Allocate a lot less

src/color.rs

@@ -1,4 +1,4 @@
-use std::{borrow::Cow, cmp, env, str::FromStr};
+use std::{borrow::Cow, env, str::FromStr};
 use Color::{
     Black, Blue, BrightBlack, BrightBlue, BrightCyan, BrightGreen, BrightMagenta, BrightRed,
     BrightWhite, BrightYellow, Cyan, Green, Magenta, Red, TrueColor, White, Yellow,
@@ -148,13 +148,10 @@ impl Color {
                 .map(|c| (c, c.into_truecolor()));
                 let distances = colors.map(|(c_original, c)| {
                     if let TrueColor { r, g, b } = c {
-                        let rd = cmp::max(r, r1) - cmp::min(r, r1);
-                        let gd = cmp::max(g, g1) - cmp::min(g, g1);
-                        let bd = cmp::max(b, b1) - cmp::min(b, b1);
-                        let rd: u32 = rd.into();
-                        let gd: u32 = gd.into();
-                        let bd: u32 = bd.into();
-                        let distance = rd.pow(2) + gd.pow(2) + bd.pow(2);
+                        fn distance(a: u8, b: u8) -> u32 {
+                            u32::from(a.abs_diff(b)).pow(2)
+                        }
+                        let distance = distance(r, r1) + distance(g, g1) + distance(b, b1);
                         (c_original, distance)
                     } else {
                         unimplemented!("{:?} not a TrueColor", c)
@@ -291,8 +288,82 @@ fn parse_hex(s: &str) -> Option<Color> {
 
 #[cfg(test)]
 mod tests {
+    use core::fmt::Display;
+
     pub use super::*;
 
+    struct FmtFgWrapper(Color);
+
+    impl Display for FmtFgWrapper {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            self.0.to_fg_fmt(f)
+        }
+    }
+    struct FmtBgWrapper(Color);
+
+    impl Display for FmtBgWrapper {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            self.0.to_bg_fmt(f)
+        }
+    }
+
+    #[test]
+    fn fmt_and_to_str_same() {
+        use Color::*;
+        let colors = &[
+            Black,
+            Red,
+            Green,
+            Yellow,
+            Blue,
+            Magenta,
+            Cyan,
+            White,
+            BrightBlack,
+            BrightRed,
+            BrightGreen,
+            BrightYellow,
+            BrightBlue,
+            BrightMagenta,
+            BrightCyan,
+            BrightWhite,
+            TrueColor { r: 0, g: 0, b: 0 },
+            TrueColor {
+                r: 255,
+                g: 255,
+                b: 255,
+            },
+            TrueColor {
+                r: 126,
+                g: 127,
+                b: 128,
+            },
+            TrueColor { r: 255, g: 0, b: 0 },
+            TrueColor {
+                r: 255,
+                g: 255,
+                b: 0,
+            },
+            TrueColor { r: 0, g: 255, b: 0 },
+            TrueColor {
+                r: 0,
+                g: 255,
+                b: 255,
+            },
+            TrueColor { r: 0, g: 0, b: 255 },
+            TrueColor {
+                r: 255,
+                g: 0,
+                b: 255,
+            },
+        ];
+
+        for color in colors {
+            assert_eq!(color.to_fg_str(), FmtFgWrapper(*color).to_string());
+            assert_eq!(color.to_bg_str(), FmtBgWrapper(*color).to_string());
+        }
+    }
+
     mod from_str {
         pub use super::*;