packages/runtime/src/bots/__tests__/telegram-utf16.test.ts

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import { strict as assert } from 'node:assert';
import { describe, it } from 'node:test';

import { __TEST__ } from '../telegram-bridge.js';

const { utf16Len, splitForTelegram } = __TEST__;

describe('Telegram UTF-16 limits', () => {
  it('splits oversized text within limits, on code points, and preferably at newlines', () => {
    assert.deepEqual(splitForTelegram('hello world'), ['hello world']);

    const asciiInput = 'a'.repeat(8500);
    const chunks = splitForTelegram(asciiInput);
    assert.ok(chunks.length >= 2);
    assert.match(chunks[0]!, /^\[1\/\d+\]\n/);
    assert.match(chunks.at(-1)!, /^\[\d+\/\d+\]\n/);
    for (const chunk of chunks) assert.ok(utf16Len(chunk) <= 4000);
    assert.equal(chunks.map((chunk) => chunk.replace(/^\[\d+\/\d+\]\n/, '')).join(''), asciiInput);

    const emojiInput = '😀'.repeat(4000);
    const emojiChunks = splitForTelegram(emojiInput);
    for (const chunk of emojiChunks) {
      const body = chunk.replace(/^\[\d+\/\d+\]\n/, '');
      for (let index = 0; index < body.length; ) {
        const codePoint = body.codePointAt(index)!;
        assert.ok(codePoint >= 0x20 || codePoint === 0x0a);
        index += codePoint > 0xffff ? 2 : 1;
      }
    }
    assert.equal(
      emojiChunks.map((chunk) => chunk.replace(/^\[\d+\/\d+\]\n/, '')).join(''),
      emojiInput,
    );

    const lineChunks = splitForTelegram('line\n'.repeat(900));
    const firstBody = lineChunks[0]!.replace(/^\[\d+\/\d+\]\n/, '');
    assert.ok(firstBody.endsWith('line') || firstBody.endsWith('line\n'));
  });
});