main runner with more meaningless output

src/main.rs

@@ -1,13 +1,35 @@
-use std::env::args;
+use std::{collections::HashMap, env::args};
 
 use advent_of_rust_2024::*;
+use itertools::Itertools;
 
 fn main() {
+    let mains: HashMap<u8, fn() -> ()> = HashMap::from_iter([
+        (1, day01::day_main as fn()),
+        (2, day02::day_main),
+        (3, day03::day_main),
+    ]);
     let day: Option<u8> = args().nth(1).and_then(|a| a.parse().ok());
-    match day {
-        Some(1) => day01::day_main(),
-        Some(2) => day02::day_main(),
-        Some(3) => day03::day_main(),
-        _ => println!("Please select a day to run"),
-    }
+    let Some(day) = day else {
+        mains
+            .iter()
+            .sorted_by_key(|entry| entry.0)
+            .for_each(|(d, f)| {
+                println!("Day {d}:");
+                f();
+            });
+        return;
+    };
+
+    let Some(f) = mains.get(&day) else {
+        println!("No implementation for day {day}.");
+        println!(
+            "Pick one of {}",
+            mains.keys().map(|k| k.to_string()).join(", ")
+        );
+        return;
+    };
+
+    println!("Day {day}:");
+    f();
 }