import { useMemo, useState } from 'preact/hooks';
import type { BarConfig, CartItem } from '@wutzcalc/shared';
import { api, formatCents, uuid } from '../api';

interface Props {
  config: BarConfig;
  onChangeBar: () => void;
}

type Line = { drink_id: number; qty: number };

export function Sale({ config, onChangeBar }: Props) {
  const { bar, drinks } = config;
  const [lines, setLines] = useState<Line[]>([]);
  const [pfandReturns, setPfandReturns] = useState(0);
  const [submitting, setSubmitting] = useState(false);

  const drinkById = useMemo(() => {
    const m = new Map<number, typeof drinks[number]>();
    drinks.forEach(d => m.set(d.id, d));
    return m;
  }, [drinks]);

  const total = useMemo(() => {
    const drinksSum = lines.reduce((sum, l) => {
      const d = drinkById.get(l.drink_id);
      if (!d) return sum;
      return sum + (d.price_cents + bar.pfand_cents) * l.qty;
    }, 0);
    return drinksSum - bar.pfand_cents * pfandReturns;
  }, [lines, drinkById, bar.pfand_cents, pfandReturns]);

  function addDrink(drinkId: number) {
    setLines(prev => {
      const i = prev.findIndex(l => l.drink_id === drinkId);
      if (i >= 0) {
        const copy = prev.slice();
        copy[i] = { ...copy[i]!, qty: copy[i]!.qty + 1 };
        return copy;
      }
      return [...prev, { drink_id: drinkId, qty: 1 }];
    });
  }

  function addPfandReturn() {
    setPfandReturns(n => n + 1);
  }

  function clear() {
    setLines([]);
    setPfandReturns(0);
  }

  const pfandCount = useMemo(() => lines.reduce((sum, l) => sum + l.qty, 0), [lines]);

  const isEmpty = lines.length === 0 && pfandReturns === 0;

  async function confirm(crew: boolean) {
    if (isEmpty || submitting) return;
    setSubmitting(true);
    const items: CartItem[] = lines.map(l => ({ drink_id: l.drink_id, qty: l.qty }));
    try {
      await api.createTransaction({
        client_uuid: uuid(),
        bar_id: bar.id,
        crew,
        items,
        pfand_returns: pfandReturns,
      });
      clear();
    } catch (e) {
      alert(`Fehler beim Speichern: ${e}`);
    } finally {
      setSubmitting(false);
    }
  }

  return (
    <div class="tablet">
      <div class="topbar">
        <div class="brand">
          <img class="logo" src="/favicon.svg" alt="" width="28" height="28" />
          <span class="bar-name">{bar.name}</span>
        </div>
        <button class="change" onClick={onChangeBar}>Bar wechseln</button>
      </div>

      <div class="grid">
        {drinks.map(d => (
          <button key={d.id} class="drink" onClick={() => addDrink(d.id)}>
            <div class="name">{d.name}</div>
            <div class="price">{formatCents(d.price_cents)}</div>
            {bar.pfand_cents > 0 && (
              <div class="pfand">+ {formatCents(bar.pfand_cents)} Pfand</div>
            )}
          </button>
        ))}
        {bar.pfand_cents > 0 && (
          <button class="drink pfand-return" onClick={addPfandReturn}>
            <div class="name">Pfand zurück</div>
            <div class="price">−{formatCents(bar.pfand_cents)}</div>
          </button>
        )}
      </div>

      <div class="cart">
        <div class="cart-items">
          {isEmpty && <div class="cart-line muted">Keine Einträge</div>}
          {lines.map((l, i) => {
            const d = drinkById.get(l.drink_id);
            if (!d) return null;
            return (
              <div key={i} class="cart-line">
                <span>{l.qty}× {d.name}</span>
                <span>{formatCents(d.price_cents * l.qty)}</span>
              </div>
            );
          })}
          {bar.pfand_cents > 0 && pfandCount > 0 && (
            <div class="cart-line pfand">
              <span>{pfandCount}× Pfand</span>
              <span>{formatCents(bar.pfand_cents * pfandCount)}</span>
            </div>
          )}
          {pfandReturns > 0 && (
            <div class="cart-line return">
              <span>{pfandReturns}× Pfand zurück</span>
              <span>{formatCents(-bar.pfand_cents * pfandReturns)}</span>
            </div>
          )}
        </div>
        <div class={`cart-total ${total < 0 ? 'negative' : ''}`}>
          {formatCents(total)}
        </div>
        <div class="actions">
          <button class="cancel" onClick={clear} disabled={isEmpty || submitting}>
            Abbrechen
          </button>
          <button class="crew" onClick={() => confirm(true)} disabled={isEmpty || submitting}>
            Crew
          </button>
          <button class="confirm" onClick={() => confirm(false)} disabled={isEmpty || submitting}>
            Bestätigen
          </button>
        </div>
      </div>
    </div>
  );
}