'use client';

import type { DocumentDto, ScanResultDto } from '@impuestos/contracts';
import { formatDateLong, formatGs, type Locale } from '@impuestos/i18n';
import { useMutation, useQueryClient } from '@tanstack/react-query';
import { Flashlight, Upload } from 'lucide-react';
import { useCallback, useEffect, useRef, useState } from 'react';
import { Button, buttonClasses } from '@/components/ui/button';
import { Card } from '@/components/ui/card';
import { Skeleton } from '@/components/ui/skeleton';
import { Link, useRouter } from '@/i18n/navigation';
import { useT } from '@/i18n/t';
import { api } from '@/lib/api';
import { enqueueCapture, listQueue, subscribeToQueue } from '@/lib/offline-queue';
import { captureFrame, decodeQr, decodeQrFromVideo } from '@/lib/qr';
import { cn } from '@/lib/utils';

/** How long to look for a QR before offering the plain photo path (FLOWS.md B1). */
const NO_QR_HINT_AFTER_MS = 4000;
const DECODE_INTERVAL_MS = 250;

type Outcome =
  | { kind: 'document'; document: DocumentDto }
  | { kind: 'needs_manual'; fileId: string };

export function ScanScreen({ locale }: { locale: string }) {
  const t = useT();
  const router = useRouter();
  const queryClient = useQueryClient();

  const video = useRef<HTMLVideoElement>(null);
  const stream = useRef<MediaStream | null>(null);
  const busy = useRef(false);

  const [cameraFailed, setCameraFailed] = useState(false);
  const [showNoQrHint, setShowNoQrHint] = useState(false);
  const [torchOn, setTorchOn] = useState(false);
  const [outcome, setOutcome] = useState<Outcome | null>(null);
  // Whether anything of this reader's is still waiting to be sent. It follows the queue
  // rather than being set once, so the notice goes away when the capture actually lands.
  const [queued, setQueued] = useState(false);

  useEffect(() => {
    const check = () => void listQueue().then((items) => setQueued(items.length > 0));
    const unsubscribe = subscribeToQueue(check);
    void Promise.resolve().then(check);
    return unsubscribe;
  }, []);

  const upload = useMutation({
    mutationFn: async (input: { file: File; qrPayload: string | null }) => {
      const result: ScanResultDto = await api.scanDocument(input.file, input.qrPayload);
      return result;
    },
    onSuccess: async (result) => {
      await queryClient.invalidateQueries({ queryKey: ['documents'] });
      if ('needsManual' in result) {
        setOutcome({ kind: 'needs_manual', fileId: result.fileId });
        return;
      }
      setOutcome({ kind: 'document', document: result });
    },
  });

  const submit = useCallback(
    (file: File, qrPayload: string | null) => {
      if (busy.current) return;

      /**
       * Offline, the capture is kept rather than lost (FLOWS.md B2). The chip in the shell
       * sends it the moment there is a connection, so this screen can say so and move on.
       */
      if (!navigator.onLine) {
        void enqueueCapture(file, qrPayload);
        return;
      }

      busy.current = true;
      upload.mutate({ file, qrPayload }, { onSettled: () => (busy.current = false) });
    },
    [upload],
  );

  // Live capture: the camera is only opened here, and always released on unmount.
  useEffect(() => {
    if (outcome) return;
    let cancelled = false;

    async function open() {
      try {
        const media = await navigator.mediaDevices.getUserMedia({
          video: { facingMode: 'environment' },
          audio: false,
        });
        if (cancelled) {
          media.getTracks().forEach((track) => track.stop());
          return;
        }
        stream.current = media;
        if (video.current) {
          video.current.srcObject = media;
          await video.current.play().catch(() => undefined);
        }
      } catch {
        if (!cancelled) setCameraFailed(true);
      }
    }

    void open();
    return () => {
      cancelled = true;
      stream.current?.getTracks().forEach((track) => track.stop());
      stream.current = null;
    };
  }, [outcome]);

  // A QR hit auto-captures: there is nothing for the user to decide once we have it.
  useEffect(() => {
    if (cameraFailed || outcome) return;
    const hintTimer = setTimeout(() => setShowNoQrHint(true), NO_QR_HINT_AFTER_MS);

    const timer = setInterval(() => {
      void (async () => {
        if (!video.current || busy.current) return;
        const payload = await decodeQrFromVideo(video.current);
        if (!payload || !video.current) return;

        const frame = await captureFrame(video.current);
        if (frame) {
          navigator.vibrate?.(40);
          submit(frame, payload);
        }
      })();
    }, DECODE_INTERVAL_MS);

    return () => {
      clearTimeout(hintTimer);
      clearInterval(timer);
    };
  }, [cameraFailed, outcome, submit]);

  async function toggleTorch() {
    const track = stream.current?.getVideoTracks()[0];
    if (!track) return;
    try {
      const next = !torchOn;
      // `torch` is a real constraint on mobile but is not in the DOM lib's type yet.
      await track.applyConstraints({ advanced: [{ torch: next }] } as unknown as MediaTrackConstraints);
      setTorchOn(next);
    } catch {
      // Most desktop cameras have no torch. Nothing to say about it.
    }
  }

  async function onPick(file: File) {
    // Decoding before upload keeps the QR path working for a photo from the gallery.
    submit(file, await decodeQr(file));
  }

  if (outcome?.kind === 'document') {
    return (
      <ScanResult
        document={outcome.document}
        locale={locale as Locale}
        onAnother={() => setOutcome(null)}
      />
    );
  }

  if (outcome?.kind === 'needs_manual') {
    router.push(`/comprobantes/nuevo?fileId=${encodeURIComponent(outcome.fileId)}`);
    return (
      <Card className="my-4">
        <Skeleton name="profile-section" />
      </Card>
    );
  }

  return (
    <div className="space-y-4 py-4">
      <h1 className="text-2xl font-semibold tracking-tight">{t('scan.title')}</h1>

