Add message history to TreeNode

backend/src/Model/RingBuffer.ts

@@ -0,0 +1,60 @@
+interface Lengthwise {
+  length: number
+}
+
+export class RingBuffer<T extends Lengthwise> {
+  private capacity: number
+  private maxItems: number
+  private usage: number = 0
+  private items: (any)[] = []
+  private start: number = 0
+  private end: number = 0
+
+  constructor(capacity: number, maxItems = Infinity) {
+    this.capacity = capacity
+    this.maxItems = maxItems
+  }
+
+  public toArray() {
+    return this.items.slice(this.start, this.end)
+  }
+
+  public add(item: T) {
+    const size = item.length
+    this.enforceCapacityConstraints(size)
+    this.usage += size
+    this.items[this.end] = item
+    this.end += 1
+  }
+
+  private enforceCapacityConstraints(addedItemSize: number) {
+    const remainingSize = this.capacity - (this.usage + addedItemSize)
+    if (remainingSize < 0) {
+      this.freeSomeSpace(Math.abs(remainingSize))
+    }
+    while ((this.end - this.start) >= this.maxItems) {
+      this.dropFirst()
+    }
+  }
+
+  private freeSpace(): number {
+    return this.capacity - this.usage
+  }
+
+  private isEmpty(): boolean {
+    return this.usage === 0
+  }
+
+  private freeSomeSpace(requiredSpace: number) {
+    while (this.freeSpace() < requiredSpace && !this.isEmpty()) {
+      this.dropFirst()
+    }
+  }
+
+  private dropFirst() {
+    const freedSpace = this.items[this.start].length
+    this.usage -= freedSpace
+    delete this.items[this.start]
+    this.start += 1
+  }
+}