Kotlin Sequence Extensions for Google Guava Immutable Collections

kotlin_sequence_for_guava_immutable_collections.kt

import com.google.common.collect.ImmutableList
import com.google.common.collect.ImmutableListMultimap
import com.google.common.collect.ImmutableMap
import com.google.common.collect.ImmutableSet

fun <T> Sequence<T>.toImmutableList(): ImmutableList<T> {
    val builder = ImmutableList.builder<T>()

    forEach { builder.add(it) }

    return builder.build()
}

fun <T> Sequence<T>.toImmutableSet(): ImmutableSet<T> {
    val builder = ImmutableSet.builder<T>()

    forEach { builder.add(it) }

    return builder.build()
}

fun <T,K> Sequence<T>.toImmutableMap(keyMapper: (T) -> K): ImmutableMap<K,T> {
    val builder = ImmutableMap.builder<K,T>()

    forEach { builder.put(keyMapper(it), it) }

    return builder.build()
}

fun <T,K,V> Sequence<T>.toImmutableMap(keyMapper: (T) -> K, valueMapper: (T) -> V): ImmutableMap<K,V> {
    val builder = ImmutableMap.builder<K,V>()

    forEach { builder.put(keyMapper(it), valueMapper(it)) }

    return builder.build()
}

fun <T,K> Sequence<T>.toImmutableListMultimap(keyMapper: (T) -> K): ImmutableListMultimap<K,T> {
    val builder = ImmutableListMultimap.builder<K,T>()

    forEach { builder.put(keyMapper(it), it) }

    return builder.build()
}

fun <T,K,V> Sequence<T>.toImmutableListMultimap(keyMapper: (T) -> K, valueMapper: (T) -> V): ImmutableListMultimap<K,V> {
    val builder = ImmutableListMultimap.builder<K,V>()

    forEach { builder.put(keyMapper(it), valueMapper(it)) }

    return builder.build()
}