add log verbose (#772)

log/verbose.go

@@ -0,0 +1,30 @@
+package log
+
+// Verbose is a verbose type that implements Logger Print.
+type Verbose struct {
+	log     Logger
+	level   Level
+	enabled bool
+}
+
+// NewVerbose new a verbose with level.
+func NewVerbose(log Logger, level Level) Verbose {
+	return Verbose{log: log, level: level}
+}
+
+// Enabled will return true if this log level is enabled, guarded by the value of v.
+func (v Verbose) Enabled(level Level) bool {
+	return v.level <= level
+}
+
+// V reports whether verbosity at the call site is at least the requested level.
+func (v Verbose) V(level Level) Verbose {
+	return Verbose{log: v.log, enabled: v.Enabled(level)}
+}
+
+// Print is equivalent to the Print function, guarded by the value of v.
+func (v Verbose) Print(a ...interface{}) {
+	if v.enabled {
+		v.log.Print(a...)
+	}
+}

log/verbose_test.go

@@ -0,0 +1,11 @@
+package log
+
+import "testing"
+
+func TestVerbose(t *testing.T) {
+	v := NewVerbose(DefaultLogger, 20)
+
+	v.V(10).Print("foo", "bar1")
+	v.V(20).Print("foo", "bar2")
+	v.V(30).Print("foo", "bar3")
+}