($inventory[0].inventory | INDEX(.sku)) as $stock
| [.orders[] | select(.status == "paid") | .cartItems[]?]
| group_by(.sku)
| map(
    .[0].sku as $sku
    | (map(.qty) | add) as $demand
    | $stock[$sku] as $item
    | {sku: $sku, demand: $demand,
       available: (if $item == null then null
                   else $item.onHand - $item.reserved end),
       shortage: (if $item == null then null
                  else ([$demand - ($item.onHand - $item.reserved), 0] | max) end),
       missingInventory: ($item == null)}
  )