use std::env;
use std::fs::{self, File};
use std::io::{BufWriter, Read, Write};
use std::path::PathBuf;
use std::process::Command;

fn main() {
    let ok = PathBuf::from("ok");
    let not_ok = PathBuf::from("not_ok");
    if env::var("YOU_ARE_A_LINKER").is_ok() {
        match env::args_os().find(|a| a.to_string_lossy().contains("@")) {
            Some(file) => {
                let file = file.to_str().unwrap();
                fs::copy(&file[1..], &ok).unwrap();
            }
            None => {
                File::create(&not_ok).unwrap();
            }
        }
        return;
    }

    let rustc = env::var_os("RUSTC").unwrap_or("rustc".into());
    let me = env::current_exe().unwrap();
    let bat = me.parent().unwrap().join("foo.bat");
    let bat_linker = format!("linker={}", bat.display());
    for i in (1..).map(|i| i * 10) {
        println!("attempt: {}", i);

        let file = PathBuf::from("bar.rs");
        let mut f = BufWriter::new(File::create(&file).unwrap());
        let mut lib_name = String::new();
        for _ in 0..i {
            lib_name.push_str("foo");
        }
        for j in 0..i {
            writeln!(f, "#[link(name = \"{}{}\")]", lib_name, j).unwrap();
        }
        writeln!(f, "extern {{}}\nfn main() {{}}").unwrap();
        f.into_inner().unwrap();

        drop(fs::remove_file(&ok));
        drop(fs::remove_file(&not_ok));
        let status = Command::new(&rustc)
            .arg(&file)
            .arg("-C")
            .arg(&bat_linker)
            .env("YOU_ARE_A_LINKER", "1")
            .env("MY_LINKER", &me)
            .status()
            .unwrap();

        if !status.success() {
            panic!("rustc didn't succeed: {}", status);
        }

        if !ok.exists() {
            assert!(not_ok.exists());
            continue;
        }

        let mut contents = Vec::new();
        File::open(&ok).unwrap().read_to_end(&mut contents).unwrap();

        for j in 0..i {
            let exp = format!("{}{}", lib_name, j);
            let exp = if cfg!(target_env = "msvc") {
                let mut out = Vec::with_capacity(exp.len() * 2);
                for c in exp.encode_utf16() {
                    // encode in little endian
                    out.push(c as u8);
                    out.push((c >> 8) as u8);
                }
                out
            } else {
                exp.into_bytes()
            };
            assert!(contents.windows(exp.len()).any(|w| w == &exp[..]));
        }

        break;
    }
}