From ba872b6d0dbefb975f8574a841ce7dd185cefd35 Mon Sep 17 00:00:00 2001
From: "robin.hubbig" <robin.hubbig@gdata.de>
Date: Fri, 5 Apr 2024 10:16:02 +0200
Subject: [PATCH] Extend remote config watch with context and callback

---
 viper.go | 52 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 44 insertions(+), 8 deletions(-)

diff --git a/viper.go b/viper.go
index 20eb4da..78b3ce6 100644
--- a/viper.go
+++ b/viper.go
@@ -21,6 +21,7 @@ package viper
 
 import (
 	"bytes"
+	"context"
 	"encoding/csv"
 	"errors"
 	"fmt"
@@ -143,6 +144,16 @@ func DecodeHook(hook mapstructure.DecodeHookFunc) DecoderConfigOption {
 	}
 }
 
+type RemoteConfigEvent uint
+
+const (
+	RemoteConfigEvent_Unknown RemoteConfigEvent = iota
+	// Remote config was updated
+	RemoteConfigEvent_Updated
+	// Remote config watch routine stopped
+	RemoteConfigEvent_Stopped
+)
+
 // Viper is a prioritized configuration registry. It
 // maintains a set of configuration sources, fetches
 // values to populate those, and provides them according
@@ -217,7 +228,8 @@ type Viper struct {
 	aliases        map[string]string
 	typeByDefValue bool
 
-	onConfigChange func(fsnotify.Event)
+	onConfigChange       func(fsnotify.Event)
+	onRemoteConfigChange func(RemoteConfigEvent)
 
 	logger *slog.Logger
 
@@ -432,6 +444,14 @@ func (v *Viper) OnConfigChange(run func(in fsnotify.Event)) {
 	v.onConfigChange = run
 }
 
+// OnRemoteConfigChange sets the event handler that is called when a remote config file changes.
+func OnRemoteConfigChange(run func(RemoteConfigEvent)) { v.OnRemoteConfigChange(run) }
+
+// OnRemoteConfigChange sets the event handler that is called when a remote config file changes.
+func (v *Viper) OnRemoteConfigChange(run func(RemoteConfigEvent)) {
+	v.onRemoteConfigChange = run
+}
+
 // WatchConfig starts watching a config file for changes.
 func WatchConfig() { v.WatchConfig() }
 
@@ -1973,7 +1993,11 @@ func (v *Viper) WatchRemoteConfig() error {
 }
 
 func (v *Viper) WatchRemoteConfigOnChannel() error {
-	return v.watchKeyValueConfigOnChannel()
+	return v.watchKeyValueConfigOnChannelWithContext(context.TODO())
+}
+
+func (v *Viper) WatchRemoteConfigOnChannelWithContext(ctx context.Context) error {
+	return v.watchKeyValueConfigOnChannelWithContext(ctx)
 }
 
 // Retrieve the first found remote configuration.
@@ -2010,20 +2034,32 @@ func (v *Viper) getRemoteConfig(provider RemoteProvider) (map[string]any, error)
 	return v.kvstore, err
 }
 
-// Retrieve the first found remote configuration.
-func (v *Viper) watchKeyValueConfigOnChannel() error {
+// Watch the first found remote configuration.
+func (v *Viper) watchKeyValueConfigOnChannelWithContext(ctx context.Context) error {
 	if len(v.remoteProviders) == 0 {
 		return RemoteConfigError("No Remote Providers")
 	}
 
 	for _, rp := range v.remoteProviders {
 		respc, _ := RemoteConfig.WatchChannel(rp)
-		// Todo: Add quit channel
 		go func(rc <-chan *RemoteResponse) {
 			for {
-				b := <-rc
-				reader := bytes.NewReader(b.Value)
-				v.unmarshalReader(reader, v.kvstore)
+				select {
+				case b := <-rc:
+					reader := bytes.NewReader(b.Value)
+					if err := v.unmarshalReader(reader, v.kvstore); err != nil {
+						v.logger.Error(fmt.Errorf("unmarshal remote config update: %w", err).Error())
+						continue
+					}
+					if v.onRemoteConfigChange != nil {
+						v.onRemoteConfigChange(RemoteConfigEvent_Updated)
+					}
+				case <-ctx.Done():
+					if v.onRemoteConfigChange != nil {
+						v.onRemoteConfigChange(RemoteConfigEvent_Stopped)
+					}
+					return
+				}
 			}
 		}(respc)
 		return nil