[rs] Detect day based on input file name

rs/src/main.rs

@@ -1,27 +1,73 @@
 mod d01;
 
-use std::fs;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+use std::str::FromStr;
+use std::{fmt, fs};
 
-use clap::{Parser, ValueEnum};
+use clap::Parser;
 
-#[derive(Clone, Copy, PartialEq, Eq, ValueEnum)]
 enum Day {
-    D01,
+    Y2022D01,
+}
+
+impl Day {
+    fn from_path(path: &Path) -> Option<Self> {
+        Self::from_str(path.file_stem()?.to_str()?).ok()
+    }
+}
+
+impl fmt::Display for Day {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Day::Y2022D01 => "2022_01",
+        }
+        .fmt(f)
+    }
+}
+
+impl FromStr for Day {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(match s {
+            "2022_01" => Self::Y2022D01,
+            _ => return Err(()),
+        })
+    }
 }
 
 #[derive(Parser)]
 struct Args {
-    day: Day,
-    file: PathBuf,
+    files: Vec<PathBuf>,
 }
 
 fn main() -> anyhow::Result<()> {
     let args = Args::parse();
-    let input = fs::read_to_string(&args.file)?;
 
-    match args.day {
-        Day::D01 => d01::solve(input)?,
+    if args.files.is_empty() {
+        eprintln!("No days specified");
+    }
+
+    let mut first_day = true;
+    for file in args.files {
+        if !first_day {
+            println!();
+        }
+        first_day = false;
+
+        let day = match Day::from_path(&file) {
+            Some(day) => day,
+            None => {
+                eprintln!("### Could not determine day: {file:?}");
+                continue;
+            }
+        };
+
+        println!("### Solving day {day}");
+        let input = fs::read_to_string(file)?;
+        match day {
+            Day::Y2022D01 => d01::solve(input)?,
+        }
     }
 
     Ok(())