add logger constructors

keygen.go

@@ -51,7 +51,7 @@ var (
 
 	// Logger is a leveled logger implementation used for printing debug,
 	// informational, warning, and error messages.
-	Logger LeveledLogger = &logger{Level: LogLevelError}
+	Logger LeveledLogger = NewLogger(LogLevelError)
 
 	// Program is the name of the current program, used when installing
 	// upgrades. Defaults to the current program name.

log.go

@@ -2,6 +2,7 @@ package keygen
 
 import (
 	"fmt"
+	"io"
 	"os"
 )
 
@@ -15,54 +16,76 @@ const (
 	LogLevelDebug
 )
 
+// LoggerOptions stores config options used for the logger e.g. log streams.
+type LoggerOptions struct {
+	Stdout io.Writer
+	Stderr io.Writer
+}
+
 type logger struct {
 	Level LogLevel
+	LoggerOptions
 }
 
 func (l *logger) Errorf(format string, v ...interface{}) {
 	if l.Level < LogLevelError {
 		return
 	}
 
-	fmt.Fprintf(os.Stderr, "[ERROR] "+format+"\n", v...)
+	fmt.Fprintf(l.Stderr, "[ERROR] "+format+"\n", v...)
 }
 
 func (l *logger) Warnf(format string, v ...interface{}) {
 	if l.Level < LogLevelWarn {
 		return
 	}
 
-	fmt.Fprintf(os.Stderr, "[WARN] "+format+"\n", v...)
+	fmt.Fprintf(l.Stderr, "[WARN] "+format+"\n", v...)
 }
 
 func (l *logger) Infof(format string, v ...interface{}) {
 	if l.Level < LogLevelInfo {
 		return
 	}
 
-	fmt.Fprintf(os.Stdout, "[INFO] "+format+"\n", v...)
+	fmt.Fprintf(l.Stdout, "[INFO] "+format+"\n", v...)
 }
 
 func (l *logger) Debugf(format string, v ...interface{}) {
 	if l.Level < LogLevelDebug {
 		return
 	}
 
-	fmt.Fprintf(os.Stdout, "[DEBUG] "+format+"\n", v...)
+	fmt.Fprintf(l.Stdout, "[DEBUG] "+format+"\n", v...)
 }
 
 // LeveledLogger provides a basic leveled logging interface for
 // printing debug, informational, warning, and error messages.
 type LeveledLogger interface {
-	// Debugf logs a debug message using Printf conventions.
-	Debugf(format string, v ...interface{})
-
 	// Errorf logs a warning message using Printf conventions.
 	Errorf(format string, v ...interface{})
 
+	// Warnf logs a warning message using Printf conventions.
+	Warnf(format string, v ...interface{})
+
 	// Infof logs an informational message using Printf conventions.
 	Infof(format string, v ...interface{})
 
-	// Warnf logs a warning message using Printf conventions.
-	Warnf(format string, v ...interface{})
+	// Debugf logs a debug message using Printf conventions.
+	Debugf(format string, v ...interface{})
+}
+
+// NewClient creates a new leveled logger with default log streams to stdout and stderr.
+func NewLogger(level LogLevel) LeveledLogger {
+	return &logger{level, LoggerOptions{os.Stdout, os.Stderr}}
+}
+
+// NewLoggerWithOptions creates a new leveled logger with custom log streams.
+func NewLoggerWithOptions(level LogLevel, options *LoggerOptions) LeveledLogger {
+	return &logger{level, *options}
+}
+
+// NewNilLogger creates a new leveled logger with discarded log steams.
+func NewNilLogger() LeveledLogger {
+	return &logger{LogLevelNone, LoggerOptions{io.Discard, io.Discard}}
 }