java/kotlin/src/main/kotlin/com/google/protobuf/UnmodifiableCollections.kt

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
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package com.google.protobuf.kotlin

/** Wraps an [Iterator] and makes it unmodifiable even from Java. */
internal class UnmodifiableIterator<E>(delegate: Iterator<E>) : Iterator<E> by delegate

/** Wraps a [ListIterator] and makes it unmodifiable even from Java. */
internal class UnmodifiableListIterator<E>(
  delegate: ListIterator<E>
) : ListIterator<E> by delegate

/** Wraps a [Collection] and makes it unmodifiable even from Java. */
internal open class UnmodifiableCollection<E>(
  private val delegate: Collection<E>
) : Collection<E> by delegate {
  override fun iterator(): Iterator<E> = UnmodifiableIterator(delegate.iterator())
}

/** Wraps a [Set] and makes it unmodifiable even from Java. */
internal class UnmodifiableSet<E>(
  delegate: Collection<E>
) : UnmodifiableCollection<E>(delegate), Set<E>

/** Wraps a [Map.Entry] and makes it unmodifiable even from Java. */
internal class UnmodifiableMapEntry<K, V>(delegate: Map.Entry<K, V>) : Map.Entry<K, V> by delegate

/** Wraps a [Set] of map entries and makes it unmodifiable even from Java. */
internal class UnmodifiableMapEntries<K, V>(
  private val delegate: Set<Map.Entry<K, V>>
) : UnmodifiableCollection<Map.Entry<K, V>>(delegate), Set<Map.Entry<K, V>> {

  // Is this overkill? Probably.

  override fun iterator(): Iterator<Map.Entry<K, V>> {
    val itr = delegate.iterator()
    return object : Iterator<Map.Entry<K, V>> by itr {
      override fun next(): Map.Entry<K, V> = UnmodifiableMapEntry(itr.next())
    }
  }
}