A feed enriched from a lookup

'data-router-join': () => ({
  rows: [], config: {},
  foot: [
    'one order feed enriched from a customer lookup, joined by the data router',
    'an order whose customer is not known yet is held, not shown half-filled',
    'load the customers and the held orders release already carrying the name and tier',
  ],
  mount: (el: HTMLElement, LG: any) => {
    const money = { style: 'currency', currency: 'USD', decimals: 0 } as const;
    const TIER_VARIANTS = { map: { Gold: 'warning', Silver: 'neutral', Bronze: 'info' } };
    const CUSTOMERS = [
      { id: 'C1', kind: 'customer', name: 'Northwind', tier: 'Gold' },
      { id: 'C2', kind: 'customer', name: 'Contoso', tier: 'Silver' },
      { id: 'C3', kind: 'customer', name: 'Fabrikam', tier: 'Gold' },
      { id: 'C4', kind: 'customer', name: 'Adventure Works', tier: 'Bronze' },
      { id: 'C5', kind: 'customer', name: 'Tailwind', tier: 'Silver' },
    ];
    let a = 20260906 >>> 0;
    const rnd = () => { a = (a + 0x6d2b79f5) >>> 0; let t = Math.imul(a ^ (a >>> 15), 1 | a); t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t; return ((t ^ (t >>> 14)) >>> 0) / 4294967296; };
    const ORDERS = Array.from({ length: 24 }, (_, i) => ({
      id: 'O-' + String(1000 + i),
      kind: 'order',
      customerId: 'C' + (1 + Math.floor(rnd() * 5)),
      amount: 200 + Math.round(rnd() * 9_800),
    }));
    el.textContent = '';
    const bar = document.createElement('div');
    bar.style.cssText = 'display:flex;gap:12px;align-items:center;margin-bottom:12px;flex-wrap:wrap';
    const loadBtn = document.createElement('button');
    loadBtn.type = 'button';
    loadBtn.textContent = 'Load the remaining customers';
    loadBtn.style.cssText = 'font:600 13px system-ui;padding:7px 13px;border:1px solid var(--rule);border-radius:8px;background:var(--paper);color:var(--ink-1);cursor:pointer';
    const note = document.createElement('span');
    note.style.cssText = 'font:12.5px system-ui;color:var(--ink-3)';
    bar.append(loadBtn, note);
    const gridsEl = document.createElement('div');
    gridsEl.style.cssText = 'display:grid;grid-template-columns:1.4fr 1fr;gap:12px';
    const ordersCol = document.createElement('div'); ordersCol.style.minWidth = '0';
    const custCol = document.createElement('div'); custCol.style.minWidth = '0';
    const ordersEl = document.createElement('div');
    ordersEl.style.cssText = 'height:360px;border:1px solid var(--rule);border-radius:9px;background:var(--paper);min-width:0';
    const custEl = document.createElement('div');
    custEl.style.cssText = 'height:360px;border:1px solid var(--rule);border-radius:9px;background:var(--paper);min-width:0';
    ordersCol.append(gridTitle('Orders, enriched with the customer'), ordersEl);
    custCol.append(gridTitle('Customers (the lookup)'), custEl);
    gridsEl.append(ordersCol, custCol);
    el.append(bar, gridsEl);
    const ordersGrid = LG.createGrid(ordersEl, {
      rowKey: 'id', theme: 'light',
      columns: [
        { field: 'id', title: 'Order', layout: { width: 110, pin: 'start' } },
        { field: 'customerId', title: 'Cust. id', layout: { width: 100 } },
        { field: 'name', title: 'Customer' },
        { field: 'tier', title: 'Tier', cell: { decoration: 'pill', variant: TIER_VARIANTS }, layout: { width: 110 } },
        { field: 'amount', title: 'Amount', type: 'number', format: money, total: 'sum' },
      ],
      rows: [],
    });
    const custGrid = LG.createGrid(custEl, {
      rowKey: 'id', theme: 'light', edit: true,
      columns: [
        { field: 'id', title: 'Id', layout: { width: 90, pin: 'start' } },
        { field: 'name', title: 'Customer' },
        { field: 'tier', title: 'Tier', edit: true, cell: { decoration: 'pill', variant: TIER_VARIANTS }, layout: { width: 120 } },
      ],
      rows: [],
    });
    let router: any;
    let ordersSrc: any;
    let customersSrc: any;
    let loaded = false;
    const refresh = () => {
      const shown = ordersGrid.rows.count();
      const held = ORDERS.length - shown;
      note.textContent = held
        ? `${shown} orders enriched, ${held} held until their customer is known`
        : `all ${shown} orders enriched`;
    };
    loadDataRouter()
      .then((dr: any) => {
        router = dr.createDataRouter({ key: 'kind', rowKey: 'id' });
        router.attach(ordersGrid, 'order');
        router.attach(custGrid, 'customer');
        ordersSrc = router.addSource('orders', {
          join: { from: 'customers', localKey: 'customerId', foreignKey: 'id', fields: ['name', 'tier'], missing: 'hold' },
        });
        customersSrc = router.addSource('customers');
        customersSrc.load(CUSTOMERS.slice(0, 2));
        ordersSrc.load(ORDERS);
        refresh();
      })
      .catch((err: any) => { note.textContent = 'could not load the data router: ' + (err?.message ?? 'error'); console.error('[data-router-join]', err); });
    loadBtn.addEventListener('click', () => {
      if (loaded || !customersSrc) return;
      loaded = true;
      loadBtn.disabled = true;
      customersSrc.load(CUSTOMERS);
      setTimeout(refresh, 0);
    });
    return () => {
      router?.destroy?.();
      ordersGrid?.destroy?.();
      custGrid?.destroy?.();
    };
  },
}),