package kbucket

import (
	"math/rand"
	"testing"
	"time"

	"github.com/libp2p/go-libp2p-core/peer"
	"github.com/libp2p/go-libp2p-core/test"
	pstore "github.com/libp2p/go-libp2p-peerstore"
)

// Test basic features of the bucket struct
func TestBucket(t *testing.T) {
	t.Parallel()

	b := newBucket()

	peers := make([]peer.ID, 100)
	for i := 0; i < 100; i++ {
		peers[i] = test.RandPeerIDFatal(t)
		b.PushFront(peers[i])
	}

	local := test.RandPeerIDFatal(t)
	localID := ConvertPeerID(local)

	i := rand.Intn(len(peers))
	if !b.Has(peers[i]) {
		t.Errorf("Failed to find peer: %v", peers[i])
	}

	spl := b.Split(0, ConvertPeerID(local))
	llist := b.list
	for e := llist.Front(); e != nil; e = e.Next() {
		p := ConvertPeerID(e.Value.(peer.ID))
		cpl := CommonPrefixLen(p, localID)
		if cpl > 0 {
			t.Fatalf("Split failed. found id with cpl > 0 in 0 bucket")
		}
	}

	rlist := spl.list
	for e := rlist.Front(); e != nil; e = e.Next() {
		p := ConvertPeerID(e.Value.(peer.ID))
		cpl := CommonPrefixLen(p, localID)
		if cpl == 0 {
			t.Fatalf("Split failed. found id with cpl == 0 in non 0 bucket")
		}
	}
}

func TestGenRandPeerID(t *testing.T) {
	t.Parallel()

	nBuckets := 21
	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(1, ConvertPeerID(local), time.Hour, m)

	// create nBuckets
	for i := 0; i < nBuckets; i++ {
		for {
			if p := test.RandPeerIDFatal(t); CommonPrefixLen(ConvertPeerID(local), ConvertPeerID(p)) == i {
				rt.Update(p)
				break
			}
		}
	}

	// test bucket for peer
	peers := rt.ListPeers()
	for _, p := range peers {
		b := rt.BucketForID(ConvertPeerID(p))
		if !b.Has(p) {
			t.Fatalf("bucket should have peers %s", p.String())
		}
	}

	// test generate rand peer ID
	for bucketID := 0; bucketID < nBuckets; bucketID++ {
		peerID := rt.GenRandPeerID(bucketID)

		// for bucketID upto maxPrefixLen of 16, CPL should be Exactly bucketID
		if bucketID < 16 {
			if CommonPrefixLen(ConvertPeerID(peerID), rt.local) != bucketID {
				t.Fatalf("cpl should be %d for bucket %d but got %d, generated peerID is %s", bucketID, bucketID,
					CommonPrefixLen(ConvertPeerID(peerID), rt.local), peerID)
			}
		} else {
			// from bucketID 16 onwards, CPL should be ATLEAST 16
			if CommonPrefixLen(ConvertPeerID(peerID), rt.local) < 16 {
				t.Fatalf("cpl should be ATLEAST 16 for bucket %d but got %d, generated peerID is %s", bucketID,
					CommonPrefixLen(ConvertPeerID(peerID), rt.local), peerID)
			}
		}

	}
}

func TestTableCallbacks(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(10, ConvertPeerID(local), time.Hour, m)

	peers := make([]peer.ID, 100)
	for i := 0; i < 100; i++ {
		peers[i] = test.RandPeerIDFatal(t)
	}

	pset := make(map[peer.ID]struct{})
	rt.PeerAdded = func(p peer.ID) {
		pset[p] = struct{}{}
	}
	rt.PeerRemoved = func(p peer.ID) {
		delete(pset, p)
	}

	rt.Update(peers[0])
	if _, ok := pset[peers[0]]; !ok {
		t.Fatal("should have this peer")
	}

	rt.Remove(peers[0])
	if _, ok := pset[peers[0]]; ok {
		t.Fatal("should not have this peer")
	}

	for _, p := range peers {
		rt.Update(p)
	}

	out := rt.ListPeers()
	for _, outp := range out {
		if _, ok := pset[outp]; !ok {
			t.Fatal("should have peer in the peerset")
		}
		delete(pset, outp)
	}

	if len(pset) > 0 {
		t.Fatal("have peers in peerset that were not in the table", len(pset))
	}
}

