RedditBot/tests/reddit-comment-client.test.ts

import { beforeEach, describe, expect, it, vi } from 'vitest';
import {
  RedditCommentClient,
  createBrowserWriteTransport,
  parseRetryAfterMs,
  type HttpTextResponse,
  type RedditWriteTransport,
} from '../src/reddit/comment-client.js';
import { createMockLogger } from './mockLogger.js';

const MODHASH_OK: HttpTextResponse = {
  status: 200,
  body: JSON.stringify({ data: { modhash: 'abc123', name: 'grower' } }),
};

function errorBody(code: string, message = ''): HttpTextResponse {
  return {
    status: 200,
    body: JSON.stringify({ json: { errors: [[code, message, 'field']], data: {} } }),
  };
}

function successBody(name = 't1_new', permalink: string | null = '/r/cats/comments/a/_/new/'): HttpTextResponse {
  return {
    status: 200,
    body: JSON.stringify({
      json: {
        errors: [],
        data: { things: [{ kind: 't1', data: { id: name.replace(/^t1_/, ''), name, permalink } }] },
      },
    }),
  };
}

interface FakeTransport extends RedditWriteTransport {
  posts: Array<{ url: string; form: Record<string, string>; headers?: Record<string, string> }>;
  gets: string[];
}

function fakeTransport(responses: {
  get?: (url: string) => HttpTextResponse | Promise<HttpTextResponse>;
  post?: (url: string, form: Record<string, string>) => HttpTextResponse | Promise<HttpTextResponse>;
}): FakeTransport {
  const posts: FakeTransport['posts'] = [];
  const gets: string[] = [];
  return {
    posts,
    gets,
    get: async (url) => {
      gets.push(url);
      return responses.get ? await responses.get(url) : MODHASH_OK;
    },
    postForm: async (url, form, headers) => {
      posts.push({ url, form, headers });
      if (!responses.post) throw new Error('unexpected post');
      return await responses.post(url, form);
    },
  };
}

describe('parseRetryAfterMs', () => {
  it('reads the wait out of Reddit’s prose', () => {
    expect(parseRetryAfterMs('You are doing that too much. try again in 9 minutes.')).toBe(540_000);
    expect(parseRetryAfterMs('try again in 32 seconds.')).toBe(32_000);
    expect(parseRetryAfterMs('try again in 1 minute.')).toBe(60_000);
    expect(parseRetryAfterMs('try again in 2 hours.')).toBe(7_200_000);
    expect(parseRetryAfterMs('try again in 1.5 minutes')).toBe(90_000);
  });

  it('returns null when there is no parseable wait', () => {
    expect(parseRetryAfterMs('slow down')).toBeNull();
    expect(parseRetryAfterMs('')).toBeNull();
  });
});

describe('RedditCommentClient.postComment', () => {
  let logger: ReturnType<typeof createMockLogger>;

  beforeEach(() => {
    logger = createMockLogger();
  });

  it('posts a comment and returns its identity', async () => {
    const transport = fakeTransport({ post: () => successBody('t1_xyz', '/r/cats/x/') });
    const client = new RedditCommentClient(transport, logger);

    const result = await client.postComment('t3_thread', 'cats', 'Mine does this too.');

    expect(result).toEqual({ status: 'posted', fullname: 't1_xyz', permalink: '/r/cats/x/' });
    expect(transport.posts[0].url).toBe('https://old.reddit.com/api/comment');
    expect(transport.posts[0].form).toEqual({
      thing_id: 't3_thread',
      text: 'Mine does this too.',
      api_type: 'json',
      uh: 'abc123',
    });
    expect(transport.posts[0].headers).toMatchObject({ 'X-Modhash': 'abc123' });
  });

  it('derives the fullname when Reddit returns only a bare id', async () => {
    const transport = fakeTransport({
      post: () => ({
        status: 200,
        body: JSON.stringify({ json: { errors: [], data: { things: [{ data: { id: 'bare' } }] } } }),
      }),
    });
    const client = new RedditCommentClient(transport, logger);

    const result = await client.postComment('t3_thread', 'cats', 'text');

    expect(result).toEqual({ status: 'posted', fullname: 't1_bare', permalink: null });
  });

  it('reuses one modhash across comments', async () => {
    const transport = fakeTransport({ post: () => successBody() });
    const client = new RedditCommentClient(transport, logger);

