fix: make color parsing prettier

src/main.rs

@@ -4,20 +4,17 @@ use std::{
     f32::consts::FRAC_PI_2,
     io::stdout,
     net::{Ipv4Addr, SocketAddr, UdpSocket},
-    num::ParseIntError,
     path::PathBuf,
-    str::FromStr,
     thread::sleep,
     time::Duration,
 };
 
 use bracket_color::prelude::{HSV, RGB};
-use clap::{Parser, Subcommand, ValueEnum};
+use clap::{builder::TypedValueParser, Parser, Subcommand, ValueEnum};
 use image::{imageops::FilterType, io::Reader as ImageReader, Pixel, Rgb, RgbImage};
 use rand::Rng;
 
 use splink_client::{send_frame, Layout};
-use thiserror::Error;
 
 /// Blinkenwall v3 prototype client
 #[derive(Parser, Debug)]
@@ -39,42 +36,37 @@ struct Args {
     action: Action,
 }
 
-#[derive(Clone, Copy, Debug, PartialEq, Eq)]
-struct Color {
-    r: u8,
-    g: u8,
-    b: u8,
-}
+#[derive(Clone, Copy)]
+struct ColorParser;
+impl TypedValueParser for ColorParser {
+    type Value = Rgb<u8>;
 
-#[derive(Clone, Debug, Error)]
-enum ColorError {
-    #[error("Wrong parameter length")]
-    WrongLength,
-    #[error("Illegal integer")]
-    BadNumber(#[from] ParseIntError),
-}
-
-impl FromStr for Color {
-    type Err = ColorError;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
+    fn parse_ref(
+        &self,
+        _cmd: &clap::Command,
+        _arg: Option<&clap::Arg>,
+        value: &std::ffi::OsStr,
+    ) -> Result<Self::Value, clap::Error> {
+        let s = value
+            .to_str()
+            .ok_or(clap::Error::raw(clap::ErrorKind::InvalidUtf8, ""))?;
         let s = s.strip_prefix('#').unwrap_or(s);
 
         if s.len() != 6 {
-            return Err(ColorError::WrongLength);
+            return Err(clap::Error::raw(
+                clap::ErrorKind::InvalidValue,
+                "Must be a 6-digit hexadecimal number",
+            ));
         }
 
-        let r = u8::from_str_radix(&s[0..2], 16)?;
-        let g = u8::from_str_radix(&s[2..4], 16)?;
-        let b = u8::from_str_radix(&s[4..6], 16)?;
+        let mut channels = [0; 3];
+        for i in 0..3 {
+            channels[i] = u8::from_str_radix(&s[i * 2..i * 2 + 2], 16).map_err(|_| {
+                clap::Error::raw(clap::ErrorKind::InvalidValue, "Invalid hex literal")
+            })?;
+        }
 
-        Ok(Self { r, g, b })
-    }
-}
-
-impl From<Color> for Rgb<u8> {
-    fn from(c: Color) -> Rgb<u8> {
-        Rgb([c.r, c.g, c.b])
+        Ok(Rgb(channels))
     }
 }
 
@@ -85,7 +77,8 @@ enum Action {
         animation: Animation,
     },
     Solid {
-        color: Color,
+        #[clap(value_parser = ColorParser)]
+        color: Rgb<u8>,
     },
     Image {
         path: PathBuf,
@@ -196,7 +189,7 @@ fn main() -> anyhow::Result<()> {
 
     let image = match args.action {
         Action::Solid { color } => {
-            RgbImage::from_pixel(layout.width_px(), layout.height_px(), color.into())
+            RgbImage::from_pixel(layout.width_px(), layout.height_px(), color)
         }
         Action::Clear => RgbImage::new(layout.width_px(), layout.height_px()),
         Action::Image { path } => ImageReader::open(path)?