const { getNextInvoiceNumber } = require("../index");

describe("getNextInvoiceNumber", () => {
  test("should return -0001 for the first invoice of the year", () => {
    const year = new Date().getFullYear();
    const invoicesData = { invoices: [] };
    expect(getNextInvoiceNumber(year, invoicesData)).toBe(`${year}-0001`);
  });

  test("should correctly increment the invoice number for the same year", () => {
    const year = new Date().getFullYear();
    const invoicesData = {
      invoices: [{ number: `${year}-0001` }, { number: `${year}-0002` }],
    };
    expect(getNextInvoiceNumber(year, invoicesData)).toBe(`${year}-0003`);
  });

  test("should reset number for a new year", () => {
    const lastYear = new Date().getFullYear() - 1;
    const year = new Date().getFullYear();
    const invoicesData = {
      invoices: [
        { number: `${lastYear}-0001` },
        { number: `${lastYear}-0002` },
      ],
    };
    expect(getNextInvoiceNumber(year, invoicesData)).toBe(`${year}-0001`);
  });

  test("should handle unordered invoice numbers correctly", () => {
    const year = new Date().getFullYear();
    const invoicesData = {
      invoices: [
        { number: `${year}-0005` },
        { number: `${year}-0001` },
        { number: `${year}-0003` },
      ],
    };
    expect(getNextInvoiceNumber(year, invoicesData)).toBe(`${year}-0006`);
  });
});