update

backend/learning.py

@@ -28,6 +28,25 @@ LEVELS = (("beginner", 0.2), ("advanced", 0.4), ("expert", 0.6), ("master", 1.0)
 
 POINTS_BASE = 25  # Points per subblock. Master cap = (all subs) × 25.
 
+# Leitner boxes for the flashcard practice deck: roughly doubling intervals cover
+# session → day → week → month. Box 1 with interval 0 = a failed card stays due in
+# the running session. Absolute UTC times, no day-boundary semantics (timezone-free).
+LEITNER_INTERVALS = {1: 0, 2: 1, 3: 3, 4: 7, 5: 21}  # days per box
+LEITNER_MAX_BOX = 5
+PRACTICE_NEW_PER_SESSION = 10  # new cards offered per deck fetch
+
+
+def leitner_step(box: int | None, correct: bool) -> tuple[int, int]:
+    """(new box, interval in days). New card + correct → box 2; wrong → box 1 (due now);
+    correct → one box up, capped at LEITNER_MAX_BOX."""
+    if not correct:
+        new = 1
+    elif box is None:
+        new = 2
+    else:
+        new = min(box + 1, LEITNER_MAX_BOX)
+    return new, LEITNER_INTERVALS[new]
+
 
 def _levels(n_je_level: dict[int, int]) -> list[int]:
     return [n_je_level.get(k, 0) for k in (1, 2, 3, 4)]