#!/usr/bin/env node
/**
 * Fixture "real implementation" of orders.openapi.yaml, for the APIFae CLI
 * scenario tests (APIFAE-102).
 *
 *   node backend.js               # faithful to the spec
 *   DRIFT=1 node backend.js       # drifted four ways, deliberately
 *   FLAKY_EVERY=5 node backend.js # every 5th GET /orders serves the drifted
 *                                 # enum — an intermittent backend, for
 *                                 # `apifae diff --samples N` (APIFAE-124)
 *
 * The four drifts are exactly the ones the backend persona said they would
 * otherwise never notice:
 *
 *   1. GET /reports/daily   500 body gains an undocumented `errorCode` field
 *   2. GET /orders/{id}     `status` returns `refunded`, an enum value the spec
 *                           does not list
 *   3. GET /orders          `note` comes back null; the spec says string
 *   4. POST /orders         responds 200 where the spec says 201
 *
 * Responses are fully deterministic — no timestamps, no random ids — so a diff
 * run is reproducible and any reported change is a real change.
 */

const http = require('http');

const PORT = Number(process.env.PORT || 9100);
const DRIFT = process.env.DRIFT === '1';
// Supplementary probe (APIFAE-102): drift ONLY the enum, on the list endpoint,
// which has no path parameters and is therefore actually checked by `diff`.
const DRIFT_ENUM = process.env.DRIFT_ENUM === '1';
// Intermittent drift (APIFAE-124): every Nth GET /orders serves the
// out-of-enum value, the rest are faithful. Counted rather than random so a
// sampling run has an exactly predictable prevalence — 1 in N — and the test
// asserting it cannot flake.
const FLAKY_EVERY = Number(process.env.FLAKY_EVERY || 0);
let ordersRequests = 0;

const order = (id, status, note) => ({
  id,
  status,
  total: 4250,
  currency: 'EUR',
  customerEmail: 'ada@example.com',
  note,
  createdAt: '2026-08-01T09:15:00Z',
});

const send = (res, status, body) => {
  const payload = JSON.stringify(body);
  res.writeHead(status, {
    'Content-Type': 'application/json',
    'Content-Length': Buffer.byteLength(payload),
  });
  res.end(payload);
};

const server = http.createServer((req, res) => {
  const url = new URL(req.url, `http://localhost:${PORT}`);
  const path = url.pathname;
  const method = req.method;

  // --- GET /orders -----------------------------------------------------
  // Drift 3: `note` becomes null.
  if (method === 'GET' && path === '/orders') {
    ordersRequests += 1;
    const note = DRIFT ? null : 'Leave with the concierge';
    const flaky = FLAKY_EVERY > 0 && ordersRequests % FLAKY_EVERY === 0;
    const s0 = DRIFT_ENUM || flaky ? 'refunded' : 'paid';
    return send(res, 200, {
      data: [
        order('ord_8f14e45fceea', s0, note),
        order('ord_1679091c5a88', 'pending', note),
        order('ord_e4da3b7fbbce', 'shipped', note),
      ],
      page: 1,
      total: 3,
      hasMore: false,
    });
  }

  // --- POST /orders ----------------------------------------------------
  // Drift 4: 201 quietly becomes 200.
  if (method === 'POST' && path === '/orders') {
    const status = DRIFT ? 200 : 201;
    return send(res, status, order('ord_8f14e45fceea', 'pending', 'Leave with the concierge'));
  }

  // --- GET /orders/{id} ------------------------------------------------
  // Drift 2: `status` returns an enum value the spec never listed.
  const match = path.match(/^\/orders\/([^/]+)$/);
  if (method === 'GET' && match) {
    if (match[1] === 'missing') {
      return send(res, 404, { error: 'not_found', message: 'No such order' });
    }
    const status = DRIFT ? 'refunded' : 'paid';
    return send(res, 200, order(match[1], status, 'Leave with the concierge'));
  }

  // --- GET /reports/daily ----------------------------------------------
  // Drift 1: an undocumented `errorCode` appears in the 500 envelope.
  if (method === 'GET' && path === '/reports/daily') {
    const body = { error: 'report_failed', message: 'Report worker is not available' };
    if (DRIFT) body.errorCode = 'RPT-500';
    return send(res, 500, body);
  }

  return send(res, 404, { error: 'not_found', message: `No route for ${method} ${path}` });
});

server.listen(PORT, () => {
  console.log(`orders backend listening on http://localhost:${PORT} (drift=${DRIFT ? 'on' : 'off'})`);
});