fix: make sampleBufferBytes generic to handle Buffer<Record>

dailyTempRecords and weeklyTempRecords are Buffer<Record>, not
Buffer<DownloadsSnapshot>. Adding a serialize parameter makes the
helper work for both element types.

Made-with: Cursor

Author: rvanasa

backend/main/DownloadLog.mo

@@ -467,7 +467,7 @@ module {
         sum * total / sampled;
       };
 
-      func sampleBufferBytes(buf : Buffer.Buffer<DownloadsSnapshot>) : Nat {
+      func sampleBufferBytes<T>(buf : Buffer.Buffer<T>, serialize : T -> Blob) : Nat {
         let total = buf.size();
         if (total == 0) return 0;
         let stride = if (total <= SAMPLE_SIZE) 1 else total / SAMPLE_SIZE;
@@ -476,7 +476,7 @@ module {
         var sampled = 0;
         for (v in buf.vals()) {
           if (i % stride == 0) {
-            sum += (to_candid (v) : Blob).size();
+            sum += serialize(v).size();
             sampled += 1;
           };
           i += 1;
@@ -495,11 +495,11 @@ module {
         };
         dailySnapshots = {
           count = dailySnapshots.size();
-          bytes = sampleBufferBytes(dailySnapshots);
+          bytes = sampleBufferBytes<DownloadsSnapshot>(dailySnapshots, func(v) = to_candid (v));
         };
         weeklySnapshots = {
           count = weeklySnapshots.size();
-          bytes = sampleBufferBytes(weeklySnapshots);
+          bytes = sampleBufferBytes<DownloadsSnapshot>(weeklySnapshots, func(v) = to_candid (v));
         };
         dailySnapshotsByPackageName = {
           count = dailySnapshotsByPackageName.size();
@@ -519,11 +519,11 @@ module {
         };
         dailyTempRecords = {
           count = dailyTempRecords.size();
-          bytes = sampleBufferBytes(dailyTempRecords);
+          bytes = sampleBufferBytes<Record>(dailyTempRecords, func(v) = to_candid (v));
         };
         weeklyTempRecords = {
           count = weeklyTempRecords.size();
-          bytes = sampleBufferBytes(weeklyTempRecords);
+          bytes = sampleBufferBytes<Record>(weeklyTempRecords, func(v) = to_candid (v));
         };
       };
     };