// Channel Benchmark
//
// `nobj` integers are sent thru a channel with queue length`buflen`
// using `nsend` sender threads and `nrec` receiver threads.
//
// The receive threads add all received numbers and send them to the
// main thread where the total sum is compare to the expected value.
const (
    nsend           = 2
    nrec            = 2
    buflen          = 100
    nobj            = 10000
    objs_per_thread = 5000
)

fn do_rec(ch chan int, resch chan i64, n int) {
    mut sum := i64(0)
    for _ in 0 .. n {
        mut r := 0
        for ch.try_pop(mut r) != .success {
        }
        sum += r
    }
    println(sum)
    resch <- sum
}

fn do_send(ch chan int, start int, end int) {
    for i in start .. end {
        for ch.try_push(i) != .success {
        }
    }
}

fn test_channel_polling() {
    ch := chan int{cap: buflen}
    resch := chan i64{}
    for _ in 0 .. nrec {
        spawn do_rec(ch, resch, objs_per_thread)
    }
    mut n := nobj
    for _ in 0 .. nsend {
        end := n
        n -= objs_per_thread
        spawn do_send(ch, n, end)
    }
    mut sum := i64(0)
    for _ in 0 .. nrec {
        sum += <-resch
        println('> running sum: ${sum}')
    }
    // use sum formula by Gauß to calculate the expected result
    expected_sum := i64(nobj) * (nobj - 1) / 2
    println('expected sum: ${expected_sum} | sum: ${sum}')
    assert sum == expected_sum
}