import { describe, expect, it, vi } from 'vitest';
import { RateService } from '../src/rates';

function fakeFetch(price: number) {
  return vi.fn(async (url: string | URL | Request) => {
    const u = String(url);
    const id = u.includes('tether') ? 'tether' : 'usd-coin';
    return new Response(JSON.stringify({ [id]: { usd: price } }), {
      status: 200,
      headers: { 'content-type': 'application/json' },
    });
  }) as unknown as typeof fetch & ReturnType<typeof vi.fn>;
}

describe('RateService', () => {
  it('fetches and converts a price to integer rate units', async () => {
    const svc = new RateService({ fetchFn: fakeFetch(0.9998) });
    const quote = await svc.getRate('USDT', 'USD');
    expect(quote.rateUnits).toBe(999800n);
    expect(quote.source).toBe('coingecko');
  });

  it('caches for 60 seconds and refetches after TTL', async () => {
    let now = 0;
    const f = fakeFetch(1);
    const svc = new RateService({ fetchFn: f, now: () => now });
    await svc.getRate('USDC', 'USD');
    now = 59_000;
    await svc.getRate('USDC', 'USD');
    expect(f).toHaveBeenCalledTimes(1);
    now = 61_000;
    await svc.getRate('USDC', 'USD');
    expect(f).toHaveBeenCalledTimes(2);
  });

  it('caches per asset+fiat pair', async () => {
    const f = fakeFetch(1);
    const svc = new RateService({ fetchFn: f, now: () => 0 });
    await svc.getRate('USDT', 'USD');
    await svc.getRate('USDC', 'USD');
    expect(f).toHaveBeenCalledTimes(2);
  });

  it('throws on provider errors and missing prices', async () => {
    const err = vi.fn(async () => new Response('nope', { status: 500 })) as unknown as typeof fetch;
    await expect(new RateService({ fetchFn: err }).getRate('USDT', 'USD')).rejects.toThrow(/HTTP 500/);
    const empty = vi.fn(async () => new Response('{}', { status: 200 })) as unknown as typeof fetch;
    await expect(new RateService({ fetchFn: empty }).getRate('USDT', 'USD')).rejects.toThrow(/no USD price/);
  });
});