CircularBuffer.ts

export class CircularBuffer<ItemType> {
    length: number;
    items: Array<ItemType> = [];
    lastPosition = -1;

    constructor(size: number) {
        this.length = size;
    }

    push(item: ItemType) {
        this.lastPosition = (this.lastPosition + 1) % this.length;

        if (this.items.length === this.length) {
            this.items[this.lastPosition] = item;
        } else {
            this.items.push(item);
        }
    }

    toArray(): Array<ItemType> {
        if (this.lastPosition === this.items.length - 1) {
            return this.items;
        } else {
            return this.items.map((_, position, array) => array[(position + this.lastPosition + 1) % this.length]);
        }
    }

    setLength(newLength: number) {
        // lazy implementation
        this.items = [];
        this.lastPosition = -1;
        this.length = newLength || 0;
    }
}