    await client.postComment('t3_a', 'cats', 'one');
    await client.postComment('t3_b', 'cats', 'two');

    expect(transport.gets.filter((url) => url.includes('me.json'))).toHaveLength(1);
  });

  it('refuses a malformed thread id and an empty comment without calling Reddit', async () => {
    const transport = fakeTransport({});
    const client = new RedditCommentClient(transport, logger);

    expect(await client.postComment('t1_comment', 'cats', 'text')).toEqual({
      status: 'failed',
      reason: '"t1_comment" is not a post fullname',
    });
    expect(await client.postComment('t3_a', 'cats', '   ')).toEqual({
      status: 'failed',
      reason: 'Refusing to post an empty comment',
    });
    expect(transport.posts).toHaveLength(0);
    expect(transport.gets).toHaveLength(0);
  });

  it('treats a missing modhash as an invalid session', async () => {
    const transport = fakeTransport({
      get: () => ({ status: 200, body: JSON.stringify({ data: { modhash: '' } }) }),
    });
    const client = new RedditCommentClient(transport, logger);

    const result = await client.postComment('t3_a', 'cats', 'text');

    expect(result.status).toBe('session-invalid');
    expect(transport.posts).toHaveLength(0);
  });

  describe('Reddit error codes', () => {
    it('maps RATELIMIT to an account-scoped wait and cools the shared scheduler', async () => {
      const extendCooldown = vi.fn();
      const transport = fakeTransport({
        post: () => errorBody('RATELIMIT', 'You are doing that too much. try again in 9 minutes.'),
      });
      const client = new RedditCommentClient(transport, logger, {
        scheduler: { schedule: (request) => request(), extendCooldown },
      });

      const result = await client.postComment('t3_a', 'cats', 'text');

      expect(result).toMatchObject({ status: 'rate-limited', scope: 'account', retryAfterMs: 540_000 });
      expect(extendCooldown).toHaveBeenCalledWith(540_000);
    });

    it('maps SUBREDDIT_RATELIMIT to a subreddit-scoped wait', async () => {
      const transport = fakeTransport({
        post: () => errorBody('SUBREDDIT_RATELIMIT', 'try again in 20 minutes'),
      });
      const client = new RedditCommentClient(transport, logger);

      expect(await client.postComment('t3_a', 'cats', 'text')).toMatchObject({
        status: 'rate-limited',
        scope: 'subreddit',
        retryAfterMs: 1_200_000,
      });
    });

    it('falls back to a default wait when the throttle message has no duration', async () => {
      const transport = fakeTransport({ post: () => errorBody('RATELIMIT', 'slow down') });
      const client = new RedditCommentClient(transport, logger);

      expect(await client.postComment('t3_a', 'cats', 'text')).toMatchObject({
        status: 'rate-limited',
        retryAfterMs: 600_000,
      });
    });

    it.each([
      ['THREAD_LOCKED', 'thread-closed'],
      ['TOO_OLD', 'thread-closed'],
      ['DELETED_COMMENT', 'thread-closed'],
      ['DELETED_LINK', 'thread-closed'],
      ['SUBREDDIT_NOTALLOWED', 'not-allowed'],
      ['BANNED_FROM_SUBREDDIT', 'not-allowed'],
      ['USER_REQUIRED', 'session-invalid'],
      ['BAD_CAPTCHA', 'blocked'],
      ['CAPTCHA_REQUIRED', 'blocked'],
      ['SOMETHING_NEW', 'failed'],
    ])('maps %s to %s', async (code, expected) => {
      const transport = fakeTransport({ post: () => errorBody(code, 'because reasons') });
      const client = new RedditCommentClient(transport, logger);

      const result = await client.postComment('t3_a', 'cats', 'text');

      expect(result.status).toBe(expected);
    });

    it('names the subreddit on a not-allowed refusal so it can be disabled', async () => {
      const transport = fakeTransport({ post: () => errorBody('SUBREDDIT_NOTALLOWED', 'you are banned') });
      const client = new RedditCommentClient(transport, logger);

      const result = await client.postComment('t3_a', 'cats', 'text');

      expect(result).toEqual({ status: 'not-allowed', reason: 'you are banned (r/cats)' });
    });

