bellperson 0.22.0

use std::env::{self, VarError};
use std::panic::{self, RefUnwindSafe, UnwindSafe};
use std::sync::Mutex;

use lazy_static::lazy_static;

lazy_static! {
    static ref SERIAL_TEST: Mutex<()> = Default::default();
}

/// Based on
/// https://stackoverflow.com/questions/35858323/how-can-i-test-rust-methods-that-depend-on-environment-variables/67433684#67433684
/// Sets environment variables to the given value for the duration of the closure.
/// Restores the previous values when the closure completes or panics, before unwinding the panic.
pub fn with_env_vars<F>(kvs: Vec<(&str, Option<&str>)>, closure: F)
where
    F: Fn() + UnwindSafe + RefUnwindSafe,
{
    let guard = SERIAL_TEST.lock().unwrap();
    let mut old_kvs: Vec<(&str, Result<String, VarError>)> = Vec::new();
    for (k, v) in kvs {
        let old_v = env::var(k);
        old_kvs.push((k, old_v));
        match v {
            None => env::remove_var(k),
            Some(v) => env::set_var(k, v),
        }
    }

    match panic::catch_unwind(|| {
        closure();
    }) {
        Ok(_) => {
            for (k, v) in old_kvs {
                reset_env(k, v);
            }
        }
        Err(err) => {
            for (k, v) in old_kvs {
                reset_env(k, v);
            }
            drop(guard);
            panic::resume_unwind(err);
        }
    };
}

fn reset_env(k: &str, old: Result<String, VarError>) {
    if let Ok(v) = old {
        env::set_var(k, v);
    } else {
        env::remove_var(k);
    }
}