'use client';

import type { IrpCategory } from '@impuestos/contracts';
import { formatDateLong, formatGs, type Locale } from '@impuestos/i18n';
import { IRP_CATEGORIES } from '@impuestos/rules';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { Check, X } from 'lucide-react';
import { useCallback, useEffect, useRef, useState } from 'react';
import { CategoryPicker } from '@/components/category-picker';
import { ConfettiMoment } from '@/components/confetti-moment';
import { Button, buttonClasses } from '@/components/ui/button';
import { CheckDraw } from '@/components/ui/check-draw';
import { Card } from '@/components/ui/card';
import { EmptyState } from '@/components/ui/empty-state';
import { Skeleton } from '@/components/ui/skeleton';
import { Link } from '@/i18n/navigation';
import { useT } from '@/i18n/t';
import { api } from '@/lib/api';
import { DURATION, EASE, gsap, usePrefersReducedMotion } from '@/lib/motion';
import { cn } from '@/lib/utils';

/** Past this many pixels, letting go commits the swipe. */
const COMMIT_PX = 96;

/**
 * Flow B4. A stack of documents waiting for a yes. Every gesture has a button and a key,
 * because a swipe is unusable with a keyboard and invisible to a screen reader.
 */
export function Bandeja({ locale }: { locale: string }) {
  const t = useT();
  const queryClient = useQueryClient();
  const [index, setIndex] = useState(0);
  const [picking, setPicking] = useState(false);
  const [celebrating, setCelebrating] = useState(false);
  const reduced = usePrefersReducedMotion();

  // The drag lives on the element rather than in state: a re-render per pointer move is
  // both slower and a fight with GSAP over who owns the transform.
  const card = useRef<HTMLDivElement>(null);
  const nextCard = useRef<HTMLDivElement>(null);
  const dragStart = useRef<number | null>(null);

  const pending = useQuery({
    queryKey: ['documents', { status: 'needs_review' }],
    queryFn: ({ signal }) => api.listDocuments({ status: 'needs_review' }, signal),
  });

  /**
   * Whether anything has ever been confirmed. FLOWS.md A6 makes the first confirmed
   * document the moment worth celebrating, and it is only the first one: the count is read
   * before the confirm so the answer is about what the user had, not what they now have.
   */
  const confirmed = useQuery({
    queryKey: ['documents', { status: 'confirmed' }],
    queryFn: ({ signal }) => api.listDocuments({ status: 'confirmed' }, signal),
  });
  const nothingConfirmedYet = confirmed.data?.total === 0;

  const documents = pending.data?.items ?? [];
  // Confirming the last card shortens the list under us. Clamping here rather than in an
  // effect keeps the render consistent and avoids a cascading update.
  const safeIndex = Math.min(index, Math.max(0, documents.length - 1));
  const current = documents[safeIndex];
  const next = documents[safeIndex + 1];

  const invalidate = useCallback(
    () => queryClient.invalidateQueries({ queryKey: ['documents'] }),
    [queryClient],
  );

  const confirm = useMutation({
    mutationFn: (id: string) => api.confirmDocument(id),
    onSuccess: async () => {
      if (nothingConfirmedYet) setCelebrating(true);
      await invalidate();
    },
  });

  const reject = useMutation({
    mutationFn: (args: { id: string; reason: 'not_mine' | 'duplicate' | 'other' }) =>
      api.rejectDocument(args.id, { reason: args.reason }),
    onSuccess: invalidate,
  });

  const reclassify = useMutation({
    mutationFn: (args: { id: string; irpCategory: IrpCategory | 'none' }) =>
      api.patchClassification(args.id, { irpCategory: args.irpCategory }),
    onSuccess: async () => {
      setPicking(false);
      await invalidate();
    },
  });

