Solution: Asynchronous Streaming Adapter

Solution explanation

• Lines 4–15: We define a legacyReader that reads data from a real file using Node’s fs module.

  • It opens a readable stream with fs.createReadStream(filename, { encoding: 'utf-8' }).

  • On each 'data' event, it passes the received chunk to the callback.

  • When the stream ends, it signals completion by calling the callback with null.

  • On errors, it logs the issue and also signals completion.

  • This mirrors how many legacy streaming APIs work—callback-driven and event-based.

• Lines 17–40: The StreamAdapter converts that push model into a pull-based async iterator. This design lets the adapter synchronize two mismatched timing models:

  • The constructor initializes three critical internal properties:

    • queue: a buffer that temporarily stores chunks that have already arrived but haven’t yet been requested by the consumer.

    • resolveNext: a reference to a promise resolver function. This is used when the consumer has called next() but no new data has arrived yet—essentially “parking” the ...