rubico/_internal/genericReduce.js

[a]synchronous functional programming

const isArray = require('./isArray')
const objectValues = require('./objectValues')
const isGeneratorFunction = require('./isGeneratorFunction')
const isAsyncGeneratorFunction = require('./isAsyncGeneratorFunction')
const iteratorReduce = require('./iteratorReduce')
const asyncIteratorReduce = require('./asyncIteratorReduce')
const symbolIterator = require('./symbolIterator')
const symbolAsyncIterator = require('./symbolAsyncIterator')
const __ = require('./placeholder')
const curry2 = require('./curry2')
const curryArgs3 = require('./curryArgs3')
const arrayReduce = require('./arrayReduce')
const objectReduce = require('./objectReduce')
const mapReduce = require('./mapReduce')
const reducerConcat = require('./reducerConcat')

/**
 * @name genericReduce
 *
 * @synopsis
 * ```coffeescript [specscript]
 * Foldable<T> = Iterable<T>|AsyncIterable<T>
 *   |{ reduce: (any, T)=>any }|Object<T>
 *
 * genericReduce<T>(
 *   collection Foldable<T>,
 *   reducer (any, T)=>any,
 *   result any?,
 * ) -> result
 * ```
 *
 * @related genericReduceConcurrent
 *
 * @TODO genericReduceSync(collection, reducer, init) - performance optimization for some of these genericReduces that we know are synchronous
 *
 * @TODO genericReducePool(poolSize, collection, reducer, init) - for some of these genericReduces that we want to race - result should not care about order of concatenations
 * reduce.pool
 * transform.pool
 * flatMap.pool
 */
const genericReduce = function (collection, reducer, result) {
  if (isArray(collection)) {
    return arrayReduce(collection, reducer, result)
  }
  if (collection == null) {
    return result === undefined
      ? curry2(reducer, collection, __)
      : reducer(result, collection)
  }

  if (collection.constructor == Map) {
    return mapReduce(collection, reducer, result)
  }
  if (typeof collection[symbolIterator] == 'function') {
    return iteratorReduce(
      collection[symbolIterator](), reducer, result)
  }
  if (typeof collection[symbolAsyncIterator] == 'function') {
    return asyncIteratorReduce(
      collection[symbolAsyncIterator](), reducer, result)
  }
  if (typeof collection.reduce == 'function') {
    return collection.reduce(reducer, result)
  }
  if (typeof collection.chain == 'function') {
    return collection.chain(curry2(reducer, result, __))
  }
  if (typeof collection.flatMap == 'function') {
    return collection.flatMap(curry2(reducer, result, __))
  }
  if (collection.constructor == Object) {
    return objectReduce(collection, reducer, result)
  }
  return result === undefined
    ? curry2(reducer, collection, __)
    : reducer(result, collection)
}

module.exports = genericReduce