Refactor CDN code (enable adding more CDNs more easily)

cdn.go

@@ -4,15 +4,22 @@ import (
 	"net/http"
 )
 
-func Purge(url string) {
-	if len(BunnyCdnKey) == 0 {
-		// BunnyCdn deactivated
-		return
-	}
+type Cdn interface {
+	// Purge url from CDN
+	Purge(url string)
+}
+
+// BunnyCDN
+type BunnyCdn struct {
+	// Access Key
+	key string
+}
+
+func (cdn BunnyCdn) Purge(url string) {
 	client := &http.Client{}
 	req, _ := http.NewRequest("POST", "https://bunnycdn.com/api/purge?url="+url, nil)
 	req.Header.Add("Content-Type", "application/json")
 	req.Header.Add("Accept", "application/json")
-	req.Header.Add("AccessKey", BunnyCdnKey)
+	req.Header.Add("AccessKey", cdn.key)
 	_, _ = client.Do(req)
 }

config.go

@@ -11,11 +11,11 @@ var (
 	BlogUrl               string
 	GiteaEndpoint         string
 	GiteaToken            string
-	BunnyCdnKey           string
 	MicroblogUrl          string
 	MicroblogToken        string
 	IgnoredWebmentionUrls []string
 	SyndicationTargets    []SyndicationTarget
+	SelectedCdn           Cdn
 )
 
 type SyndicationTarget struct {
@@ -41,12 +41,6 @@ func init() {
 		log.Fatal(err)
 	}
 	GiteaToken = giteaToken
-	// BunnyCDN (optional)
-	bunnyCdnKey, err := bunnyCdnKey()
-	if err != nil {
-		log.Println(err)
-	}
-	BunnyCdnKey = bunnyCdnKey
 	// Microblog (optional)
 	microblogUrl, err := microblogUrl()
 	if err != nil {
@@ -70,6 +64,17 @@ func init() {
 		log.Println(err)
 	}
 	SyndicationTargets = syndicationTargets
+	// Find selected CDN (currently only BunnyCDN)
+	SelectedCdn = func() Cdn {
+		// BunnyCDN (optional)
+		bunnyCdnKey, err := bunnyCdnKey()
+		if err != nil {
+			log.Println(err)
+		} else {
+			return BunnyCdn{key: bunnyCdnKey}
+		}
+		return nil
+	}()
 }
 
 func giteaEndpoint() (string, error) {

micropub.go

@@ -83,7 +83,7 @@ func HandleMicroPub(w http.ResponseWriter, r *http.Request) {
 			// Purge BunnyCDN in 10 seconds
 			go func() {
 				time.Sleep(10 * time.Second)
-				Purge(location)
+				SelectedCdn.Purge(location)
 				time.Sleep(3 * time.Second)
 				// Send webmentions
 				go SendWebmentions(location)

webmention.go

@@ -177,7 +177,7 @@ func returnSuccess(target string, w http.ResponseWriter, r *http.Request) {
 	// Purge BunnyCDN in 10 seconds
 	go func() {
 		time.Sleep(10 * time.Second)
-		Purge(target)
+		SelectedCdn.Purge(target)
 	}()
 	return
 }