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use anomaly::BoxError;
use crossbeam_channel::{Receiver, Select};

pub fn try_recv_multiple<K, T>(rs: &[(K, Receiver<T>)]) -> Option<(&K, T)> {
    // Build a list of operations.
    let mut sel = Select::new();
    for (_, r) in rs {
        sel.recv(r);
    }

    // Complete the selected operation.
    let oper = sel.try_select().ok()?;
    let index = oper.index();

    // Get the receiver who is ready
    let (k, r) = &rs[index];

    // Receive the message
    let result = oper.recv(r).ok()?;

    Some((k, result))
}

pub fn recv_multiple<K, T>(rs: &[(K, Receiver<T>)]) -> Result<(&K, T), BoxError> {
    // Build a list of operations.
    let mut sel = Select::new();
    for (_, r) in rs {
        sel.recv(r);
    }

    // Complete the selected operation.
    let oper = sel.select();
    let index = oper.index();

    // Get the receiver who is ready
    let (k, r) = &rs[index];

    // Receive the message
    let result = oper.recv(r)?;

    Ok((k, result))
}