package events

import (
	"testing"
	"time"

	"github.com/kamelion/ratatoskr-go/internal/model"
)

// receiveOne помогает получить одно событие с таймаутом.
func receiveOne(t *testing.T, ch <-chan Event) Event {
	t.Helper()
	select {
	case e := <-ch:
		return e
	case <-time.After(2 * time.Second):
		t.Fatal("timeout waiting for event")
		return nil
	}
}

func TestBusPublishToSubscriber(t *testing.T) {
	bus := New(10)
	ch, unsub := bus.Subscribe()
	defer unsub()

	want := TaskStatusChanged{ID: 42, From: model.StatusReady, To: model.StatusRunning}
	bus.Publish(want)

	got := receiveOne(t, ch)
	ev, ok := got.(TaskStatusChanged)
	if !ok {
		t.Fatalf("got %T, want TaskStatusChanged", got)
	}
	if ev.ID != 42 || ev.From != model.StatusReady || ev.To != model.StatusRunning {
		t.Fatalf("unexpected event: %+v", ev)
	}
}

func TestBusFanout(t *testing.T) {
	bus := New(10)
	ch1, unsub1 := bus.Subscribe()
	defer unsub1()
	ch2, unsub2 := bus.Subscribe()
	defer unsub2()

	e := LogLine{Level: "log", Text: "hello"}
	bus.Publish(e)

	if got := receiveOne(t, ch1); got != e {
		t.Fatalf("subscriber 1 got %#v, want %#v", got, e)
	}
	if got := receiveOne(t, ch2); got != e {
		t.Fatalf("subscriber 2 got %#v, want %#v", got, e)
	}
}

func TestBusPreservesOrder(t *testing.T) {
	bus := New(64)
	ch, unsub := bus.Subscribe()
	defer unsub()

	const n = 25
	for i := 0; i < n; i++ {
		bus.Publish(TraceAppended{TaskID: int64(i)})
	}
	for i := 0; i < n; i++ {
		ev := receiveOne(t, ch)
		ta, ok := ev.(TraceAppended)
		if !ok {
			t.Fatalf("got %T, want TraceAppended", ev)
		}
		if ta.TaskID != int64(i) {
			t.Fatalf("out of order: got %d, want %d", ta.TaskID, i)
		}
	}
}

func TestUnsubscribeStopsDelivery(t *testing.T) {
	bus := New(10)
	ch, unsub := bus.Subscribe()
	bus.Publish(TaskCreated{ID: 1})
	receiveOne(t, ch)

	unsub()
	if got := bus.SubscribersCount(); got != 0 {
		t.Fatalf("SubscribersCount = %d, want 0", got)
	}

	// Убеждаемся, что Publish не блокируется навечно отписанным подписчиком.
	bus.Publish(TaskCreated{ID: 2})

	select {
	case got := <-ch:
		t.Fatalf("received %#v after unsubscribe", got)
	case <-time.After(200 * time.Millisecond):
	}
}

func TestBusSubscribersCount(t *testing.T) {
	bus := New(10)
	if got := bus.SubscribersCount(); got != 0 {
		t.Fatalf("initial count = %d, want 0", got)
	}
	_, unsub1 := bus.Subscribe()
	_, unsub2 := bus.Subscribe()
	if got := bus.SubscribersCount(); got != 2 {
		t.Fatalf("count = %d, want 2", got)
	}
	unsub1()
	unsub2()
	if got := bus.SubscribersCount(); got != 0 {
		t.Fatalf("after unsub count = %d, want 0", got)
	}
}

func TestNilPublisherNoOp(t *testing.T) {
	NilPublisher{}.Publish(TaskCreated{ID: 1}) // must not panic
}