// vtest retry: 3
module context

import time

fn test_with_cancel_cause_no_cause() {
    mut bg := background()
    mut ctx, cancel := with_cancel_cause(mut bg)
    defer {
        cancel(none)
    }

    assert ctx.err() is none
    assert cause(ctx) is none

    cancel(none)
    assert ctx.err().str() == 'context canceled'
    // cause falls back to err() when no cause was set
    assert cause(ctx).str() == 'context canceled'
}

fn test_with_cancel_cause_with_cause() {
    my_err := error('my custom cause')

    mut bg := background()
    mut ctx, cancel := with_cancel_cause(mut bg)
    defer {
        cancel(none)
    }

    assert ctx.err() is none

    cancel(my_err)
    assert ctx.err().str() == 'context canceled'
    assert cause(ctx).str() == 'my custom cause'
}

fn test_with_cancel_cause_first_cause_wins() {
    first := error('first cause')
    second := error('second cause')

    mut bg := background()
    mut ctx, cancel := with_cancel_cause(mut bg)

    cancel(first)
    cancel(second) // should be ignored
    cancel(none) // should be ignored

    assert cause(ctx).str() == 'first cause'
}

fn test_with_cancel_cause_parent_cancel_propagates() {
    mut bg := background()
    mut parent, parent_cancel := with_cancel(mut bg)
    mut ctx, _ := with_cancel_cause(mut parent)

    assert ctx.err() is none

    parent_cancel()
    // give goroutine a moment to propagate
    time.sleep(5 * time.millisecond)

    assert ctx.err().str() == 'context canceled'
}

fn test_with_timeout_cause_fires_cause() {
    my_cause := error('timed out for testing')

    mut bg := background()
    mut ctx, cancel := with_timeout_cause(mut bg, 30 * time.millisecond, my_cause)
    defer {
        cancel()
    }

    // not done yet
    assert ctx.err() is none

    // poll for the deadline goroutine to record the cancellation; busy CI
    // runners can take well over 60ms to schedule it.
    deadline := time.now().add(2 * time.second)
    for ctx.err() is none && time.now() < deadline {
        time.sleep(5 * time.millisecond)
    }

    assert ctx.err().str() == 'context deadline exceeded'
    assert cause(ctx).str() == 'timed out for testing'
}

fn test_with_timeout_cause_cancel_before_deadline() {
    my_cause := error('deadline cause')

    mut bg := background()
    mut ctx, cancel := with_timeout_cause(mut bg, 500 * time.millisecond, my_cause)

    // cancel before deadline fires
    cancel()
    time.sleep(5 * time.millisecond)

    assert ctx.err().str() == 'context canceled'
    // no cause was set via CancelCauseFunc; cause falls back to err()
    assert cause(ctx).str() == 'context canceled'
}

fn test_cause_on_plain_cancel_context() {
    // cause() on a non-cause context should just return ctx.err()
    mut bg := background()
    mut ctx, cancel := with_cancel(mut bg)
    defer {
        cancel()
    }

    assert cause(ctx) is none

    cancel()
    assert cause(ctx).str() == 'context canceled'
}