import "source-map-support/register";

import { SimpleSnapshot, Snapshot } from "./snapshot";

/**
 * Represents a collection of values.
 *
 * @export
 * @interface Reservoir
 */
export interface Reservoir {

  /**
   * Gets the capacity of this reservoir.
   *
   * @returns {number}
   * @memberof Reservoir
   */
  size(): number;

  /**
   * Adds a value to the reservoir.
   *
   * @param {number} value
   * @returns {this}
   * @memberof Reservoir
   */
  update(value: number): this;

  /**
   * Creates a new snapshot of this reservoir.
   *
   * @returns {Snapshot}
   * @memberof Reservoir
   */
  snapshot(): Snapshot;

}

/**
 * Simple implementation of a reservoir.
 * It has a maximum number of values, if the maximum
 * is reached old values are replaced by new values.
 *
 * @export
 * @class DefaultReservoir
 * @implements {Reservoir}
 */
export class DefaultReservoir implements Reservoir {

  /**
   * The values.
   *
   * @private
   * @type {number[]}
   * @memberof DefaultReservoir
   */
  private values: number[] = [];
  /**
   * The capacity of this reservoir.
   *
   * @private
   * @type {number}
   * @memberof DefaultReservoir
   */
  private maxSize: number;

  /**
   * Creates an instance of DefaultReservoir.
   *
   * @param {number} maxSize
   * @memberof DefaultReservoir
   */
  public constructor(maxSize: number) {
    this.maxSize = maxSize;
  }

  /**
   * Gets the actual number of value, but at max the specified maximum.
   *
   * @returns {number}
   * @memberof DefaultReservoir
   */
  public size(): number {
    return this.values.length;
  }

  /**
   * Adds the value to the array of numbers until the maximum number of
   * values is reached. If the maximum number of values is reached
   * an old value at a random position is replaced with the specified value.
   *
   * @param {number} value
   * @returns {this}
   * @memberof DefaultReservoir
   */
  public update(value: number): this {
    if (this.values.length < this.maxSize) {
      this.values.push(value);
    } else {
      const randomIndex: number = Math.round(Math.random() * this.values.length);
      this.values[randomIndex % this.values.length] = value;
    }
    return this;
  }

  /**
   * Creates a new snapshot instance.
   *
   * @returns {Snapshot}
   * @memberof DefaultReservoir
   */
  public snapshot(): Snapshot {
    return new SimpleSnapshot(this.values);
  }

}

/**
 * A reservoir that keeps the order of values and restarts
 * at the beginning if the maximum number of values is reached.
 *
 * @export
 * @class SlidingWindowReservoir
 * @implements {Reservoir}
 */
export class SlidingWindowReservoir implements Reservoir {

  /**
   * The values.
   *
   * @private
   * @type {number[]}
   * @memberof SlidingWindowReservoir
   */
  private values: number[] = [];
  /**
   * The capacity of the reservoir.
   *
   * @private
   * @type {number}
   * @memberof SlidingWindowReservoir
   */
  private maxSize: number;
  /**
   * The current index in the value array.
   *
   * @private
   * @type {number}
   * @memberof SlidingWindowReservoir
   */
  private index: number = 0;

  /**
   * Creates an instance of SlidingWindowReservoir.
   *
   * @param {number} maxSize
   * @memberof SlidingWindowReservoir
   */
  public constructor(maxSize: number) {
    this.maxSize = maxSize;
  }

  /**
   * Gets the number of values, but at may the capacity of the reservoir.
   *
   * @returns {number}
   * @memberof SlidingWindowReservoir
   */
  public size(): number {
    return this.values.length;
  }

  /**
   * Adds the value to the array of values until the capacity
   * of the reservoir is reached. If the maximum number of
   * values is reached, the insertion restarts at the beginning.
   *
   * @param {number} value
   * @returns {this}
   * @memberof SlidingWindowReservoir
   */
  public update(value: number): this {
    if (this.values.length < this.maxSize) {
      this.values.push(value);
    } else {
      this.values[this.index++ % this.values.length] = value;
    }
    return this;
  }

  /**
   * Creates a new snapshot using the values array.
   *
   * @returns {Snapshot}
   * @memberof SlidingWindowReservoir
   */
  public snapshot(): Snapshot {
    return new SimpleSnapshot(this.values);
  }

}