add dbg info helper

Author: NiloCK

packages/db/src/impl/common/BaseUserDB.ts

@@ -722,12 +722,22 @@ Currently logged-in as ${this._username}.`
 
   /**
    * Logs a record of the user's interaction with the card and returns the card's
-   * up-to-date history
+   * up-to-date history.
+   *
+   * **Automatic Initialization:**
+   * If this is the user's first interaction with the card (CardHistory doesn't exist),
+   * this method automatically creates the CardHistory document with initial values
+   * (lapses: 0, streak: 0, bestInterval: 0).
+   *
+   * **Error Handling:**
+   * - Handles 404 errors by creating initial CardHistory document
+   * - Re-throws all other errors from UpdateQueue
    *
    * // [ ] #db-refactor extract to a smaller scope - eg, UserStudySession
    *
-   * @param record the recent recorded interaction between user and card
+   * @param record - The recent recorded interaction between user and card
    * @returns The updated state of the card's CardHistory data
+   * @throws Error if document creation fails or non-404 database error occurs
    */
 
   public async putCardRecord<T extends CardRecord>(

packages/db/src/study/SessionController.ts

@@ -208,6 +208,56 @@ export class SessionController<TView = unknown> extends Loggable {
     return `${this.reviewQ.dequeueCount} Reviews, ${this.newQ.dequeueCount} New, ${this.failedQ.dequeueCount} failed`;
   }
 
+  /**
+   * Returns debug information about the current session state.
+   * Used by SessionControllerDebug component for runtime inspection.
+   */
+  public getDebugInfo() {
+    const extractQueueItems = (queue: ItemQueue<any>, limit: number = 10) => {
+      const items = [];
+      for (let i = 0; i < Math.min(queue.length, limit); i++) {
+        const item = queue.peek(i);
+        items.push({
+          courseID: item.courseID || 'unknown',
+          cardID: item.cardID || 'unknown',
+          status: item.status || 'unknown',
+        });
+      }
+      return items;
+    };
+
+    const extractHydratedItems = (limit: number = 10) => {
+      const items = [];
+      const hydratedCount = this.hydrationService.hydratedCount;
+      // We can't easily iterate the hydrated queue without dequeuing,
+      // so we'll just report the count
+      return items;
+    };
+
+    return {
+      reviewQueue: {
+        length: this.reviewQ.length,
+        dequeueCount: this.reviewQ.dequeueCount,
+        items: extractQueueItems(this.reviewQ),
+      },
+      newQueue: {
+        length: this.newQ.length,
+        dequeueCount: this.newQ.dequeueCount,
+        items: extractQueueItems(this.newQ),
+      },
+      failedQueue: {
+        length: this.failedQ.length,
+        dequeueCount: this.failedQ.dequeueCount,
+        items: extractQueueItems(this.failedQ),
+      },
+      hydratedCache: {
+        count: this.hydrationService.hydratedCount,
+        failedCacheSize: this.hydrationService.failedCacheSize,
+        items: extractHydratedItems(),
+      },
+    };
+  }
+
   private async getScheduledReviews() {
     const reviews = await Promise.all(
       this.sources.map((c) =>