From 4f3150d0f33a132a327a19bce9906d4fadaec6cb Mon Sep 17 00:00:00 2001
From: Thomas Nordquist <xxnerowingerxx@gmail.com>
Date: Thu, 11 Jul 2019 18:10:42 +0200
Subject: [PATCH] Add RingBuffer compactation

---
 backend/src/Model/RingBuffer.ts           | 19 +++++++++++++++++--
 backend/src/Model/spec/RingBuffer.spec.ts | 13 +++++++++++++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/backend/src/Model/RingBuffer.ts b/backend/src/Model/RingBuffer.ts
index dc15f72..5a83ec3 100644
--- a/backend/src/Model/RingBuffer.ts
+++ b/backend/src/Model/RingBuffer.ts
@@ -9,10 +9,12 @@ export class RingBuffer<T extends Lengthwise> {
   private items: Array<T> = []
   private start: number = 0
   private end: number = 0
+  private compactationFactor: number
 
-  constructor(capacity: number, maxItems = Infinity, ringBuffer?: RingBuffer<T>) {
+  constructor(capacity: number, maxItems = Infinity, compactationFactor: number = 10, ringBuffer?: RingBuffer<T>) {
     this.capacity = capacity
     this.maxItems = maxItems
+    this.compactationFactor = compactationFactor
 
     if (ringBuffer) {
       this.items = ringBuffer.toArray()
@@ -31,6 +33,11 @@ export class RingBuffer<T extends Lengthwise> {
     }
   }
 
+  private compact() {
+    this.items = this.toArray()
+    this.end = this.items.length
+  }
+
   private freeSpace(): number {
     return this.capacity - this.usage
   }
@@ -60,7 +67,7 @@ export class RingBuffer<T extends Lengthwise> {
   }
 
   public clone(): RingBuffer<T> {
-    return new RingBuffer(this.capacity, this.maxItems, this)
+    return new RingBuffer(this.capacity, this.maxItems, this.compactationFactor, this)
   }
 
   public toArray() {
@@ -71,11 +78,19 @@ export class RingBuffer<T extends Lengthwise> {
     return this.end - this.start
   }
 
+  public last(): T | undefined {
+    return this.items[this.end - 1]
+  }
+
   public add(item: T) {
     const size = item.length
     this.enforceCapacityConstraints(size)
     this.usage += size
     this.items[this.end] = item
     this.end += 1
+
+    if (this.end > 10 * this.maxItems) {
+      this.compact()
+    }
   }
 }
diff --git a/backend/src/Model/spec/RingBuffer.spec.ts b/backend/src/Model/spec/RingBuffer.spec.ts
index df4eb65..4ac8df6 100644
--- a/backend/src/Model/spec/RingBuffer.spec.ts
+++ b/backend/src/Model/spec/RingBuffer.spec.ts
@@ -16,6 +16,19 @@ describe('RingBuffer', () => {
     expect(b.toArray()[1]).to.eq('world')
   })
 
+  it('should compact array', () => {
+    const b = new RingBuffer(Infinity, 1, 3)
+    b.add('1')
+    expect((b as any).items[0]).to.eq('1')
+    b.add('2')
+    expect((b as any).items[0]).to.eq(undefined)
+    expect((b as any).items[1]).to.eq('2')
+
+    // Expect the third item to be at index 0
+    b.add('3')
+    expect((b as any).items[2]).to.eq('3')
+  })
+
   it('should remove old values if buffer size is reached', () => {
     const b = new RingBuffer(6)
     b.add('hello')