import {
  ArrTypeId,
  concreteChunk,
  SingletonTypeId
} from "@tsplus/stdlib/collections/Chunk/definition"

/**
 * Folds over the elements in this chunk from the right.
 *
 * @tsplus static Chunk.Aspects reduceRight
 * @tsplus pipeable Chunk reduceRight
 */
export function reduceRight<A, S>(s: S, f: (a: A, s: S) => S) {
  return (self: Chunk<A>): S => {
    concreteChunk(self)

    switch (self._typeId) {
      case SingletonTypeId: {
        return f(self.a, s)
      }
      case ArrTypeId: {
        const arr = self._arrayLike()
        const len = arr.length
        let s1 = s
        let i = len - 1
        while (i >= 0) {
          s1 = f(arr[i]!, s1)
          i--
        }
        return s1
      }
      default: {
        const iterator = self._reverseArrayLikeIterator()
        let next
        let s1 = s

        while ((next = iterator.next()) && !next.done) {
          const array = next.value
          const len = array.length
          let i = len - 1
          while (i >= 0) {
            const a = array[i]!
            s1 = f(a, s1)
            i--
          }
        }

        return s1
      }
    }
  }
}