From 6f663b0bc1d9fcc6bbdfbb37c28d912ee267d98b Mon Sep 17 00:00:00 2001
From: Alexander Demidenko <hurd@yandex-team.ru>
Date: Thu, 14 Dec 2023 14:45:46 +0300
Subject: [PATCH] fix for deleting the last element

---
 ring.go      | 26 +++++++++++++++++---------
 ring_test.go | 11 +++++++++++
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/ring.go b/ring.go
index 38dc2b5..3408b47 100644
--- a/ring.go
+++ b/ring.go
@@ -14,9 +14,9 @@ import (
 
 const DefaultMagicFactor = 1020
 
-type Item interface {
-	io.WriterTo
-}
+// this will allow you to have multiple hashring implementations
+// in a third-party project
+type Item = io.WriterTo
 
 // Ring is a consistent hashing hashring.
 // It is goroutine safe. Ring instances must not be copied.
@@ -329,19 +329,27 @@ func (r *Ring) deletePoint(tree avl.Tree, p *point) (_ avl.Tree, removed bool) {
 	return tree, true
 }
 
-func (r *Ring) magicFactor() int {
+func (r *Ring) magicFactor() float64 {
 	if m := r.MagicFactor; m > 0 {
-		return m
+		return float64(m)
 	}
 	return DefaultMagicFactor
 }
 
 // r.mu must be held.
-func (r *Ring) rebuild() {
-	numPoints := line(
-		r.maxWeight, float64(r.magicFactor()),
-		r.minWeight, math.Ceil(float64(r.magicFactor())*(r.minWeight/r.maxWeight)),
+func (r *Ring) numPoints() func(float64) int {
+	if r.maxWeight == 0 {
+		return func(float64) int { return 0 }
+	}
+	return line(
+		r.maxWeight, r.magicFactor(),
+		r.minWeight, math.Ceil(r.magicFactor())*(r.minWeight/r.maxWeight),
 	)
+}
+
+// r.mu must be held.
+func (r *Ring) rebuild() {
+	numPoints := r.numPoints()
 
 	r.ringMu.RLock()
 	root := r.ring
diff --git a/ring_test.go b/ring_test.go
index 7b88996..6e29781 100644
--- a/ring_test.go
+++ b/ring_test.go
@@ -321,6 +321,17 @@ func TestRingDeleteNotExisting(t *testing.T) {
 	}
 }
 
+func TestRingInsertDelete(t *testing.T) {
+	var r Ring
+	x := StringItem("foo")
+	if err := r.Insert(x, 1); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if err := r.Delete(x); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
 func TestRingUpdateNotExisting(t *testing.T) {
 	var r Ring
 	x := StringItem("foo")