deepseek-harness/packages/session-persistence/session-persistence-jsonl/tests/zstd.compat.spec.ts

import { describe, expect, it } from 'vitest'
import { compressZstdFrame, decompressZstdFrame, decompressZstdPrefix, scanZstdFrames } from '../src/zstd.ts'

describe('JSONL Zstandard compatibility', () => {
  it('round-trips concatenated checksummed frames through the built-in Node API', async () => {
    const encoded = Buffer.concat([
      await compressZstdFrame('{"type":"session","version":0,"id":"compat","createdAt":1}\n'),
      await compressZstdFrame('{"type":"turn/start","seq":0,"turn":1}\n'),
    ])
    const { frames, tornStart } = scanZstdFrames(encoded)

    expect(tornStart).toBeUndefined()
    expect(frames).toHaveLength(2)
    expect(frames.map(frame => encoded.subarray(frame.start, frame.start + 4).toString('hex')))
      .toEqual(['28b52ffd', '28b52ffd'])
    const decoded = await Promise.all(frames.map(frame => decompressZstdFrame(encoded.subarray(frame.start, frame.end))))
    expect(Buffer.concat(decoded).toString()).toContain('"type":"turn/start"')

    const eventFrame = encoded.subarray(frames[1]!.start, frames[1]!.end)
    const missingChecksumByte = eventFrame.subarray(0, -1)
    expect(scanZstdFrames(missingChecksumByte)).toEqual({ frames: [], tornStart: 0 })
    expect((await decompressZstdPrefix(missingChecksumByte)).toString()).toContain('"type":"turn/start"')
  })
})