Add log level support

Signed-off-by: Monis Khan <mok@vmware.com>

internal/plog/level.go

@@ -0,0 +1,64 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package plog
+
+import (
+	"strconv"
+
+	"k8s.io/component-base/logs"
+
+	"go.pinniped.dev/internal/constable"
+)
+
+// LogLevel is an enum that controls verbosity of logs.
+// Valid values in order of increasing verbosity are leaving it unset, info, debug, trace and all.
+type LogLevel string
+
+const (
+	// LevelWarning (i.e. leaving the log level unset) maps to klog log level 0.
+	LevelWarning LogLevel = ""
+	// LevelInfo maps to klog log level 2.
+	LevelInfo LogLevel = "info"
+	// LevelDebug maps to klog log level 4.
+	LevelDebug LogLevel = "debug"
+	// LevelTrace maps to klog log level 6.
+	LevelTrace LogLevel = "trace"
+	// LevelAll maps to klog log level 100 (conceptually it is log level 8).
+	LevelAll LogLevel = "all"
+
+	errInvalidLogLevel = constable.Error("invalid log level, valid choices are the empty string, info, debug, trace and all")
+)
+
+const (
+	klogLevelWarning = iota * 2
+	klogLevelInfo
+	klogLevelDebug
+	klogLevelTrace
+	klogLevelAll
+)
+
+func ValidateAndSetLogLevelGlobally(level LogLevel) error {
+	var klogLogLevel int
+
+	switch level {
+	case LevelWarning:
+		klogLogLevel = klogLevelWarning // unset means minimal logs (Error and Warning)
+	case LevelInfo:
+		klogLogLevel = klogLevelInfo
+	case LevelDebug:
+		klogLogLevel = klogLevelDebug
+	case LevelTrace:
+		klogLogLevel = klogLevelTrace
+	case LevelAll:
+		klogLogLevel = klogLevelAll + 100 // make all really mean all
+	default:
+		return errInvalidLogLevel
+	}
+
+	if _, err := logs.GlogSetter(strconv.Itoa(klogLogLevel)); err != nil {
+		panic(err) // programmer error
+	}
+
+	return nil
+}