import { applyMonthlyCredit } from '../src/billing/credit';
import { DEFAULT_TIERS } from '../src/pricing';
import { UsageSummary } from '../src/usage';

const freeTier = DEFAULT_TIERS.find((t) => t.id === 'free')!; // monthlyCreditCents: 100

const summary = (totalCents: number): UsageSummary => ({
  customerId: 'cust_1',
  totalCents,
  calls: 1,
  byEndpoint: {},
});

describe('applyMonthlyCredit', () => {
  it('covers usage fully when under the monthly credit', () => {
    const billed = applyMonthlyCredit(summary(60), freeTier);
    expect(billed.includedCents).toBe(60);
    expect(billed.billableCents).toBe(0);
    expect(billed.totalCents).toBe(60);
  });

  it('bills only the overage when usage exceeds the credit', () => {
    const billed = applyMonthlyCredit(summary(250), freeTier);
    expect(billed.includedCents).toBe(100);
    expect(billed.billableCents).toBe(150);
  });

  it('bills nothing when there is no usage', () => {
    const billed = applyMonthlyCredit(summary(0), freeTier);
    expect(billed.includedCents).toBe(0);
    expect(billed.billableCents).toBe(0);
  });
});