use std::sync::mpsc::{Sender, Receiver};
use std::sync::mpsc;
use std::thread;

struct User {
    reference: String,
    email: String,
}

fn main() {
    let rows = vec![
        vec!["abcd", "test@test.com"],
        vec!["efgh", "test1@test.com"],
        vec!["wfee", "test2@test.com"],
        vec!["rrgr", "test3@test.com"],
    ];

    let chunk_len = (rows.len() / 2) as usize;
    let mut chunks = Vec::new();
    for chunk in rows.chunks(chunk_len) {
        chunks.push(chunk);
    }

    let (tx, rx): (Sender<Vec<User>>, Receiver<Vec<User>>) = mpsc::channel();

    for chunk in chunks {
        let thread_tx = tx.clone();
        thread::spawn(move || {
            let result = chunk
                .iter()
                .map(|row| {
                    User {
                        reference: row[0].to_string(),
                        email: row[1].to_string(),
                    }
                })
                .collect::<Vec<User>>();
            thread_tx.send(result).unwrap();
        });
    }

    let mut users = Vec::new();
    for _ in 0..chunk_len {
        users.push(rx.recv());
    }
}

for chunk in rows.chunks(chunk_len) {
    chunks.push(chunk.to_owned());
}

let mut chunks = Vec::new();
for chunk in rows.chunks(chunk_len) {
    chunks.push(chunk);
}

for chunk in rows.chunks(chunk_len) {
    let mut v = Vec::new();
    v.push_all(chunk);
    chunks.push(v);
}