From b1142c12d9e25827fcd94bf3b00a36a5b664a680 Mon Sep 17 00:00:00 2001
From: RumovZ <gp5glkw78@relay.firefox.com>
Date: Mon, 15 Nov 2021 06:41:43 +0100
Subject: [PATCH] Fix `constrained_fuzz_bounds()` (#1490)

... for cases where the entire fuzz range is above `maximum`.
Also improve hanling if the entire range is below `minimum` and
readability.
---
 rslib/src/scheduler/states/mod.rs    | 14 ++++++++++----
 rslib/src/scheduler/states/review.rs |  9 +++++++--
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/rslib/src/scheduler/states/mod.rs b/rslib/src/scheduler/states/mod.rs
index 831db55c9..3bd977183 100644
--- a/rslib/src/scheduler/states/mod.rs
+++ b/rslib/src/scheduler/states/mod.rs
@@ -151,12 +151,18 @@ impl<'a> StateContext<'a> {
 /// Ensure the upper bound is larger than the lower bound, if `maximum` allows
 /// it and it is larger than 1.
 fn constrained_fuzz_bounds(interval: f32, minimum: u32, maximum: u32) -> (u32, u32) {
-    let (lower, mut upper) = fuzz_bounds(interval);
-    let lower = lower.max(minimum);
-    if upper == lower && upper != 1 {
+    let (mut lower, mut upper) = fuzz_bounds(interval);
+
+    // minimum <= maximum and lower <= upper are assumed
+    // now ensure minimum <= lower <= upper <= maximum
+    lower = lower.max(minimum).min(maximum);
+    upper = upper.max(minimum).min(maximum);
+
+    if upper == lower && upper > 1 && upper < maximum {
         upper = lower + 1;
     };
-    (lower, upper.min(maximum).max(lower))
+
+    (lower, upper)
 }
 
 fn fuzz_bounds(interval: f32) -> (u32, u32) {
diff --git a/rslib/src/scheduler/states/review.rs b/rslib/src/scheduler/states/review.rs
index 2aa6774b2..986fec254 100644
--- a/rslib/src/scheduler/states/review.rs
+++ b/rslib/src/scheduler/states/review.rs
@@ -255,7 +255,7 @@ mod test {
     }
 
     #[test]
-    fn low_multiplier_fuzz() {
+    fn extreme_multiplier_fuzz() {
         let mut ctx = StateContext::defaults_for_testing();
         // our calculations should work correctly with a low ease or non-default multiplier
         let state = ReviewState {
@@ -272,6 +272,11 @@ mod test {
         ctx.interval_multiplier = 0.1;
         assert_eq!(state.passing_review_intervals(&ctx), (2, 3, 4));
         ctx.fuzz_factor = Some(0.99);
-        assert_eq!(state.passing_review_intervals(&ctx), (2, 3, 4));
+        assert_eq!(state.passing_review_intervals(&ctx), (3, 5, 7));
+
+        // maximum must be respected no matter what
+        ctx.interval_multiplier = 10.0;
+        ctx.maximum_review_interval = 5;
+        assert_eq!(state.passing_review_intervals(&ctx), (5, 5, 5));
     }
 }