sangria.marshalling.ArrayMapBuilder.scala Maven / Gradle / Ivy

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package sangria.marshalling

import scala.annotation.tailrec
import scala.collection.immutable.{ListMap, VectorBuilder}
import scala.collection.mutable.{Set => MutableSet}

/** GraphQL `Map` builder that knows keys in advance and able to preserve an original fields sort
  * order
  */
class ArrayMapBuilder[T](keys: Seq[String]) extends Iterable[(String, T)] {
  private val elements = new Array[(String, T)](keys.size)
  private val indexLookup = keys.iterator.zipWithIndex.toMap
  private val indexesSet = MutableSet[Int]()

  def add(key: String, elem: T) = {
    val idx = indexLookup(key)

    elements(idx) = key -> elem
    indexesSet += idx

    this
  }

  override lazy val toList: List[(String, T)] = {
    val builder = List.newBuilder[(String, T)]
    val elementsLength = elements.length

    for (i <- 0 to elementsLength)
      if (indexesSet.contains(i)) builder += elements(i)

    builder.result()
  }

  lazy val toMap: Map[String, T] = {
    val builder = Map.newBuilder[String, T]
    val elementsLength = elements.length

    for (i <- 0 to elementsLength)
      if (indexesSet.contains(i)) builder += elements(i)

    builder.result()
  }

  lazy val toListMap: ListMap[String, T] = {
    val builder = ListMap.newBuilder[String, T]
    val elementsLength = elements.length

    for (i <- 0 to elementsLength)
      if (indexesSet.contains(i)) builder += elements(i)

    builder.result()
  }

  override lazy val toSeq: Seq[(String, T)] = toVector

  override lazy val toVector: Vector[(String, T)] = {
    val builder = new VectorBuilder[(String, T)]
    val elementsLength = elements.length

    for (i <- 0 to elementsLength)
      if (indexesSet.contains(i)) builder += elements(i)

    builder.result()
  }

  override def iterator: Iterator[(String, T)] =
    new Iterator[(String, T)] {
      var index = -1
      var nextIndex = -1
      val elementsLength = elements.length

      @tailrec def nextIndex(current: Int): Int = {
        val next = current + 1

        if (next >= elementsLength) -1
        else if (indexesSet.contains(next)) next
        else nextIndex(next)
      }

      override def hasNext: Boolean = {
        nextIndex = nextIndex(index)
        nextIndex != -1
      }

      override def next(): (String, T) = {
        index = nextIndex

        if (index < 0) throw new NoSuchElementException("reached iterator end")

        elements(nextIndex)
      }
    }
}