From f1886a930238854dbbba8245d0f98d0dc65c1837 Mon Sep 17 00:00:00 2001
From: mokurin000 <1348292515a@gmail.com>
Date: Wed, 20 Aug 2025 21:05:16 +0800
Subject: [PATCH] feat: calculate dx rating func

---
 music_db/src/lib.rs | 88 ++++++++++++++++++++++++---------------------
 1 file changed, 47 insertions(+), 41 deletions(-)

diff --git a/music_db/src/lib.rs b/music_db/src/lib.rs
index 391ac57..eddb525 100644
--- a/music_db/src/lib.rs
+++ b/music_db/src/lib.rs
@@ -1,4 +1,4 @@
-use std::sync::LazyLock;
+use std::{ops::RangeInclusive, sync::LazyLock};
 
 use rust_decimal::{Decimal, dec, serde::DecimalFromString};
 use rustc_hash::FxHashMap;
@@ -58,51 +58,57 @@ impl Level {
     ///
     /// On invalid input, it returns 0.
     pub fn dx_rating(&self, achievement: i32) -> (&'static str, u32) {
-        let achievement = achievement.min(1005000); // SSS+ case
-        let (rank, _, factor) = RANKS
-            .into_iter()
-            .rev()
-            .find(|&(_, threshold, _)| threshold <= achievement)
-            .unwrap(); // save here, due to zero threshold
         let difficulty_rank: Decimal = self.difficulty.value;
-        let achievement = Decimal::new(achievement as _, 4);
+        let achievement = achievement.min(1005000); // SSS+ case
 
-        #[cfg(feature = "log")]
-        spdlog::info!("factor: {factor}, achievement: {achievement}");
-
-        // when ach > 100.5%, calculate as 100.5%
-        let rating: u32 = (factor * difficulty_rank * achievement)
-            .floor()
-            .try_into()
-            .unwrap_or_default();
-        (rank, rating)
+        dx_rating(difficulty_rank, achievement)
     }
 }
 
-const RANKS: [(&'static str, i32, Decimal); 23] = [
-    ("D", 0, dec!(0.0)),
-    ("D", 100000, dec!(0.016)),
-    ("D", 200000, dec!(0.032)),
-    ("D", 300000, dec!(0.048)),
-    ("D", 400000, dec!(0.064)),
-    ("C", 500000, dec!(0.080)),
-    ("B", 600000, dec!(0.096)),
-    ("BB", 700000, dec!(0.112)),
-    ("BBB", 750000, dec!(0.120)),
-    ("BBB", 799999, dec!(0.128)),
-    ("A", 800000, dec!(0.136)),
-    ("AA", 900000, dec!(0.152)),
-    ("AAA", 940000, dec!(0.168)),
-    ("AAA", 969999, dec!(0.176)),
-    ("S", 970000, dec!(0.200)),
-    ("S+", 980000, dec!(0.203)),
-    ("S+", 989999, dec!(0.206)),
-    ("SS", 990000, dec!(0.208)),
-    ("SS+", 995000, dec!(0.211)),
-    ("SS+", 999999, dec!(0.214)),
-    ("SSS", 1000000, dec!(0.216)),
-    ("SSS", 1004999, dec!(0.222)),
-    ("SSS+", 1005000, dec!(0.224)),
+pub fn dx_rating(difficulty_rank: Decimal, achievement: i32) -> (&'static str, u32) {
+    let (rank, _, factor) = RANKS
+        .into_iter()
+        .rev()
+        .find(|(_, threshold, _)| threshold.contains(&achievement))
+        .unwrap(); // save here, due to zero threshold
+    let achievement = Decimal::new(achievement as _, 4);
+
+    #[cfg(feature = "log")]
+    spdlog::info!("factor: {factor}, achievement: {achievement}");
+
+    // when ach > 100.5%, calculate as 100.5%
+    let rating: u32 = (factor * difficulty_rank * achievement)
+        .floor()
+        .try_into()
+        .unwrap_or_default();
+
+    (rank, rating)
+}
+
+const RANKS: [(&'static str, RangeInclusive<i32>, Decimal); 23] = [
+    ("D", 0..=99999, dec!(0.0)),
+    ("D", 100000..=199999, dec!(0.016)),
+    ("D", 200000..=299999, dec!(0.032)),
+    ("D", 300000..=399999, dec!(0.048)),
+    ("D", 400000..=499999, dec!(0.064)),
+    ("C", 500000..=599999, dec!(0.080)),
+    ("B", 600000..=699999, dec!(0.096)),
+    ("BB", 700000..=749999, dec!(0.112)),
+    ("BBB", 750000..=799998, dec!(0.120)),
+    ("BBB", 799999..=799999, dec!(0.128)),
+    ("A", 800000..=899999, dec!(0.136)),
+    ("AA", 900000..=939999, dec!(0.152)),
+    ("AAA", 940000..=969998, dec!(0.168)),
+    ("AAA", 969999..=969999, dec!(0.176)),
+    ("S", 970000..=979999, dec!(0.200)),
+    ("S+", 980000..=989998, dec!(0.203)),
+    ("S+", 989999..=989999, dec!(0.206)),
+    ("SS", 990000..=994999, dec!(0.208)),
+    ("SS+", 995000..=999998, dec!(0.211)),
+    ("SS+", 999999..=999999, dec!(0.214)),
+    ("SSS", 1000000..=1004998, dec!(0.216)),
+    ("SSS", 1004999..=1004999, dec!(0.222)),
+    ("SSS+", 1005000..=1005000, dec!(0.224)),
 ];
 
 #[cfg(test)]