apiserver: output flags in logical sections

Kubernetes-commit: 42d533e40c112f62635a8aa0e3c3def298b26cc9

pkg/util/flag/sectioned.go

@@ -0,0 +1,92 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package flag
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/docker/docker/pkg/term"
+	"github.com/spf13/pflag"
+)
+
+// NamedFlagSets stores named flag sets in the order of calling FlagSet.
+type NamedFlagSets struct {
+	// Order is an ordered list of flag set names.
+	Order []string
+	// FlagSets stores the flag sets by name.
+	FlagSets map[string]*pflag.FlagSet
+}
+
+// FlagSet returns the flag set with the given name and adds it to the
+// ordered name list if it is not in there yet.
+func (nfs *NamedFlagSets) FlagSet(name string) *pflag.FlagSet {
+	if nfs.FlagSets == nil {
+		nfs.FlagSets = map[string]*pflag.FlagSet{}
+	}
+	if _, ok := nfs.FlagSets[name]; !ok {
+		nfs.FlagSets[name] = pflag.NewFlagSet(name, pflag.ExitOnError)
+		nfs.Order = append(nfs.Order, name)
+	}
+	return nfs.FlagSets[name]
+}
+
+// PrintSections prints the given names flag sets in sections, with the maximal given column number.
+// If cols is zero, lines are not wrapped.
+func PrintSections(w io.Writer, fss NamedFlagSets, cols int) {
+	for _, name := range fss.Order {
+		fs := fss.FlagSets[name]
+
+		wideFS := pflag.NewFlagSet("", pflag.ExitOnError)
+		wideFS.AddFlagSet(fs)
+
+		var zzz string
+		if cols > 24 {
+			zzz = strings.Repeat("z", cols-24)
+			wideFS.Int(zzz, 0, strings.Repeat("z", cols-24))
+		}
+
+		var buf bytes.Buffer
+		fmt.Fprintf(&buf, "\n%s flags:\n\n%s", strings.ToUpper(name[:1])+name[1:], wideFS.FlagUsagesWrapped(cols))
+
+		if cols > 24 {
+			i := strings.Index(buf.String(), zzz)
+			lines := strings.Split(buf.String()[:i], "\n")
+			fmt.Fprint(w, strings.Join(lines[:len(lines)-1], "\n"))
+			fmt.Fprintln(w)
+		} else {
+			fmt.Fprint(w, buf.String())
+		}
+	}
+}
+
+// TerminalSize returns the current width and height of the user's terminal. If it isn't a terminal,
+// nil is returned. On error, zero values are returned for width and height.
+// Usually w must be the stdout of the process. Stderr won't work.
+func TerminalSize(w io.Writer) (int, int, error) {
+	outFd, isTerminal := term.GetFdInfo(w)
+	if !isTerminal {
+		return 0, 0, fmt.Errorf("given writer is no terminal")
+	}
+	winsize, err := term.GetWinsize(outFd)
+	if err != nil {
+		return 0, 0, err
+	}
+	return int(winsize.Width), int(winsize.Height), nil
+}