package comm

import (
	"context"
	"errors"
	"fmt"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/bus"
)

// recvEvent 阻塞到 ch 上到达一个事件或 d 到期，超时则判测试失败。它让投递断言确定化，
// 而不必依赖干等的 sleep。
func recvEvent(t *testing.T, ch <-chan Event, d time.Duration) Event {
	t.Helper()
	select {
	case e := <-ch:
		return e
	case <-time.After(d):
		t.Fatalf("timed out waiting for an event after %v", d)
		return Event{}
	}
}

func TestSubjectConvention(t *testing.T) {
	t.Parallel()

	cases := []struct {
		name string
		got  string
		want string
	}{
		{"ask", askSubject("alice", "bob"), "cyrene.agent.alice.bob.ask"},
		{"reply carries ask id", replySubject("bob", "alice", "alice-3"), "cyrene.agent.bob.alice.reply.alice-3"},
		{"event addressed", eventSubject("alice", "bob"), "cyrene.agent.alice.bob.event"},
		{"event broadcast", broadcastEventSubject("alice"), "cyrene.agent.alice.event"},
		{"ask receive pattern", askReceivePattern("bob"), "cyrene.agent.*.bob.ask"},
		{"agent ids sanitized", askSubject("a.b", "c d"), "cyrene.agent.a_b.c_d.ask"},
	}
	for _, c := range cases {
		c := c
		t.Run(c.name, func(t *testing.T) {
			t.Parallel()
			if c.got != c.want {
				t.Fatalf("subject = %q, want %q", c.got, c.want)
			}
		})
	}
}

func TestEventReceivePatterns(t *testing.T) {
	t.Parallel()

	got := eventReceivePatterns("bob")
	want := []string{"cyrene.agent.*.event", "cyrene.agent.*.bob.event"}
	if len(got) != len(want) {
		t.Fatalf("patterns = %v, want %v", got, want)
	}
	for i := range want {
		if got[i] != want[i] {
			t.Fatalf("patterns[%d] = %q, want %q", i, got[i], want[i])
		}
	}
}

func TestAskReply_RoundTrip(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")
	bob := New(b, "bob")

	unsub, err := bob.SubscribeAsk(context.Background(), func(ctx context.Context, a Ask) error {
		return bob.Answer(ctx, a.From, a.ID, "pong:"+a.Question, a.Data)
	})
	if err != nil {
		t.Fatalf("SubscribeAsk: %v", err)
	}
	defer unsub()

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	reply, err := alice.Ask(ctx, "bob", "ping", "payload")
	if err != nil {
		t.Fatalf("Ask: %v", err)
	}
	if reply.Text != "pong:ping" {
		t.Fatalf("reply.Text = %q, want pong:ping", reply.Text)
	}
	if reply.From != "bob" {
		t.Fatalf("reply.From = %q, want bob", reply.From)
	}
	if reply.To != "alice" {
		t.Fatalf("reply.To = %q, want alice", reply.To)
	}
	if reply.Data != "payload" {
		t.Fatalf("reply.Data = %#v, want payload", reply.Data)
	}
}

func TestAsk_TimeoutNoReply(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")
	// bob 没有任何 ask 处理函数，因此永远不会有人回复。

	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
	defer cancel()

	_, err := alice.Ask(ctx, "bob", "hello", nil)
	if !errors.Is(err, ErrTimeout) {
		t.Fatalf("Ask err = %v, want ErrTimeout", err)
	}
}

func TestAsk_ContextCanceled(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")

	ctx, cancel := context.WithCancel(context.Background())
	got := make(chan error, 1)
	go func() {
		_, err := alice.Ask(ctx, "bob", "hello", nil)
		got <- err
	}()
	time.Sleep(50 * time.Millisecond)
	cancel()

	select {
	case err := <-got:
		if !errors.Is(err, context.Canceled) {
			t.Fatalf("Ask err = %v, want context.Canceled", err)
		}
	case <-time.After(2 * time.Second):
		t.Fatal("Ask did not return after ctx cancel")
	}
}

func TestAsk_ContextPreCanceled(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")

	ctx, cancel := context.WithCancel(context.Background())
	cancel()

	_, err := alice.Ask(ctx, "bob", "q", nil)
	if !errors.Is(err, context.Canceled) {
		t.Fatalf("Ask err = %v, want context.Canceled", err)
	}
}

func TestEventBroadcast(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")
	bob := New(b, "bob")

	events := make(chan Event, 4)
	unsub, err := bob.SubscribeEvent(context.Background(), func(ctx context.Context, e Event) error {
		events <- e
		return nil
	})
	if err != nil {
		t.Fatalf("SubscribeEvent: %v", err)
	}
	defer unsub()

