ApiCore/ApiCore-Backend/test/utils/telegram.ts

import { randomUUID } from 'node:crypto';
import { INestApplication } from '@nestjs/common';
import { NestExpressApplication } from '@nestjs/platform-express';
import { Test } from '@nestjs/testing';
import { App } from 'supertest/types';
import { AppModule } from '../../src/app.module';
import { configureApp } from '../../src/app.config';
import { THROTTLER_NAMESPACE } from '../../src/common/throttler/prisma-throttler.storage';
import { TelegramApiError } from '../../src/telegram/telegram-api-error';
import {
  TelegramClient,
  type TelegramUpdate,
  type TelegramUpdateBatch,
} from '../../src/telegram/telegram-client';
import { TelegramModule } from '../../src/telegram/telegram.module';

export interface SentMessage {
  chatId: bigint;
  text: string;
}

/**
 * Stands in for the Bot API: no network. Every sendMessage is recorded;
 * `failWith` scripts the next answers (an error is thrown once per entry,
 * in order, for the given chat or any chat).
 */
export class FakeTelegramClient {
  readonly sent: SentMessage[] = [];
  private readonly failures: { chatId: bigint | null; error: Error }[] = [];
  private readonly updates: TelegramUpdate[] = [];
  /** Every offset getUpdates was asked for, in order. */
  readonly polledOffsets: bigint[] = [];
  /** Runs inside getUpdates, after the updates are chosen (e.g. steal the lease). */
  onGetUpdates: (() => Promise<void>) | null = null;
  private getUpdatesError: Error | null = null;

  isConfigured(): boolean {
    return true;
  }

  failWith(statusCode: number, description: string, chatId?: bigint): void {
    this.failures.push({
      chatId: chatId ?? null,
      error: new TelegramApiError('sendMessage', statusCode, description, null),
    });
  }

  sendMessage(chatId: bigint, text: string): Promise<void> {
    const index = this.failures.findIndex(
      (failure) => failure.chatId === null || failure.chatId === chatId,
    );
    if (index >= 0) {
      const [failure] = this.failures.splice(index, 1);
      return Promise.reject(failure.error);
    }
    this.sent.push({ chatId, text });
    return Promise.resolve();
  }

  /** What the next getUpdates calls return (from `offset` on, like Telegram). */
  queueUpdate(update: TelegramUpdate): void {
    this.updates.push(update);
  }

  failNextGetUpdates(error: Error): void {
    this.getUpdatesError = error;
  }

  async getUpdates(offset: bigint): Promise<TelegramUpdateBatch> {
    this.polledOffsets.push(offset);
    if (this.getUpdatesError !== null) {
      const error = this.getUpdatesError;
      this.getUpdatesError = null;
      throw error;
    }
    const due = this.updates.filter((update) => update.updateId >= offset);
    await this.onGetUpdates?.();
    const highestUpdateId = due.reduce<bigint | null>(
      (highest, update) =>
        highest === null || update.updateId > highest
          ? update.updateId
          : highest,
      null,
    );
    return { updates: due, highestUpdateId, received: due.length };
  }

  sentTo(chatId: bigint): SentMessage[] {
    return this.sent.filter((message) => message.chatId === chatId);
  }
}

export interface TelegramTestApp {
  app: INestApplication<App>;
  telegram: FakeTelegramClient;
}

/**
 * The whole API plus TelegramModule, with the Bot API client replaced by a
 * FakeTelegramClient. The TelegramSender is taken from the app and driven
 * by the test (no worker loop runs).
 */
export async function createTelegramTestApp(): Promise<TelegramTestApp> {
  const telegram = new FakeTelegramClient();
  const moduleFixture = await Test.createTestingModule({
    imports: [AppModule, TelegramModule],
  })
    .overrideProvider(THROTTLER_NAMESPACE)
    .useValue(randomUUID())
    .overrideProvider(TelegramClient)
    .useValue(telegram)
    .compile();
  const app = moduleFixture.createNestApplication<NestExpressApplication>();
  configureApp(app);
  await app.init();
  return { app, telegram };
}