import "source-map-support/register";

/**
 * A static state of a collection of values.
 *
 * @export
 * @interface Snapshot
 */
export interface Snapshot {

  /**
   * Gets the value of 75% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  get75thPercentile(): number;

  /**
   * Gets the value of 95% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  get95thPercentile(): number;

  /**
   * Gets the value of 98% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  get98thPercentile(): number;

  /**
   * Gets the value of 99.9% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  get999thPercentile(): number;

  /**
   * Gets the value of 99% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  get99thPercentile(): number;

  /**
   * Gets the value of 50% boundary.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  getMedian(): number;

  /**
   * Gets the maximum value.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  getMax(): number;

  /**
   * Gets the minimum value.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  getMin(): number;

  /**
   * Gets all values.
   *
   * @returns {number[]}
   * @memberof Snapshot
   */
  getValues(): number[];

  /**
   * Gets the number of values.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  size(): number;

  /**
   * Gets the average of all values.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  getMean(): number;

  /**
   * Gets the average deviation among the values.
   *
   * @returns {number}
   * @memberof Snapshot
   */
  getStdDev(): number;

  /**
   * Gets the value of boundary specified.
   *
   * @param {number} quantile
   * @returns {number}
   * @memberof Snapshot
   */
  getValue(quantile: number): number;

}

/**
 * A serialized version of {@link Snapshot}.
 *
 * @export
 * @interface SerializedSnapshot
 */
export interface SerializedSnapshot {
  /**
   * A sorted array of samples.
   *
   * @type {number[]}
   * @memberof SerializedSnapshot
   */
  values: number[];
}

/**
 * Default implementation of the {@link Snapshot} interface.
 *
 * @export
 * @class SimpleSnapshot
 * @implements {Snapshot}
 */
export class SimpleSnapshot implements Snapshot, SerializedSnapshot {

  /**
   * Sorted collection of values.
   *
   * @public
   * @type {number[]}
   * @memberof SimpleSnapshot
   */
  public values: number[] = [];

  /**
   * Creates an instance of SimpleSnapshot.
   *
   * @param {number[]} values
   * @memberof SimpleSnapshot
   */
  public constructor(values: number[]) {
    this.values = values.slice(0, values.length);
    this.values = this.values.sort((a, b) => a - b);
  }

  /**
   * Calls getValue(0.75) to get the value of the 75% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public get75thPercentile(): number {
    return this.getValue(0.75);
  }

  /**
   * Calls getValue(0.95) to get the value of the 95% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public get95thPercentile(): number {
    return this.getValue(0.95);
  }

  /**
   * Calls getValue(0.98) to get the value of the 98% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public get98thPercentile(): number {
    return this.getValue(0.98);
  }

  /**
   * Calls getValue(0.999) to get the value of the 99.9% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public get999thPercentile(): number {
    return this.getValue(0.999);
  }

  /**
   * Calls getValue(0.99) to get the value of the 99% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public get99thPercentile(): number {
    return this.getValue(0.99);
  }

  /**
   * Calls getValue(0.5) to get the value of the 50% boundary
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getMedian(): number {
    return this.getValue(0.5);
  }

  /**
   * Gets the last value of the value array.
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getMax(): number {
    return this.values[this.values.length - 1];
  }

  /**
   * Gets the first value of the value array.
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getMin(): number {
    return this.values[0];
  }

  /**
   * Gets the value array.
   *
   * @returns {number[]}
   * @memberof SimpleSnapshot
   */
  public getValues(): number[] {
    return this.values;
  }

  /**
   * Gets the length of the value array.
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public size(): number {
    return this.values.length;
  }

  /**
   * Gets average value of the value array.
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getMean(): number {
    if (this.values.length === 0) {
      return 0;
    }

    let sum = 0;
    this.values.forEach((value) => sum += value);
    return sum / this.values.length;
  }

  /**
   * Gets the average deviation among the values.
   *
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getStdDev(): number {
    if (this.values.length === 0) {
      return 0;
    }

    const mean = this.getMean();
    let sum = 0;
    this.values.forEach((value) => {
      const diff = value - mean;
      sum += diff * diff;
    });

    return Math.sqrt(sum / (this.values.length - 1));
  }

  /**
   * Gets the value of the boundary specified.
   *
   * E.g. considering the following values (sorted): [12, 20, 22, 25, 30, 32, 40, 50, 55, 56]
   *
   * quantile | position / index | value
   *
   * 0.25 | 3 | 24.25
   *
   * 0.5 | 5 | 36
   *
   * 0.75 | 8 | 51,25
   *
   * 0.95 | 10 | NaN
   *
   * @param {number} quantile
   * @returns {number}
   * @memberof SimpleSnapshot
   */
  public getValue(quantile: number): number {
    if (quantile < 0.0 || quantile > 1.0 || isNaN(quantile)) {
      return NaN;
    }

    if (this.values.length === 0) {
      return 0;
    }

    const pos = quantile * (this.values.length + 1);
    const index = Math.round(pos);

    if (index < 1) {
      return this.getMin();
    } else if (index >= this.values.length) {
      return this.getMax();
    }

    const lower = this.values[index - 1];
    const upper = this.values[index];
    return lower + (pos - Math.floor(pos)) * (upper - lower);
  }

}