parking_solution/packages/devices/src/printer-routing.test.ts

import { describe, expect, it, vi } from "vitest";
import {
  orderForRole,
  printWithFailover,
  NoPrinterAvailableError,
  type PrinterInstance,
} from "./printer-routing.js";
import type { PrinterDevice } from "./interfaces.js";

// Printer routing is pure selection over (config, health): which printer prints a job,
// best-first, with failover. The key business rules: the booth printer is a FALLBACK for
// entry tickets but a receipt NEVER prints on the outside dispenser; rank then id break
// ties deterministically; printWithFailover walks the order and surfaces all failures.

function inst(id: string, role: PrinterInstance["role"], failoverRank = 0, device?: PrinterDevice): PrinterInstance {
  return { id, role, failoverRank, device: device ?? ({} as PrinterDevice) };
}

describe("orderForRole", () => {
  it("entry-dispenser job: dispensers first, booth-receipt as fallback", () => {
    const printers = [inst("booth", "booth-receipt"), inst("disp", "entry-dispenser")];
    expect(orderForRole(printers, "entry-dispenser").map((p) => p.id)).toEqual(["disp", "booth"]);
  });

  it("booth-receipt job: NEVER falls back to the outside dispenser", () => {
    const printers = [inst("disp", "entry-dispenser"), inst("booth", "booth-receipt")];
    expect(orderForRole(printers, "booth-receipt").map((p) => p.id)).toEqual(["booth"]);
  });

  it("wash-desk job: the desk printer first, the booth printer as fallback, never the dispenser", () => {
    const printers = [inst("disp", "entry-dispenser"), inst("booth", "booth-receipt"), inst("desk", "wash-desk")];
    expect(orderForRole(printers, "wash-desk").map((p) => p.id)).toEqual(["desk", "booth"]);
    // A site without a desk printer keeps printing wash slips in the booth.
    expect(orderForRole(printers.slice(0, 2), "wash-desk").map((p) => p.id)).toEqual(["booth"]);
  });

  it("nothing ever falls back TO the wash desk (booth receipts and entry tickets stay off it)", () => {
    const printers = [inst("desk", "wash-desk")];
    expect(orderForRole(printers, "booth-receipt")).toEqual([]);
    expect(orderForRole(printers, "entry-dispenser")).toEqual([]);
  });

  it("breaks ties by failoverRank (higher first), then id", () => {
    const printers = [
      inst("b", "entry-dispenser", 1),
      inst("a", "entry-dispenser", 1),
      inst("c", "entry-dispenser", 5),
    ];
    expect(orderForRole(printers, "entry-dispenser").map((p) => p.id)).toEqual(["c", "a", "b"]);
  });

  it("excludes printers of no relevant role", () => {
    const printers = [inst("booth", "booth-receipt")];
    expect(orderForRole(printers, "booth-receipt").map((p) => p.id)).toEqual(["booth"]);
    // For a receipt job, an entry dispenser is excluded entirely.
    expect(orderForRole([inst("disp", "entry-dispenser")], "booth-receipt")).toEqual([]);
  });
});

describe("printWithFailover", () => {
  function device(behavior: "ok" | "fail"): PrinterDevice {
    return {
      printTicket: vi.fn(behavior === "ok" ? async () => {} : async () => { throw new Error("offline"); }),
    } as unknown as PrinterDevice;
  }

  it("prints on the first healthy candidate and returns its id", async () => {
    const printers = [inst("disp", "entry-dispenser", 0, device("ok")), inst("booth", "booth-receipt", 0, device("ok"))];
    const job = vi.fn(async (d: PrinterDevice) => d.printTicket({} as never));
    const used = await printWithFailover(printers, "entry-dispenser", job);
    expect(used).toBe("disp");
    expect(job).toHaveBeenCalledTimes(1);
  });

  it("fails over to the booth printer when the dispenser throws", async () => {
    const printers = [inst("disp", "entry-dispenser", 0, device("fail")), inst("booth", "booth-receipt", 0, device("ok"))];
    const used = await printWithFailover(printers, "entry-dispenser", (d) => d.printTicket({} as never));
    expect(used).toBe("booth");
  });

  it("throws NoPrinterAvailableError listing every failed attempt", async () => {
    const printers = [inst("disp", "entry-dispenser", 0, device("fail")), inst("booth", "booth-receipt", 0, device("fail"))];
    await expect(printWithFailover(printers, "entry-dispenser", (d) => d.printTicket({} as never)))
      .rejects.toBeInstanceOf(NoPrinterAvailableError);
  });

  it("throws when no printer is configured for the role", async () => {
    await expect(printWithFailover([], "entry-dispenser", async () => {}))
      .rejects.toBeInstanceOf(NoPrinterAvailableError);
  });
});