array.ts

import { isNumber, isArray, isEmpty } from './is'
import { defaults } from './object'

/**
 * Check if an array contains any elements.
 * null/undefined are considered empty.
 *
 * @export
 * @param {(any[] | undefined | null)} arr
 * @returns
 */
export function isNullOrEmpty(arr: any[] | undefined | null) {
  return arr === null || arr === undefined || arr.length === 0
}

/**
 * Like flatMap, this function walks through the nested(multi-dimension) array.
 * This function keep the original dimension.
 * e.g.: deepMap([1, [2, 3]], x => x + 1) => [2, [3, 4]]
 *
 * @export
 * @param {any[]} deepArray
 * @param {(item: any, cord: number[], index: number) => any} iteratee
 * @returns
 */
export function deepMap(
  deepArray: any[],
  iteratee: (item: any, cord: number[], index: number) => any,
  pos: number[] = [],
  index: any = { i: 0 },
) {
  if (!isArray(deepArray)) {
    throw new Error(`Argument is not an array: ${deepArray}. position: ${pos}`)
  }

  return deepArray.map((item, i) => {
    if (isArray(item)) {
      return deepMap(item, iteratee, [...pos, i], index)
    } else {
      return iteratee(item, [...pos, i], index.i++)
    }
  })
}

/**
 * Swap value of array's two positions
 *
 * @export
 * @param {any[]} arr
 * @param {*} pos1
 * @param {*} pos2
 * @returns arr
 */
export function swap(arr: any[], pos1: number | number[], pos2: number | number[]): void {
  if (isNumber(pos1)) pos1 = [pos1]
  if (isNumber(pos2)) pos2 = [pos2]

  let parent1: any = []
  let parent2: any = []
  let val1 = pick(arr, ...pos1, parent1)
  let val2 = pick(arr, ...pos2, parent2)

  parent1[parent1.length - 1][pos1[pos1.length - 1]] = val2
  parent2[parent2.length - 1][pos2[pos2.length - 1]] = val1
}

/**
 * Pick a value from a deep array by its indices.
 * e.g.: pick(arr, 1, 2, 3) = arr[1][2][3]
 * if an array is supplied as the last parameter, it will be filled with arrays in each level
 * e.g.: [rootArray, subArray, ..., parentArray]
 * @export
 * @param {any[]} array
 * @param {any} indices target value indices in a deep array. e.g. the indice of value `arr[i1][i2][i3]` is [i1, i2, i3]
 * the last one can be an empty array to hold parents in each level
 * @returns {any}
 */
export function pick(array: any[], ...indices): any {
  let last = indices.pop()
  if (!isArray(last)) {
    indices.push(last)
    last = undefined
  }

  if (indices.length === 1) {
    let [i] = indices
    if (typeof i !== 'number') {
      throw Error(`Index ${JSON.stringify(i)} is not a number`)
    }
    if (array !== undefined && array.length > i && i > -1) {
      last && last.push(array)
      return array[i]
    }
    throw Error(`Out of bound`)
  }

  let [first, ...rest] = indices
  last && last.push(array) && rest.push(last)
  return pick(array[first], ...rest)
}

/**
 * Perform binary search on a sorted array. Element will be fed to predict function, if true, the target is
 * found and returned, otherwise onward function is called and the returned value determins the next
 * move:
 *   true  - left-ward continuance
 *   false - right-ward continuance
 *
 * null is returned if none is suitable
 *
 * @export
 * @template T
 * @param {T[]} array
 * @param {((i: T) => boolean | undefined)} predict
 * @param {(i: T) => boolean} onward
 * @returns {[T, number]| null} result and its index, null if not found
 */
export function binarySearch<T>(
  array: T[],
  predict: (i: T) => boolean,
  onward: (i: T) => boolean,
  start: number = 0,
  end?: number,
): [T, number] | null {
  if (isEmpty(array)) return null

  end = end || array.length

  let midIndex = ((start + end) / 2) | 0
  let testee = array[midIndex]
  if (predict(testee)) {
    return [testee, midIndex]
  }
  if (midIndex === 0 || midIndex === array.length - 1) {
    return null
  }

  let nextSection = onward(testee) ? [start, midIndex] : [midIndex, end]

  return binarySearch(array, predict, onward, ...nextSection)
}

/**
 * Experiment feature...
 *
 * @export
 * @template T
 * @param {T[]} arr
 * @param {string} keyProperty
 * @param {string} linkProperty
 * @param {string} [childrenProp='__children__']
 * @returns {T[]}
 */
export function unflatten<T>(
  arr: T[],
  keyProperty: string,
  linkProperty: string,
  childrenProp: string = '__children__',
): T[] {
  if (arr.length === 0 || arr.length === 1) {
    return arr
  }

  let result = new Array()
  let allMap = new Map<any, any>()
  let deferred = new Map<any, T[]>()

  arr.forEach(element => {
    let link = element[linkProperty]
    let key = element[keyProperty]
    allMap.set(key, element)
    if (!link) {
      result.push(element)
      let deferredChildren = deferred.get(key)
      if (deferredChildren) {
        defaults(element as any, childrenProp, [])[childrenProp].push(element)
      }
    } else {
      let parent = allMap.get(link)
      if (parent) {
        defaults(parent as any, childrenProp, [])[childrenProp].push(element)
      } else {
        let deferredList = deferred.get(link) || new Array()
        deferredList.push(element)
        deferred.set(link, deferredList)
      }
    }
  }) // cleanup
  // tslint:disable-next-line:align
  ; [deferred, allMap].forEach(m => m.clear())
  return result
}