From 5bf8bb3a36ddfd9c4d85b143af6f7a556a47230a Mon Sep 17 00:00:00 2001
From: Gregory Eremin <g@erem.in>
Date: Fri, 27 Jul 2018 20:24:57 +0200
Subject: [PATCH] Introduce log levels

---
 log/log.go | 69 +++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 55 insertions(+), 14 deletions(-)

diff --git a/log/log.go b/log/log.go
index eb010e1..9113631 100644
--- a/log/log.go
+++ b/log/log.go
@@ -6,64 +6,105 @@ import (
 	"github.com/sirupsen/logrus"
 )
 
-// Logger is a Logrus logger used by the package.
-var Logger *logrus.Logger
-
 // F is a short alias for a string to interface map.
 type F map[string]interface{}
 
-func init() {
+// Level defines logging level.
+type Level byte
+
+const (
+	// LevelDebug is a logging level of debug messages.
+	LevelDebug Level = iota
+	// LevelInfo is a logging level of info messages.
+	LevelInfo
+	// LevelWarn is a logging level of warning messages.
+	LevelWarn
+	// LevelError is a logging level of error messages.
+	LevelError
+	// LevelFatal is a logging level of fatal messages.
+	LevelFatal
+)
+
+var (
+	// Logger is a Logrus logger used by the package.
 	Logger = logrus.New()
+
+	level = LevelDebug
+)
+
+// SetLevel sets up minimum logging level.
+func SetLevel(l Level) {
+	level = l
 }
 
 // Debug prints a debug message with given fields attached.
 func Debug(ctx context.Context, msg string, fields ...F) {
-	withFields(mergeFields(ctx, fields)).Debug(msg)
+	if level >= LevelDebug {
+		withFields(mergeFields(ctx, fields)).Debug(msg)
+	}
 }
 
 // Debugf prints a formatted debug message.
 func Debugf(ctx context.Context, format string, args ...interface{}) {
-	withFields(contextFields(ctx)).Debugf(format, args...)
+	if level >= LevelDebug {
+		withFields(contextFields(ctx)).Debugf(format, args...)
+	}
 }
 
 // Info prints an info message with given fields attached.
 func Info(ctx context.Context, msg string, fields ...F) {
-	withFields(mergeFields(ctx, fields)).Info(msg)
+	if level >= LevelInfo {
+		withFields(mergeFields(ctx, fields)).Info(msg)
+	}
 }
 
 // Infof prints a formatted info message.
 func Infof(ctx context.Context, format string, args ...interface{}) {
-	withFields(contextFields(ctx)).Infof(format, args...)
+	if level >= LevelInfo {
+		withFields(contextFields(ctx)).Infof(format, args...)
+	}
 }
 
 // Warn prints an warning message with given fields attached.
 func Warn(ctx context.Context, msg string, fields ...F) {
-	withFields(mergeFields(ctx, fields)).Warn(msg)
+	if level >= LevelWarn {
+		withFields(mergeFields(ctx, fields)).Warn(msg)
+	}
 }
 
 // Warnf prints a formatted warning message.
 func Warnf(ctx context.Context, format string, args ...interface{}) {
-	withFields(contextFields(ctx)).Warnf(format, args...)
+	if level >= LevelWarn {
+		withFields(contextFields(ctx)).Warnf(format, args...)
+	}
 }
 
 // Error prints an error message with given fields attached.
 func Error(ctx context.Context, msg string, fields ...F) {
-	withFields(mergeFields(ctx, fields)).Error(msg)
+	if level >= LevelError {
+		withFields(mergeFields(ctx, fields)).Error(msg)
+	}
 }
 
 // Errorf prints a formatted error message.
 func Errorf(ctx context.Context, format string, args ...interface{}) {
-	withFields(contextFields(ctx)).Errorf(format, args...)
+	if level >= LevelError {
+		withFields(contextFields(ctx)).Errorf(format, args...)
+	}
 }
 
 // Fatal prints an error message with given fields attached and then exits.
 func Fatal(ctx context.Context, msg string, fields ...F) {
-	withFields(mergeFields(ctx, fields)).Fatal(msg)
+	if level >= LevelFatal {
+		withFields(mergeFields(ctx, fields)).Fatal(msg)
+	}
 }
 
 // Fatalf prints a formatted error message and then exits.
 func Fatalf(ctx context.Context, format string, args ...interface{}) {
-	withFields(contextFields(ctx)).Fatalf(format, args...)
+	if level >= LevelFatal {
+		withFields(contextFields(ctx)).Fatalf(format, args...)
+	}
 }
 
 func mergeFields(ctx context.Context, fields []F) F {