cmd/tsconnect: extract NPM package for reusing in other projects

`src/` is broken up into several subdirectories:
- `lib/` and `types`/ for shared code and type definitions (more code
  will be moved here)
- `app/` for the existing Preact-app
- `pkg/` for the new NPM package

A new `build-pkg` esbuild-based command is added to generate the files
for the NPM package. To generate type definitions (something that esbuild
does not do), we set up `dts-bundle-generator`.

Includes additional cleanups to the Wasm type definitions (we switch to
string literals for enums, since exported const enums are hard to use
via packages).

Also allows the control URL to be set a runtime (in addition to the
current build option), so that we don't have to rebuild the package
for dev vs. prod use.

Updates #5415

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/wasm/wasm_js.go

@@ -69,6 +69,12 @@ func newIPN(jsConfig js.Value) map[string]any {
 		store = &jsStateStore{jsStateStorage}
 	}
 
+	jsControlURL := jsConfig.Get("controlURL")
+	controlURL := ControlURL
+	if jsControlURL.Type() == js.TypeString {
+		controlURL = jsControlURL.String()
+	}
+
 	jsAuthKey := jsConfig.Get("authKey")
 	var authKey string
 	if jsAuthKey.Type() == js.TypeString {
@@ -125,9 +131,11 @@ func newIPN(jsConfig js.Value) map[string]any {
 	ns.SetLocalBackend(lb)
 
 	jsIPN := &jsIPN{
-		dialer: dialer,
-		srv:    srv,
-		lb:     lb,
+		dialer:     dialer,
+		srv:        srv,
+		lb:         lb,
+		controlURL: controlURL,
+		authKey:    authKey,
 	}
 
 	return map[string]any{
@@ -141,7 +149,7 @@ func newIPN(jsConfig js.Value) map[string]any {
 				})`)
 				return nil
 			}
-			jsIPN.run(args[0], authKey)
+			jsIPN.run(args[0])
 			return nil
 		}),
 		"login": js.FuncOf(func(this js.Value, args []js.Value) interface{} {
@@ -183,14 +191,33 @@ func newIPN(jsConfig js.Value) map[string]any {
 }
 
 type jsIPN struct {
-	dialer *tsdial.Dialer
-	srv    *ipnserver.Server
-	lb     *ipnlocal.LocalBackend
+	dialer     *tsdial.Dialer
+	srv        *ipnserver.Server
+	lb         *ipnlocal.LocalBackend
+	controlURL string
+	authKey    string
 }
 
-func (i *jsIPN) run(jsCallbacks js.Value, authKey string) {
+var jsIPNState = map[ipn.State]string{
+	ipn.NoState:          "NoState",
+	ipn.InUseOtherUser:   "InUseOtherUser",
+	ipn.NeedsLogin:       "NeedsLogin",
+	ipn.NeedsMachineAuth: "NeedsMachineAuth",
+	ipn.Stopped:          "Stopped",
+	ipn.Starting:         "Starting",
+	ipn.Running:          "Running",
+}
+
+var jsMachineStatus = map[tailcfg.MachineStatus]string{
+	tailcfg.MachineUnknown:      "MachineUnknown",
+	tailcfg.MachineUnauthorized: "MachineUnauthorized",
+	tailcfg.MachineAuthorized:   "MachineAuthorized",
+	tailcfg.MachineInvalid:      "MachineInvalid",
+}
+
+func (i *jsIPN) run(jsCallbacks js.Value) {
 	notifyState := func(state ipn.State) {
-		jsCallbacks.Call("notifyState", int(state))
+		jsCallbacks.Call("notifyState", jsIPNState[state])
 	}
 	notifyState(ipn.NoState)
 
@@ -218,7 +245,7 @@ func (i *jsIPN) run(jsCallbacks js.Value, authKey string) {
 						NodeKey:    nm.NodeKey.String(),
 						MachineKey: nm.MachineKey.String(),
 					},
-					MachineStatus: int(nm.MachineStatus),
+					MachineStatus: jsMachineStatus[nm.MachineStatus],
 				},
 				Peers: mapSlice(nm.Peers, func(p *tailcfg.Node) jsNetMapPeerNode {
 					name := p.Name
@@ -253,13 +280,13 @@ func (i *jsIPN) run(jsCallbacks js.Value, authKey string) {
 		err := i.lb.Start(ipn.Options{
 			StateKey: "wasm",
 			UpdatePrefs: &ipn.Prefs{
-				ControlURL:       ControlURL,
+				ControlURL:       i.controlURL,
 				RouteAll:         false,
 				AllowSingleHosts: true,
 				WantRunning:      true,
 				Hostname:         generateHostname(),
 			},
-			AuthKey: authKey,
+			AuthKey: i.authKey,
 		})
 		if err != nil {
 			log.Printf("Start error: %v", err)
@@ -467,7 +494,7 @@ type jsNetMapNode struct {
 
 type jsNetMapSelfNode struct {
 	jsNetMapNode
-	MachineStatus int `json:"machineStatus"`
+	MachineStatus string `json:"machineStatus"`
 }
 
 type jsNetMapPeerNode struct {