      <div className="relative overflow-hidden rounded-2xl bg-black">
        <video
          ref={video}
          playsInline
          muted
          aria-label={t('scan.hint')}
          className={cn('aspect-3/4 w-full object-cover', cameraFailed && 'hidden')}
        />
        {cameraFailed ? (
          <p className="p-8 text-center text-sm text-white">{t('scan.cameraDenied')}</p>
        ) : (
          <>
            {/* Frame guide: shows where the QR has to sit. */}
            <div
              aria-hidden
              className="pointer-events-none absolute inset-x-8 top-1/4 aspect-square rounded-2xl border-2 border-white/70"
            />
            <button
              type="button"
              onClick={() => void toggleTorch()}
              aria-pressed={torchOn}
              className="absolute top-3 right-3 rounded-full bg-black/50 p-2.5 text-white"
            >
              <Flashlight aria-hidden className="size-5" />
              <span className="sr-only">{t('scan.torch')}</span>
            </button>
          </>
        )}
      </div>

      <p className="text-center text-sm text-[var(--text-muted)]">
        {showNoQrHint || cameraFailed ? t('scan.noQrHint') : t('scan.hint')}
      </p>

      {upload.isPending ? (
        <Card>
          <p className="mb-3 text-sm text-[var(--text-muted)]">{t('scan.processing')}</p>
          <Skeleton name="bandeja-card" />
        </Card>
      ) : null}

      {queued ? (
        <p role="status" className="text-center text-sm text-[var(--text-muted)]">
          {t('offline.queued')}
        </p>
      ) : null}

      {upload.isError ? (
        <p role="alert" className="text-center text-sm text-overdue">
          {t('common.error.generic')}
        </p>
      ) : null}

      <div className="space-y-2">
        <label className={cn(buttonClasses({ variant: 'secondary', size: 'lg', block: true }), 'cursor-pointer')}>
          <Upload aria-hidden className="size-4" />
          {t('scan.upload')}
          <input
            type="file"
            accept="image/*,application/pdf"
            className="sr-only"
            onChange={(event) => {
              const file = event.target.files?.[0];
              if (file) void onPick(file);
            }}
          />
        </label>

        {!cameraFailed ? (
          <Button
            type="button"
            size="lg"
            block
            disabled={upload.isPending}
            onClick={() => {
              void (async () => {
                if (!video.current) return;
                const frame = await captureFrame(video.current);
                if (frame) submit(frame, await decodeQr(frame));
              })();
            }}
          >
            {t('scan.shutter')}
          </Button>
        ) : null}
      </div>
    </div>
  );
}

function ScanResult({
  document,
  locale,
  onAnother,
}: {
  document: DocumentDto;
  locale: Locale;
  onAnother: () => void;
}) {
  const t = useT();
  const merged = document.merged === true;

  return (
    <div className="space-y-4 py-4">
      <Card className="space-y-4">
        <div className="flex items-center justify-between gap-3">
          <h1 className="text-xl font-semibold tracking-tight text-balance">
            {merged ? t('scan.duplicate.title') : t('scan.result.title')}
          </h1>
          <span className="shrink-0 rounded-full bg-positive-soft px-2.5 py-0.5 text-xs font-medium text-positive">
            {document.verifiedDnit ? t('scan.verified') : t('scan.registered')}
          </span>
        </div>

        {merged ? (
          <p className="text-sm text-[var(--text-muted)] text-pretty">
            {t('scan.duplicate.body', { date: formatDateLong(locale, document.issueDate) })}
          </p>
        ) : null}

        <dl className="space-y-2 text-sm">
          <Row label={t('scan.result.emitter')} value={document.emitterName} />
          <Row label={t('scan.result.date')} value={formatDateLong(locale, document.issueDate)} />
          <Row label={t('scan.result.total')} value={formatGs(document.total)} />
          {document.classification ? (
            <Row
              label={t('bandeja.category')}
              value={t(`categories.${document.classification.irpCategory}` as const)}
            />
          ) : null}
        </dl>

        <div className="flex flex-col gap-2">
          <Link href="/bandeja" className={buttonClasses({ size: 'lg', block: true })}>
            {t('scan.goToBandeja')}
          </Link>
          <Button type="button" variant="secondary" block onClick={onAnother}>
            {t('scan.another')}
          </Button>
        </div>
      </Card>
    </div>
  );
}

function Row({ label, value }: { label: string; value: string }) {
  return (
    <div className="flex items-baseline justify-between gap-4">
      <dt className="text-[var(--text-muted)]">{label}</dt>
      <dd className="text-right font-medium">{value}</dd>
    </div>
  );
}