Add Solver trait and move common functionality out of concrete solvers

src/solvers.rs

@@ -1,2 +1,77 @@
+use std::fs::File;
+use std::io;
+use std::io::BufRead;
+use std::path::Path;
+
 pub mod cafeteria;
 pub mod printing_department;
+
+pub trait Solver {
+    fn get_puzzle_index(&self) -> u8;
+    fn get_puzzle_name(&self) -> &str;
+    fn get_input_filename(&self) -> &str;
+    fn get_part1(&self) -> u64;
+    fn get_part2(&self) -> u64;
+    fn process_data(&mut self, lines: io::Lines<io::BufReader<File>>);
+}
+
+pub fn run(mut solver: Box<dyn Solver>) {
+    println!(
+        "--- Day {}: {} ---",
+        solver.get_puzzle_index(),
+        solver.get_puzzle_name()
+    );
+
+    // The "../../data" and "../../../data" paths are useful for running the binary from
+    // "target/release/" directory with "data/" directory in package root or parent directory.
+    let paths = vec!["./data", "../data", "../../data", "../../../data"];
+
+    match read_data_file(solver.get_input_filename(), &paths) {
+        Ok(lines) => {
+            solver.process_data(lines);
+            print_result(solver);
+        }
+        Err(error) => eprintln!("{}", error),
+    };
+}
+
+fn print_result(solver: Box<dyn Solver>) {
+    println!(
+        "Part 1: {:?}\nPart 2: {:?}\n",
+        solver.get_part1(),
+        solver.get_part2()
+    );
+}
+
+fn read_data_file<T>(
+    filename: T,
+    search_paths: &Vec<T>,
+) -> Result<io::Lines<io::BufReader<File>>, String>
+where
+    T: AsRef<Path>,
+{
+    for path in search_paths {
+        if let Ok(lines) = read_lines(path.as_ref().join(&filename)) {
+            return Ok(lines);
+        }
+    }
+
+    let message = search_paths
+        .iter()
+        .map(|path| path.as_ref().join(&filename).display().to_string())
+        .collect::<Vec<_>>()
+        .join("\n");
+    Err(format!(
+        "Cannot open puzzle input file, searched these paths:\n{}",
+        message
+    ))
+}
+
+// This code is taken from https://doc.rust-lang.org/stable/rust-by-example/std_misc/file/read_lines.html
+fn read_lines<T>(filename: T) -> io::Result<io::Lines<io::BufReader<File>>>
+where
+    T: AsRef<Path>,
+{
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}