source: node_modules/mimic-response/index.js@ 81bc7da

'use strict';

// We define these manually to ensure they're always copied
// even if they would move up the prototype chain
// https://nodejs.org/api/http.html#http_class_http_incomingmessage
const knownProperties = [
        'aborted',
        'complete',
        'headers',
        'httpVersion',
        'httpVersionMinor',
        'httpVersionMajor',
        'method',
        'rawHeaders',
        'rawTrailers',
        'setTimeout',
        'socket',
        'statusCode',
        'statusMessage',
        'trailers',
        'url'
];

module.exports = (fromStream, toStream) => {
        if (toStream._readableState.autoDestroy) {
                throw new Error('The second stream must have the `autoDestroy` option set to `false`');
        }

        const fromProperties = new Set(Object.keys(fromStream).concat(knownProperties));

        const properties = {};

        for (const property of fromProperties) {
                // Don't overwrite existing properties.
                if (property in toStream) {
                        continue;
                }

                properties[property] = {
                        get() {
                                const value = fromStream[property];
                                const isFunction = typeof value === 'function';

                                return isFunction ? value.bind(fromStream) : value;
                        },
                        set(value) {
                                fromStream[property] = value;
                        },
                        enumerable: true,
                        configurable: false
                };
        }

        Object.defineProperties(toStream, properties);

        fromStream.once('aborted', () => {
                toStream.destroy();

                toStream.emit('aborted');
        });

        fromStream.once('close', () => {
                if (fromStream.complete) {
                        if (toStream.readable) {
                                toStream.once('end', () => {
                                        toStream.emit('close');
                                });
                        } else {
                                toStream.emit('close');
                        }
                } else {
                        toStream.emit('close');
                }
        });

        return toStream;
};