Implement User Avatar spoofing of XMPP users (#1090)

* Implement User Avatar spoofing of XMPP users

bridge/xmpp/helpers.go

@@ -0,0 +1,30 @@
+package bxmpp
+
+import (
+	"regexp"
+
+	"github.com/42wim/matterbridge/bridge/config"
+)
+
+var pathRegex = regexp.MustCompile("[^a-zA-Z0-9]+")
+
+// GetAvatar constructs a URL for a given user-avatar if it is available in the cache.
+func getAvatar(av map[string]string, userid string, general *config.Protocol) string {
+	if hash, ok := av[userid]; ok {
+		// NOTE: This does not happen in bridge/helper/helper.go but messes up XMPP
+		id := pathRegex.ReplaceAllString(userid, "_")
+		return general.MediaServerDownload + "/" + hash + "/" + id + ".png"
+	}
+	return ""
+}
+
+func (b *Bxmpp) cacheAvatar(msg *config.Message) string {
+	fi := msg.Extra["file"][0].(config.FileInfo)
+	/* if we have a sha we have successfully uploaded the file to the media server,
+	so we can now cache the sha */
+	if fi.SHA != "" {
+		b.Log.Debugf("Added %s to %s in avatarMap", fi.SHA, msg.UserID)
+		b.avatarMap[msg.UserID] = fi.SHA
+	}
+	return ""
+}