walkmc.collections.LimitedList.kt Maven / Gradle / Ivy

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package walkmc.collections

/**
 * Represents a limited list. A limited list only can have specified [limit] of elements.
 */
open class LimitedList(
	var limit: Int,
	private val delegate: MutableList = ArrayList()
) : MutableList by delegate {
	
	/**
	 * Adds the specified element to the end of this list.
	 *
	 * @return false if the size of this list is reached to [limit], otherwise, true
	 */
	override fun add(element: T): Boolean {
		if (size >= limit)
			return false
		
		return delegate.add(element)
	}
	
	/**
	 * Inserts an element into the list at the specified [index].
	 */
	override fun add(index: Int, element: T) {
		if (index >= limit)
			return
		
		delegate.add(index, element)
	}
	
	/**
	 * Adds all of the elements of the specified collection to the end of this list.
	 *
	 * The elements are appended in the order they appear in the elements collection.
	 */
	override fun addAll(elements: Collection): Boolean {
		if (size >= limit)
			return false

		return delegate.addAll(elements.take(limit - size))
	}
}

/**
 * Creates a empty limited list.
 */
fun  limitedListOf(limit: Int) = LimitedList(limit)

/**
 * Creates a limited list by [elements].
 */
fun  limitedListOf(limit: Int, vararg elements: T) = LimitedList(limit, elements.toMutableList())

/**
 * Converts this mutable list to a limited list.
 */
fun  MutableList.toLimitedList(limit: Int) = LimitedList(limit, subList(0, limit))

/**
 * Converts this iterable to a limited list.
 */
fun  Iterable.toLimitedList(limit: Int): LimitedList =
	if (this is MutableList) this.toLimitedList(limit) else toMutableList().toLimitedList(limit)