    it('maps QUOTA_FILLED to a long account cooldown', async () => {
      const transport = fakeTransport({ post: () => errorBody('QUOTA_FILLED') });
      const client = new RedditCommentClient(transport, logger);

      expect(await client.postComment('t3_a', 'cats', 'text')).toMatchObject({
        status: 'rate-limited',
        scope: 'account',
        retryAfterMs: 21_600_000,
      });
    });

    it('re-derives the modhash after USER_REQUIRED', async () => {
      const transport = fakeTransport({ post: () => errorBody('USER_REQUIRED') });
      const client = new RedditCommentClient(transport, logger);

      await client.postComment('t3_a', 'cats', 'text');
      await client.postComment('t3_b', 'cats', 'text');

      expect(transport.gets.filter((url) => url.includes('me.json'))).toHaveLength(2);
    });
  });

  describe('HTTP failures', () => {
    it('treats 403 as an invalid session and clears the cached modhash', async () => {
      const transport = fakeTransport({ post: () => ({ status: 403, body: '' }) });
      const client = new RedditCommentClient(transport, logger);

      expect((await client.postComment('t3_a', 'cats', 'text')).status).toBe('session-invalid');
      await client.postComment('t3_b', 'cats', 'text');
      expect(transport.gets.filter((url) => url.includes('me.json'))).toHaveLength(2);
    });

    it('treats 429 as an account rate limit', async () => {
      const transport = fakeTransport({ post: () => ({ status: 429, body: '' }) });
      const client = new RedditCommentClient(transport, logger);

      expect(await client.postComment('t3_a', 'cats', 'text')).toMatchObject({
        status: 'rate-limited',
        scope: 'account',
      });
    });

    it('treats 5xx and unreadable bodies as retryable failures', async () => {
      const serverError = new RedditCommentClient(
        fakeTransport({ post: () => ({ status: 503, body: 'nope' }) }),
        logger,
      );
      expect(await serverError.postComment('t3_a', 'cats', 'text')).toEqual({
        status: 'failed',
        reason: 'Reddit returned HTTP 503',
      });

      const garbage = new RedditCommentClient(
        fakeTransport({ post: () => ({ status: 200, body: '<html>error</html>' }) }),
        logger,
      );
      expect((await garbage.postComment('t3_a', 'cats', 'text')).status).toBe('failed');
    });

    it('turns a thrown transport error into a retryable failure', async () => {
      const transport = fakeTransport({
        post: () => { throw new Error('socket hang up'); },
      });
      const client = new RedditCommentClient(transport, logger);

      expect(await client.postComment('t3_a', 'cats', 'text')).toEqual({
        status: 'failed',
        reason: 'socket hang up',
      });
    });

    it('does not claim success when Reddit returns no comment identity', async () => {
      const transport = fakeTransport({
        post: () => ({ status: 200, body: JSON.stringify({ json: { errors: [], data: { things: [] } } }) }),
      });
      const client = new RedditCommentClient(transport, logger);

      expect((await client.postComment('t3_a', 'cats', 'text')).status).toBe('failed');
    });
  });
});

describe('RedditCommentClient.fetchCommentStates', () => {
  const logger = createMockLogger();

  function infoBody(children: Array<Record<string, unknown>>): HttpTextResponse {
    return {
      status: 200,
      body: JSON.stringify({ data: { children: children.map((data) => ({ kind: 't1', data })) } }),
    };
  }

  it('returns scores and flags removals', async () => {
    const transport = fakeTransport({
      get: () => infoBody([
        { name: 't1_a', score: 12, body: 'nice' },
        { name: 't1_b', score: 1, body: '[removed]' },
        { name: 't1_c', score: 3, body: 'ok', banned_by: 'AutoModerator' },
      ]),
    });
    const client = new RedditCommentClient(transport, logger);

    const states = await client.fetchCommentStates(['t1_a', 't1_b', 't1_c']);

    expect(states).toEqual([
      { fullname: 't1_a', score: 12, removed: false, missing: false },
      { fullname: 't1_b', score: 1, removed: true, missing: false },
      { fullname: 't1_c', score: 3, removed: true, missing: false },
    ]);
  });

  it('reports comments Reddit does not return as missing', async () => {
    const transport = fakeTransport({ get: () => infoBody([{ name: 't1_a', score: 2, body: 'hi' }]) });
    const client = new RedditCommentClient(transport, logger);