  /**
   * Sends the card off the way it was pushed, brings the one behind it forward, and only
   * then does the thing (FLOWS.md B4: fly out on commit, next card scales up). Under
   * reduced motion the action happens immediately and nothing moves.
   */
  const flyOut = useCallback(
    (direction: 1 | -1, run: () => void) => {
      const node = card.current;
      if (reduced || !node) {
        run();
        return;
      }
      gsap.to(node, {
        x: direction * 520,
        rotation: direction * 16,
        autoAlpha: 0,
        duration: DURATION.base,
        ease: 'power2.in',
        onComplete: () => {
          gsap.set(node, { clearProps: 'all' });
          run();
        },
      });
      if (nextCard.current) {
        gsap.to(nextCard.current, { scale: 1, opacity: 1, duration: DURATION.base, ease: EASE });
      }
    },
    [reduced],
  );

  const settle = useCallback(() => {
    const node = card.current;
    if (!node) return;
    if (reduced) {
      gsap.set(node, { x: 0, rotation: 0 });
      return;
    }
    gsap.to(node, { x: 0, rotation: 0, duration: DURATION.base, ease: EASE });
  }, [reduced]);

  // Desktop keyboard mirrors of every gesture (FLOWS.md B4).
  useEffect(() => {
    function onKey(event: KeyboardEvent) {
      if (!current || picking) return;
      if (event.key === 'j') setIndex(Math.min(safeIndex + 1, documents.length - 1));
      else if (event.key === 'k') setIndex(Math.max(safeIndex - 1, 0));
      else if (event.key === 'Enter') flyOut(1, () => confirm.mutate(current.id));
      else if (event.key === 'x' || event.key === 'X')
        flyOut(-1, () => reject.mutate({ id: current.id, reason: 'other' }));
      else if (/^[1-8]$/.test(event.key)) {
        const category = IRP_CATEGORIES[Number(event.key) - 1];
        if (category) reclassify.mutate({ id: current.id, irpCategory: category });
      } else return;
      event.preventDefault();
    }

    window.addEventListener('keydown', onKey);
    return () => window.removeEventListener('keydown', onKey);
  }, [current, documents.length, safeIndex, picking, confirm, reject, reclassify, flyOut]);

  if (pending.isPending) {
    return (
      <div className="space-y-4 py-4">
        <Card>
          <Skeleton name="bandeja-card" />
        </Card>
        <Card>
          <Skeleton name="bandeja-card" />
        </Card>
      </div>
    );
  }

  if (pending.isError) {
    return (
      <Card className="my-4 space-y-3">
        <p role="alert" className="text-sm">
          {t('common.error.generic')}
        </p>
        <Button type="button" onClick={() => void pending.refetch()}>
          {t('common.retry')}
        </Button>
      </Card>
    );
  }

  if (!current) {
    return (
      <div className="py-4">
        <Card>
          <EmptyState
            icon={<CheckDraw className="size-8" />}
            title={t('bandeja.empty')}
            body={t('bandeja.emptyBody')}
            action={
              <Link href="/escanear" className={buttonClasses({ size: 'lg' })}>
                {t('scan.fab')}
              </Link>
            }
          />
        </Card>
      </div>
    );
  }

  const category = current.classification?.irpCategory ?? 'none';
  const highConfidence = (current.classification?.confidence ?? 0) >= 0.8;

  return (
    <div className="space-y-4 py-4">
      <ConfettiMoment play={celebrating} />

      <div className="flex items-baseline justify-between">
        <h1 className="text-2xl font-semibold tracking-tight">{t('bandeja.title')}</h1>
        <span className="text-sm text-[var(--text-muted)]">
          {t('bandeja.count', { count: documents.length })}
        </span>
      </div>

      <div className="relative">
        {/*
          The shoulder of the next card, so the stack is visible and committing this one
          has somewhere to go. A shoulder rather than a whole card behind: the front card's
          height depends on its content, and a full card would sit entirely hidden behind a
          tall one and entirely exposed behind a short one.
        */}
        {next ? (
          <div
            ref={nextCard}
            aria-hidden
            className="absolute inset-x-4 -top-2 h-8 origin-bottom scale-95 rounded-2xl border bg-[var(--surface-raised)] opacity-70"
          />
        ) : null}

