import test from 'node:test';
import assert from 'node:assert/strict';
import { Readable } from 'node:stream';
import { createSseBillingTransform } from './sse-billing.mjs';

function collectFinishEvents(payload) {
  return new Promise((resolve, reject) => {
    const finishes = [];
    const transform = createSseBillingTransform({
      onFinish: async (event) => {
        finishes.push(event);
      },
    });
    const chunks = [];
    transform.on('data', (chunk) => chunks.push(chunk));
    transform.on('error', reject);
    transform.on('finish', () => resolve({ finishes, output: Buffer.concat(chunks).toString('utf8') }));
    Readable.from([payload]).pipe(transform);
  });
}

test('createSseBillingTransform bills each Finish only once per stream', async () => {
  const frame =
    'data: {"type":"Finish","request_id":"req-1","token_state":{"accumulatedInputTokens":100,"accumulatedOutputTokens":20}}\n\n';
  const { finishes, output } = await collectFinishEvents(frame);
  assert.equal(finishes.length, 1);
  assert.equal(output, frame);
});

test('createSseBillingTransform dedupes Finish replayed in flush buffer', async () => {
  const partial = 'data: {"type":"Finish","request_id":"req-2","token_state":{"accumulatedInputTokens":50,"accumulatedOutputTokens":5}}';
  const { finishes } = await collectFinishEvents(partial);
  assert.equal(finishes.length, 1);
});