Ensure good is at least previous+1 even if low hard factor set

https://forums.ankiweb.net/t/anki-scheduler-broken/27987/8

rslib/src/scheduler/states/review.rs

@@ -137,21 +137,29 @@ impl ReviewState {
     fn passing_nonearly_review_intervals(self, ctx: &StateContext) -> (u32, u32, u32) {
         let current_interval = self.scheduled_days as f32;
         let days_late = self.days_late().max(0) as f32;
+
+        // hard
         let hard_factor = ctx.hard_multiplier;
         let hard_minimum = if hard_factor <= 1.0 {
             0
         } else {
             self.scheduled_days + 1
         };
-
         let hard_interval =
             constrain_passing_interval(ctx, current_interval * hard_factor, hard_minimum, true);
+        // good
+        let good_minimum = if hard_factor <= 1.0 {
+            self.scheduled_days + 1
+        } else {
+            hard_interval + 1
+        };
         let good_interval = constrain_passing_interval(
             ctx,
             (current_interval + days_late / 2.0) * self.ease_factor,
-            hard_interval + 1,
+            good_minimum,
             true,
         );
+        // easy
         let easy_interval = constrain_passing_interval(
             ctx,
             (current_interval + days_late) * self.ease_factor * ctx.easy_multiplier,
@@ -284,4 +292,21 @@ mod test {
         ctx.maximum_review_interval = 5;
         assert_eq!(state.passing_review_intervals(&ctx), (5, 5, 5));
     }
+
+    #[test]
+    fn low_hard_multiplier_does_not_pull_good_down() {
+        let mut ctx = StateContext::defaults_for_testing();
+        // our calculations should work correctly with a low ease or non-default
+        // multiplier
+        ctx.hard_multiplier = 0.1;
+        let state = ReviewState {
+            scheduled_days: 2,
+            elapsed_days: 2,
+            ease_factor: 1.3,
+            lapses: 0,
+            leeched: false,
+        };
+        ctx.fuzz_factor = Some(0.0);
+        assert_eq!(state.passing_review_intervals(&ctx), (1, 3, 4));
+    }
 }