export class CircularQueue<T> {
  private startIndex: number;
  private endIndex: number;
  private _data: T[];
  private _size: number;
  private _capacity: number;

  constructor(
    size: number,
  ) {
    // See the Mozilla documentation on sparse arrays (*not* undefined values)
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Indexed_collections#sparse_arrays
    this._data = new Array<T>(size);
    this.startIndex = 0;
    this.endIndex = 0;
    this._size = 0;
    this._capacity = size;
  }

  size = (): number => this._size;

  get = (index: number): T | undefined => {
    if (index < 0 || index >= this._size) {
      return undefined;
    }
    const actualIndex = (this.startIndex + index) % this._capacity;
    return this._data[actualIndex];
  };

  appendWithSorting = (
    data: T,
    sortingCallback: (a: T, b: T) => number
  ) => {
    if (this._size === 0) {
      this._data[this.startIndex] = data;
      this._size = 1;
      this.endIndex = this.startIndex;
      return;
    }

    const lastItem = this.get(this._size - 1);
    const isAlreadyInOrder = lastItem && sortingCallback(lastItem, data) <= 0;

    if (this._size < this._capacity) {
      this.endIndex = (this.endIndex + 1) % this._capacity;
      this._data[this.endIndex] = data;
      this._size++;
    } else {
      this.startIndex = (this.startIndex + 1) % this._capacity;
      this.endIndex = (this.endIndex + 1) % this._capacity;
      this._data[this.endIndex] = data;
    }

    if (!isAlreadyInOrder) {
      this.sortData(sortingCallback);
    }
  }

  popFront = () => {
    if (this._size === 0) {
      return;
    }

    this._data[this.startIndex] = undefined as any;
    if (this._size === 1) {
      this._size = 0;
      this.startIndex = 0;
      this.endIndex = 0;
    } else {
      this.startIndex = (this.startIndex + 1) % this._capacity;
      this._size--;
    }
  }

  binarySearch = <K>(
    searchKey: K,
    keyExtractor: (item: T) => K
  ): T | undefined => {
    if (this._size === 0) {
      return undefined;
    }

    let left = 0;
    let right = this._size - 1;

    while (left <= right) {
      const mid = Math.floor((left + right) / 2);
      const midItem = this.get(mid)!;
      const midKey = keyExtractor(midItem);

      if (midKey === searchKey) {
        return midItem;
      } else if (midKey < searchKey) {
        left = mid + 1;
      } else {
        right = mid - 1;
      }
    }

    return undefined;
  }

  private sortData = (sortingCallback: (a: T, b: T) => number) => {
    const items: T[] = [];
    for (let i = 0; i < this._size; i++) {
      const item = this.get(i);
      if (item !== undefined) {
        items.push(item);
      }
    }

    items.sort(sortingCallback);

    for (let i = 0; i < items.length; i++) {
      const actualIndex = (this.startIndex + i) % this._capacity;
      this._data[actualIndex] = items[i];
    }
  };
}