      <Card
        ref={card}
        data-testid="bandeja-card"
        className="relative touch-pan-y space-y-4 select-none"
        onPointerDown={(event) => {
          dragStart.current = event.clientX;
          event.currentTarget.setPointerCapture(event.pointerId);
        }}
        onPointerMove={(event) => {
          if (dragStart.current === null) return;
          const offset = event.clientX - dragStart.current;
          gsap.set(card.current, { x: offset, rotation: offset / 40 });
        }}
        onPointerUp={(event) => {
          const start = dragStart.current;
          dragStart.current = null;
          if (start === null) return;
          const offset = event.clientX - start;

          if (offset > COMMIT_PX) flyOut(1, () => confirm.mutate(current.id));
          else if (offset < -COMMIT_PX) {
            settle();
            setPicking(true);
          } else settle();
        }}
      >
        <div className="flex items-start justify-between gap-4">
          <div className="min-w-0">
            <p className="truncate text-lg font-medium">{current.emitterName}</p>
            <p className="text-sm text-[var(--text-muted)]">
              {formatDateLong(locale as Locale, current.issueDate)}
            </p>
          </div>
          <span
            className={cn(
              'shrink-0 rounded-full px-2.5 py-0.5 text-xs font-medium',
              highConfidence ? 'bg-positive-soft text-positive' : 'bg-attention-soft text-attention',
            )}
          >
            {highConfidence ? t('bandeja.confidence.high') : t('bandeja.confidence.low')}
          </span>
        </div>

        <p className="tnum text-4xl font-semibold tracking-tight">{formatGs(current.total)}</p>

        <p className="text-sm text-[var(--text-muted)]">
          {t('scan.result.suggested', { category: t(`categories.${category}` as const) })}
        </p>

        {current.classification?.reasons.length ? (
          <ul className="space-y-1 text-xs text-[var(--text-muted)]">
            {current.classification.reasons.map((reason) => (
              <li key={reason}>{t(`classification.reason.${reason}` as 'classification.reason.irp_no_category')}</li>
            ))}
          </ul>
        ) : null}
      </Card>
      </div>

      {picking ? (
        <Card className="space-y-3">
          <h2 className="font-medium">{t('scan.result.changeCat')}</h2>
          <CategoryPicker
            value={category}
            onSelect={(next) => reclassify.mutate({ id: current.id, irpCategory: next })}
          />
          <Button type="button" variant="ghost" block onClick={() => setPicking(false)}>
            {t('common.cancel')}
          </Button>
        </Card>
      ) : (
        /* Confirm leads and takes the full width: it is the action on almost every card,
           and three buttons across a 390px screen wraps the longest label. */
        <div className="space-y-2">
          <Button
            type="button"
            size="lg"
            block
            disabled={confirm.isPending}
            onClick={() => flyOut(1, () => confirm.mutate(current.id))}
          >
            <Check aria-hidden className="size-4" />
            {t('bandeja.confirm')}
          </Button>
          <div className="grid grid-cols-2 gap-2">
            <Button
              type="button"
              variant="secondary"
              disabled={reject.isPending}
              onClick={() => flyOut(-1, () => reject.mutate({ id: current.id, reason: 'other' }))}
            >
              <X aria-hidden className="size-4" />
              {t('scan.result.discard')}
            </Button>
            <Button type="button" variant="secondary" onClick={() => setPicking(true)}>
              {t('scan.result.changeCat')}
            </Button>
          </div>
        </div>
      )}

      <div className="space-y-1 text-xs text-[var(--text-muted)]">
        <p>{t('bandeja.swipeHint')}</p>
        <p className="hidden sm:block">{t('bandeja.keyboardHint')}</p>
        <p>
          {t('bandeja.autoConfirmNote', { days: 7 })}{' '}
          <Link href="/perfil" className="underline">
            {t('bandeja.autoConfirmLink')}
          </Link>
        </p>
      </div>
    </div>
  );
}