// tests/kb-update/test-learn-api.test.mjs
// Unit tests for scripts/kb-update/lib/learn-api.mjs (C3.1) — the Claude-free
// network client for the Microsoft Learn Platform API. Covers the gate criteria
// in c3-course-detection-plan.md §7 (C3.1):
//   - token-body building (client-credentials)
//   - buildUpdatedAtGt: throws on date-only, emits full ISO (gotcha #1)
//   - nextLink pagination + product param
//   - robustness contract (§6, decision §8 (a)): non-ok HTTP throws (fetch does
//     not), 429 retries respecting Retry-After, 4xx≠429 not retried, timeout
//     (AbortSignal) propagates fail-closed.
// All network is stubbed via injected fetchImpl/sleep — no live calls in CI.

import { test } from 'node:test';
import assert from 'node:assert/strict';
import {
  buildUpdatedAtGt,
  buildApiUrl,
  getToken,
  paginate,
} from '../../scripts/kb-update/lib/learn-api.mjs';

// --- test helpers ---------------------------------------------------------

// A minimal Response-shaped object: the wrapper relies on .ok, .status,
// .headers.get(), and .json() — nothing else.
function res(body, { status = 200, headers = {} } = {}) {
  return {
    ok: status >= 200 && status < 300,
    status,
    headers: new Headers(headers),
    json: async () => body,
  };
}

// fetch stub: a queue of responses (or (url,options)=>response fns). Records calls.
function stubFetch(queue) {
  const calls = [];
  const impl = async (url, options) => {
    calls.push({ url, options });
    const next = queue.shift();
    if (next === undefined) throw new Error('stubFetch: no more queued responses');
    return typeof next === 'function' ? next(url, options) : next;
  };
  impl.calls = calls;
  return impl;
}

// sleep spy: records requested delays, resolves immediately (no real waiting).
function spySleep() {
  const delays = [];
  const fn = async (ms) => { delays.push(ms); };
  fn.delays = delays;
  return fn;
}

async function drain(asyncIter) {
  const out = [];
  for await (const x of asyncIter) out.push(x);
  return out;
}

// --- buildUpdatedAtGt (gotcha #1: full ISO required) ----------------------

test('buildUpdatedAtGt — throws on date-only input (fail-closed on server)', () => {
  assert.throws(() => buildUpdatedAtGt('2026-01-01'), /full ISO|datetime/i);
});

test('buildUpdatedAtGt — accepts full ISO and emits canonical Z form', () => {
  assert.equal(buildUpdatedAtGt('2026-01-01T00:00:00Z'), '2026-01-01T00:00:00.000Z');
  // an explicit offset is normalized to UTC Z
  assert.equal(buildUpdatedAtGt('2026-01-01T02:00:00+02:00'), '2026-01-01T00:00:00.000Z');
});

// --- buildApiUrl (api-version pin + product param) ------------------------

test('buildApiUrl — pins api-version and serializes the product param', () => {
  const u = new URL(buildApiUrl('modules', { products: 'azure-openai' }));
  assert.equal(u.pathname, '/api/v1/modules');
  assert.equal(u.searchParams.get('api-version'), '2023-11-01-preview');
  assert.equal(u.searchParams.get('products'), 'azure-openai');
});

test('buildApiUrl — comma-separated products survive (OR semantics)', () => {
  const u = new URL(buildApiUrl('modules', { products: 'azure-openai,power-automate' }));
  assert.equal(u.searchParams.get('products'), 'azure-openai,power-automate');
});

test('buildApiUrl — learning-paths is the kebab-case endpoint', () => {
  const u = new URL(buildApiUrl('learning-paths', {}));
  assert.equal(u.pathname, '/api/v1/learning-paths');
});

test('buildApiUrl — rejects an unknown endpoint', () => {
  assert.throws(() => buildApiUrl('catalog', {}), /endpoint/i);
});

test('buildApiUrl — omits null/empty params', () => {
  const u = new URL(buildApiUrl('modules', { products: '', 'updatedAt.gt': null }));
  assert.equal(u.searchParams.has('products'), false);
  assert.equal(u.searchParams.has('updatedAt.gt'), false);
});

