Add configuration property for thumbnail directory used in LNURL-pay metadata

README.md

@@ -65,6 +65,7 @@ Instead of the path to the macaroon and cert files you can also provide the hex
 - `static-path`: Path to a folder that you want to serve with LnMe (e.g. /home/bitcoin/lnme/website). Use this if you want to customize your ⚡website. default: disabled
 - `lnurlp-min-sendable`: Min sendable amount in sats via LNURL-pay. (default: 1)
 - `lnurlp-max-sendable`: Max sendable amount in sats via LNURL-pay. (default: 1000000)
+- `lnurlp-thumbnail-dir`: Path to a PNG thumbnail directory for LNURL-pay metadata. 
 - `lnurlp-comment-allowed`: Allowed length of LNURL-pay comments, maximum around [~2000 characters](https://stackoverflow.com/a/417184). (default: 210)
 - `disable-website`: Disable the default LnMe website. Disable the website if you only want to embed the LnMe widget on your existing website.
 - `disable-cors`: Disable CORS headers. (default: false)

lnme.go

@@ -164,7 +164,16 @@ func main() {
 			lightningAddress := name + "@" + host
 			lnurlpMinSendable := msats(cfg.Int64("lnurlp-min-sendable"))
 			lnurlpMaxSendable := msats(cfg.Int64("lnurlp-max-sendable"))
-			lnurlMetadata := "[[\"text/identifier\", \"" + lightningAddress + "\"], [\"text/plain\", \"Sats for " + lightningAddress + "\"]]"
+			lnurlpThumbnailPath := cfg.String("lnurlp-thumbnail-dir") + "/" + name + ".png"
+			lnurlpThumbnailData, err := os.ReadFile(lnurlpThumbnailPath)
+			if lnurlpThumbnailPath != "" && err != nil {
+				stdOutLogger.Println("Error reading thumbnail:", err)
+			}
+			lnurlMetadata := lnurl.Metadata{}.
+				Identifier(lightningAddress).
+				Description("Sats for " + lightningAddress).
+				Thumbnail(lnurlpThumbnailData).
+				String()
 			lnurlpCommentAllowed := cfg.Int64("lnurlp-comment-allowed")
 
 			if amount := c.QueryParam("amount"); amount == "" {
@@ -251,6 +260,7 @@ func LoadConfig() *koanf.Koanf {
 	f.String("lnd-cert", "", "HEX string of LND tls cert file.")
 	f.Int64("lnurlp-min-sendable", 1, "Min sendable amount in sats via LNURL-pay.")
 	f.Int64("lnurlp-max-sendable", 1000000, "Max sendable amount in sats via LNURL-pay.")
+	f.String("lnurlp-thumbnail-dir", "", "Path to a PNG thumbnail directory for LNURL-pay metadata.")
 	f.Int64("lnurlp-comment-allowed", 210, "Allowed length of LNURL-pay comments.")
 	f.Bool("disable-website", false, "Disable default embedded website.")
 	f.Bool("disable-ln-address", false, "Disable Lightning Address handling")

lnurl/types.go

@@ -2,7 +2,12 @@
 // only using the LNURL types here
 package lnurl
 
-import "net/url"
+import (
+	"encoding/base64"
+	"encoding/json"
+	"net/http"
+	"net/url"
+)
 
 type LNURLResponse struct {
 	Status string `json:"status,omitempty"`
@@ -50,3 +55,28 @@ type LNURLErrorResponse struct {
 }
 
 type Metadata [][]string
+
+func (metadata Metadata) Identifier(identifier string) Metadata {
+	return append(metadata, []string{"text/identifier", identifier})
+}
+
+func (metadata Metadata) Description(description string) Metadata {
+	return append(metadata, []string{"text/plain", description})
+}
+
+func (metadata Metadata) Thumbnail(imageData []byte) Metadata {
+	if len(imageData) == 0 {
+		return metadata
+	}
+
+	mimeType := http.DetectContentType(imageData)
+	imageDataBase64 := base64.StdEncoding.EncodeToString(imageData)
+
+	return append(metadata, []string{mimeType + ";base64", imageDataBase64})
+}
+
+func (metadata Metadata) String() string {
+	bytes, _ := json.Marshal(metadata)
+
+	return string(bytes)
+}