use std::{env, fs, path::Path, process::Command};

fn main() -> Result<(), std::io::Error> {
    let args: Vec<String> = env::args().collect();

    if args.len() == 1 {
        println!("Too few arguments");
        println!("Please enter a year, or a year and day");
        return Err(std::io::ErrorKind::InvalidInput.into());
    } else if args.len() > 3 {
        println!("Too many arguments");
        println!("Please enter a year, or a year and day");
        return Err(std::io::ErrorKind::InvalidInput.into());
    } else if args.len() == 2 {
        prepare_year(&args[1])?;
    } else if args.len() == 3 {
        prepare_day(&args[1], &args[2])?;
    }
    match Command::new("cargo").arg("fmt").status() {
        Ok(_) => Ok(()),
        Err(e) => Err(e),
    }
}

fn prepare_year(year: &str) -> Result<(), std::io::Error> {
    let root = env!("CARGO_MANIFEST_DIR");
    if Path::new(&format!("{root}/y{year}")).exists() {
        panic!("Folder y{year} already exists")
    }
    // create workspace
    match Command::new("cargo")
        .arg("new")
        .arg(format!("y{year}"))
        .status()
    {
        Ok(_status) => Ok(()),
        Err(e) => Err(e),
    }?;
    // remove main.rs
    fs::remove_file(format!("{root}/y{year}/src/main.rs"))?;
    fs::create_dir(format!("{root}/y{year}/src/bin"))?;
    fs::create_dir(format!("{root}/y{year}/src/days"))?;
    fs::write(format!("{root}/y{year}/src/lib.rs"), "pub mod days;")?;
    fs::write(format!("{root}/y{year}/src/days/mod.rs"), "")?;
    prepare_day(year, "1")
}

fn prepare_day(year: &str, day: &str) -> Result<(), std::io::Error> {
    let root = env!("CARGO_MANIFEST_DIR");
    if Path::new(&format!("{root}/y{year}/src/bin/d{day}.rs")).exists() {
        panic!("Day y{year}d{day} already exists")
    }
    let bin = fs::read_to_string(format!("{root}/template/bin/d.rs.tmpl"))?
        .replace("{{YEAR}}", year)
        .replace("{{DAY}}", day);
    let dayfile = fs::read_to_string(format!("{root}/template/days/d.rs.tmpl"))?;
    let mut modfile = fs::read_to_string(format!("{root}/y{year}/src/days/mod.rs"))?;
    modfile.push_str(format!("\npub mod d{day};").as_str());
    let bin_path = format!("{root}/y{year}/src/bin/d{day}.rs");
    fs::write(bin_path, bin)?;
    fs::write(format!("{root}/y{year}/src/days/d{day}.rs"), dayfile)?;
    fs::write(format!("{root}/y{year}/src/days/mod.rs"), modfile)?;
    Ok(())
}