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	if err := alice.PublishEvent(ctx, Event{Name: "tick", Data: 7}); err != nil {
		t.Fatalf("PublishEvent: %v", err)
	}
	e := recvEvent(t, events, 2*time.Second)
	if e.Name != "tick" || e.Data != 7 || e.From != "alice" {
		t.Fatalf("event = %+v, want name=tick data=7 from=alice", e)
	}
}

func TestEventSend_AddressedAndIsolated(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")
	bob := New(b, "bob")
	carol := New(b, "carol")

	bobEvents := make(chan Event, 4)
	carolEvents := make(chan Event, 4)

	unsubBob, err := bob.SubscribeEvent(context.Background(), func(ctx context.Context, e Event) error {
		bobEvents <- e
		return nil
	})
	if err != nil {
		t.Fatalf("SubscribeEvent bob: %v", err)
	}
	defer unsubBob()
	unsubCarol, err := carol.SubscribeEvent(context.Background(), func(ctx context.Context, e Event) error {
		carolEvents <- e
		return nil
	})
	if err != nil {
		t.Fatalf("SubscribeEvent carol: %v", err)
	}
	defer unsubCarol()

	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()

	if err := alice.Send(ctx, "bob", Event{Name: "direct"}); err != nil {
		t.Fatalf("Send: %v", err)
	}
	e := recvEvent(t, bobEvents, 2*time.Second)
	if e.Name != "direct" || e.From != "alice" {
		t.Fatalf("bob event = %+v, want name=direct from=alice", e)
	}

	// 定向给 bob 的事件不得抵达 carol。
	select {
	case e := <-carolEvents:
		t.Fatalf("carol unexpectedly received %+v", e)
	case <-time.After(100 * time.Millisecond):
	}
}

func TestEventHandler_Concurrent(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	emitter := New(b, "emit")
	recv := New(b, "recv")

	const n = 100
	var got atomic.Int64
	done := make(chan struct{})
	unsub, err := recv.SubscribeEvent(context.Background(), func(ctx context.Context, e Event) error {
		if got.Add(1) == n {
			close(done)
		}
		return nil
	})
	if err != nil {
		t.Fatalf("SubscribeEvent: %v", err)
	}
	defer unsub()

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	// 混合发射广播与定向给 recv 的事件，使两个事件订阅（及其各自的工作 goroutine）
	// 并发调用处理函数。
	var wg sync.WaitGroup
	for i := 0; i < n; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			if i%2 == 0 {
				_ = emitter.PublishEvent(ctx, Event{Name: "bc", Data: i})
			} else {
				_ = emitter.Send(ctx, "recv", Event{Name: "to", Data: i})
			}
		}(i)
	}
	wg.Wait()

	select {
	case <-done:
	case <-time.After(3 * time.Second):
		t.Fatalf("only %d of %d events delivered", got.Load(), n)
	}
}

func TestAsk_ConcurrentDistinct(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")
	bob := New(b, "bob")

	unsub, err := bob.SubscribeAsk(context.Background(), func(ctx context.Context, a Ask) error {
		return bob.Answer(ctx, a.From, a.ID, "ack:"+a.Question, a.Data)
	})
	if err != nil {
		t.Fatalf("SubscribeAsk: %v", err)
	}
	defer unsub()

	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	const n = 20
	var wg sync.WaitGroup
	errs := make(chan error, n)
	for i := 0; i < n; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			q := fmt.Sprintf("q%d", i)
			reply, err := alice.Ask(ctx, "bob", q, i)
			if err != nil {
				errs <- fmt.Errorf("ask %d: %w", i, err)
				return
			}
			if reply.Text != "ack:"+q {
				errs <- fmt.Errorf("ask %d: reply.Text = %q, want %q", i, reply.Text, "ack:"+q)
				return
			}
			if reply.Data != i {
				errs <- fmt.Errorf("ask %d: reply.Data = %#v, want %d", i, reply.Data, i)
				return
			}
		}(i)
	}
	wg.Wait()
	close(errs)
	for err := range errs {
		t.Fatal(err)
	}
}

func TestSend_NoErrorAndNoReceiver(t *testing.T) {
	t.Parallel()

	b := bus.New()
	defer b.Close()
	alice := New(b, "alice")

	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	// 向没有订阅者的 subject 发布是空操作，不是错误。
	if err := alice.Send(ctx, "ghost", Event{Name: "nobody"}); err != nil {
		t.Fatalf("Send to lost receiver: %v", err)
	}
	if err := alice.PublishEvent(ctx, Event{Name: "nobody"}); err != nil {
		t.Fatalf("PublishEvent with no subscriber: %v", err)
	}
}