package agent_test

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

	"chat-agent-system/internal/agent"
)

type slowBackend struct {
	running atomic.Int32
	peak    atomic.Int32
}

func (s *slowBackend) Name() string { return "slow" }

func (s *slowBackend) Execute(ctx context.Context, req agent.Request) (*agent.Result, error) {
	cur := s.running.Add(1)
	for {
		p := s.peak.Load()
		if cur <= p || s.peak.CompareAndSwap(p, cur) {
			break
		}
	}
	time.Sleep(40 * time.Millisecond)
	s.running.Add(-1)
	return &agent.Result{Success: true}, nil
}

func TestLimitingBackendCapsConcurrency(t *testing.T) {
	inner := &slowBackend{}
	limited := agent.WrapWithConcurrencyLimit(inner, 2)

	var wg sync.WaitGroup
	for i := 0; i < 6; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			_, _ = limited.Execute(context.Background(), agent.Request{})
		}()
	}
	wg.Wait()

	if peak := inner.peak.Load(); peak > 2 {
		t.Fatalf("expected peak concurrency <= 2, got %d", peak)
	}
}