build.rs

use std::env;
use std::fs::File;
use std::io::{BufRead, BufReader, BufWriter, Write};
use std::path::Path;

fn main() {
    let out_path = Path::new(&env::var("OUT_DIR").unwrap()).join("gen_tokens.rs");
    let mut writer = BufWriter::new(File::create(&out_path).unwrap());
    writeln!(writer, "match token {{").unwrap();

    println!("cargo:rerun-if-env-changed=CK3_IRONMAN_TOKENS");
    match env::var("CK3_IRONMAN_TOKENS") {
        Ok(v) if !v.is_empty() => {
            println!("cargo:rustc-cfg=ironman");
            println!("cargo:rerun-if-changed={}", v);
            let file = File::open(&v).unwrap();
            let mut reader = BufReader::new(file);

            let mut line = String::new();
            while reader.read_line(&mut line).unwrap() != 0 {
                let (token_val, token_s) = line.split_once(' ').unwrap();
                writeln!(writer, "{} => Some(\"{}\"),", token_val, token_s.trim()).unwrap();
                line.clear();
            }
        }
        _ => {}
    }

    writeln!(writer, "_ => None,").unwrap();
    writeln!(writer, "}}").unwrap();
}