package link

import (
	"context"
	"reflect"
	"testing"
	"time"
)

// The order the build queue hands asks out in (novox/hq issue 558): a build a walk waits for before any
// pull request's check, a check that has waited ten minutes before every delivery asked after it, and
// first come, first served within a kind.

func anAsk(seq uint64, id string, asked time.Time, check bool) QueuedAsk {
	r := BuildRequest{ID: id, Repository: "/r"}
	if check {
		r.Check = &CheckRequest{Owner: "novox", Repo: "r"}
	}
	return QueuedAsk{Seq: seq, ID: id, AskedAt: asked, Request: r, State: AskWaiting}
}

func idsOf(asks []QueuedAsk) []string {
	out := []string{}
	for _, a := range asks {
		out = append(out, a.ID)
	}
	return out
}

func TestADeliveryIsHandedOutBeforeTheChecksAskedBeforeIt(t *testing.T) {
	now := time.Date(2026, 10, 12, 12, 0, 0, 0, time.UTC)
	waiting := []QueuedAsk{
		anAsk(1, "check-a", now.Add(-3*time.Minute), true),
		anAsk(2, "check-b", now.Add(-2*time.Minute), true),
		anAsk(3, "delivery-d", now.Add(-time.Minute), false),
	}
	want := []string{"delivery-d", "check-a", "check-b"}
	if got := idsOf(QueueOrder(waiting, now)); !reflect.DeepEqual(got, want) {
		t.Fatalf("handed out as %v, want %v", got, want)
	}
	// Only the checks ahead of it move behind it; the delivery stays where it is.
	if got := idsOf(toMove(waiting, QueueOrder(waiting, now))); !reflect.DeepEqual(got, []string{"check-a", "check-b"}) {
		t.Fatalf("moved %v", got)
	}
}

func TestACheckThatWaitedTenMinutesGoesBeforeALaterDelivery(t *testing.T) {
	now := time.Date(2026, 10, 12, 12, 0, 0, 0, time.UTC)
	// As the queue stands after a delivery put the young checks behind it, ten minutes ago and since.
	waiting := []QueuedAsk{
		anAsk(5, "delivery-early", now.Add(-12*time.Minute), false),
		anAsk(6, "delivery-later", now.Add(-time.Minute), false),
		anAsk(7, "check-old", now.Add(-11*time.Minute), true),
		anAsk(8, "check-young", now.Add(-9*time.Minute), true),
	}
	want := []string{"delivery-early", "check-old", "delivery-later", "check-young"}
	if got := idsOf(QueueOrder(waiting, now)); !reflect.DeepEqual(got, want) {
		t.Fatalf("handed out as %v, want %v", got, want)
	}
	if got := idsOf(toMove(waiting, QueueOrder(waiting, now))); !reflect.DeepEqual(got, []string{"delivery-later", "check-young"}) {
		t.Fatalf("moved %v", got)
	}
}

func TestAnAskWhoseKindCannotBeToldIsACheck(t *testing.T) {
	for _, r := range []BuildRequest{
		{},                                      // unreadable: nothing was read from it
		{ID: "build-1", Check: &CheckRequest{}}, // a pull request's check, or a recheck the merge tool asked
		{ID: "build-2", DryRun: true},           // looked at, never delivered
	} {
		if got := KindOf(r); got != KindCheck {
			t.Errorf("%+v is a %s", r, got)
		}
	}
	if got := KindOf(BuildRequest{ID: "build-3", Repository: "/r"}); got != KindDelivery {
		t.Errorf("a build is a %s", got)
	}
}

// Against a real server: two checks wait, a delivery is asked, and the next free holder takes the delivery.
func TestNatsADeliveryIsTakenBeforeTheChecksQueuedAheadOfIt(t *testing.T) {
	js := aBusWithTheBuildRole(t)
	ctx, stop := context.WithCancel(context.Background())
	defer stop()
	asks := BuildsOn(js, TheBuildMachine)
	now := time.Now()
	for i, r := range []BuildRequest{
		{ID: NewBuildID(now.Add(-3 * time.Minute)), Repository: "/a", Check: &CheckRequest{Owner: "novox", Repo: "a"}},
		{ID: NewBuildID(now.Add(-2 * time.Minute)), Repository: "/b", Check: &CheckRequest{Owner: "novox", Repo: "b"}},
		{ID: NewBuildID(now), Repository: "/d"},
	} {
		if i == 2 {
			// And one nobody can read, whose kind cannot be told: it waits with the checks.
			if _, err := js.Context().Publish(BuildWork(), []byte("not an ask")); err != nil {
				t.Fatal(err)
			}
		}
		if err := asks.Ask(ctx, r); err != nil {
			t.Fatal(err)
		}
	}
	took := make(chan string, 4)
	machine := MachineOverNATS(js, "anchor")
	defer machine.Close()
	go func() {
		_ = machine.Take(ctx, func(ctx context.Context, work Build) {
			took <- work.Request().Repository
			_ = work.Announce(ctx, BuildResult{ID: work.Request().ID, On: "anchor", Failed: "no"})
			_ = work.Done()
		})
	}()
	var order []string
	for len(order) < 3 {
		select {
		case r := <-took:
			order = append(order, r)
		case <-time.After(10 * time.Second):
			t.Fatalf("taken so far: %v", order)
		}
	}
	if want := []string{"/d", "/a", "/b"}; !reflect.DeepEqual(order, want) {
		t.Fatalf("taken as %v, want %v", order, want)
	}
}