From 9e654521ae12debf40f181dfe291ad4ded0f7524 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julian=20T=C3=B6lle?= <julian.toelle97@gmail.com>
Date: Sat, 4 May 2024 23:45:58 +0200
Subject: [PATCH] feat(cli): hide redundant log attributes

---
 cmd/root.go                 | 28 ++++++++++++++++++-------
 internal/ui/slog_handler.go | 42 +++++++++++++++++++++++++++++++++++++
 main.go                     |  8 -------
 3 files changed, 63 insertions(+), 15 deletions(-)

diff --git a/cmd/root.go b/cmd/root.go
index feacb5c..9863f51 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -37,13 +37,7 @@ var rootCmd = &cobra.Command{
 	PersistentPreRun: func(cmd *cobra.Command, _ []string) {
 		ctx := cmd.Context()
 
-		logLevel := slog.LevelInfo
-		if verbose >= 1 {
-			logLevel = slog.LevelDebug
-		}
-		slog.SetDefault(slog.New(ui.NewHandler(os.Stdout, &ui.HandlerOptions{
-			Level: logLevel,
-		})))
+		slog.SetDefault(initLogger())
 
 		// Add logger to command context
 		logger := slog.Default()
@@ -54,6 +48,26 @@ var rootCmd = &cobra.Command{
 	},
 }
 
+func initLogger() *slog.Logger {
+	logLevel := slog.LevelInfo
+	if verbose >= 1 {
+		logLevel = slog.LevelDebug
+	}
+
+	return slog.New(ui.NewHandler(os.Stdout, &ui.HandlerOptions{
+		Level: logLevel,
+		ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
+			// Remove attributes that are unnecessary for the cli context
+			if a.Key == "library" || a.Key == "method" {
+				return slog.Attr{}
+			}
+
+			return a
+		},
+	}))
+
+}
+
 func newClient(ctx context.Context) *hcloudimages.Client {
 	logger := contextlogger.From(ctx)
 	// Build hcloud-go client
diff --git a/internal/ui/slog_handler.go b/internal/ui/slog_handler.go
index d688d3d..6b6dd96 100644
--- a/internal/ui/slog_handler.go
+++ b/internal/ui/slog_handler.go
@@ -8,6 +8,9 @@ import (
 	"sync"
 )
 
+// Developed with guidance from golang docs:
+// https://github.com/golang/example/blob/32022caedd6a177a7717aa8680cbe179e1045935/slog-handler-guide/README.md
+
 const (
 	ansiClear      = "\033[0m"
 	ansiBold       = "\033[1m"
@@ -23,8 +26,41 @@ type Handler struct {
 	out  io.Writer
 }
 
+// HandlerOptions are a subset of [slog.HandlerOptions] that are implemented for the UI handler.
 type HandlerOptions struct {
+	// Level reports the minimum record level that will be logged.
+	// The handler discards records with lower levels.
+	// If Level is nil, the handler assumes LevelInfo.
+	// The handler calls Level.Level for each record processed;
+	// to adjust the minimum level dynamically, use a LevelVar.
 	Level slog.Leveler
+
+	// ReplaceAttr is called to rewrite each non-group attribute before it is logged.
+	// The attribute's value has been resolved (see [Value.Resolve]).
+	// If ReplaceAttr returns a zero Attr, the attribute is discarded.
+	//
+	// The built-in attributes with keys "time", "level", "source", and "msg"
+	// are passed to this function, except that time is omitted
+	// if zero, and source is omitted if AddSource is false.
+	//
+	// The first argument is a list of currently open groups that contain the
+	// Attr. It must not be retained or modified. ReplaceAttr is never called
+	// for Group attributes, only their contents. For example, the attribute
+	// list
+	//
+	//     Int("a", 1), Group("g", Int("b", 2)), Int("c", 3)
+	//
+	// results in consecutive calls to ReplaceAttr with the following arguments:
+	//
+	//     nil, Int("a", 1)
+	//     []string{"g"}, Int("b", 2)
+	//     nil, Int("c", 3)
+	//
+	// ReplaceAttr can be used to change the default keys of the built-in
+	// attributes, convert types (for example, to replace a `time.Time` with the
+	// integer seconds since the Unix epoch), sanitize personal information, or
+	// remove attributes from the output.
+	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
 }
 
 // groupOrAttrs holds either a group name or a list of [slog.Attr].
@@ -108,6 +144,12 @@ func (h *Handler) Handle(_ context.Context, record slog.Record) error {
 
 func (h *Handler) appendAttr(buf []byte, group string, a slog.Attr) []byte {
 	a.Value = a.Value.Resolve()
+
+	if h.opts.ReplaceAttr != nil {
+		a = h.opts.ReplaceAttr([]string{group}, a)
+	}
+
+	// No-op if null attr
 	if a.Equal(slog.Attr{}) {
 		return buf
 	}
diff --git a/main.go b/main.go
index afb6e32..4e74f2c 100644
--- a/main.go
+++ b/main.go
@@ -1,17 +1,9 @@
 package main
 
 import (
-	"log/slog"
-	"os"
-
 	"github.com/apricote/hcloud-upload-image/cmd"
-	"github.com/apricote/hcloud-upload-image/internal/ui"
 )
 
-func init() {
-	slog.SetDefault(slog.New(ui.NewHandler(os.Stdout, &ui.HandlerOptions{Level: slog.LevelDebug})))
-}
-
 func main() {
 	cmd.Execute()
 }