Move solutions from bin into lib.

The files src/bin/01.rs, 02.rs, etc are still created by scaffold, but they now
call the solution in the src/day01.rs, src/day02.rs, thereby allowing benchmarking.

This means that scaffold also updates lib.rs to add the module definitions. Right now
this is done using a simple replace of "// pub mod day01;" with "pub mod day01;".
There is a probably a nicer way to do this, but it works.

Also due to an issue in cargo we need to run "cargo clean -p advent_of_code".
Otherwise "cargo check" will fail.
See https://github.com/rust-lang/cargo/issues/6529

src/bin/scaffold.rs

@@ -4,11 +4,11 @@
  */
 use std::{
     fs::{File, OpenOptions},
-    io::Write,
+    io::{Error, Read, Seek, Write},
-    process,
+    process::{self, Command},
 };
 
-const MODULE_TEMPLATE: &str = r###"pub fn part_one(input: &str) -> Option<u32> {
+const MODULE_LIB_TEMPLATE: &str = r###"pub fn part_one(input: &str) -> Option<u32> {
     None
 }
 
@@ -16,30 +16,33 @@ pub fn part_two(input: &str) -> Option<u32> {
     None
 }
 
-fn main() {
-    let input = &advent_of_code::read_file("inputs", DAY);
-    advent_of_code::solve!(1, part_one, input);
-    advent_of_code::solve!(2, part_two, input);
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
 
     #[test]
     fn test_part_one() {
-        let input = advent_of_code::read_file("examples", DAY);
+        let input = crate::read_file("examples", DAY);
         assert_eq!(part_one(&input), None);
     }
 
     #[test]
     fn test_part_two() {
-        let input = advent_of_code::read_file("examples", DAY);
+        let input = crate::read_file("examples", DAY);
         assert_eq!(part_two(&input), None);
     }
 }
 "###;
 
+const MODULE_BIN_TEMPLATE: &str = r###"use advent_of_code::dayDAYPAD::{part_one, part_two};
+
+fn main() {
+    let input = &advent_of_code::read_file("inputs", DAY);
+    advent_of_code::solve!(1, part_one, input);
+    advent_of_code::solve!(2, part_two, input);
+}
+"###;
+
 fn parse_args() -> Result<u8, pico_args::Error> {
     let mut args = pico_args::Arguments::from_env();
     args.free_from_str()
@@ -53,6 +56,46 @@ fn create_file(path: &str) -> Result<File, std::io::Error> {
     OpenOptions::new().write(true).create(true).open(path)
 }
 
+fn modify_lib(day: u8) -> Result<(), Error> {
+    let lib_path = "src/lib.rs";
+
+    let mut file = OpenOptions::new()
+        .read(true)
+        .write(true)
+        .create(false)
+        .open(lib_path)?;
+
+    let mut old_code = String::new();
+    file.read_to_string(&mut old_code)?;
+
+    file.rewind()?;
+    file.set_len(0)?;
+
+    match file.write_all(
+        old_code
+            .replace(
+                &format!("// pub mod day{:02};", day),
+                &format!("pub mod day{:02};", day),
+            )
+            .as_bytes(),
+    ) {
+        Ok(_) => {
+            println!("Updated lib.rs to include 'day{:02}' module", day);
+        }
+        Err(e) => {
+            eprintln!(
+                "Failed to write updateded lib.rs to include 'day{:02}' module: {}",
+                day, e
+            );
+            process::exit(1);
+        }
+    }
+
+    file.flush()?;
+
+    Ok(())
+}
+
 fn main() {
     let day = match parse_args() {
         Ok(day) => day,
@@ -66,22 +109,59 @@ fn main() {
 
     let input_path = format!("src/inputs/{}.txt", day_padded);
     let example_path = format!("src/examples/{}.txt", day_padded);
-    let module_path = format!("src/bin/{}.rs", day_padded);
+    let module_bin_path = format!("src/bin/{}.rs", day_padded);
+    let module_lib_path = format!("src/day{}.rs", day_padded);
 
-    let mut file = match safe_create_file(&module_path) {
+    match modify_lib(day) {
+        Ok(_) => {}
+        Err(e) => {
+            eprintln!("Failed to update lib.rs file: {}", e);
+            process::exit(1);
+        }
+    }
+
+    let mut bin_file = match safe_create_file(&module_bin_path) {
         Ok(file) => file,
         Err(e) => {
-            eprintln!("Failed to create module file: {}", e);
+            eprintln!("Failed to create module bin file: {}", e);
             process::exit(1);
         }
     };
 
-    match file.write_all(MODULE_TEMPLATE.replace("DAY", &day.to_string()).as_bytes()) {
+    match bin_file.write_all(
+        MODULE_BIN_TEMPLATE
+            .replace("DAYPAD", &day_padded)
+            .replace("DAY", &day.to_string())
+            .as_bytes(),
+    ) {
         Ok(_) => {
-            println!("Created module file \"{}\"", &module_path);
+            println!("Created module bin file \"{}\"", &module_bin_path);
         }
         Err(e) => {
-            eprintln!("Failed to write module contents: {}", e);
+            eprintln!("Failed to write bin module contents: {}", e);
+            process::exit(1);
+        }
+    }
+
+    let mut lib_file = match safe_create_file(&module_lib_path) {
+        Ok(file) => file,
+        Err(e) => {
+            eprintln!("Failed to create module lib file: {}", e);
+            process::exit(1);
+        }
+    };
+
+    match lib_file.write_all(
+        MODULE_LIB_TEMPLATE
+            .replace("DAYPAD", &day_padded)
+            .replace("DAY", &day.to_string())
+            .as_bytes(),
+    ) {
+        Ok(_) => {
+            println!("Created module lib file \"{}\"", &module_bin_path);
+        }
+        Err(e) => {
+            eprintln!("Failed to write lib module contents: {}", e);
             process::exit(1);
         }
     }
@@ -106,6 +186,17 @@ fn main() {
         }
     }
 
+    // We need to execute cargo clean -p advent_of_code otherwise there can be cache issues when executing cargo check
+    // As far as I can tell this relates to https://github.com/rust-lang/cargo/issues/6529
+    let clean_output = Command::new("cargo")
+        .args(["clean", "-p", "advent_of_code"])
+        .output()
+        .unwrap();
+
+    if !clean_output.status.success() {
+        eprint!("Failed to execute 'cargo clean -p advent_of_code'.");
+    }
+
     println!("---");
     println!(
         "🎄 Type `cargo solve {}` to run your solution.",

src/lib.rs

@@ -6,6 +6,32 @@
 use std::env;
 use std::fs;
 
+// modules for the different days are automatically uncomented by the scaffold command
+pub mod day01;
+pub mod day02;
+// pub mod day03;
+// pub mod day04;
+// pub mod day05;
+// pub mod day06;
+// pub mod day07;
+// pub mod day08;
+// pub mod day09;
+// pub mod day10;
+// pub mod day11;
+// pub mod day12;
+// pub mod day13;
+// pub mod day14;
+// pub mod day15;
+// pub mod day16;
+// pub mod day17;
+// pub mod day18;
+// pub mod day19;
+// pub mod day20;
+// pub mod day21;
+// pub mod day22;
+// pub mod day23;
+// pub mod day24;
+// pub mod day25;
 pub mod helpers;
 
 pub const ANSI_ITALIC: &str = "\x1b[3m";