module executor

import time

fn test_run_one_executes_one_job_and_reports_true() {
    mut ex := new(queue_size: 4)!
    values := chan int{cap: 2}

    ex.try_post(fn [values] () ! {
        values <- 1
    })!
    ex.try_post(fn [values] () ! {
        values <- 2
    })!

    assert ex.run_one()!
    assert wait_for_int(values, 'first job did not run') == 1
    assert ex.run_one()!
    assert wait_for_int(values, 'second job did not run') == 2
    assert !ex.run_one()!

    ex.stop()
    assert !ex.run_one()!
    ex.wait()!
}

fn test_drain_pending_runs_at_most_limit() {
    mut ex := new(queue_size: 4)!
    values := chan int{cap: 4}
    for i in 0 .. 4 {
        ex.try_post(fn [values, i] () ! {
            values <- i
        })!
    }

    assert ex.drain_pending(2)! == 2
    assert wait_for_int(values, 'first drained job missing') == 0
    assert wait_for_int(values, 'second drained job missing') == 1

    assert ex.drain_pending(8)! == 2
    assert wait_for_int(values, 'third drained job missing') == 2
    assert wait_for_int(values, 'fourth drained job missing') == 3

    ex.stop()
    assert ex.drain_pending(1)! == 0
    ex.wait()!
}

fn test_drain_pending_rejects_non_positive_limit() {
    mut ex := new(queue_size: 1)!
    ex.drain_pending(0) or {
        assert err.msg() == 'executor: drain limit must be positive'
        ex.stop()
        return
    }
    assert false, 'drain_pending accepted a zero limit'
}

fn test_single_producer_fifo_order_is_preserved() {
    mut ex := new(queue_size: 8)!
    values := chan int{cap: 5}
    for i in 0 .. 5 {
        ex.try_post(fn [values, i] () ! {
            values <- i
        })!
    }

    assert ex.drain_pending(5)! == 5
    for expected in 0 .. 5 {
        assert wait_for_int(values, 'FIFO job missing') == expected
    }

    ex.stop()
    assert !ex.run_one()!
    ex.wait()!
}

fn wait_for_int(signal chan int, message string) int {
    select {
        value := <-signal {
            return value
        }
        1 * time.second {
            assert false, message
        }
    }
    return 0
}