import sync

const num_iterations = 10000

fn get_val_from_chan(ch chan i64) ?i64 {
    r := <-ch?
    return r
}

// this function gets an array of channels for `i64`
fn do_rec_calc_send(chs []chan i64, mut sem sync.Semaphore) {
    mut msg := ''
    for {
        mut s := get_val_from_chan(chs[0]) or {
            msg = err.msg()
            break
        }
        s++
        chs[1] <- s
    }
    assert msg == 'channel closed'
    sem.post()
}

fn test_channel_array_mut() {
    mut chs := [chan i64{}, chan i64{cap: 10}]
    mut sem := sync.new_semaphore()
    spawn do_rec_calc_send(chs, mut sem)
    mut t := i64(100)
    for _ in 0 .. num_iterations {
        chs[0] <- t
        t = <-chs[1]
    }
    chs[0].close()
    sem.wait()
    assert t == 100 + num_iterations
}

fn test_channel_close_with_error_propagates_after_buffer_drain() {
    ch := chan i64{cap: 1}
    ch <- i64(7)
    ch.close(error('async failure'))
    assert <-ch == i64(7)
    _ := get_val_from_chan(ch) or {
        assert err.msg() == 'async failure'
        return
    }
    assert false
}