// Right now, this just makes sure that it doesnt hang or crash
func TestTableUpdate(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(10, ConvertPeerID(local), time.Hour, m)

	peers := make([]peer.ID, 100)
	for i := 0; i < 100; i++ {
		peers[i] = test.RandPeerIDFatal(t)
	}

	// Testing Update
	for i := 0; i < 10000; i++ {
		rt.Update(peers[rand.Intn(len(peers))])
	}

	for i := 0; i < 100; i++ {
		id := ConvertPeerID(test.RandPeerIDFatal(t))
		ret := rt.NearestPeers(id, 5)
		if len(ret) == 0 {
			t.Fatal("Failed to find node near ID.")
		}
	}
}

func TestTableFind(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(10, ConvertPeerID(local), time.Hour, m)

	peers := make([]peer.ID, 100)
	for i := 0; i < 5; i++ {
		peers[i] = test.RandPeerIDFatal(t)
		rt.Update(peers[i])
	}

	t.Logf("Searching for peer: '%s'", peers[2])
	found := rt.NearestPeer(ConvertPeerID(peers[2]))
	if !(found == peers[2]) {
		t.Fatalf("Failed to lookup known node...")
	}
}

func TestTableEldestPreferred(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(10, ConvertPeerID(local), time.Hour, m)

	// generate size + 1 peers to saturate a bucket
	peers := make([]peer.ID, 15)
	for i := 0; i < 15; {
		if p := test.RandPeerIDFatal(t); CommonPrefixLen(ConvertPeerID(local), ConvertPeerID(p)) == 0 {
			peers[i] = p
			i++
		}
	}

	// test 10 first peers are accepted.
	for _, p := range peers[:10] {
		if _, err := rt.Update(p); err != nil {
			t.Errorf("expected all 10 peers to be accepted; instead got: %v", err)
		}
	}

	// test next 5 peers are rejected.
	for _, p := range peers[10:] {
		if _, err := rt.Update(p); err != ErrPeerRejectedNoCapacity {
			t.Errorf("expected extra 5 peers to be rejected; instead got: %v", err)
		}
	}
}

func TestTableFindMultiple(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	m := pstore.NewMetrics()
	rt := NewRoutingTable(20, ConvertPeerID(local), time.Hour, m)

	peers := make([]peer.ID, 100)
	for i := 0; i < 18; i++ {
		peers[i] = test.RandPeerIDFatal(t)
		rt.Update(peers[i])
	}

	t.Logf("Searching for peer: '%s'", peers[2])
	found := rt.NearestPeers(ConvertPeerID(peers[2]), 15)
	if len(found) != 15 {
		t.Fatalf("Got back different number of peers than we expected.")
	}
}

func assertSortedPeerIdsEqual(t *testing.T, a, b []peer.ID) {
	t.Helper()
	if len(a) != len(b) {
		t.Fatal("slices aren't the same length")
	}
	for i, p := range a {
		if p != b[i] {
			t.Fatalf("unexpected peer %d", i)
		}
	}
}

func TestTableFindMultipleBuckets(t *testing.T) {
	t.Parallel()

	local := test.RandPeerIDFatal(t)
	localID := ConvertPeerID(local)
	m := pstore.NewMetrics()

	rt := NewRoutingTable(5, localID, time.Hour, m)

	peers := make([]peer.ID, 100)
	for i := 0; i < 100; i++ {
		peers[i] = test.RandPeerIDFatal(t)
		rt.Update(peers[i])
	}

	targetID := ConvertPeerID(peers[2])

	closest := SortClosestPeers(rt.ListPeers(), targetID)
	targetCpl := CommonPrefixLen(localID, targetID)

	// Split the peers into closer, same, and further from the key (than us).
	var (
		closer, same, further []peer.ID
	)
	var i int
	for i = 0; i < len(closest); i++ {
		cpl := CommonPrefixLen(ConvertPeerID(closest[i]), targetID)
		if targetCpl >= cpl {
			break
		}
	}
	closer = closest[:i]

	var j int
	for j = len(closer); j < len(closest); j++ {
		cpl := CommonPrefixLen(ConvertPeerID(closest[j]), targetID)
		if targetCpl > cpl {
			break
		}
	}
	same = closest[i:j]
	further = closest[j:]

	// should be able to find at least 30
	// ~31 (logtwo(100) * 5)
	found := rt.NearestPeers(targetID, 20)
	if len(found) != 20 {
		t.Fatalf("asked for 20 peers, got %d", len(found))
	}

	// We expect this list to include:
	// * All peers with a common prefix length > than the CPL between our key
	//   and the target (peers in the target bucket).
	// * Then a subset of the peers with the _same_ CPL (peers in buckets to the right).
	// * Finally, other peers to the left of the target bucket.

