package names

import (
	"context"
	"errors"
	"net"
	"net/netip"
	"sync/atomic"
	"testing"
	"time"
)

func TestNames(t *testing.T) {
	var calls atomic.Int32
	slow := make(chan struct{})
	r := NewFunc(func(ctx context.Context, addr string) ([]string, error) {
		calls.Add(1)
		switch addr {
		case "10.0.0.1":
			return []string{"nas.example.net."}, nil
		case "10.0.0.2":
			return nil, &net.DNSError{Err: "no such host", Name: addr, IsNotFound: true}
		case "10.0.0.3":
			return nil, errors.New("server failure")
		case "10.0.0.4":
			<-slow
			return []string{"slow.example.net."}, nil
		}
		return nil, nil
	}, time.Hour)
	a := netip.MustParseAddr
	all := []netip.Addr{a("10.0.0.1"), a("10.0.0.2"), a("10.0.0.3"), a("10.0.0.4")}

	got := r.Names(context.Background(), all, 200*time.Millisecond)
	if len(got) != 1 || got[a("10.0.0.1")] != "nas.example.net" {
		t.Fatalf("first call: %v", got)
	}
	// The slow lookup finishes later and is there next time; the others
	// come from the cache, the failure too until it is retried.
	close(slow)
	time.Sleep(50 * time.Millisecond)
	got = r.Names(context.Background(), all, 200*time.Millisecond)
	if len(got) != 2 || got[a("10.0.0.4")] != "slow.example.net" {
		t.Fatalf("second call: %v", got)
	}
	if n := calls.Load(); n != 4 {
		t.Fatalf("%d lookups, want 4 (cached)", n)
	}

	// A failure is tried again after retry, a missing name after ttl.
	now := time.Now().Add(2 * time.Minute)
	r.now = func() time.Time { return now }
	r.Names(context.Background(), all, 200*time.Millisecond)
	if n := calls.Load(); n != 5 {
		t.Fatalf("%d lookups, want 5 (the failure again)", n)
	}
}