lib0/list.js

import { id } from './function.js'
import * as error from './error.js'

export class ListNode {
  constructor () {
    /**
     * @type {this|null}
     */
    this.next = null
    /**
     * @type {this|null}
     */
    this.prev = null
  }
}

/**
 * @template {ListNode} N
 */
export class List {
  constructor () {
    /**
     * @type {N | null}
     */
    this.start = null
    /**
     * @type {N | null}
     */
    this.end = null
    this.len = 0
  }
}

/**
 * @note The queue implementation is experimental and unfinished.
 * Don't use this in production yet.
 *
 * @template {ListNode} N
 *
 * @return {List<N>}
 */
export const create = () => new List()

/**
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 */
export const isEmpty = queue => queue.start === null

/**
 * Remove a single node from the queue. Only works with Queues that operate on Doubly-linked lists of nodes.
 *
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 * @param {N} node
 */
export const remove = (queue, node) => {
  const prev = node.prev
  const next = node.next
  if (prev) {
    prev.next = next
  } else {
    queue.start = next
  }
  if (next) {
    next.prev = prev
  } else {
    queue.end = prev
  }
  queue.len--
  return node
}

/**
 * @deprecated @todo remove in next major release
 */
export const removeNode = remove

/**
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 * @param {N| null} left
 * @param {N| null} right
 * @param {N} node
 */
export const insertBetween = (queue, left, right, node) => {
  /* c8 ignore start */
  if (left != null && left.next !== right) {
    throw error.unexpectedCase()
  }
  /* c8 ignore stop */
  if (left) {
    left.next = node
  } else {
    queue.start = node
  }
  if (right) {
    right.prev = node
  } else {
    queue.end = node
  }
  node.prev = left
  node.next = right
  queue.len++
}

/**
 * Remove a single node from the queue. Only works with Queues that operate on Doubly-linked lists of nodes.
 *
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 * @param {N} node
 * @param {N} newNode
 */
export const replace = (queue, node, newNode) => {
  insertBetween(queue, node, node.next, newNode)
  remove(queue, node)
}

/**
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 * @param {N} n
 */
export const pushEnd = (queue, n) =>
  insertBetween(queue, queue.end, null, n)

/**
 * @template {ListNode} N
 *
 * @param {List<N>} queue
 * @param {N} n
 */
export const pushFront = (queue, n) =>
  insertBetween(queue, null, queue.start, n)

/**
 * @template {ListNode} N
 *
 * @param {List<N>} list
 * @return {N| null}
 */
export const popFront = list =>
  list.start ? removeNode(list, list.start) : null

/**
 * @template {ListNode} N
 *
 * @param {List<N>} list
 * @return {N| null}
 */
export const popEnd = list =>
  list.end ? removeNode(list, list.end) : null

/**
 * @template {ListNode} N
 * @template M
 *
 * @param {List<N>} list
 * @param {function(N):M} f
 * @return {Array<M>}
 */
export const map = (list, f) => {
  /**
   * @type {Array<M>}
   */
  const arr = []
  let n = list.start
  while (n) {
    arr.push(f(n))
    n = n.next
  }
  return arr
}

/**
 * @template {ListNode} N
 *
 * @param {List<N>} list
 */
export const toArray = list => map(list, id)

/**
 * @template {ListNode} N
 * @template M
 *
 * @param {List<N>} list
 * @param {function(N):M} f
 */
export const forEach = (list, f) => {
  let n = list.start
  while (n) {
    f(n)
    n = n.next
  }
}