Combine things, move stuff

server/util.go

@@ -0,0 +1,55 @@
+package server
+
+import (
+	"encoding/json"
+	"firebase.google.com/go/messaging"
+	"net/http"
+	"strings"
+)
+
+const (
+	fcmMessageLimit = 4000
+)
+
+// maybeTruncateFCMMessage performs best-effort truncation of FCM messages.
+// The docs say the limit is 4000 characters, but during testing it wasn't quite clear
+// what fields matter; so we're just capping the serialized JSON to 4000 bytes.
+func maybeTruncateFCMMessage(m *messaging.Message) *messaging.Message {
+	s, err := json.Marshal(m)
+	if err != nil {
+		return m
+	}
+	if len(s) > fcmMessageLimit {
+		over := len(s) - fcmMessageLimit + 16 // = len("truncated":"1",), sigh ...
+		message, ok := m.Data["message"]
+		if ok && len(message) > over {
+			m.Data["truncated"] = "1"
+			m.Data["message"] = message[:len(message)-over]
+		}
+	}
+	return m
+}
+
+func readBoolParam(r *http.Request, defaultValue bool, names ...string) bool {
+	value := strings.ToLower(readParam(r, names...))
+	if value == "" {
+		return defaultValue
+	}
+	return value == "1" || value == "yes" || value == "true"
+}
+
+func readParam(r *http.Request, names ...string) string {
+	for _, name := range names {
+		value := r.Header.Get(name)
+		if value != "" {
+			return strings.TrimSpace(value)
+		}
+	}
+	for _, name := range names {
+		value := r.URL.Query().Get(strings.ToLower(name))
+		if value != "" {
+			return strings.TrimSpace(value)
+		}
+	}
+	return ""
+}