package graph

import (
	"sync"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"gitea.unbound.se/unboundsoftware/schemas/graph/model"
)

func TestPubSub_SubscribeAndPublish(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	// Subscribe
	ch := ps.Subscribe(ref)
	require.NotNil(t, ch, "Subscribe should return a channel")

	// Publish
	update := &model.SchemaUpdate{
		Ref: ref,
		ID:  "test-id-1",
		SubGraphs: []*model.SubGraph{
			{
				ID:      "sg1",
				Service: "test-service",
				Sdl:     "type Query { test: String }",
			},
		},
	}

	go ps.Publish(ref, update)

	// Receive
	select {
	case received := <-ch:
		assert.Equal(t, update.Ref, received.Ref, "Ref should match")
		assert.Equal(t, update.ID, received.ID, "ID should match")
		assert.Equal(t, len(update.SubGraphs), len(received.SubGraphs), "SubGraphs count should match")
	case <-time.After(1 * time.Second):
		t.Fatal("Timeout waiting for published update")
	}
}

func TestPubSub_MultipleSubscribers(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	// Create multiple subscribers
	ch1 := ps.Subscribe(ref)
	ch2 := ps.Subscribe(ref)
	ch3 := ps.Subscribe(ref)

	update := &model.SchemaUpdate{
		Ref: ref,
		ID:  "test-id-2",
	}

	// Publish once
	ps.Publish(ref, update)

	// All subscribers should receive the update
	var wg sync.WaitGroup
	wg.Add(3)

	checkReceived := func(ch <-chan *model.SchemaUpdate, name string) {
		defer wg.Done()
		select {
		case received := <-ch:
			assert.Equal(t, update.ID, received.ID, "%s should receive correct update", name)
		case <-time.After(1 * time.Second):
			t.Errorf("%s: Timeout waiting for update", name)
		}
	}

	go checkReceived(ch1, "Subscriber 1")
	go checkReceived(ch2, "Subscriber 2")
	go checkReceived(ch3, "Subscriber 3")

	wg.Wait()
}

func TestPubSub_DifferentRefs(t *testing.T) {
	ps := NewPubSub()

	ref1 := "Test1@dev"
	ref2 := "Test2@dev"

	ch1 := ps.Subscribe(ref1)
	ch2 := ps.Subscribe(ref2)

	update1 := &model.SchemaUpdate{Ref: ref1, ID: "id1"}
	update2 := &model.SchemaUpdate{Ref: ref2, ID: "id2"}

	// Publish to ref1
	ps.Publish(ref1, update1)

	// Only ch1 should receive
	select {
	case received := <-ch1:
		assert.Equal(t, "id1", received.ID)
	case <-time.After(100 * time.Millisecond):
		t.Fatal("ch1 should have received update")
	}

	// ch2 should not receive ref1's update
	select {
	case <-ch2:
		t.Fatal("ch2 should not receive ref1's update")
	case <-time.After(100 * time.Millisecond):
		// Expected - no update
	}

	// Publish to ref2
	ps.Publish(ref2, update2)

	// Now ch2 should receive
	select {
	case received := <-ch2:
		assert.Equal(t, "id2", received.ID)
	case <-time.After(100 * time.Millisecond):
		t.Fatal("ch2 should have received update")
	}
}

func TestPubSub_Unsubscribe(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	ch := ps.Subscribe(ref)

	// Unsubscribe
	ps.Unsubscribe(ref, ch)

	// Channel should be closed
	_, ok := <-ch
	assert.False(t, ok, "Channel should be closed after unsubscribe")

	// Publishing after unsubscribe should not panic
	assert.NotPanics(t, func() {
		ps.Publish(ref, &model.SchemaUpdate{Ref: ref})
	})
}

func TestPubSub_BufferedChannel(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	ch := ps.Subscribe(ref)

	// Publish multiple updates quickly (up to buffer size of 10)
	for i := 0; i < 10; i++ {
		update := &model.SchemaUpdate{
			Ref: ref,
			ID:  string(rune('a' + i)),
		}
		ps.Publish(ref, update)
	}

	// All 10 should be buffered and receivable
	received := 0
	timeout := time.After(1 * time.Second)

	for received < 10 {
		select {
		case <-ch:
			received++
		case <-timeout:
			t.Fatalf("Only received %d out of 10 updates", received)
		}
	}

	assert.Equal(t, 10, received, "Should receive all buffered updates")
}

func TestPubSub_SlowSubscriber(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	ch := ps.Subscribe(ref)

	// Fill the buffer (10 items)
	for i := 0; i < 10; i++ {
		ps.Publish(ref, &model.SchemaUpdate{Ref: ref})
	}

	// Publish one more - this should be dropped (channel full, non-blocking send)
	ps.Publish(ref, &model.SchemaUpdate{Ref: ref, ID: "should-be-dropped"})

	// Drain the channel
	count := 0
	timeout := time.After(500 * time.Millisecond)

drainLoop:
	for {
		select {
		case update := <-ch:
			count++
			// Should not receive the dropped update
			assert.NotEqual(t, "should-be-dropped", update.ID, "Should not receive dropped update")
		case <-timeout:
			break drainLoop
		}
	}

	// Should have received exactly 10 (the buffer size), not 11
	assert.Equal(t, 10, count, "Should only receive buffered updates, not the dropped one")
}

func TestPubSub_ConcurrentPublish(t *testing.T) {
	ps := NewPubSub()
	ref := "Test@dev"

	ch := ps.Subscribe(ref)

	numPublishers := 10
	updatesPerPublisher := 10

	var wg sync.WaitGroup
	wg.Add(numPublishers)

	// Multiple goroutines publishing concurrently
	for i := 0; i < numPublishers; i++ {
		go func(publisherID int) {
			defer wg.Done()
			for j := 0; j < updatesPerPublisher; j++ {
				ps.Publish(ref, &model.SchemaUpdate{
					Ref: ref,
					ID:  string(rune('a' + publisherID)),
				})
			}
		}(i)
	}

	wg.Wait()

	// Should not panic and subscriber should receive updates
	// (exact count may vary due to buffer and timing)
	timeout := time.After(1 * time.Second)
	received := 0

receiveLoop:
	for {
		select {
		case <-ch:
			received++
		case <-timeout:
			break receiveLoop
		}
	}

	assert.Greater(t, received, 0, "Should have received some updates")
}