package lock

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

func TestTryAcquireLLM(t *testing.T) {
	lk := New(nil)
	if !lk.TryAcquireLLM() {
		t.Fatal("TryAcquireLLM on idle lock should succeed")
	}
	if _, n, _ := lk.Snapshot(); n != 1 {
		t.Fatalf("n = %d, want 1", n)
	}

	// While an image job is pending, TryAcquireLLM must fail.
	imageWaiting := make(chan struct{})
	go func() {
		lk.AcquireImage(context.Background())
		close(imageWaiting)
	}()
	deadline := time.Now().Add(2 * time.Second)
	for {
		lk.mu.Lock()
		queued := len(lk.imageQ)
		lk.mu.Unlock()
		if queued == 1 {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("image waiter never queued")
		}
		time.Sleep(time.Millisecond)
	}
	if lk.TryAcquireLLM() {
		t.Fatal("TryAcquireLLM with image pending should fail")
	}

	lk.ReleaseLLM()
	<-imageWaiting
	if lk.TryAcquireLLM() {
		t.Fatal("TryAcquireLLM with image active should fail")
	}
	lk.ReleaseImage()
	if !lk.TryAcquireLLM() {
		t.Fatal("TryAcquireLLM after image release should succeed")
	}
	lk.ReleaseLLM()
}