Refactor server.MapNamespace

[magiconair]

A couple of observations on MapNamespace while I was working on #800

• make Mu and Data private
• guard access to Data through a method
• pass in ExternalNotification through the constructor method

[danomagnum]

Making the Mu private makes it more difficult to actually use the map in a convenient way - you can't just lock it then iterate or whatever. So I would propose something like this where I added iterators (named the same way as the iterators in the map package). I also started playing around with making it generic for even more usability.

main...MapNamespaceRefactor

I haven't had a chance to test this or anything yet.

[magiconair]

1. That looks like a reasonable approach.

You could also make SetValue accept varargs, e.g.

type KV struct {
	Key string
	Val any
}

func (ns *MapNamespace) SetValue(kvs ...KV) {
	ns.Lock()
	var nodes []*ua.NodeID
	for _, kv := range kvs {
		ns.Data[kv.Key] = kv.Val
		nodes = append(nodes, ua.NewStringNodeID(ns.id, kv.Key))
	}
	ns.Unlock()
	for _, node := range nodes {
		ns.srv.ChangeNotification(node)
	}
}

2. SetValue should take a context since ChangeNotification writes to a channel. Same goes for the write to the external notif channel.

3. I'd inject the external notif channel since that lets the caller decide whether the channel is buffered or not. Also, make it write only.

type MapNamespace struct {
	mu   sync.Mutex
	data map[string]any

	srv   *Server
	name  string
	id    uint16
	notif chan<- string
}

func NewMapNamespace(srv *Server, name string, notif chan<- string) *MapNamespace {
	ns := &MapNamespace{
		data:  make(map[string]any),
		srv:   srv,
		name:  name,
		notif: notif,
	}
	srv.AddNamespace(ns)
	return ns
}