The process, end to end

ruleCascade: 1.0.0
kind: RuleSet

metadata:
  id: shop.orders
  version: 1.0.0
  title: Orders
  owner: shop-team
  status: active

scope:
  - { level: organization, id: shop }

entities:
  Order:
    schema: { $ref: "./orders.openapi.yaml#/components/schemas/Order" }

params:
  maxQuantity:
    type: integer
    default: 10
    overridePolicy: tighten-only
    tightenDirection: lower

rules:
  - id: order.quantity.max
    kind: validation
    title: An order has at most maxQuantity items
    target: { entity: Order, field: /quantity }
    operations: [create, update]
    triggers: [change, submit]
    when: { op: exists, args: [{ var: data.quantity }] }
    assert: { op: lte, args: [{ var: data.quantity }, { var: params.maxQuantity }] }
    severity: error
    finding:
      code: SHOP-ORD-001
      message: order.quantityTooHigh
      args: { max: { var: params.maxQuantity } }

  - id: order.placed
    kind: action
    title: Announce a new order once it is saved
    target: { entity: Order }
    operations: [create]
    enforcement: server
    commands:
      - name: order.placed
        type: event
        ref: OrderPlaced
        payload: { orderId: { var: data.id }, quantity: { var: data.quantity } }
        idempotencyKey: ["order.placed", { var: data.id }]

messages:
  en:
    order.quantityTooHigh: "You can order at most {max} items."

tests:
  - name: ten items are allowed and announced
    entity: Order
    operation: create
    given:
      data: { id: o-1, quantity: 10 }
    expect:
      decision: allow
      findings: []
      commands: [order.placed]

  - name: eleven items are denied and nothing is announced
    entity: Order
    operation: create
    given:
      data: { id: o-2, quantity: 11 }
    expect:
      decision: deny
      findings:
        - { rule: order.quantity.max, fields: [/quantity], message: You can order at most 10 items. }
      commands: []

  - name: the browser checks the quantity too
    entity: Order
    operation: create
    channel: client
    given:
      data: { id: o-3, quantity: 11 }
      trigger: change
    expect:
      decision: deny
      findings:
        - { rule: order.quantity.max }