Change proxy in ProxyAgent instance

ProxyAgent already handles other agents' instances and is able to instantiate them after its own construction. Can we make a proxy switchable in ProxyAgent instance?

So an instance could created, passed as agent to request library of choice and still able to change proxy URI on the fly.

In its most simple form it may be like that.

class SwitchableProxyAgent extends ProxyAgent {
    get proxyUri() {
        return this._uri;
    }

    set proxyUri(uri) {
        this._uri = uri;
        this.proxy = url.parse(uri);
    }
}

A few problems persist with extending existing ProxyAgent

original opts object isn't reusable after construction, there's no way to tell from this.proxy if the option is there on purpose (like opts.secureEndpoint) or it was parsed from URI
custom proxy types are private and cannot be reached from outside the constructor (incidentally, they were available once)
the only way to switch proxy type (proxyFn) after instantiation is to recreate the whole constructor logic

This could be fixed by exposing this.opts and this.proxies and moving almost all constructor code to something like this.setProxyUri (proxyUri accessors would be ok, too). BTW, this may improve unit-testability.

TooTallNate / node-proxy-agent

Change proxy in ProxyAgent instance #8