FulfillmentHandler

let shipomatic;export const shipomaticFulfillmentHandler = new FulfillmentHandler({  code: 'ship-o-matic',  description: [{    languageCode: LanguageCode.en,    value: 'Generate tracking codes via the Ship-o-matic API'  }],  args: {    preferredService: {      type: 'string',      ui: {        component: 'select-form-input',        options: [          { value: 'first_class' },          { value: 'priority'},          { value: 'standard' },        ],      },    }  },  init: () => {    // some imaginary shipping service    shipomatic = new ShipomaticClient(API_KEY);  },  createFulfillment: async (ctx, orders, lines, args) => {     const shipment = getShipmentFromOrders(orders, lines);     try {       const transaction = await shipomatic.transaction.create({         shipment,         service_level: args.preferredService,         label_file_type: 'png',       })       return {         method: `Ship-o-matic ${args.preferredService}`,         trackingCode: transaction.tracking_code,         customFields: {           shippingTransactionId: transaction.id,         }       };     } catch (e: any) {       // Errors thrown from within this function will       // result in a CreateFulfillmentError being returned       throw e;     }  },  onFulfillmentTransition: async (fromState, toState, { fulfillment }) => {    if (toState === 'Cancelled') {      await shipomatic.transaction.cancel({        transaction_id: fulfillment.customFields.shippingTransactionId,      });    }  }});

class FulfillmentHandler<T extends ConfigArgs = ConfigArgs> extends ConfigurableOperationDef<T> {    constructor(config: FulfillmentHandlerConfig<T>)}

interface FulfillmentHandlerConfig<T extends ConfigArgs> extends ConfigurableOperationDefOptions<T> {    createFulfillment: CreateFulfillmentFn<T>;    onFulfillmentTransition?: OnTransitionStartFn<FulfillmentState, FulfillmentTransitionData>;}

type CreateFulfillmentFn<T extends ConfigArgs> = (    ctx: RequestContext,    orders: Order[],    lines: OrderLineInput[],    args: ConfigArgValues<T>,) => CreateFulfillmentResult | Promise<CreateFulfillmentResult>

type CreateFulfillmentResult = Partial<Pick<Fulfillment, 'trackingCode' | 'method' | 'customFields'>>