jsonl-webstream/dist/receiver.js

Lightweight library for JSON Lines web stream between browsers and Node.js environments

class JsonLineScanner {
    onChunk;
    onError;
    #fragment = "";
    constructor(onChunk, onError) {
        this.onChunk = onChunk;
        this.onError = onError;
    }
    append(buffer) {
        this.#fragment += buffer;
        while (this.#scan())
            ;
    }
    #scan() {
        const lfPos = this.#fragment.indexOf("\n");
        if (lfPos === -1)
            return false;
        const json = this.#fragment.substring(0, lfPos);
        this.#fragment = this.#fragment.substring(lfPos + 1);
        try {
            const chunk = JSON.parse(json);
            this.onChunk(chunk);
            return true;
        }
        catch (err) {
            this.onError(err);
            return false;
        }
    }
}
/**
 * Creates a ReadableStream that parses JSON Lines from a binary stream.
 * Reads binary data from the provided reader, decodes it to text, and parses
 * each line as a JSON object of type T.
 *
 * @param reader A ReadableStreamDefaultReader providing binary data
 * @returns A ReadableStream that emits parsed JSON objects of type T
 */
export function createJsonLinesReceiver(reader) {
    return new ReadableStream({
        start(controller) {
            const decoder = new TextDecoder();
            const scanner = new JsonLineScanner((chunk) => {
                controller.enqueue(chunk);
            }, (err) => {
                controller.error(err);
            });
            const proceed = () => {
                return reader
                    .read()
                    .then(({ done, value }) => {
                    if (done) {
                        scanner.append(decoder.decode());
                        controller.close();
                        return;
                    }
                    scanner.append(decoder.decode(value, { stream: true }));
                    proceed();
                })
                    .catch((err) => {
                    controller.error(err);
                });
            };
            proceed();
        },
        cancel() {
            reader.cancel();
        },
    });
}