package geo

import (
	"net"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

func TestSwappableEmptyAnswersNotLoaded(t *testing.T) {
	s := NewSwappable()
	if snap := s.Lookup(net.ParseIP("81.2.69.142")); snap.Loaded || snap.Found || snap.Source != "" {
		t.Fatalf("empty swappable = %+v", snap)
	}
	if _, ok := s.Locate(net.ParseIP("81.2.69.142")); ok {
		t.Fatal("empty swappable located")
	}
	var _ Locator = s
}

func TestSwappableSnapshotCarriesItsReadersSource(t *testing.T) {
	s := NewSwappable()
	m, err := OpenMMDB("testdata/GeoIP2-City-Test.mmdb")
	if err != nil {
		t.Fatal(err)
	}
	s.Swap(m)
	snap := s.Lookup(net.ParseIP("81.2.69.142"))
	if !snap.Loaded || !snap.Found || snap.Source != "GeoIP2-City" || snap.Result.Country != "GB" {
		t.Fatalf("snapshot = %+v", snap)
	}
	miss := s.Lookup(net.ParseIP("10.0.0.1"))
	if !miss.Loaded || miss.Found || miss.Source != "GeoIP2-City" {
		t.Fatalf("a miss with a loaded reader must say Loaded and name the source: %+v", miss)
	}
	s.Swap(nil)
	if snap := s.Lookup(net.ParseIP("81.2.69.142")); snap.Loaded {
		t.Fatalf("after Swap(nil) = %+v", snap)
	}
}

// Review Focus 3: no lookup ever runs on a closed reader, and a snapshot's
// source always belongs to the reader that answered.
func TestSwappableNeverLooksUpAClosedReader(t *testing.T) {
	s := NewSwappable()
	var closedWhileInUse atomic.Bool
	mk := func(src string) *MMDB {
		var inUse atomic.Int32
		var closed atomic.Bool
		m := &MMDB{source: src}
		m.lookup = func(_ net.IP, result any) error {
			inUse.Add(1)
			defer inUse.Add(-1)
			if closed.Load() {
				closedWhileInUse.Store(true)
			}
			rec := result.(*mmdbRecord)
			rec.Country.ISOCode = src[:2]
			time.Sleep(time.Microsecond)
			return nil
		}
		m.closeHook = func() {
			if inUse.Load() != 0 {
				closedWhileInUse.Store(true)
			}
			closed.Store(true)
		}
		return m
	}
	s.Swap(mk("AAsrc"))
	var wg sync.WaitGroup
	stop := make(chan struct{})
	var mismatched atomic.Bool
	for i := 0; i < 32; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for {
				select {
				case <-stop:
					return
				default:
				}
				snap := s.Lookup(net.ParseIP("81.2.69.142"))
				if snap.Found && snap.Result.Country != snap.Source[:2] {
					mismatched.Store(true)
				}
				s.Locate(net.ParseIP("81.2.69.142"))
			}
		}()
	}
	for i := 0; i < 100; i++ {
		if i%2 == 0 {
			s.Swap(mk("BBsrc"))
		} else {
			s.Swap(mk("AAsrc"))
		}
	}
	close(stop)
	wg.Wait()
	if closedWhileInUse.Load() {
		t.Fatal("a reader was closed while a lookup was using it")
	}
	if mismatched.Load() {
		t.Fatal("a snapshot carried a different reader's source")
	}
}