nest-ndjson-req-stream/dist/index.js

Accept and automatically parse NDJSON request streams.

import { Injectable, createParamDecorator, BadRequestException } from '@nestjs/common';
import { Transform } from 'stream';

var __getOwnPropDesc = Object.getOwnPropertyDescriptor;
var __decorateClass = (decorators, target, key, kind) => {
  var result = kind > 1 ? void 0 : kind ? __getOwnPropDesc(target, key) : target;
  for (var i = decorators.length - 1, decorator; i >= 0; i--)
    if (decorator = decorators[i])
      result = (decorator(result)) || result;
  return result;
};
var NdJsonStreamParser = class {
  /**
   * Creates a Transform stream that parses NDJSON data
   * @template T - The type of objects in the NDJSON stream
   * @returns A Transform stream that emits parsed objects
   */
  static createParser() {
    let buffer = "";
    let itemCount = 0;
    return new Transform({
      objectMode: true,
      transform(chunk, encoding, callback) {
        buffer += chunk.toString();
        const lines = buffer.split("\n");
        buffer = lines.pop() || "";
        for (const line of lines) {
          itemCount++;
          if (line.trim()) {
            try {
              const parsed = JSON.parse(line);
              this.push(parsed);
            } catch (error) {
              this.emit(`Error occurred parsing stream item ${itemCount}: ${error.message}`);
            }
          }
        }
        callback();
      },
      flush(callback) {
        if (buffer.trim()) {
          try {
            this.push(JSON.parse(buffer));
          } catch (error) {
            this.emit(`Error occurred parsing stream item ${itemCount}: ${error.message}`);
          }
        }
        callback();
      }
    });
  }
  /**
   * Parses a readable stream as NDJSON and yields parsed objects
   * @template T - The type of objects in the NDJSON stream
   * @param stream - The readable stream containing NDJSON data
   * @returns An async generator that yields parsed objects
   */
  static async *parseStream(stream) {
    const parser = this.createParser();
    const errors = [];
    parser.on("parse-error", (error) => errors.push(error));
    stream.pipe(parser);
    for await (const item of parser) {
      yield item;
    }
    if (errors.length > 0) {
      console.warn("Parse errors encountered:", errors);
    }
  }
};
NdJsonStreamParser = __decorateClass([
  Injectable()
], NdJsonStreamParser);

// src/decorators/ndjson-stream.decorator.ts
var NdJsonStreamReq = createParamDecorator(
  (data, ctx) => {
    const request = ctx.switchToHttp().getRequest();
    const batchSize = data?.batchSize ?? 25;
    const contentType = request.headers["content-type"];
    if (!contentType.toLowerCase().includes("application/x-ndjson")) {
      throw new BadRequestException(
        `Invalid content-type: ${contentType}. Expected application/x-ndjson`
      );
    }
    const asyncGenerator = NdJsonStreamParser.parseStream(request);
    const streamRequest = request;
    streamRequest.body = asyncGenerator;
    streamRequest.batchSize = batchSize;
    return streamRequest;
  }
);

export { NdJsonStreamReq };