fix(vocab): keep SRS cards and counters aligned

frontend/src/dialogues/socialnetwork/VocabPracticeDialog.vue

@@ -143,9 +143,9 @@ const PRACTICE_MIN_EXPOSURES = 3;
 // The original daily batch remains stable when the dialog is reopened.
 // Keep in sync with VocabCourseView. v3 discards legacy empty sessions that
 // could block cards due later on the same calendar day.
-// Keep this in sync with VocabCourseView. Version 4 discards stale empty
-// sessions that could mask a new daily SRS batch.
-const SRS_SESSION_STORAGE_VERSION = 4;
+// Keep this in sync with VocabCourseView. Version 5 discards sessions that
+// counted cards removed by the client-side duplicate filter as still open.
+const SRS_SESSION_STORAGE_VERSION = 5;
 const HARD_REQUIRED_CONSECUTIVE_CORRECT = 5;
 const MAX_DAILY_DUE = 50;
 const MAX_DAILY_HARD_VOCABS = 7;
@@ -517,7 +517,11 @@ export default {
       }
 
       if (!this.srsSession) {
-        const initialTotal = Math.min(MAX_DAILY_DUE, Number.isFinite(Number(this.srsServerTotalDue)) ? Number(this.srsServerTotalDue) : dueIds.length);
+        // `dueIds` is the actual exercise pool.  The server's total can be
+        // larger than the requested page (and formerly also included cards
+        // that the client filtered), so it must never define this batch's
+        // counter.
+        const initialTotal = Math.min(MAX_DAILY_DUE, dueIds.length);
         this.srsSession = {
           version: SRS_SESSION_STORAGE_VERSION,
           dateKey: this.getLocalDateKey(),
@@ -551,6 +555,12 @@ export default {
       const initialDueIds = Array.isArray(this.srsSession.initialDueIds)
         ? this.srsSession.initialDueIds.slice(0, MAX_DAILY_DUE)
         : [];
+      // A resumed session can only count cards that were actually stored in
+      // its batch.  This prevents an empty prompt when an older client had
+      // collapsed distinct SRS cards with identical wording.
+      if (this.srsSession.initialTotalDue !== initialDueIds.length) {
+        this.srsSession.initialTotalDue = initialDueIds.length;
+      }
       const doneSet = new Set(Array.isArray(this.srsSession.doneIds) ? this.srsSession.doneIds : []);
       const finalReviewIds = Array.isArray(this.srsSession.finalReviewIds) ? this.srsSession.finalReviewIds : [];
       const finalReviewSet = new Set(finalReviewIds);
@@ -813,12 +823,17 @@ export default {
             const learning = String(normalizedCandidate?.learning || '').trim();
             const reference = String(normalizedCandidate?.reference || '').trim();
             if (!this.isTrainablePair(learning, reference)) return null;
-            const key = `${this.normalize(learning)}|${this.normalize(reference)}`;
+            const pairKey = `${this.normalize(learning)}|${this.normalize(reference)}`;
+            // In normal practice, identical pairs are duplicates.  In SRS,
+            // however, the same pair may intentionally occur in both
+            // directions and is represented by separate item keys.
+            const srsItemId = candidate?.id || candidate?.itemKey;
+            const key = this.srsMode && srsItemId ? `srs:${srsItemId}` : pairKey;
             if (seen.has(key)) return null;
             seen.add(key);
             return {
               ...normalizedCandidate,
-              id: candidate?.id || candidate?.itemKey || candidate?.key || `${key}|${index}|${altIndex}`,
+              id: srsItemId || candidate?.key || `${pairKey}|${index}|${altIndex}`,
               learning,
               reference
             };