From 052596214da5d536afa7ba277d41cfb514583fb0 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg@phi-gamma.net>
Date: Wed, 10 Nov 2021 21:30:41 +0100
Subject: use trait for deriving Color

---
 src/vtcol.rs | 70 +++++++++++++++++++++++++++++++-----------------------------
 1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/src/vtcol.rs b/src/vtcol.rs
index 361b8fe..d886f2b 100644
--- a/src/vtcol.rs
+++ b/src/vtcol.rs
@@ -1,5 +1,6 @@
 use anyhow::{anyhow, Result};
-use std::{fmt,
+use std::{convert::TryFrom,
+          fmt,
           io::Error,
           path::{Path, PathBuf},
           sync::atomic::{AtomicBool, Ordering}};
@@ -41,33 +42,38 @@ enum Color
     White(bool),
 }
 
-impl Color
+impl TryFrom<u8> for Color
 {
-    fn of_value(val: u8) -> Color
+    type Error = anyhow::Error;
+
+    fn try_from(val: u8) -> Result<Self, Self::Error>
     {
         match val {
-            0x00_u8 => Color::Black(false),
-            0x01_u8 => Color::Red(false),
-            0x02_u8 => Color::Green(false),
-            0x03_u8 => Color::Yellow(false),
-            0x04_u8 => Color::Blue(false),
-            0x05_u8 => Color::Magenta(false),
-            0x06_u8 => Color::Cyan(false),
-            0x07_u8 => Color::White(false),
-
-            0x08_u8 => Color::Black(true),
-            0x09_u8 => Color::Red(true),
-            0x0a_u8 => Color::Green(true),
-            0x0b_u8 => Color::Yellow(true),
-            0x0c_u8 => Color::Blue(true),
-            0x0d_u8 => Color::Magenta(true),
-            0x0e_u8 => Color::Cyan(true),
-            0x0f_u8 => Color::White(true),
-
-            _ => panic!("invalid color value: {}", val),
+            0x00 => Ok(Color::Black(false)),
+            0x01 => Ok(Color::Red(false)),
+            0x02 => Ok(Color::Green(false)),
+            0x03 => Ok(Color::Yellow(false)),
+            0x04 => Ok(Color::Blue(false)),
+            0x05 => Ok(Color::Magenta(false)),
+            0x06 => Ok(Color::Cyan(false)),
+            0x07 => Ok(Color::White(false)),
+
+            0x08 => Ok(Color::Black(true)),
+            0x09 => Ok(Color::Red(true)),
+            0x0a => Ok(Color::Green(true)),
+            0x0b => Ok(Color::Yellow(true)),
+            0x0c => Ok(Color::Blue(true)),
+            0x0d => Ok(Color::Magenta(true)),
+            0x0e => Ok(Color::Cyan(true)),
+            0x0f => Ok(Color::White(true)),
+
+            _ => Err(anyhow!("invalid color value: {}", val)),
         }
     }
+} /* [impl TryFrom<u8> for Color] */
 
+impl Color
+{
     fn format_brightness(b: bool, s: &str) -> String
     {
         if b {
@@ -437,12 +443,12 @@ impl Palette
             let idx: usize = i % 3;
             buf[idx] = *col;
             if idx == 2 {
+                let col = Color::try_from((i / 3) as u8)
+                    .map(|c| format!("{}", c))
+                    .unwrap_or_else(|_| "??".into());
                 println!(
                     "{:>15} => 0x{:02.X}{:02.X}{:02.X}",
-                    Color::of_value((i / 3) as u8).to_string(),
-                    buf[0],
-                    buf[1],
-                    buf[2]
+                    col, buf[0], buf[1], buf[2]
                 );
             }
         }
@@ -509,14 +515,10 @@ impl fmt::Debug for Palette
             let r = self.0[i as usize];
             let g = self.0[i as usize + 1];
             let b = self.0[i as usize + 2];
-            let _ = writeln!(
-                f,
-                "{} => 0x{:02.X}{:02.X}{:02.X}",
-                Color::of_value(i),
-                r,
-                g,
-                b
-            );
+            let col = Color::try_from((i / 3) as u8)
+                .map(|c| format!("{}", c))
+                .unwrap_or_else(|_| "??".into());
+            let _ = writeln!(f, "{} => 0x{:02.X}{:02.X}{:02.X}", col, r, g, b);
             i += 3_u8;
         }
         std::result::Result::Ok(())
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