    const states = await client.fetchCommentStates(['t1_a', 't1_gone']);

    expect(states[1]).toEqual({ fullname: 't1_gone', score: null, removed: false, missing: true });
  });

  it('batches into a single request and ignores non-comment ids', async () => {
    const transport = fakeTransport({ get: () => infoBody([]) });
    const client = new RedditCommentClient(transport, logger);

    await client.fetchCommentStates(['t1_a', 't1_a', 't3_post', 'rubbish']);

    expect(transport.gets).toHaveLength(1);
    expect(transport.gets[0]).toContain('id=t1_a&');
  });

  it('does nothing when there is nothing to check', async () => {
    const transport = fakeTransport({});
    const client = new RedditCommentClient(transport, logger);

    expect(await client.fetchCommentStates([])).toEqual([]);
    expect(transport.gets).toHaveLength(0);
  });

  it('rejects an oversized batch and a failed lookup', async () => {
    const client = new RedditCommentClient(
      fakeTransport({ get: () => ({ status: 500, body: '' }) }),
      logger,
    );

    await expect(client.fetchCommentStates(
      Array.from({ length: 101 }, (_, index) => `t1_x${index}`),
    )).rejects.toThrow(/at most 100/);
    await expect(client.fetchCommentStates(['t1_a'])).rejects.toThrow(/HTTP 500/);
  });
});

describe('RedditCommentClient.fetchPubliclyVisible', () => {
  const logger = createMockLogger();

  it('reports which comments a signed-out visitor can see', async () => {
    const anonymousFetch = vi.fn(async () => ({
      status: 200,
      body: JSON.stringify({
        data: {
          children: [
            { data: { name: 't1_visible', score: 3, body: 'hello' } },
            { data: { name: 't1_filtered', score: 1, body: '[removed]' } },
          ],
        },
      }),
    }));
    const client = new RedditCommentClient(fakeTransport({}), logger, { anonymousFetch });

    const visible = await client.fetchPubliclyVisible(['t1_visible', 't1_filtered', 't1_absent']);

    expect([...visible]).toEqual(['t1_visible']);
    // The probe must be signed out, so it never touches the browser transport.
    expect(anonymousFetch).toHaveBeenCalledTimes(1);
  });

  it('never concludes a shadowban from a failed probe', async () => {
    const client = new RedditCommentClient(fakeTransport({}), logger, {
      anonymousFetch: async () => ({ status: 502, body: '' }),
    });

    await expect(client.fetchPubliclyVisible(['t1_a'])).rejects.toThrow(/HTTP 502/);
  });

  it('treats every comment as visible when no anonymous fetcher is configured', async () => {
    const client = new RedditCommentClient(fakeTransport({}), logger);

    expect([...await client.fetchPubliclyVisible(['t1_a'])]).toEqual(['t1_a']);
  });
});

describe('createBrowserWriteTransport', () => {
  it('runs both verbs inside the page so requests carry the profile session', async () => {
    const calls: unknown[] = [];
    const page = {
      evaluate: async <Result, Argument>(
        fn: (argument: Argument) => Promise<Result>,
        argument: Argument,
      ): Promise<Result> => {
        calls.push(argument);
        const fetchStub = async (url: string, init?: { method?: string; body?: string }) => ({
          status: 200,
          text: async () => JSON.stringify({ url, method: init?.method ?? 'GET', body: init?.body }),
        });
        const original = globalThis.fetch;
        (globalThis as { fetch: unknown }).fetch = fetchStub;
        try {
          return await fn(argument);
        } finally {
          (globalThis as { fetch: unknown }).fetch = original;
        }
      },
    };
    const transport = createBrowserWriteTransport(page);

    const got = await transport.get('https://old.reddit.com/api/me.json');
    const posted = await transport.postForm(
      'https://old.reddit.com/api/comment',
      { text: 'hi there', uh: 'abc' },
      { 'X-Modhash': 'abc' },
    );

    expect(JSON.parse(got.body).url).toBe('https://old.reddit.com/api/me.json');
    expect(JSON.parse(posted.body).method).toBe('POST');
    expect(JSON.parse(posted.body).body).toBe('text=hi+there&uh=abc');
    expect(calls).toHaveLength(2);
  });
});