From 27152cb1450f26363e5b6d55f308dfe958728a4d Mon Sep 17 00:00:00 2001
From: Kleissner <peter@kleissner.investments>
Date: Thu, 22 Apr 2021 05:45:46 +0200
Subject: [PATCH] Provide old and new peer in ShouldEvict. New comparison
 function IsNodeCloser. Remove unused code (which was likely buggy anyway).

---
 dht/DHT Lite.go   | 12 ++++++++++--
 dht/Hash Table.go | 30 ++----------------------------
 dht/Node.go       |  6 +-----
 3 files changed, 13 insertions(+), 35 deletions(-)

diff --git a/dht/DHT Lite.go b/dht/DHT Lite.go
index 87cecef..36b2063 100644
--- a/dht/DHT Lite.go	
+++ b/dht/DHT Lite.go	
@@ -25,8 +25,8 @@ type DHT struct {
 
 	// Functions below must be set and provided by the caller.
 
-	// ShouldEvict determines whether the given node shall be evicted
-	ShouldEvict func(node *Node) bool
+	// ShouldEvict determines whether node 1 shall be evicted in favor of node 2
+	ShouldEvict func(node1, node2 *Node) bool
 
 	// SendRequestStore sends an announcement-store message to the remote node. It informs the remote node that the local one stores the given key-value.
 	SendRequestStore func(node *Node, key []byte, dataSize uint64)
@@ -88,6 +88,14 @@ func (dht *DHT) MarkNodeAsSeen(ID []byte) {
 	dht.ht.markNodeAsSeen(dht.ht.getBucketIndexFromDifferingBit(ID), ID)
 }
 
+// IsNodeCloser compares 2 nodes to self. If true, the first node is closer (= smaller distance) to self than the second.
+func (dht *DHT) IsNodeCloser(node1, node2 []byte) bool {
+	iDist := getDistance(node1, dht.ht.Self.ID)
+	jDist := getDistance(node2, dht.ht.Self.ID)
+
+	return iDist.Cmp(jDist) == -1
+}
+
 // ---- Synchronous network query functions below ----
 
 // Store informs the network about data stored locally.
diff --git a/dht/Hash Table.go b/dht/Hash Table.go
index 551a3f5..3dc48ca 100644
--- a/dht/Hash Table.go	
+++ b/dht/Hash Table.go	
@@ -9,7 +9,6 @@ package dht
 import (
 	"bytes"
 	"math"
-	"math/big"
 	"math/rand"
 	"sort"
 	"sync"
@@ -137,7 +136,7 @@ func (ht *hashTable) getClosestContacts(num int, target []byte, filterFunc NodeF
 	return sl
 }
 
-func (ht *hashTable) insertNode(node *Node, shouldEvict func(*Node) bool) {
+func (ht *hashTable) insertNode(node *Node, shouldEvict func(nodeOld *Node, nodeNew *Node) bool) {
 	index := ht.getBucketIndexFromDifferingBit(node.ID)
 
 	// If the node already exist, mark it as seen
@@ -154,7 +153,7 @@ func (ht *hashTable) insertNode(node *Node, shouldEvict func(*Node) bool) {
 	bucket := ht.RoutingTable[index]
 
 	if len(bucket) == ht.bSize {
-		if shouldEvict(bucket[0]) {
+		if shouldEvict(bucket[0], node) {
 			bucket = append(bucket, node)
 			bucket = bucket[1:]
 		}
@@ -181,37 +180,12 @@ func (ht *hashTable) removeNode(ID []byte) {
 	ht.RoutingTable[index] = bucket
 }
 
-func (ht *hashTable) getAllNodesInBucketCloserThan(bucket int, id []byte) [][]byte {
-	b := ht.RoutingTable[bucket]
-	var nodes [][]byte
-	for _, v := range b {
-		d1 := ht.getDistance(id, ht.Self.ID)
-		d2 := ht.getDistance(id, v.ID)
-
-		result := d1.Sub(d1, d2)
-		if result.Sign() > -1 {
-			nodes = append(nodes, v.ID)
-		}
-	}
-
-	return nodes
-}
-
 func (ht *hashTable) getTotalNodesInBucket(bucket int) int {
 	ht.mutex.Lock()
 	defer ht.mutex.Unlock()
 	return len(ht.RoutingTable[bucket])
 }
 
-func (ht *hashTable) getDistance(id1 []byte, id2 []byte) *big.Int {
-	dst := make([]byte, ht.bSize)
-	for i := 0; i < ht.bSize; i++ {
-		dst[i] = id1[i] ^ id2[i]
-	}
-	ret := big.NewInt(0)
-	return ret.SetBytes(dst[:])
-}
-
 func (ht *hashTable) getRandomIDFromBucket(bucket int) []byte {
 	ht.mutex.Lock()
 	defer ht.mutex.Unlock()
diff --git a/dht/Node.go b/dht/Node.go
index ff849c8..22611a4 100644
--- a/dht/Node.go
+++ b/dht/Node.go
@@ -90,11 +90,7 @@ func (n *shortList) Less(i, j int) bool {
 	iDist := getDistance(n.Nodes[i].ID, n.Comparator)
 	jDist := getDistance(n.Nodes[j].ID, n.Comparator)
 
-	if iDist.Cmp(jDist) == -1 {
-		return true
-	}
-
-	return false
+	return iDist.Cmp(jDist) == -1
 }
 
 func getDistance(id1 []byte, id2 []byte) *big.Int {