How the Crumbloom Engine Works

export function deriveBakeList(
  orders: readonly CakeOrder[],
  subscriptions: readonly StandingSubscription[],
  parLevels: readonly ParLevel[],
  now: Date,
): BakeListRow[] {
  const tomorrow = addDays(now, 1)

  // Monday closure rule: bakery is closed on Mondays, zero bake list
  if (getDay(tomorrow) === 1) {
    return []
  }

  const tomorrowDateStr = format(tomorrow, 'yyyy-MM-dd')

  // 1. Tally pre-orders due tomorrow
  const preOrderCounts: Record<
    string,
    { count: number; eggless: boolean; station: string; unit: string }
  > = {}

  for (const order of orders) {
    const isTomorrow =
      order.pickup.date === tomorrowDateStr ||
      (order.pickup.slot && order.pickup.slot.toLowerCase().includes('tomorrow'))

    if (isTomorrow) {
      const spongeName =
        FLAVOUR_TO_SPONGE_NAME[order.flavour] ?? `${order.flavour} Sponge`
      const spongesNeeded = Math.max(1, order.tiers)
      const isEggless = order.egg === 'eggless'

      const existing = preOrderCounts[spongeName] ?? {
        count: 0,
        eggless: isEggless,
        station: 'Cake Station',
        unit: 'sponges',
      }
      existing.count += spongesNeeded
      if (isEggless) existing.eggless = true
      preOrderCounts[spongeName] = existing
    }
  }

  // 2. Tally active standing subscriptions
  const subscriptionCounts: Record<string, number> = {}
  for (const sub of subscriptions) {
    if (!sub.isPaused && !sub.isTomorrowSkipped) {
      subscriptionCounts[sub.item] =
        (subscriptionCounts[sub.item] ?? 0) + sub.quantity
    }
  }

  // 3. Merge with station par levels (floored by statutory buffer)
  const rows: BakeListRow[] = []
  for (const par of parLevels) {
    const preOrders = preOrderCounts[par.item]?.count ?? 0
    const subCount = subscriptionCounts[par.item] ?? 0
    const demand = preOrders + subCount
    const totalQuantity = Math.max(par.parLevel, demand)
    const eggless = par.eggless ?? preOrderCounts[par.item]?.eggless ?? false

    rows.push({
      id: par.item.toLowerCase().replace(/[^a-z0-9]+/g, '-'),
      station: par.station,
      item: par.item,
      preOrders,
      subscriptions: subCount,
      parLevel: par.parLevel,
      totalQuantity,
      unit: par.unit,
      eggless,
    })
  }

  return rows
}