import { describe, expect, it } from "vitest";
import {
  computePoMoney,
  poNetPayable,
  amountToPercent,
  percentToAmount,
} from "@/lib/po-money";

const items = [
  { quantity: 10, unitPrice: 100, gstRate: 0.18 }, // taxable 1000, gst 180
  { quantity: 2, unitPrice: 50, gstRate: 0.05 },   // taxable 100,  gst 5
];

describe("computePoMoney", () => {
  it("breaks down taxable, GST and incl-GST", () => {
    const m = computePoMoney(items);
    expect(m.taxable).toBe(1100);
    expect(m.gst).toBeCloseTo(185, 5);
    expect(m.inclGst).toBeCloseTo(1285, 5);
    expect(m.netPayable).toBeCloseTo(1285, 5); // no charges ⇒ equals inclGst
  });

  it("adds TCS and subtracts Discount post-GST", () => {
    const m = computePoMoney(items, 50, 85);
    expect(m.tcs).toBe(50);
    expect(m.discount).toBe(85);
    expect(m.netPayable).toBeCloseTo(1285 + 50 - 85, 5);
  });

  it("defaults a missing gstRate to 18%", () => {
    expect(computePoMoney([{ quantity: 1, unitPrice: 100 }]).gst).toBeCloseTo(18, 5);
  });

  it("treats nullish charges as zero", () => {
    const m = computePoMoney(items, undefined, undefined);
    expect(m.netPayable).toBeCloseTo(1285, 5);
  });
});

describe("poNetPayable", () => {
  it("is incl-GST + TCS − Discount", () => {
    expect(poNetPayable(items, 100, 200)).toBeCloseTo(1285 + 100 - 200, 5);
  });
});

describe("percent ↔ amount conversion", () => {
  it("round-trips against a base", () => {
    expect(amountToPercent(128.5, 1285)).toBeCloseTo(10, 5);
    expect(percentToAmount(10, 1285)).toBeCloseTo(128.5, 5);
  });

  it("is zero-safe when the base is zero", () => {
    expect(amountToPercent(50, 0)).toBe(0);
    expect(percentToAmount(10, 0)).toBe(0);
  });
});