convert palette id to int

src/palette.rs

@@ -1,8 +1,9 @@
 use crate::colour::Colour;
+use crate::{from_base36, to_base36};
 
 #[derive(Debug, Eq, PartialEq)]
 pub struct Palette {
-    pub id: String, // base36 string (why??)
+    pub id: u64,
     pub name: Option<String>,
     pub colours: Vec<Colour>,
 }
@@ -11,7 +12,7 @@ impl From<String> for Palette {
     fn from(string: String) -> Palette {
         let lines: Vec<&str> = string.lines().collect();
 
-        let id = lines[0].replace("PAL ", "");
+        let id = from_base36(&lines[0].replace("PAL ", ""));
 
         let name = match lines[1].starts_with("NAME") {
             true => Some(lines[1].replace("NAME ", "").to_string()),
@@ -43,7 +44,7 @@ impl ToString for Palette {
         }
         colours.pop();
 
-        format!("PAL {}\n{}{}", self.id, name, colours)
+        format!("PAL {}\n{}{}", to_base36(self.id), name, colours)
     }
 }
 
@@ -54,7 +55,7 @@ fn test_palette_from_string() {
     );
 
     let expected = Palette {
-        id: "1".to_string(),
+        id: 1,
         name: Some("lamplight".to_string()),
         colours: vec![
             Colour {red: 45,  green: 45, blue: 59},
@@ -73,7 +74,7 @@ fn test_palette_from_string_no_name() {
     );
 
     let expected = Palette {
-        id: "9".to_string(),
+        id: 9,
         name: None,
         colours: vec![
             Colour {red: 45,  green: 45, blue: 59},
@@ -88,7 +89,7 @@ fn test_palette_from_string_no_name() {
 #[test]
 fn test_palette_to_string() {
     let output = Palette {
-        id: "g".to_string(),
+        id: 16,
         name: Some("moss".to_string()),
         colours: vec![
             Colour {red: 1,   green: 2,   blue: 3  },