An educational pure functional programming library in TypeScript
Refactor workflow-engine functions to expression style
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examples/workflow-engine/with-purus.ts
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examples/workflow-engine/with-purus.ts
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// SIGNATURE: DraftOrder -> Result<PaidOrder, OrderError>
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// Only accepts DraftOrder. Try passing a ShippedOrder - won't compile.
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const payOrder = (order: DraftOrder): Result<PaidOrder, OrderError> => {
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console.log(`[Payment] Processing payment for order ${order.id}`)
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const toPaid = transition<OrderData, "Draft", "Paid">()
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return ok(toPaid(order))
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}
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const payOrder = (order: DraftOrder): Result<PaidOrder, OrderError> => (
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console.log(`[Payment] Processing payment for order ${order.id}`),
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ok(transition<OrderData, "Draft", "Paid">()(order))
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)
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// SIGNATURE: PaidOrder -> ShippedOrder
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// Only accepts PaidOrder. No runtime check needed.
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const shipOrder = (order: PaidOrder): ShippedOrder => {
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console.log(`[Shipping] Shipping order ${order.id}`)
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const toShipped = transition<OrderData, "Paid", "Shipped">()
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return toShipped(order)
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}
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const shipOrder = (order: PaidOrder): ShippedOrder => (
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console.log(`[Shipping] Shipping order ${order.id}`),
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transition<OrderData, "Paid", "Shipped">()(order)
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)
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// Branded types in action - compare with without-purus.ts line 71
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const lookupOrder = (
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orderId: OrderId, // First parameter is OrderId
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customerId: CustomerId // Second parameter is CustomerId
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): Result<DraftOrder, OrderError> => {
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if (orderId === "order-1" && customerId === "cust-1") {
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const data: OrderData = {
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id: orderId,
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customerId: customerId,
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productId: ProductId("prod-1"),
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quantity: 2,
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}
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return ok(entity<OrderData, "Draft">(data))
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}
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return err(OrderError.orderNotFound(orderId))
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}
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): Result<DraftOrder, OrderError> =>
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orderId === "order-1" && customerId === "cust-1"
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? ok(entity<OrderData, "Draft">({
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id: orderId,
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customerId: customerId,
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productId: ProductId("prod-1"),
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quantity: 2,
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}))
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: err(OrderError.orderNotFound(orderId))
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// =============================================================================
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// THE BUG THAT BRANDED TYPES PREVENT