some small refactoring

src/helpers/difficulty.rs

@@ -1,3 +1,4 @@
+#[derive(PartialEq, Copy, Clone)]
 pub enum LevelDifficulty {
     Auto,
     Easy,
@@ -9,7 +10,32 @@ pub enum LevelDifficulty {
 }
 
 impl LevelDifficulty {
-    pub fn to_star_difficulty(&self) -> i32 {
+    pub fn new(value: i32) -> LevelDifficulty {
+        match value {
+            0 => LevelDifficulty::Auto,
+            1 => LevelDifficulty::Easy,
+            2 => LevelDifficulty::Normal,
+            3 => LevelDifficulty::Hard,
+            4 => LevelDifficulty::Harder,
+            5 => LevelDifficulty::Insane,
+            6 => LevelDifficulty::Demon,
+            _ => panic!("invalid level difficulty")
+        }
+    }
+
+    pub fn value(self) -> i32 {
+        match self {
+            LevelDifficulty::Auto => 0,
+            LevelDifficulty::Easy => 1,
+            LevelDifficulty::Normal => 2,
+            LevelDifficulty::Hard => 3,
+            LevelDifficulty::Harder => 4,
+            LevelDifficulty::Insane => 5,
+            LevelDifficulty::Demon => 6,
+        }
+    }
+
+    pub fn to_star_difficulty(self) -> i32 {
         match self {
             LevelDifficulty::Auto => 5,
             LevelDifficulty::Easy => 1,
@@ -20,4 +46,59 @@ impl LevelDifficulty {
             LevelDifficulty::Demon => 5,
         }
     }
+
+    pub fn stars_to_diff(stars: i32) -> Self {
+        match stars {
+            1 => LevelDifficulty::Auto,
+            2 => LevelDifficulty::Easy,
+            3 => LevelDifficulty::Normal,
+            4 | 5 => LevelDifficulty::Hard,
+            6 | 7 => LevelDifficulty::Harder,
+            8 | 9 => LevelDifficulty::Insane,
+            10 => LevelDifficulty::Demon,
+            _ => panic!("invalid difficulty!")
+        }
+    }
+}
+
+pub enum DemonDifficulty {
+    Easy,
+    Medium,
+    Hard,
+    Insane,
+    Extreme
+}
+
+impl DemonDifficulty {
+    pub fn new(value: i32) -> DemonDifficulty {
+        match value {
+            0 => DemonDifficulty::Easy,
+            1 => DemonDifficulty::Medium,
+            2 => DemonDifficulty::Hard,
+            3 => DemonDifficulty::Insane,
+            4 => DemonDifficulty::Extreme,
+            5 => DemonDifficulty::Insane,
+            _ => panic!("invalid demon difficulty")
+        }
+    }
+
+    pub fn value(self) -> i32 {
+        match self {
+            DemonDifficulty::Easy => 0,
+            DemonDifficulty::Medium => 1,
+            DemonDifficulty::Hard => 2,
+            DemonDifficulty::Insane => 3,
+            DemonDifficulty::Extreme => 4
+        }
+    }
+
+    pub fn to_demon_difficulty(self) -> i32 {
+        match self {
+            DemonDifficulty::Easy => 3,
+            DemonDifficulty::Medium => 4,
+            DemonDifficulty::Hard => 0,
+            DemonDifficulty::Insane => 5,
+            DemonDifficulty::Extreme => 6
+        }
+    }
 }