Implement channel name formatting and handle channel updates

bridge/avatar.go

@@ -0,0 +1,31 @@
+package bridge
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+
+	"maunium.net/go/mautrix/appservice"
+	"maunium.net/go/mautrix/id"
+)
+
+func uploadAvatar(intent *appservice.IntentAPI, url string) (id.ContentURI, error) {
+	getResp, err := http.DefaultClient.Get(url)
+	if err != nil {
+		return id.ContentURI{}, fmt.Errorf("failed to download avatar: %w", err)
+	}
+
+	data, err := io.ReadAll(getResp.Body)
+	getResp.Body.Close()
+	if err != nil {
+		return id.ContentURI{}, fmt.Errorf("failed to read avatar data: %w", err)
+	}
+
+	mime := http.DetectContentType(data)
+	resp, err := intent.UploadBytes(data, mime)
+	if err != nil {
+		return id.ContentURI{}, fmt.Errorf("failed to upload avatar to Matrix: %w", err)
+	}
+
+	return resp.ContentURI, nil
+}