'use client';

import type { DashboardDto } from '@impuestos/contracts';
import { formatDateLong, formatGs, formatGsAmount, formatMonthName, type Locale } from '@impuestos/i18n';
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query';
import { ScanLine, X } from 'lucide-react';
import { TraceableNumber } from '@/components/traceable-number';
import { Button, buttonClasses } from '@/components/ui/button';
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';

/** Flow C: position header, then exactly one next action, then the insight feed. */
export function Dashboard({ locale, fullName }: { locale: Locale; fullName: string }) {
  const t = useT();

  const dashboard = useQuery({
    queryKey: ['dashboard'],
    queryFn: ({ signal }) => api.getDashboard(signal),
  });

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

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

  const data = dashboard.data;
  // Flow A6: until the first comprobante arrives there is nothing to show but the way in.
  const nothingYet = !data.hasDocuments;

  return (
    <div className="space-y-4 py-4">
      <div>
        <h1 className="text-2xl font-semibold tracking-tight">{t('home.title')}</h1>
        <p className="text-sm text-[var(--text-muted)]">{fullName}</p>
      </div>

      {nothingYet ? (
        <Card>
          <EmptyState
            icon={<ScanLine aria-hidden className="size-8" />}
            title={t('home.firstRun.title')}
            body={t('home.noPosition')}
            action={
              <Link href="/escanear" className={buttonClasses({ size: 'lg' })}>
                {t('home.firstRun.scan')}
              </Link>
            }
          />
        </Card>
      ) : null}

      {!nothingYet ? (
        <>
          {/* Zone 1: the position, one card per obligation, swipeable on a phone. */}
          <div className="flex snap-x snap-mandatory gap-4 overflow-x-auto pb-1">
            {data.iva ? <IvaCard iva={data.iva} locale={locale} /> : null}
            {data.irp ? <IrpCard irp={data.irp} locale={locale} /> : null}
          </div>

          {/* Zone 2: exactly one next action. */}
          <NextAction action={data.nextAction} locale={locale} />

          {/* Zone 3: the insight feed. */}
          <InsightFeed insights={data.insights} locale={locale} />
        </>
      ) : null}
    </div>
  );
}

function IvaCard({ iva, locale }: { iva: NonNullable<DashboardDto['iva']>; locale: Locale }) {
  const t = useT();
  const owes = iva.aPagar > 0;

  return (
    <Card className="min-w-[85%] shrink-0 snap-start space-y-2 sm:min-w-0 sm:flex-1">
      <p className="text-sm font-medium text-[var(--text-muted)]">
        {t('home.iva.title', { month: formatMonthName(locale, iva.period) })}
      </p>
      <p className="text-sm text-[var(--text-muted)]">
        {owes ? t('home.iva.aPagar') : t('home.iva.aFavor')}
      </p>

      {/* Owing tax on time is neutral, never red (FLOWS.md section 1). */}
      <TraceableNumber
        value={owes ? iva.aPagar : iva.aFavor}
        kind={owes ? 'iva_debito' : 'iva_credito'}
        locale={locale}
        className={owes ? undefined : 'text-positive'}
      />

      <p className="text-sm text-[var(--text-muted)]">
        {t('home.iva.breakdown', {
          debito: formatGsAmount(iva.debito),
          credito: formatGsAmount(iva.credito),
        })}
      </p>
    </Card>
  );
}

function IrpCard({ irp, locale }: { irp: NonNullable<DashboardDto['irp']>; locale: Locale }) {
  const t = useT();

  return (
    <Card className="min-w-[85%] shrink-0 snap-start space-y-2 sm:min-w-0 sm:flex-1">
      <p className="text-sm font-medium text-[var(--text-muted)]">
        {t('home.irp.title', { year: irp.year })}
      </p>
      <TraceableNumber value={irp.projectedTax} kind="irp_deductions" locale={locale} />

      {irp.monthDelta > 0 ? (
        <p className="text-sm text-positive">
          {t('home.irp.delta', { amount: formatGsAmount(irp.monthDelta) })}
        </p>
      ) : null}

