Implement support for external HTTP(S) servers

Add a new headless WebWire server constructor.
Make the server interface implement the HTTP handler interface.

interfaces.go

@@ -9,6 +9,8 @@ import (
 
 // Server defines the interface of a webwire server instance
 type Server interface {
+	// ServeHTTP implements the HTTP handler interface
+	ServeHTTP(resp http.ResponseWriter, req *http.Request)
 
 	// Run will luanch the webwire server blocking the calling goroutine
 	// until the server is either gracefully shut down

newServer.go

@@ -7,10 +7,46 @@ import (
 	"sync"
 )
 
-// NewServer creates a new WebWire server instance
+// NewServer creates a new headed WebWire server instance
+// with a built-in HTTP server hosting it
 func NewServer(
 	implementation ServerImplementation,
 	opts ServerOptions,
+) (instance Server, err error) {
+	instance, err = NewHeadlessServer(implementation, opts)
+	if err != nil {
+		return nil, err
+	}
+
+	srv := instance.(*server)
+
+	// Initialize HTTP server
+	srv.httpServer = &http.Server{
+		Addr:    opts.Address,
+		Handler: srv,
+	}
+
+	// Determine final address
+	if opts.Address == "" {
+		opts.Address = ":http"
+	}
+
+	// Initialize TCP/IP listener
+	srv.listener, err = net.Listen("tcp", opts.Address)
+	if err != nil {
+		return nil, fmt.Errorf("Failed setting up TCP/IP listener: %s", err)
+	}
+
+	srv.addr = srv.listener.Addr()
+
+	return srv, nil
+}
+
+// NewHeadlessServer creates a new headless WebWire server instance
+// which relies on an external HTTP server to host it
+func NewHeadlessServer(
+	implementation ServerImplementation,
+	opts ServerOptions,
 ) (instance Server, err error) {
 	if implementation == nil {
 		panic(fmt.Errorf("A headed webwire server requires a server implementation, got nil"))
@@ -23,7 +59,7 @@ func NewServer(
 		sessionsEnabled = true
 	}
 
-	srv := &server{
+	return &server{
 		impl:              implementation,
 		sessionManager:    opts.SessionManager,
 		sessionKeyGen:     opts.SessionKeyGenerator,
@@ -44,26 +80,5 @@ func NewServer(
 		connUpgrader: newConnUpgrader(),
 		warnLog:      opts.WarnLog,
 		errorLog:     opts.ErrorLog,
-	}
-
-	// Initialize HTTP server
-	srv.httpServer = &http.Server{
-		Addr:    opts.Address,
-		Handler: srv,
-	}
-
-	// Determine final address
-	if opts.Address == "" {
-		opts.Address = ":http"
-	}
-
-	// Initialize TCP/IP listener
-	srv.listener, err = net.Listen("tcp", opts.Address)
-	if err != nil {
-		return nil, fmt.Errorf("Failed setting up TCP/IP listener: %s", err)
-	}
-
-	srv.addr = srv.listener.Addr()
-
-	return srv, nil
+	}, nil
 }

server.go

@@ -81,6 +81,7 @@ func (srv *server) Shutdown() error {
 	srv.shutdown = true
 	// Don't block if there's no currently processed operations
 	if srv.currentOps < 1 {
+		srv.opsLock.Unlock()
 		return srv.shutdownHTTPServer()
 	}
 	srv.opsLock.Unlock()