add server package

go.mod

@@ -1,3 +1,5 @@
 module github.com/kjk/common
 
-go 1.17
+go 1.16
+
+require github.com/andybalholm/brotli v1.0.3

go.sum

@@ -0,0 +1,2 @@
+github.com/andybalholm/brotli v1.0.3 h1:fpcw+r1N1h0Poc1F/pHbW40cUm/lMEQslZtCkBQ0UnM=
+github.com/andybalholm/brotli v1.0.3/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=

server/readme.md

@@ -0,0 +1,149 @@
+Those are useful snippets that use the server code for re-use.
+Copy & paste & modify for your purpose.
+
+```go
+import (
+	"github.com/kjk/cheatsheets/pkg/server"
+)
+```
+
+```go
+func MakeHTTPServer(srv *server.Server) *http.Server {
+	panicIf(srv == nil, "must provide files")
+	httpPort := 8080
+	if srv.Port != 0 {
+		httpPort = srv.Port
+	}
+	httpAddr := fmt.Sprintf(":%d", httpPort)
+	if isWindows() {
+		httpAddr = "localhost" + httpAddr
+	}
+	httpSrv := &http.Server{
+		ReadTimeout:  120 * time.Second,
+		WriteTimeout: 120 * time.Second,
+		IdleTimeout:  120 * time.Second, // introduced in Go 1.8
+		Handler:      srv,
+	}
+	httpSrv.Addr = httpAddr
+	return httpSrv
+}
+
+// returns function that will wait for SIGTERM signal (e.g. Ctrl-C) and
+// shutdown the server
+func StartHTTPServer(httpSrv *http.Server) func() {
+	logf(ctx(), "Starting server on http://%s'\n", httpSrv.Addr)
+	if isWindows() {
+		openBrowser(fmt.Sprintf("http://%s", httpSrv.Addr))
+	}
+
+	chServerClosed := make(chan bool, 1)
+	go func() {
+		err := httpSrv.ListenAndServe()
+		// mute error caused by Shutdown()
+		if err == http.ErrServerClosed {
+			err = nil
+		}
+		must(err)
+		logf(ctx(), "trying to shutdown HTTP server\n")
+		chServerClosed <- true
+	}()
+
+	return func() {
+		c := make(chan os.Signal, 2)
+		signal.Notify(c, os.Interrupt /* SIGINT */, syscall.SIGTERM)
+
+		sig := <-c
+		logf(ctx(), "Got signal %s\n", sig)
+
+		if httpSrv != nil {
+			go func() {
+				// Shutdown() needs a non-nil context
+				_ = httpSrv.Shutdown(ctx())
+			}()
+			select {
+			case <-chServerClosed:
+				// do nothing
+				logf(ctx(), "server shutdown cleanly\n")
+			case <-time.After(time.Second * 5):
+				// timeout
+				logf(ctx(), "server killed due to shutdown timeout\n")
+			}
+		}
+	}
+}
+
+func StartServer(srv *server.Server) func() {
+	httpServer := MakeHTTPServer(srv)
+	return StartHTTPServer(httpServer)
+}
+```
+
+```
+
+Utility functions used above:
+
+```go
+func must(err error) {
+	if err != nil {
+		panic(err.Error())
+	}
+}
+
+func ctx() context.Context {
+	return context.Background()
+}
+
+func panicIf(cond bool, arg ...interface{}) {
+	if !cond {
+		return
+	}
+	s := "condition failed"
+	if len(arg) > 0 {
+		s = fmt.Sprintf("%s", arg[0])
+		if len(arg) > 1 {
+			s = fmt.Sprintf(s, arg[1:]...)
+		}
+	}
+	panic(s)
+}
+
+func isWindows() bool {
+	return strings.Contains(runtime.GOOS, "windows")
+}
+
+func openBrowser(url string) {
+	var err error
+
+	switch runtime.GOOS {
+	case "linux":
+		err = exec.Command("xdg-open", url).Start()
+	case "windows":
+		err = exec.Command("rundll32", "url.dll,FileProtocolHandler", url).Start()
+	case "darwin":
+		err = exec.Command("open", url).Start()
+	default:
+		err = fmt.Errorf("unsupported platform")
+	}
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func isWindows() bool {
+	return strings.Contains(runtime.GOOS, "windows")
+}
+
+func formatSize(n int64) string {
+	sizes := []int64{1024 * 1024 * 1024, 1024 * 1024, 1024}
+	suffixes := []string{"GB", "MB", "kB"}
+
+	for i, size := range sizes {
+		if n >= size {
+			s := fmt.Sprintf("%.2f", float64(n)/float64(size))
+			return strings.TrimSuffix(s, ".00") + " " + suffixes[i]
+		}
+	}
+	return fmt.Sprintf("%d bytes", n)
+}
+
+```