	// First, handle the peers that are _closer_ than us.
	if len(found) <= len(closer) {
		// All of our peers are "closer".
		assertSortedPeerIdsEqual(t, found, closer[:len(found)])
		return
	}
	assertSortedPeerIdsEqual(t, found[:len(closer)], closer)

	// We've worked through closer peers, let's work through peers at the
	// "same" distance.
	found = found[len(closer):]

	// Next, handle peers that are at the same distance as us.
	if len(found) <= len(same) {
		// Ok, all the remaining peers are at the same distance.
		// unfortunately, that means we may be missing peers that are
		// technically closer.

		// Make sure all remaining peers are _somewhere_ in the "closer" set.
		pset := peer.NewSet()
		for _, p := range same {
			pset.Add(p)
		}
		for _, p := range found {
			if !pset.Contains(p) {
				t.Fatalf("unexpected peer %s", p)
			}
		}
		return
	}
	assertSortedPeerIdsEqual(t, found[:len(same)], same)

	// We've worked through closer peers, let's work through the further
	// peers.
	found = found[len(same):]

	// All _further_ peers will be correctly sorted.
	assertSortedPeerIdsEqual(t, found, further[:len(found)])

	// Finally, test getting _all_ peers. These should be in the correct
	// order.

	// Ok, now let's try finding all of them.
	found = rt.NearestPeers(ConvertPeerID(peers[2]), 100)
	if len(found) != rt.Size() {
		t.Fatalf("asked for %d peers, got %d", rt.Size(), len(found))
	}

	// We should get _all_ peers in sorted order.
	for i, p := range found {
		if p != closest[i] {
			t.Fatalf("unexpected peer %d", i)
		}
	}
}

// Looks for race conditions in table operations. For a more 'certain'
// test, increase the loop counter from 1000 to a much higher number
// and set GOMAXPROCS above 1
func TestTableMultithreaded(t *testing.T) {
	t.Parallel()

	local := peer.ID("localPeer")
	m := pstore.NewMetrics()
	tab := NewRoutingTable(20, ConvertPeerID(local), time.Hour, m)
	var peers []peer.ID
	for i := 0; i < 500; i++ {
		peers = append(peers, test.RandPeerIDFatal(t))
	}

	done := make(chan struct{})
	go func() {
		for i := 0; i < 1000; i++ {
			n := rand.Intn(len(peers))
			tab.Update(peers[n])
		}
		done <- struct{}{}
	}()

	go func() {
		for i := 0; i < 1000; i++ {
			n := rand.Intn(len(peers))
			tab.Update(peers[n])
		}
		done <- struct{}{}
	}()

	go func() {
		for i := 0; i < 1000; i++ {
			n := rand.Intn(len(peers))
			tab.Find(peers[n])
		}
		done <- struct{}{}
	}()
	<-done
	<-done
	<-done
}

func BenchmarkUpdates(b *testing.B) {
	b.StopTimer()
	local := ConvertKey("localKey")
	m := pstore.NewMetrics()
	tab := NewRoutingTable(20, local, time.Hour, m)

	var peers []peer.ID
	for i := 0; i < b.N; i++ {
		peers = append(peers, test.RandPeerIDFatal(b))
	}

	b.StartTimer()
	for i := 0; i < b.N; i++ {
		tab.Update(peers[i])
	}
}

func BenchmarkFinds(b *testing.B) {
	b.StopTimer()
	local := ConvertKey("localKey")
	m := pstore.NewMetrics()
	tab := NewRoutingTable(20, local, time.Hour, m)

	var peers []peer.ID
	for i := 0; i < b.N; i++ {
		peers = append(peers, test.RandPeerIDFatal(b))
		tab.Update(peers[i])
	}

	b.StartTimer()
	for i := 0; i < b.N; i++ {
		tab.Find(peers[i])
	}
}