import { purry } from './purry';

export interface Stats {
  min: number;
  max: number;
  arithmetic_mean: number;
  median: number;
  geometric_mean: number;
  middle: number;
  quadratic_mean: number;
  sum: number;
}

function _stats<X>(data: ReadonlyArray<X>, fn?: (q: X) => number): Stats {
  const dfFn = (data: X) => {
    return (data as unknown) as number;
  };
  const numbers = data.map(fn || dfFn);
  function calcMedian(values: ReadonlyArray<number>) {
    if (values.length === 0) return 0;
    [...values].sort((a, b) => {
      return a - b;
    });

    const half = Math.floor(values.length / 2);
    if (values.length % 2) return values[half];

    return (values[half - 1] + values[half]) / 2.0;
  }
  const min = Math.min(...numbers);
  const max = Math.max(...numbers);
  const sum = numbers.reduce((acc, c) => acc + c, 0);
  return {
    sum,
    middle: (max + min) / 2,
    min: Math.min(...numbers),
    max: Math.max(...numbers),
    arithmetic_mean: sum / numbers.length,
    geometric_mean:
      numbers.reduce((acc, c) => acc * (c === 0 ? 1 : c), 1) / numbers.length,
    median: calcMedian(numbers),
    quadratic_mean: Math.sqrt(
      numbers.map(q => Math.pow(q, 2)).reduce((acc, c) => acc + c, 0)
    ),
  };
}

/**
 * Calculate objet numeric statistics
 * @param data - Array of data
 * @param fn - Function that maps to numeric data
 * @signature
 *    P.stats(data, fn)
 * @signature
 *    P.pipe(data,P.stats(fn))
 * @example
 *    P.stats([{ data: 1 }, { data: 2 }, { data: 3 }], (q) => q.data) // => { sum: 6, middle: 2, min: 1, max: 3, arithmetic_mean: 2, geometric_mean: 6, median: 2, quadratic_mean: 14 }
 *    P.pipe([1, 2, 3], P.stats((q) => q)) // => { sum: 6, middle: 2, min: 1, max: 3, arithmetic_mean: 2, geometric_mean: 6, median: 2, quadratic_mean: 14 }
 * @category Number, Pipe
 */
export function stats<T>(data: readonly T[], fn: (item: T) => number): Stats;
export function stats(data: readonly number[]): Stats;
export function stats<T>(
  fn: (item: T) => number
): (array: readonly T[]) => Stats;

export function stats() {
  return purry(_stats, arguments);
}