// --- getToken (client-credentials body) -----------------------------------

test('getToken — builds the client-credentials body and returns access_token', async () => {
  const fetchImpl = stubFetch([res({ access_token: 'tok-123', expires_in: 3599 })]);
  const token = await getToken(
    { tenantId: 'TENANT', clientId: 'CLIENT', clientSecret: 'SECRET' },
    { fetchImpl },
  );
  assert.equal(token, 'tok-123');

  const { url, options } = fetchImpl.calls[0];
  assert.equal(url, 'https://login.microsoftonline.com/TENANT/oauth2/v2.0/token');
  assert.equal(options.method, 'POST');
  const body = options.body; // URLSearchParams
  assert.equal(body.get('grant_type'), 'client_credentials');
  assert.equal(body.get('client_id'), 'CLIENT');
  assert.equal(body.get('client_secret'), 'SECRET');
  assert.equal(body.get('scope'), 'https://learn.microsoft.com/.default');
});

test('getToken — throws if the response lacks an access_token', async () => {
  const fetchImpl = stubFetch([res({ error: 'invalid_client' })]);
  await assert.rejects(
    getToken({ tenantId: 't', clientId: 'c', clientSecret: 's' }, { fetchImpl }),
    /access_token/i,
  );
});

// --- paginate (nextLink cursor) -------------------------------------------

test('paginate — follows nextLink across pages and yields all items', async () => {
  const fetchImpl = stubFetch([
    res({ value: [{ id: 'a' }, { id: 'b' }], nextLink: 'https://learn.microsoft.com/api/v1/modules?page=2' }),
    res({ value: [{ id: 'c' }], nextLink: null }),
  ]);
  const items = [];
  for await (const it of paginate('modules', { products: 'azure-openai' }, 'tok', { fetchImpl })) {
    items.push(it.id);
  }
  assert.deepEqual(items, ['a', 'b', 'c']);
  // the second request uses the nextLink verbatim
  assert.equal(fetchImpl.calls[1].url, 'https://learn.microsoft.com/api/v1/modules?page=2');
  // bearer token on every request
  assert.equal(fetchImpl.calls[0].options.headers.authorization, 'Bearer tok');
  assert.equal(fetchImpl.calls[1].options.headers.authorization, 'Bearer tok');
});

test('paginate — empty value array yields nothing', async () => {
  const fetchImpl = stubFetch([res({ value: [], nextLink: null })]);
  assert.equal((await drain(paginate('modules', {}, 'tok', { fetchImpl }))).length, 0);
});

// --- robustness contract (§6 / decision §8 (a)) ---------------------------

test('robustness — non-ok status throws (fetch does not; the wrapper must)', async () => {
  const fetchImpl = stubFetch([res({}, { status: 404 })]);
  const sleep = spySleep();
  await assert.rejects(drain(paginate('modules', {}, 'tok', { fetchImpl, sleep })), /404/);
  assert.equal(sleep.delays.length, 0, '404 is not retried');
});

test('robustness — 429 retries and respects Retry-After', async () => {
  const fetchImpl = stubFetch([
    res({}, { status: 429, headers: { 'retry-after': '2' } }),
    res({ value: [{ id: 'a' }], nextLink: null }),
  ]);
  const sleep = spySleep();
  const items = await drain(paginate('modules', {}, 'tok', { fetchImpl, sleep }));
  assert.deepEqual(items.map((i) => i.id), ['a']);
  assert.deepEqual(sleep.delays, [2000], 'waited Retry-After seconds, in ms');
});

test('robustness — 4xx other than 429 is not retried (immediate throw)', async () => {
  const fetchImpl = stubFetch([res({}, { status: 401 })]);
  const sleep = spySleep();
  await assert.rejects(drain(paginate('modules', {}, 'tok', { fetchImpl, sleep })), /401/);
  assert.equal(fetchImpl.calls.length, 1, '401 is not retried');
  assert.equal(sleep.delays.length, 0);
});

test('robustness — 5xx retries up to maxAttempts then fails closed', async () => {
  const fetchImpl = stubFetch([
    res({}, { status: 503 }),
    res({}, { status: 503 }),
    res({}, { status: 503 }),
  ]);
  const sleep = spySleep();
  await assert.rejects(
    drain(paginate('modules', {}, 'tok', { fetchImpl, sleep, maxAttempts: 3 })),
    /503/,
  );
  assert.equal(fetchImpl.calls.length, 3, 'three attempts');
  assert.equal(sleep.delays.length, 2, 'slept between the three attempts');
});

test('robustness — timeout (AbortSignal) propagates fail-closed, not retried', async () => {
  let signalSeen = null;
  const fetchImpl = async (_url, options) => {
    signalSeen = options.signal;
    throw new DOMException('The operation timed out.', 'TimeoutError');
  };
  const sleep = spySleep();
  await assert.rejects(
    drain(paginate('modules', {}, 'tok', { fetchImpl, sleep })),
    (e) => e.name === 'TimeoutError',
  );
  assert.ok(signalSeen instanceof AbortSignal, 'the request wired an AbortSignal.timeout');
  assert.equal(sleep.delays.length, 0, 'a timeout is not retried');
});