2 files changed, 54 insertions, 0 deletions
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..42e64cf
--- /dev/null
+++ b/main.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+	"net/http"
+	"net/url"
+)
+
+const (
+	errSrcInvalid = "source contains no valid URL"
+)
+
+// endpoint is a webmention receiver.
+type endpoint struct {
+	allowPrefix string
+}
+
+// ServeHTTP is http.Handler implementation.
+func (ep endpoint) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	_, err := url.Parse(r.PostFormValue("source"))
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Write([]byte(errSrcInvalid))
+	}
+}
diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..d1b864d
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,30 @@
+package main
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+)
+
+func TestSyncRejection(t *testing.T) {
+	server := httptest.NewServer(endpoint{"my.site"})
+	defer server.Close()
+
+	client := http.DefaultClient
+	r, err := client.PostForm(server.URL, url.Values{
+		"source": []string{"https||:example.org/somewhere"},
+		"target": []string{"my.site/target"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if r.StatusCode != 400 {
+		t.Fatalf("want 400, got %v", r.Status)
+	}
+	bb, _ := io.ReadAll(r.Body)
+	if string(bb) != errSrcInvalid {
+		t.Fatalf("want %s, got %s", errSrcInvalid, string(bb))
+	}
+}