feat(common-lib): derive routes df instead of fetch (#337)

This change will save us from doing one additional request each time we
need to fetch the `Routes` dynamic field.

It derives the dynamic field object ID of `Routes` instead of fetching
it.

portal/common/lib/routing.ts

@@ -7,11 +7,12 @@ import { DynamicFieldStruct, RoutesStruct } from "./bcs_data_parsing";
 import { bcs, fromBase64 } from "@mysten/bcs";
 import logger from "./logger";
 import { RPCSelector } from "./rpc_selector";
+import { deriveDynamicFieldID } from "@mysten/sui/utils";
 
 /**
-* The WalrusSiteRouter class is responsible for handling the routing logic for published
-* Walrus Sites, depending by the definition of the `routes` field inside the `ws-resources.json`.
-*/
+ * The WalrusSiteRouter class is responsible for handling the routing logic for published
+ * Walrus Sites, depending by the definition of the `routes` field inside the `ws-resources.json`.
+ */
 export class WalrusSitesRouter {
     constructor(private rpcSelector: RPCSelector) {}
 
@@ -23,67 +24,47 @@ export class WalrusSitesRouter {
      * @param siteObjectId - The ID of the site object.
      * @returns The routes list.
      */
-    public async getRoutes(
-        siteObjectId: string,
-    ): Promise<Routes | undefined> {
-        logger.info({ message: "Fetching routes dynamic field.", siteObjectId })
-        const routesDF = await this.fetchRoutesDynamicField(siteObjectId);
-        if (!routesDF.data) {
-            logger.warn({
-                message: "No routes dynamic field found for site object. Exiting getRoutes.",
-                siteObjectId
-            });
-            return;
-        }
-        const routesObj = await this.fetchRoutesObject(routesDF.data.objectId);
+    public async getRoutes(siteObjectId: string): Promise<Routes | undefined> {
+        logger.info({ message: "Fetching routes dynamic field.", siteObjectId });
+        const routesObj = await this.fetchRoutesDynamicFieldObject(siteObjectId);
         const objectData = routesObj.data;
         if (objectData && objectData.bcs && objectData.bcs.dataType === "moveObject") {
             return this.parseRoutesData(objectData.bcs.bcsBytes);
         }
         if (!objectData) {
             logger.warn({
-                message: "Routes dynamic field does not contain a `data` field."
+                message: "Routes dynamic field does not contain a `data` field.",
             });
         } else if (!objectData.bcs) {
             logger.warn({
-                message: "Routes dynamic field does not contain a `bcs` field."
+                message: "Routes dynamic field does not contain a `bcs` field.",
             });
         } else if (!objectData.bcs.dataType) {
             logger.warn({
-                message: "Routes dynamic field does not contain a `dataType` field."
+                message: "Routes dynamic field does not contain a `dataType` field.",
             });
         }
         throw new Error("Routes object data could not be fetched.");
     }
 
     /**
-     * Fetches the dynamic field object for routes.
-     *
-     * @param client - The SuiClient instance.
-     * @param siteObjectId - The ID of the site object.
-     * @returns The dynamic field object for routes.
-     */
-    private async fetchRoutesDynamicField(
-        siteObjectId: string,
-    ): Promise<SuiObjectResponse> {
-        return await this.rpcSelector.getDynamicFieldObject({
-            parentId: siteObjectId,
-            name: { type: "vector<u8>", value: "routes" },
-        });
-    }
-
-    /**
-     * Fetches the routes object using the dynamic field object ID.
+     * Derives and fetches the Routes dynamic field object.
      *
-     * @param client - The SuiClient instance.
-     * @param objectId - The ID of the dynamic field object.
+     * @param siteObjectId - The site object ID.
      * @returns The routes object.
      */
-    private async fetchRoutesObject(objectId: string): Promise<SuiObjectResponse> {
-        return await this.rpcSelector.getObject({
-            id: objectId,
+    private async fetchRoutesDynamicFieldObject(siteObjectId: string): Promise<SuiObjectResponse> {
+        const routesMoveType = "vector<u8>";
+        const dynamicFieldId = deriveDynamicFieldID(
+            siteObjectId,
+            routesMoveType,
+            bcs.vector(bcs.u8()).serialize(Buffer.from("routes")).toBytes(),
+        );
+        const dfObjectResponse = await this.rpcSelector.getObject({
+            id: dynamicFieldId,
             options: { showBcs: true },
         });
+        return dfObjectResponse;
     }
 
     /**