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

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package walkmc.collections

import kotlin.math.*
import java.util.*

/**
 * An implementation of [LinkedList] that's adds supports to
 * search for the current/next/previous indexes.
 *
 * Optionally all elements specified in the constructor will be added in the list.
 */
open class IndexList : LinkedList {
	
	constructor() : super()
	
	constructor(elements: Iterable) : super() {
		addAll(elements)
	}
	
	/**
	 * The current index of this index list.
	 *
	 * This can be changed to set's the current index by the specified value directly without
	 * calling the function [toNext] or [toPrevious] one by one.
	 */
	var index = 0
	
	/**
	 * Returns if this index list has next elements.
	 */
	val hasNext get() = index < lastIndex
	
	/**
	 * Returns if this index list has previous elements.
	 */
	val hasPrevious get() = index > 0
	
	/**
	 * Returns the next index of this index list, or the last index
	 * if is reached to the end of this list.
	 */
	val nextIndex get() = min(index + 1, lastIndex)
	
	/**
	 * Returns the previous index of this index list, or the first index
	 * if is reached to the start of this list.
	 */
	val previousIndex get() = max(index - 1, 0)
	
	/**
	 * Returns all previously elements of this index list,
	 * or an empty list if not contains any previous elements.
	 */
	val previously get() = subList(0, index)
	
	/**
	 * Returns all nextly elements of this index list,
	 * or an empty list if not contains any next elements.
	 */
	val nextly get() = subList(nextIndex, size)
	
	/**
	 * Returns the current element of this index list, or throws a
	 * [NoSuchElementException] if not contains any element in the current [index].
	 */
	fun current() = get(index)
	
	/**
	 * Returns the current element of this index list,
	 * or nulls if not contains any element in the current [index].
	 */
	fun currentOrNull() = getOrNull(index)
	
	/**
	 * Returns the next element of this index list, or throws a
	 * [NoSuchElementException] if not contains any element in the next index.
	 */
	fun next() = get(index + 1)
	
	/**
	 * Returns the next element of this index list, or nulls
	 * if not contains any element in the next index.
	 */
	fun nextOrNull() = getOrNull(index + 1)
	
	/**
	 * Returns the next element of this index list, or the first element if not
	 * contains any element in the next index.
	 */
	fun nextOrFirst(): E = nextOrNull() ?: first
	
	/**
	 * Returns the previous element of this index list, or throws a
	 * [NoSuchElementException] if not contains any element in the previous index.
	 */
	fun previous() = get(index - 1)
	
	/**
	 * Returns the previous element of this index list, or nulls
	 * if not contains any element in the previous index.
	 */
	fun previousOrNull() = getOrNull(index - 1)
	
	/**
	 * Returns the previous element of this index list, or the last element if not
	 * contains any element in the previous index.
	 */
	fun previousOrLast(): E = previousOrNull() ?: last
	
	/**
	 * Go to the first index of this index list and returns the first element.
	 */
	fun toFirst(): E {
		index = 0
		return first
	}
	
	/**
	 * Go to the last index of this index list and returns the first element.
	 */
	fun toLast(): E {
		index = lastIndex
		return last
	}
	
	/**
	 * Go to the next index of this index list and returns the next element.
	 *
	 * If the next index is reached to the end of this list nothing will be changed.
	 */
	fun toNext(): E {
		index++
		return current()
	}
	
	/**
	 * Go to the next index of this index list and returns the next element.
	 *
	 * If the next index is reached to the end of this list will return null.
	 */
	fun toNextOrNull(): E? {
		index++
		return currentOrNull()
	}
	
	/**
	 * Go to the next index or the first index and returns the current element.
	 */
	fun toNextOrFirst(): E {
		index++
		if (index >= size)
			index = 0
		
		return current()
	}
	
	/**
	 * Go to the previous index of this index list and returns the next element.
	 *
	 * If the previous index is reached to the start of this list nothing will be changed.
	 */
	fun toPrevious(): E {
		index--
		return current()
	}
	
	/**
	 * Go to the previous index of this index list and returns the next element.
	 *
	 * If the previous index is reached to the start of this list will return null.
	 */
	fun toPreviousOrNull(): E? {
		index--
		return currentOrNull()
	}
	
	/**
	 * Go to the previous index or the last index and returns the current element.
	 */
	fun toPreviousOrLast(): E {
		index--
		if (index < 0)
			index = lastIndex
		
		return current()
	}
}

/**
 * Returns an empty [IndexList].
 */
fun  newIndexList() = IndexList()

/**
 * Returns a [IndexList] filled with all [elements].
 */
fun  newIndexList(vararg elements: E) = IndexList(elements.toMutableList())

/**
 * Returns a new [IndexList] filled with all elements of this collection.
 */
fun  Iterable.toIndexList(): IndexList = IndexList(this)