Better CLI with clap and day runner macro

src/day01/mod.rs

@@ -4,7 +4,7 @@ use color_eyre::{
     Result,
     eyre::{Error, eyre},
 };
-use tracing::{debug, info, instrument};
+use tracing::{debug, instrument};
 
 pub const INPUT: &str = include_str!("input/input.txt");
 
@@ -98,18 +98,6 @@ pub fn part2(input: &str) -> Result<i32> {
     Ok(visited_zero_count)
 }
 
-pub fn solve() -> Result<()> {
-    info!("Day 1");
-    {
-        let _span = tracing::info_span!("day01").entered();
-        let p1 = part1(INPUT)?;
-        info!("Part 1: {}", p1);
-        let p2 = part2(INPUT)?;
-        info!("Part 2: {}", p2);
-    }
-    Ok(())
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src/day02/mod.rs

@@ -5,7 +5,7 @@ use color_eyre::{
     eyre::{Error, OptionExt, eyre},
 };
 use itertools::Itertools;
-use tracing::{debug, debug_span, info, info_span, instrument};
+use tracing::{debug, debug_span, instrument};
 
 pub const INPUT: &str = include_str!("input/input.txt");
 
@@ -141,18 +141,6 @@ pub fn part2(input: &str) -> Result<i64> {
     Ok(total_invalid)
 }
 
-pub fn solve() -> Result<()> {
-    info!("Day 2");
-    {
-        let _span = info_span!("day02").entered();
-        let p1 = part1(INPUT)?;
-        info!("Part 1: {}", p1);
-        let p2 = part2(INPUT)?;
-        info!("Part 2: {}", p2);
-    }
-    Ok(())
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

src/main.rs

@@ -1,6 +1,9 @@
+mod runner;
+
 pub mod day01;
 pub mod day02;
 
+use clap::Parser;
 use color_eyre::Result;
 use tracing::info;
 use tracing_error::ErrorLayer;
@@ -8,6 +11,24 @@ use tracing_subscriber::EnvFilter;
 use tracing_subscriber::fmt::format::FmtSpan;
 use tracing_subscriber::prelude::*;
 
+#[derive(Parser, Debug)]
+#[command(name = "Advent of Code 2025")]
+#[command(about = "Solutions for Advent of Code 2025", long_about = None)]
+struct Args {
+    /// Day to run (1-25). If not specified, runs all days.
+    #[arg(short, long)]
+    day: Option<u8>,
+
+    /// Part to run (1 or 2). If not specified, runs all parts.
+    #[arg(short, long)]
+    part: Option<u8>,
+}
+
+runner::days! {
+    1 => day01,
+    2 => day02,
+}
+
 fn main() -> Result<()> {
     color_eyre::install()?;
 
@@ -21,11 +42,12 @@ fn main() -> Result<()> {
         )
         .init();
 
+    let args = Args::parse();
+
     info!("Advent of Code 2025");
-    {
-        let _span = tracing::info_span!("aoc").entered();
-        day01::solve()?;
-        day02::solve()?;
-    }
+    let _span = tracing::info_span!("aoc").entered();
+
+    run_days(args.day, args.part)?;
+
     Ok(())
 }

src/runner.rs

@@ -0,0 +1,57 @@
+use color_eyre::Result;
+use tracing::info;
+
+macro_rules! days {
+    ($($day_num:literal => $day_mod:ident),* $(,)?) => {
+        pub fn run_days(day: Option<u8>, part: Option<u8>) -> Result<()> {
+            match day {
+                $(
+                    Some($day_num) => $crate::runner::run_day($day_num, part, $day_mod::part1, $day_mod::part2, $day_mod::INPUT)?,
+                )*
+                Some(d) => color_eyre::eyre::bail!("Day {} is not yet implemented", d),
+                None => {
+                    $(
+                        $crate::runner::run_day($day_num, None, $day_mod::part1, $day_mod::part2, $day_mod::INPUT)?;
+                    )*
+                }
+            }
+            Ok(())
+        }
+    };
+}
+
+pub(crate) use days;
+
+pub fn run_day<T1, T2>(
+    day: u8,
+    part: Option<u8>,
+    part1_fn: fn(&str) -> Result<T1>,
+    part2_fn: fn(&str) -> Result<T2>,
+    input: &str,
+) -> Result<()>
+where
+    T1: std::fmt::Display,
+    T2: std::fmt::Display,
+{
+    info!("Day {}", day);
+    let day_name = format!("{:02}", day);
+    let _span = tracing::info_span!("day", day = %day_name).entered();
+
+    if part.is_none() || part == Some(1) {
+        let result = part1_fn(input)?;
+        info!("Part 1: {}", result);
+    }
+
+    if part.is_none() || part == Some(2) {
+        let result = part2_fn(input)?;
+        info!("Part 2: {}", result);
+    }
+
+    if let Some(p) = part {
+        if p != 1 && p != 2 {
+            color_eyre::eyre::bail!("Part {} is invalid. Must be 1 or 2.", p);
+        }
+    }
+
+    Ok(())
+}