chore: improve preparePushMessage (#1509)

* chore: improve readability a bit

* rename

* decople to a type

* fix error

packages/core/src/lib/light_push/index.ts

@@ -27,6 +27,16 @@ const log = debug("waku:light-push");
 export const LightPushCodec = "/vac/waku/lightpush/2.0.0-beta1";
 export { PushResponse };
 
+type PreparePushMessageResult =
+  | {
+      query: PushRpc;
+      error: null;
+    }
+  | {
+      query: null;
+      error: SendError;
+    };
+
 /**
  * Implements the [Waku v2 Light Push protocol](https://rfc.vac.dev/spec/19/).
  */
@@ -42,10 +52,8 @@ class LightPush extends BaseProtocol implements ILightPush {
     encoder: IEncoder,
     message: IMessage,
     pubSubTopic: string
-  ): Promise<{
-    query: PushRpc | null;
-    error?: SendError;
-  }> {
+  ): Promise<PreparePushMessageResult> {
+    try {
       if (!isSizeValid(message.payload)) {
         log("Failed to send waku light push: message is bigger than 1MB");
         return { query: null, error: SendError.SIZE_TOO_BIG };
@@ -61,7 +69,15 @@ class LightPush extends BaseProtocol implements ILightPush {
       }
 
       const query = PushRpc.createRequest(protoMessage, pubSubTopic);
-    return { query };
+      return { query, error: null };
+    } catch (error) {
+      log("Failed to prepare push message", error);
+
+      return {
+        query: null,
+        error: SendError.GENERIC_FAIL
+      };
+    }
   }
 
   async send(
@@ -71,33 +87,21 @@ class LightPush extends BaseProtocol implements ILightPush {
   ): Promise<SendResult> {
     const { pubSubTopic = DefaultPubSubTopic } = this.options;
     const recipients: PeerId[] = [];
-    let error: undefined | SendError = undefined;
 
-    let query: PushRpc | null = null;
+    const { query, error: preparationError } = await this.preparePushMessage(
+      encoder,
+      message,
+      pubSubTopic
+    );
 
-    try {
-      const { query: preparedQuery, error: preparationError } =
-        await this.preparePushMessage(encoder, message, pubSubTopic);
-
-      if (preparationError) {
+    if (preparationError || !query) {
       return {
         recipients,
         error: preparationError
       };
     }
 
-      query = preparedQuery;
-    } catch (error) {
-      log("Failed to prepare push message", error);
-    }
-
-    if (!query) {
-      return {
-        recipients,
-        error: SendError.GENERIC_FAIL
-      };
-    }
-
+    let error: undefined | SendError = undefined;
     const peer = await this.getPeer(opts?.peerId);
     const stream = await this.newStream(peer);