kubens: Start implementing stubs

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

cmd/kubens/current.go

@@ -0,0 +1,9 @@
+package main
+
+import "io"
+
+type CurrentOp struct{}
+
+func (c CurrentOp) Run(stdout, stderr io.Writer) error {
+	panic("implement me")
+}

cmd/kubens/flags.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+// UnsupportedOp indicates an unsupported flag.
+type UnsupportedOp struct{ Err error }
+
+func (op UnsupportedOp) Run(_, _ io.Writer) error {
+	return op.Err
+}
+
+// parseArgs looks at flags (excl. executable name, i.e. argv[0])
+// and decides which operation should be taken.
+func parseArgs(argv []string) Op {
+	if len(argv) == 0 {
+		//if env.IsInteractiveMode(os.Stdout) {
+		//	return InteractiveSwitchOp{SelfCmd: os.Args[0]}
+		//}
+		return ListOp{}
+	}
+
+	if len(argv) == 1 {
+		v := argv[0]
+		if v == "--help" || v == "-h" {
+			return HelpOp{}
+		}
+		if v == "--current" || v == "-c" {
+			return CurrentOp{}
+		}
+		if strings.HasPrefix(v, "-") && v != "-" {
+			return UnsupportedOp{Err: fmt.Errorf("unsupported option '%s'", v)}
+		}
+		return SwitchOp{Target: argv[0]}
+	}
+	return UnsupportedOp{Err: fmt.Errorf("too many arguments")}
+}

cmd/kubens/flags_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+)
+
+func Test_parseArgs_new(t *testing.T) {
+	tests := []struct {
+		name string
+		args []string
+		want Op
+	}{
+		{name: "nil Args",
+			args: nil,
+			want: ListOp{}},
+		{name: "empty Args",
+			args: []string{},
+			want: ListOp{}},
+		{name: "help shorthand",
+			args: []string{"-h"},
+			want: HelpOp{}},
+		{name: "help long form",
+			args: []string{"--help"},
+			want: HelpOp{}},
+		{name: "current shorthand",
+			args: []string{"-c"},
+			want: CurrentOp{}},
+		{name: "current long form",
+			args: []string{"--current"},
+			want: CurrentOp{}},
+		{name: "switch by name",
+			args: []string{"foo"},
+			want: SwitchOp{Target: "foo"}},
+		{name: "switch by swap",
+			args: []string{"-"},
+			want: SwitchOp{Target: "-"}},
+		{name: "unrecognized flag",
+			args: []string{"-x"},
+			want: UnsupportedOp{Err: fmt.Errorf("unsupported option '-x'")}},
+		{name: "too many args",
+			args: []string{"a", "b", "c"},
+			want: UnsupportedOp{Err: fmt.Errorf("too many arguments")}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := parseArgs(tt.args)
+
+			var opts cmp.Options
+			if _, ok := tt.want.(UnsupportedOp); ok {
+				opts = append(opts, cmp.Comparer(func(x, y UnsupportedOp) bool {
+					return (x.Err == nil && y.Err == nil) || (x.Err.Error() == y.Err.Error())
+				}))
+			}
+
+			if diff := cmp.Diff(got, tt.want, opts...); diff != "" {
+				t.Errorf("parseArgs(%#v) diff: %s", tt.args, diff)
+			}
+		})
+	}
+}

cmd/kubens/help.go

@@ -0,0 +1,44 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/pkg/errors"
+)
+
+// HelpOp describes printing help.
+type HelpOp struct{}
+
+func (_ HelpOp) Run(stdout, _ io.Writer) error {
+	return printUsage(stdout)
+}
+
+func printUsage(out io.Writer) error {
+	help := `USAGE:
+  %PROG%                    : list the namespaces in the current context
+  %PROG% <NAME>             : change the active namespace of current context
+  %PROG% -                  : switch to the previous namespace in this context
+  %PROG% -c, --current      : show the current namespace
+  %PROG% -h,--help          : show this message
+`
+	// TODO this replace logic is duplicated between this and kubectx
+	help = strings.ReplaceAll(help, "%PROG%", selfName())
+
+	_, err := fmt.Fprintf(out, "%s\n", help)
+	return errors.Wrap(err, "write error")
+}
+
+// selfName guesses how the user invoked the program.
+func selfName() string {
+	// TODO this method is duplicated between this and kubectx
+	me := filepath.Base(os.Args[0])
+	pluginPrefix := "kubectl-"
+	if strings.HasPrefix(me, pluginPrefix) {
+		return "kubectl " + strings.TrimPrefix(me, pluginPrefix)
+	}
+	return "kubectx"
+}

cmd/kubens/list.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"io"
+)
+
+type ListOp struct{}
+
+func (op ListOp) Run(stdout, stderr io.Writer) error {
+	panic("implement me")
+}

cmd/kubens/main.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/ahmetb/kubectx/internal/env"
+	"github.com/ahmetb/kubectx/internal/printer"
+)
+
+type Op interface {
+	Run(stdout, stderr io.Writer) error
+}
+
+func main() {
+	op := parseArgs(os.Args[1:])
+	if err := op.Run(os.Stdout, os.Stderr); err != nil {
+		printer.Error(os.Stderr, err.Error())
+
+		if _, ok := os.LookupEnv(env.EnvDebug); ok {
+			// print stack trace in verbose mode
+			fmt.Fprintf(os.Stderr, "[DEBUG] error: %+v\n", err)
+		}
+		defer os.Exit(1)
+	}
+}

cmd/kubens/switch.go

@@ -0,0 +1,11 @@
+package main
+
+import (
+	"io"
+)
+
+type SwitchOp struct{ Target string }
+
+func (s SwitchOp) Run(stdout, stderr io.Writer) error {
+	panic("implement me")
+}