      {irp.belowThreshold ? (
        <p className="text-sm text-[var(--text-muted)] text-pretty">
          {t('home.irp.belowThreshold')}
        </p>
      ) : null}
    </Card>
  );
}

function NextAction({
  action,
  locale,
}: {
  action: DashboardDto['nextAction'];
  locale: Locale;
}) {
  const t = useT();

  switch (action.kind) {
    case 'overdue':
      return (
        <Card className="space-y-3 border-overdue">
          <p className="font-medium text-overdue">
            {t('home.next.overdue', {
              form: action.form ?? '120',
              date: action.dueDate ? formatDateLong(locale, action.dueDate) : '',
            })}
          </p>
          <Link href="/vencimientos" className={buttonClasses({ block: true })}>
            {t('home.next.overdueCta')}
          </Link>
        </Card>
      );

    case 'declaration_ready':
      return (
        <Card className="space-y-3 border-attention">
          <p className="font-medium">{t('decl.status.ready')}</p>
          <Link
            href={`/declaraciones/${action.declarationId ?? ''}`}
            className={buttonClasses({ block: true })}
          >
            {t('home.next.reviewCta')}
          </Link>
        </Card>
      );

    case 'deadline_soon':
      return (
        <Card className="space-y-3 border-attention">
          <p className="font-medium text-attention">
            {t('home.next.upcoming', {
              date: action.dueDate ? formatDateLong(locale, action.dueDate) : '',
            })}
          </p>
          <Link href="/vencimientos" className={buttonClasses({ block: true })}>
            {t('home.next.deadlineCta')}
          </Link>
        </Card>
      );

    case 'bandeja':
      return (
        <Card className="space-y-3">
          <p className="font-medium">{t('home.next.bandeja', { count: action.count ?? 0 })}</p>
          <Link href="/bandeja" className={buttonClasses({ block: true })}>
            {t('home.next.bandejaCta')}
          </Link>
        </Card>
      );

    case 'all_clear':
      return (
        <Card className="space-y-1">
          <p className="font-medium text-positive">{t('home.next.allClear')}</p>
          {action.dueDate ? (
            <p className="text-sm text-[var(--text-muted)]">
              {t('home.next.upcoming', { date: formatDateLong(locale, action.dueDate) })}
            </p>
          ) : null}
        </Card>
      );
  }
}

function InsightFeed({
  insights,
  locale,
}: {
  insights: DashboardDto['insights'];
  locale: Locale;
}) {
  const t = useT();
  const queryClient = useQueryClient();

  const dismiss = useMutation({
    mutationFn: (id: string) => api.dismissInsight(id),
    onSuccess: () => queryClient.invalidateQueries({ queryKey: ['dashboard'] }),
  });

  if (insights.length === 0) return null;

  return (
    <ul className="space-y-3">
      {insights.map((insight) => (
        <li key={insight.id}>
          <Card className="space-y-2">
            <p className="font-medium">{insightTitle(insight, t)}</p>
            <p className="text-sm text-[var(--text-muted)] text-pretty">
              {insightBody(insight, t, locale)}
            </p>
            <Button
              type="button"
              variant="ghost"
              disabled={dismiss.isPending}
              onClick={() => dismiss.mutate(insight.id)}
            >
              <X aria-hidden className="size-4" />
              {t('home.insight.dismiss')}
            </Button>
          </Card>
        </li>
      ))}
    </ul>
  );
}

type Translate = ReturnType<typeof useT>;

function insightTitle(insight: DashboardDto['insights'][number], t: Translate): string {
  if (insight.kind === 'deduction_gap') return t('home.insight.gapTitle');
  if (insight.kind === 'month_close') return t('decl.status.ready');
  return t('vto.title');
}

function insightBody(
  insight: DashboardDto['insights'][number],
  t: Translate,
  locale: Locale,
): string {
  if (insight.kind === 'deduction_gap') {
    const category = String(insight.params['category'] ?? 'none');
    return t('home.insight.gapBody', {
      category: t(`categories.${category}` as 'categories.none'),
    });
  }

  if (insight.kind === 'month_close') {
    return t('home.insight.monthClose', {
      month: formatMonthName(locale, String(insight.params['month'] ?? '')),
      savings: formatGsAmount(Number(insight.params['savings'] ?? 0)),
    });
  }

  return t('home.insight.deadline', {
    form: String(insight.params['form'] ?? '120'),
    date: formatDateLong(locale, String(insight.params['date'] ?? '')),
  });
}

export { formatGs };