import { describe, expect, it } from "vitest";
import { computeLineAmount, computeTotals } from "./invoice";
import { EMPTY_ITEM, type InvoiceItem } from "./types";

// These cases mirror the unit tests in src-tauri/src/gst.rs, so the on-screen preview
// and the stored totals stay identical.

const fixed = (amount: number): InvoiceItem => ({ ...EMPTY_ITEM, mode: "fixed", amount });
const rate = (r: number, quantity: number): InvoiceItem => ({
  ...EMPTY_ITEM,
  mode: "rate",
  rate: r,
  quantity,
  unit: "hour",
});

describe("computeTotals", () => {
  it("splits 18% on 7310.00 into 657.90 CGST and SGST", () => {
    const t = computeTotals([fixed(7310)], 0, "cgst_sgst", 18);
    expect(t.subtotal).toBe(7310);
    expect(t.cgst).toBe(657.9);
    expect(t.sgst).toBe(657.9);
    expect(t.igst).toBe(0);
    expect(t.total).toBe(8625.8);
  });

  it("rounds odd paise half up for IGST and per head for CGST/SGST", () => {
    const igst = computeTotals([fixed(33.33)], 0, "igst", 5);
    expect(igst.igst).toBe(1.67);
    expect(igst.total).toBe(35);
    const split = computeTotals([fixed(33.33)], 0, "cgst_sgst", 5);
    expect([split.cgst, split.sgst]).toEqual([0.83, 0.83]);
    expect(split.total).toBe(34.99);
  });

  it("handles fractional quantities", () => {
    const t = computeTotals([rate(1200, 1.5)], 0, "none", 0);
    expect(t.subtotal).toBe(1800);
    expect(t.total).toBe(1800);
    expect(computeLineAmount(rate(99.99, 2.5))).toBe(249.98);
  });

  it("clamps the discount to the subtotal", () => {
    const items = [fixed(100), fixed(50.5)];
    const over = computeTotals(items, 999.99, "igst", 18);
    expect(over.discount).toBe(150.5);
    expect(over.taxable).toBe(0);
    expect(over.total).toBe(0);
    expect(computeTotals(items, -5, "none", 0).discount).toBe(0);
    expect(computeTotals(items, 50.5, "none", 0).taxable).toBe(100);
  });

  it("ignores the rate when no tax applies", () => {
    const t = computeTotals([fixed(1000)], 0, "none", 18);
    expect(t.taxTotal).toBe(0);
    expect(t.total).toBe(1000);
  });
});