootRef.current ?? panel, panel);
    };
    window.addEventListener("keydown", onKey);
    return () => window.removeEventListener("keydown", onKey);
  }, [layer]);

  // Are we currently importing (or about to)? Show a progress screen instead of the
  // "you're connected" step until the first import settles.
  const importing =
    me.can_read &&
    !importSubs.isError &&
    (importSubs.isPending ||
      (importTriggered.current && !importSubs.isSuccess) ||
      (myStatus.data?.channels_total === 0 && !importSubs.isSuccess));

  const step = !me.can_read ? "read" : !me.can_write ? "write" : "done";
  const stepIndex = step === "read" ? 0 : step === "write" ? 1 : 2;

  return (
    <Overlay>
      <div ref={rootRef} className="fixed inset-0 z-overlay grid place-items-center p-4">
        <div
          className="absolute inset-0 bg-black/50 animate-[overlayIn_0.2s_ease]"
          onClick={close}
        />
        <div
          ref={panelRef}
          tabIndex={-1}
          role="dialog"
          aria-modal="true"
          aria-labelledby={titleId}
          className={`${SURFACE.panel} relative w-[min(94vw,460px)] p-7 text-center outline-none animate-[panelIn_0.26s_cubic-bezier(0.22,1,0.36,1)]`}
        >
          <IconButton
            size="md"
            onClick={close}
            className="absolute top-3 right-3"
            label={t("onboarding.close")}
          >
            <X />
          </IconButton>

          {step === "read" && (
            <>
              <div className="mx-auto mb-4 grid place-items-center w-12 h-12 rounded-2xl bg-accent/15 text-accent">
                <Youtube className="w-6 h-6" />
              </div>
              <h2 id={titleId} className="text-lg font-semibold">
                {t("onboarding.read.title")}
              </h2>
              <p className="text-sm text-muted leading-relaxed mt-2 mb-4">
                <Trans
                  i18nKey="onboarding.read.body"
                  components={[<span className="text-fg/90" />]}
                />
              </p>
              <ConsentHeadsUp />
              <div className="mt-5 flex flex-col gap-2">
                <Button size="lg" icon={<Youtube />} onClick={() => beginGrant("read")}>
                  {t("onboarding.read.connect")}
                </Button>
                <Button variant="ghost" size="md" onClick={close}>
                  {t("onboarding.read.skip")}
                </Button>
              </div>
            </>
          )}

          {/* Read granted: show import progress before the optional write step. */}
          {me.can_read && importing && (
            <>
              <div className="mx-auto mb-4 grid place-items-center w-12 h-12 rounded-2xl bg-accent/15 text-accent">
                <Loader2 className="w-6 h-6 animate-spin" />
              </div>
              <h2 id={titleId} className="text-lg font-semibold">
                {t("onboarding.importing.title")}
              </h2>
              <p className="text-sm text-muted leading-relaxed mt-2 mb-2">
                {t("onboarding.importing.body")}
              </p>
            </>
          )}

          {step === "write" && !importing && (
            <>
              <div className="mx-auto mb-4 grid place-items-center w-12 h-12 rounded-2xl bg-accent/15 text-accent">
                <Check className="w-6 h-6" />
              </div>
              <h2 id={titleId} className="text-lg font-semibold">
                {t("onboarding.write.title")}
              </h2>
              <p className="text-sm text-muted leading-relaxed mt-2 mb-4">
                {importSubs.isError ? (
                  <>{t("onboarding.write.importFailed")}</>
                ) : (
                  <>
                    {t("onboarding.write.feedReady", {
                      channels: myStatus.data
                        ? t("onboarding.write.feedReadyChannels", {
                            count: myStatus.data.channels_total,
                          })
                        : "",
                    })}
                  </>
                )}
                {!importSubs.isError && (
                  <Trans
                    i18nKey="onboarding.write.rationale"
                    components={[<span className="text-fg/90" />]}
                  />
                )}
              </p>
              {importSubs.isError && (
                <Button
                  variant="outline"
                  icon={<RefreshCw />}
                  loading={importSubs.isPending}
                  onClick={() => importSubs.mutate()}
                  className="mb-3"
                >
                  {t("onboarding.write.retryImport")}
                </Button>
              )}
              <ConsentHeadsUp />
              <div className="mt-5 flex flex-col gap-2">
                <Button size="lg" icon={<ShieldCheck />} onClick={() => beginGrant("write")}>
                  {t("onboarding.write.enableUnsubscribe")}
                </Button>
                <Button
                  variant="ghost"
                  size="md"
                  onClick={() => {
                    endOnboarding(false);
                    onClose();
                  }}
                >
                  {t("onboarding.write.keepReadOnly")}
                </Button>
              </div>
            </>
          )}

          {step === "done" && !importing && (
            <>
              <div className="mx-auto mb-4 grid place-items-center w-12 h-12 rounded-2xl bg-accent/15 text-accent">
                <Check className="w-6 h-6" />
              </div>
              <h2 id={titleId} className="text-lg font-semibold">
                {t("onboarding.done.title")}
              </h2>
              <p className="text-sm text-muted leading-relaxed mt-2 mb-5">
                {t("onboarding.done.body")}
              </p>
              <Button
                size="lg"
                fullWidth
                onClick={() => {
                  endOnboarding(false);
                  onClose();
                }}
              >
                {t("onboarding.done.done")}
              </Button>
            </>
          )}

          <div className="mt-6">
            <Dots index={stepIndex} total={3} />
          </div>
        </div>
        {/* Toasts raised while the wizard is up (the connection notice among them) show above its
            scrim, not under it — see ui/Toaster. */}
        <Toaster overlay order={overlayOrder} />
      </div>
    </Overlay>
  );
}