Uniq deprecated notes

experimental/deprecated/stderr.go

@@ -0,0 +1,38 @@
+package deprecated
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/sagernet/sing/common/logger"
+)
+
+type stderrManager struct {
+	logger   logger.Logger
+	reported map[string]bool
+}
+
+func NewStderrManager(logger logger.Logger) Manager {
+	return &stderrManager{
+		logger:   logger,
+		reported: make(map[string]bool),
+	}
+}
+
+func (f *stderrManager) ReportDeprecated(feature Note) {
+	if f.reported[feature.Name] {
+		return
+	}
+	f.reported[feature.Name] = true
+	if !feature.Impending() {
+		f.logger.Warn(feature.MessageWithLink())
+		return
+	}
+	enable, enableErr := strconv.ParseBool(os.Getenv("ENABLE_DEPRECATED_" + feature.EnvName))
+	if enableErr == nil && enable {
+		f.logger.Warn(feature.MessageWithLink())
+		return
+	}
+	f.logger.Error(feature.MessageWithLink())
+	f.logger.Fatal("to continuing using this feature, set ENABLE_DEPRECATED_" + feature.EnvName + "=true")
+}