package link

import (
	"testing"
	"time"

	amqp "github.com/rabbitmq/amqp091-go"
)

// 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) {
	deliveries := make(chan amqp.Delivery, 8)
	for _, id := range []string{"two", "three", "four"} {
		deliveries <- amqp.Delivery{Body: []byte(id)}
	}
	apply, superseded := newest(deliveries, amqp.Delivery{Body: []byte("one")}, 50*time.Millisecond)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	if len(superseded) != 3 || string(superseded[0].Body) != "one" || string(superseded[2].Body) != "three" {
		t.Fatalf("set aside %d: %v", len(superseded), superseded)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) {
	deliveries := make(chan amqp.Delivery, 1)
	began := time.Now()
	apply, superseded := newest(deliveries, amqp.Delivery{Body: []byte("only")}, 30*time.Millisecond)
	if string(apply.Body) != "only" || len(superseded) != 0 {
		t.Fatalf("got %q with %d set aside", apply.Body, len(superseded))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) {
	deliveries := make(chan amqp.Delivery, 2)
	go func() {
		time.Sleep(20 * time.Millisecond)
		deliveries <- amqp.Delivery{Body: []byte("late")}
	}()
	apply, superseded := newest(deliveries, amqp.Delivery{Body: []byte("first")}, 100*time.Millisecond)
	if string(apply.Body) != "late" || len(superseded) != 1 {
		t.Fatalf("got %q with %d set aside", apply.Body, len(superseded))
	}
}