Phase 8: history

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/db/repo.go

@@ -445,6 +445,81 @@ func (r *Repo) GetStatsForUser(userID int64, questionIDs []string) (map[string]*
 	return result, rows.Err()
 }
 
+// ── History ──────────────────────────────────────────────────────────────────
+
+// GetCorrectCountsForUser returns a map of test_id → correct-answer count for
+// all completed tests belonging to userID.
+func (r *Repo) GetCorrectCountsForUser(userID int64) (map[int64]int, error) {
+	rows, err := r.db.Query(`
+		SELECT ta.test_id, SUM(CASE WHEN ta.is_correct = 1 THEN 1 ELSE 0 END)
+		FROM test_answers ta
+		JOIN tests t ON ta.test_id = t.id
+		WHERE t.user_id = ? AND t.completed_at IS NOT NULL
+		GROUP BY ta.test_id`, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	result := make(map[int64]int)
+	for rows.Next() {
+		var testID int64
+		var correct int
+		if err := rows.Scan(&testID, &correct); err != nil {
+			return nil, err
+		}
+		result[testID] = correct
+	}
+	return result, rows.Err()
+}
+
+// GetAggregateStats returns total correct and total answered across all
+// completed tests for userID.
+func (r *Repo) GetAggregateStats(userID int64) (totalCorrect, totalAnswered int, err error) {
+	err = r.db.QueryRow(`
+		SELECT
+			COALESCE(SUM(CASE WHEN ta.is_correct = 1 THEN 1 ELSE 0 END), 0),
+			COALESCE(COUNT(ta.question_id), 0)
+		FROM test_answers ta
+		JOIN tests t ON ta.test_id = t.id
+		WHERE t.user_id = ? AND t.completed_at IS NOT NULL`, userID,
+	).Scan(&totalCorrect, &totalAnswered)
+	return
+}
+
+// WeakSpot is a question the user has answered incorrectly more than once.
+type WeakSpot struct {
+	QuestionID   string
+	QuestionText string
+	TimesWrong   int
+	TimesSeen    int
+}
+
+// GetWeakSpots returns up to 10 questions the user has gotten wrong more than
+// once, ordered by wrong-answer count descending.
+func (r *Repo) GetWeakSpots(userID int64) ([]*WeakSpot, error) {
+	rows, err := r.db.Query(`
+		SELECT uqs.question_id, q.text, uqs.times_seen,
+		       (uqs.times_seen - uqs.times_correct) AS times_wrong
+		FROM user_question_stats uqs
+		JOIN questions q ON uqs.question_id = q.id
+		WHERE uqs.user_id = ? AND (uqs.times_seen - uqs.times_correct) > 1
+		ORDER BY times_wrong DESC, uqs.times_seen DESC
+		LIMIT 10`, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var spots []*WeakSpot
+	for rows.Next() {
+		s := &WeakSpot{}
+		if err := rows.Scan(&s.QuestionID, &s.QuestionText, &s.TimesSeen, &s.TimesWrong); err != nil {
+			return nil, err
+		}
+		spots = append(spots, s)
+	}
+	return spots, rows.Err()
+}
+
 // ── Draft (import review) ────────────────────────────────────────────────────
 
 func newDraftID() string {