index.js

'use strict';
const {
	pipeline: streamPipeline,
	PassThrough: PassThroughStream
} = require('stream');
const zlib = require('zlib');
const mimicResponse = require('mimic-response');

const decompressResponse = response => {
	const contentEncoding = (response.headers['content-encoding'] || '').toLowerCase();

	if (!['gzip', 'deflate', 'br'].includes(contentEncoding)) {
		return response;
	}

	// TODO: Remove this when targeting Node.js 12.
	const isBrotli = contentEncoding === 'br';
	if (isBrotli && typeof zlib.createBrotliDecompress !== 'function') {
		return response;
	}

	const decompress = isBrotli ? zlib.createBrotliDecompress() : zlib.createUnzip();
	const stream = new PassThroughStream();

	decompress.on('error', error => {
		// Ignore empty response
		if (error.code === 'Z_BUF_ERROR') {
			stream.end();
			return;
		}

		stream.emit('error', error);
	});

	const finalStream = streamPipeline(response, decompress, stream, () => {});

	mimicResponse(response, finalStream);

	return finalStream;
};

module.exports = decompressResponse;