From 8a7ab2c06f39492974808998616792bcc120315e Mon Sep 17 00:00:00 2001
From: Xe Iaso <me@xeiaso.net>
Date: Thu, 27 Jul 2023 09:26:08 -0400
Subject: internal/slog: add debug route for changing the slog level on the fly

Signed-off-by: Xe Iaso <me@xeiaso.net>
---
 internal/slog/slog.go | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/internal/slog/slog.go b/internal/slog/slog.go
index 839417c..cdb83b9 100644
--- a/internal/slog/slog.go
+++ b/internal/slog/slog.go
@@ -4,6 +4,8 @@ package slog
 import (
 	"flag"
 	"fmt"
+	"io"
+	"net/http"
 	"os"
 
 	"golang.org/x/exp/slog"
@@ -14,6 +16,8 @@ var (
 
 	// The current slog handler.
 	Handler slog.Handler
+
+	leveler *slog.LevelVar
 )
 
 func Init() {
@@ -23,11 +27,36 @@ func Init() {
 		programLevel = slog.LevelInfo
 	}
 
+	leveler = &slog.LevelVar{}
+	leveler.Set(programLevel)
+
 	h := slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
 		AddSource: true,
-		Level:     programLevel,
+		Level:     leveler,
 	})
 	slog.SetDefault(slog.New(h))
 
 	Handler = h
+
+	http.HandleFunc("/.within/debug/slog-level", func(w http.ResponseWriter, r *http.Request) {
+		var level, old slog.Level
+		defer r.Body.Close()
+
+		old = leveler.Level()
+
+		data, err := io.ReadAll(http.MaxBytesReader(w, r.Body, 64))
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+
+		if err := (&level).UnmarshalText(data); err != nil {
+			http.Error(w, err.Error(), http.StatusBadRequest)
+			return
+		}
+
+		leveler.Set(level)
+		slog.Info("changed level", "from", old, "to", level)
+		fmt.Fprintln(w, level)
+	})
 }
-- 
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