Initial 2021 runner

.gitignore

@@ -56,3 +56,6 @@ docs/_build/
 # PyBuilder
 target/
 *.swp
+
+# Rust lock
+*.lock

2021/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "aoc-2021"
+version = "0.1.0"
+edition = "2021"
+
+
+[dependencies]
+clap = "3.0.0-beta.5"

2021/src/day01.rs

@@ -0,0 +1,10 @@
+use crate::Solution;
+
+#[derive(Default)]
+pub struct Day01;
+
+impl Solution for Day01 {
+    fn part1(&mut self, _input: &mut dyn std::io::Read) -> String {
+        todo!()
+    }
+}

2021/src/lib.rs

@@ -0,0 +1,29 @@
+use std::io::Read;
+
+mod day01;
+
+pub trait Solution {
+    fn part1(&mut self, input: &mut dyn Read) -> String;
+
+    fn part2(&mut self, _input: &mut dyn Read) -> String {
+        unimplemented!("Still working on part 1");
+    }
+}
+
+pub fn get_implementation(day: usize) -> Box<dyn Solution> {
+    match day {
+        1 => Box::new(day01::Day01::default()),
+        _ => panic!("Unsupported day {}", day),
+    }
+}
+
+#[cfg(test)]
+fn test_implementation(mut day: impl Solution, part: u8, mut input: &[u8], answer: impl ToString) {
+    let result = match part {
+        1 => day.part1(&mut input),
+        2 => day.part2(&mut input),
+        _ => panic!("Invalid part: {}", part),
+    };
+
+    assert_eq!(answer.to_string(), result);
+}

2021/src/main.rs

@@ -0,0 +1,52 @@
+use std::fs::File;
+use std::io::Read;
+use std::num::NonZeroUsize;
+use std::path::PathBuf;
+use std::time::Instant;
+
+use clap::Parser;
+
+use aoc_2021::get_implementation;
+
+/// Advent of Code 2021 runner
+#[derive(Parser)]
+struct Opts {
+    /// Which day to run
+    day: NonZeroUsize,
+
+    /// Print time taken
+    #[clap(short, long)]
+    time: bool,
+
+    /// Run part 2 instead of part 1
+    #[clap(short = '2', long)]
+    part2: bool,
+
+    /// Read input from the given file instead of stdin
+    #[clap(short, long)]
+    input: Option<PathBuf>,
+}
+
+fn main() {
+    let opts: Opts = Opts::parse();
+
+    let mut implementation = get_implementation(opts.day.get());
+    let mut input: Box<dyn Read> = if let Some(input) = opts.input {
+        Box::new(File::open(&input).expect("Failed to open input"))
+    } else {
+        Box::new(std::io::stdin())
+    };
+
+    let begin = Instant::now();
+    let result = if opts.part2 {
+        implementation.part2(&mut input)
+    } else {
+        implementation.part1(&mut input)
+    };
+
+    if opts.time {
+        eprintln!("Execution time: {:?}", Instant::now().duration_since(begin));
+    }
+
+    println!("{}", result);
+}