package link

import (
	"testing"
	"time"
)

// said is one declaration as a test hands it over, with no transport under it — which is what the
// seam bought: the drain's reasoning was reachable only through a real broker before.
type said struct {
	body    []byte
	handled bool
}

func (s *said) Body() []byte   { return s.body }
func (s *said) Handled() error { s.handled = true; return nil }

func arriving(bodies ...string) chan Declaration {
	ch := make(chan Declaration, 8)
	for _, b := range bodies {
		ch <- &said{body: []byte(b)}
	}
	return ch
}

// A machine asked to be five things becomes the last one: what is already waiting supersedes what
// arrived first, and everything set aside is named so it can be reported.
func TestWhatIsAlreadyWaitingSupersedesWhatArrivedFirst(t *testing.T) {
	waiting := arriving("two", "three", "four")
	apply, superseded := newest(waiting, &said{body: []byte("one")}, 50*time.Millisecond)
	if string(apply.Body()) != "four" {
		t.Fatalf("applied %q, not the newest", apply.Body())
	}
	if len(superseded) != 3 || string(superseded[0].Body()) != "one" ||
		string(superseded[2].Body()) != "three" {
		t.Fatalf("set aside %d: %v", len(superseded), superseded)
	}
}

// One declaration with nothing behind it is applied as it always was, after the window.
func TestALoneDeclarationIsAppliedAfterTheWindow(t *testing.T) {
	began := time.Now()
	apply, superseded := newest(arriving(), &said{body: []byte("only")}, 30*time.Millisecond)
	if string(apply.Body()) != "only" || len(superseded) != 0 {
		t.Fatalf("got %q with %d set aside", apply.Body(), len(superseded))
	}
	if time.Since(began) < 30*time.Millisecond {
		t.Fatal("did not wait the window for a straggler")
	}
}

// A straggler within the window is taken; one after it is the next push.
func TestAStragglerWithinTheWindowIsTaken(t *testing.T) {
	waiting := arriving()
	go func() {
		time.Sleep(20 * time.Millisecond)
		waiting <- &said{body: []byte("late")}
	}()
	apply, superseded := newest(waiting, &said{body: []byte("first")}, 100*time.Millisecond)
	if string(apply.Body()) != "late" || len(superseded) != 1 {
		t.Fatalf("got %q with %d set aside", apply.Body(), len(superseded))
	}
}