Pull request: websvc: add system info

Merge in DNS/adguard-home from websvc-system-info to master

Squashed commit of the following:

commit 333aaa0602da254e25e0262a10080bf44a3718a7
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 12 16:32:32 2022 +0300

    websvc: fmt

commit d8a35bf71dcc59fdd595494e5b220e3d24516728
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 12 16:10:11 2022 +0300

    websvc: refactor, imp tests

commit dfeb24f3f35513bf51323d3ab6f717f582a1defc
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 11 20:52:02 2022 +0300

    websvc: add system info

internal/v1/websvc/websvc.go

@@ -17,6 +17,7 @@ import (
 	"github.com/AdguardTeam/golibs/errors"
 	"github.com/AdguardTeam/golibs/log"
 	"github.com/AdguardTeam/golibs/netutil"
+	httptreemux "github.com/dimfeld/httptreemux/v5"
 )
 
 // Config is the AdGuard Home web service configuration structure.
@@ -32,6 +33,9 @@ type Config struct {
 	// SecureAddresses is not empty, TLS must not be nil.
 	SecureAddresses []*netutil.IPPort
 
+	// Start is the time of start of AdGuard Home.
+	Start time.Time
+
 	// Timeout is the timeout for all server operations.
 	Timeout time.Duration
 }
@@ -41,6 +45,7 @@ type Config struct {
 type Service struct {
 	tls     *tls.Config
 	servers []*http.Server
+	start   time.Time
 	timeout time.Duration
 }
 
@@ -53,11 +58,11 @@ func New(c *Config) (svc *Service) {
 
 	svc = &Service{
 		tls:     c.TLS,
+		start:   c.Start,
 		timeout: c.Timeout,
 	}
 
-	mux := http.NewServeMux()
-	mux.HandleFunc("/health-check", svc.handleGetHealthCheck)
+	mux := newMux(svc)
 
 	for _, a := range c.Addresses {
 		addr := a.String()
@@ -91,6 +96,43 @@ func New(c *Config) (svc *Service) {
 	return svc
 }
 
+// newMux returns a new HTTP request multiplexor for the AdGuard Home web
+// service.
+func newMux(svc *Service) (mux *httptreemux.ContextMux) {
+	mux = httptreemux.NewContextMux()
+
+	routes := []struct {
+		handler http.HandlerFunc
+		method  string
+		path    string
+		isJSON  bool
+	}{{
+		handler: svc.handleGetHealthCheck,
+		method:  http.MethodGet,
+		path:    PathHealthCheck,
+		isJSON:  false,
+	}, {
+		handler: svc.handleGetV1SystemInfo,
+		method:  http.MethodGet,
+		path:    PathV1SystemInfo,
+		isJSON:  true,
+	}}
+
+	for _, r := range routes {
+		var h http.HandlerFunc
+		if r.isJSON {
+			// TODO(a.garipov): Consider using httptreemux's MiddlewareFunc.
+			h = jsonMw(r.handler)
+		} else {
+			h = r.handler
+		}
+
+		mux.Handle(r.method, r.path, h)
+	}
+
+	return mux
+}
+
 // Addrs returns all addresses on which this server serves the HTTP API.  Addrs
 // must not be called until Start returns.
 func (svc *Service) Addrs() (addrs []string) {