import sync

// Note: this is the same test as `vlib/sync/once_test.v`, but
// it uses an explicit passing of the voidptr parameter in
// once.do_with_param/2, instead of passing a closure of it
// in once.do/1.

struct One {
pub mut:
    i int
}

fn (mut o One) add(i int) {
    o.i = o.i + i
}

fn run(mut once sync.Once, mut o One, c chan bool) {
    once.do_with_param(fn (mut o One) {
        o.add(5)
    }, o)
    c <- true
}

fn test_once() {
    mut o := &One{}
    mut once := sync.new_once()
    c := chan bool{}
    n := 10

    // It is executed 10 times, but only once actually.
    for i := 0; i < n; i++ {
        spawn run(mut once, mut o, c)
    }
    for i := 0; i < n; i++ {
        <-c
    }
    assert o.i == 5
}