refactor: optimise fetching last result timestamp when adding a result

Author: Miodec

backend/src/api/controllers/result.ts

@@ -329,7 +329,9 @@ export async function addResult(
   //   );
   //   return res.status(400).json({ message: "Time traveler detected" });
 
-  const { data: lastResult } = await tryCatch(ResultDAL.getLastResult(uid));
+  const { data: lastResultTimestamp } = await tryCatch(
+    ResultDAL.getLastResultTimestamp(uid)
+  );
 
   //convert result test duration to miliseconds
   completedEvent.timestamp = Math.floor(Date.now() / 1000) * 1000;
@@ -338,16 +340,16 @@ export async function addResult(
   const testDurationMilis = completedEvent.testDuration * 1000;
   const incompleteTestsMilis = completedEvent.incompleteTestSeconds * 1000;
   const earliestPossible =
-    (lastResult?.timestamp ?? 0) + testDurationMilis + incompleteTestsMilis;
+    (lastResultTimestamp ?? 0) + testDurationMilis + incompleteTestsMilis;
   const nowNoMilis = Math.floor(Date.now() / 1000) * 1000;
   if (
-    isSafeNumber(lastResult?.timestamp) &&
+    isSafeNumber(lastResultTimestamp) &&
     nowNoMilis < earliestPossible - 1000
   ) {
     void addLog(
       "invalid_result_spacing",
       {
-        lastTimestamp: lastResult.timestamp,
+        lastTimestamp: lastResultTimestamp,
         earliestPossible,
         now: nowNoMilis,
         testDuration: testDurationMilis,
@@ -590,7 +592,7 @@ export async function addResult(
   const xpGained = await calculateXp(
     completedEvent,
     req.ctx.configuration.users.xp,
-    uid,
+    lastResultTimestamp,
     user.xp ?? 0,
     streak
   );
@@ -689,7 +691,7 @@ type XpResult = {
 async function calculateXp(
   result: CompletedEvent,
   xpConfiguration: Configuration["users"]["xp"],
-  uid: string,
+  lastResultTimestamp: number | null,
   currentTotalXp: number,
   streak: number
 ): Promise<XpResult> {
@@ -802,16 +804,8 @@ async function calculateXp(
   const accuracyModifier = (acc - 50) / 50;
 
   let dailyBonus = 0;
-  const { data: lastResult, error: getLastResultError } = await tryCatch(
-    ResultDAL.getLastResult(uid)
-  );
-
-  if (getLastResultError) {
-    Logger.error(`Could not fetch last result: ${getLastResultError}`);
-  }
-
-  if (isSafeNumber(lastResult?.timestamp)) {
-    const lastResultDay = getStartOfDayTimestamp(lastResult.timestamp);
+  if (isSafeNumber(lastResultTimestamp)) {
+    const lastResultDay = getStartOfDayTimestamp(lastResultTimestamp);
     const today = getCurrentDayTimestamp();
     if (lastResultDay !== today) {
       const proportionalXp = Math.round(currentTotalXp * 0.05);

backend/src/dal/result.ts

@@ -75,10 +75,20 @@ export async function getLastResult(uid: string): Promise<DBResult> {
     .sort({ timestamp: -1 })
     .limit(1)
     .toArray();
-  if (!lastResult) throw new MonkeyError(404, "No results found");
+  if (!lastResult) throw new MonkeyError(404, "No last result found");
   return convert(lastResult);
 }
 
+export async function getLastResultTimestamp(uid: string): Promise<number> {
+  const [lastResult] = await getResultCollection()
+    .find({ uid }, { projection: { timestamp: 1, _id: 0 } })
+    .sort({ timestamp: -1 })
+    .limit(1)
+    .toArray();
+  if (!lastResult) throw new MonkeyError(404, "No last result found");
+  return lastResult.timestamp;
+}
+
 export async function getResultByTimestamp(
   uid: string,
   timestamp: number