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/*
* Copyright 2019 Spotify AB.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package com.spotify.scio.extra
import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.MinMaxPriorityQueue
import scala.jdk.CollectionConverters._
/**
* Utilities for Scala collection library.
*
* Adds a `top` method to `Array[T]` and `Iterable[T]` and a `topByKey` method to `Array[(K, V)]`
* and `Iterable[(K, V)]`.
*
* {{{
* import com.spotify.scio.extra.Collections._
*
* val xs: Array[(String, Int)] = // ...
* xs.top(5)(Ordering.by(_._2))
* xs.topByKey(5)
* }}}
*/
object Collections {
private def topImpl[T](xs: Iterable[T], num: Int, ord: Ordering[T]): Iterable[T] = {
require(num > 0, "num must be > 0")
if (xs.isEmpty) {
Iterable.empty[T]
} else {
val size = math.min(num, xs.size)
MinMaxPriorityQueue
.orderedBy(ord.reverse)
.expectedSize(size)
.maximumSize(size)
.create[T](xs.asJava)
.asScala
}
}
private def topByKeyImpl[K, V](
xs: Iterable[(K, V)],
num: Int,
ord: Ordering[V]
): Map[K, Iterable[V]] = {
require(num > 0, "num must be > 0")
val size = math.min(num, xs.size)
val m = scala.collection.mutable.Map[K, MinMaxPriorityQueue[V]]()
val i = xs.iterator
while (i.hasNext) {
val (k, v) = i.next()
if (!m.contains(k)) {
val pq = MinMaxPriorityQueue
.orderedBy(ord.reverse)
.expectedSize(size)
.maximumSize(size)
.create[V]()
pq.add(v)
m(k) = pq
} else {
m(k).add(v)
}
}
m.map { case (k, v) => k -> v.asScala }.toMap
}
/** Enhance Array by adding a `top` method. */
implicit class TopArray[T](private val self: Array[T]) extends AnyVal {
def top(num: Int)(implicit ord: Ordering[T]): Iterable[T] =
topImpl(self, num, ord)
}
/** Enhance Iterable by adding a `top` method. */
implicit class TopIterable[T](private val self: Iterable[T]) extends AnyVal {
def top(num: Int)(implicit ord: Ordering[T]): Iterable[T] =
topImpl(self, num, ord)
}
/** Enhance Array by adding a `topByKey` method. */
implicit class TopByKeyArray[K, V](private val self: Array[(K, V)]) extends AnyVal {
def topByKey(num: Int)(implicit ord: Ordering[V]): Map[K, Iterable[V]] =
topByKeyImpl(self, num, ord)
}
/** Enhance Iterable by adding a `topByKey` method. */
implicit class TopByKeyIterable[K, V](private val self: Iterable[(K, V)]) extends AnyVal {
def topByKey(num: Int)(implicit ord: Ordering[V]): Map[K, Iterable[V]] =
topByKeyImpl(self, num, ord)
}
}
