Implement is_cramming method in RevlogEntry and update scheduling logic

This commit adds the `is_cramming` method to the `RevlogEntry` struct, which identifies entries representing cramming operations. The scheduling logic in `params.rs` has been updated to utilize this new method, improving the clarity and maintainability of the code.

rslib/src/revlog/mod.rs

@@ -92,6 +92,16 @@ impl RevlogEntry {
         self.review_kind == RevlogReviewKind::Manual && self.ease_factor == 0
     }
 
+    /// Returns true if this entry represents a cramming operation.
+    /// These entries are created when a card is previewed using
+    /// [`crate::scheduler::answering::CardStateUpdater::apply_preview_state`].
+    /// The `ease_factor` should be 0 because
+    /// [`crate::scheduler::states::ReviewState::revlog_kind`] returns
+    /// `RevlogReviewKind::Filtered` when `days_late() < 0`.
+    pub(crate) fn is_cramming(&self) -> bool {
+        self.review_kind == RevlogReviewKind::Filtered && self.ease_factor == 0
+    }
+
     /// Returns true if the review entry is not manually rescheduled and not
     /// cramming. Used to filter out entries that shouldn't be considered
     /// for statistics and scheduling.
@@ -99,7 +109,7 @@ impl RevlogEntry {
         // not rescheduled/set due date/reset
         self.button_chosen > 0
             // not cramming
-            && (self.review_kind != RevlogReviewKind::Filtered || self.ease_factor != 0)
+            && !self.is_cramming()
     }
 }
 

rslib/src/scheduler/fsrs/params.rs

@@ -394,7 +394,7 @@ pub(crate) fn reviews_for_fsrs(
     let mut revlogs_complete = false;
     // Working backwards from the latest review...
     for (index, entry) in entries.iter().enumerate().rev() {
-        if entry.review_kind == RevlogReviewKind::Filtered && entry.ease_factor == 0 {
+        if entry.is_cramming() {
             continue;
         }
         // For incomplete review histories, initial memory state is based on the first
@@ -474,7 +474,7 @@ pub(crate) fn reviews_for_fsrs(
             // set due date, reset or rescheduled
             (entry.review_kind == RevlogReviewKind::Manual || entry.button_chosen == 0)
             || // cram
-            (entry.review_kind == RevlogReviewKind::Filtered && entry.ease_factor == 0)
+            entry.is_cramming()
             || // rescheduled
             (entry.review_kind == RevlogReviewKind::Rescheduled)
         )