Composing Workflow Patterns

async function intake(file) {
  const sorted = await sortDocument(file)                 // Routing
  if (sorted.kind !== "invoice") return otherPath(sorted, file)

  const invoice = await extractFields(file)               // Chain step, with a schema
  if (!totalsMatch(invoice)) return toEmployee(file, "The totals differ")

  const flags = await Promise.all([                       // Sections, inside one chain step
    checkSupplier(invoice),
    checkCharges(invoice),
    checkTerms(invoice),
  ])