veloze/src/FindRoute.js

A modern and fast express-like webserver for the web

import { LRUCache } from 'mnemonist'
import { safeDecodeUriComponent } from './utils/safeDecode.js'

const METHODS = Symbol('methods')
const PARAM = Symbol('param')
const PARAM_PART = Symbol('paramPart')
const WILDCARD = Symbol('*')

/**
 * @typedef {import('./types.js').Method} Method
 */

/**
 * Radix Tree Router
 *
 * - Case-sensitive router according to [RFC3986](https://www.rfc-editor.org/rfc/rfc3986).
 * - Duplicate slashes are NOT ignored.
 * - No regular expressions.
 * - Tailing slash resolves to different route. E.g. `/path !== /path/`
 * - supports wildcard routes `/path/*`.
 * - parameters `/users/:user`, e.g. `/users/andi` resolves to `params = { user: 'andi' }`
 */
export class FindRoute {
  #tree = {}
  _cache

  /**
   * @param {number} [size=1000]
   */
  constructor(size = 1000) {
    this._cache = size > 0 ? new LRUCache(size) : null
  }

  /**
   * add handler by method and pathname to routing tree
   * @param {Method} method
   * @param {string|string[]} pathname
   * @param {Function} handler
   */
  add(method, pathname, handler) {
    if (Array.isArray(pathname)) {
      pathname.forEach((path) => this.add(method, path, handler))
      return
    }
    const parts = pathname.replace(/[/]{1,5}$/, '/').split('/')
    let tmp = this.#tree
    for (const part of parts) {
      if (part === '*') {
        tmp = tmp[WILDCARD] = tmp[WILDCARD] || {}
      } else if (part.startsWith(':')) {
        tmp[PARAM] = part.slice(1)
        tmp = tmp[PARAM_PART] = tmp[PARAM_PART] || {}
      } else {
        tmp = tmp[part] = tmp[part] || {}
      }
    }
    tmp[METHODS] = tmp[METHODS] || {}
    tmp[METHODS][method] = handler
  }

  /**
   * print routing tree on console
   */
  print() {
    console.dir(this.#tree, { depth: null })
  }

  /**
   * find route handlers by method and url
   * @param {object} param0
   * @param {Method} param0.method
   * @param {string} param0.url
   * @returns {{
   *  handler: Function
   *  params: object
   *  path: string
   * }|undefined}
   */
  find({ method, url }) {
    const [path] = url.split('?')
    const cached = this._cache?.get(method + path)
    if (cached) {
      return cached
    }
    const parts = (path || '/').split('/')
    const params = {}
    let wildcard
    let tmp = this.#tree
    for (let i = 0; i < parts.length; i += 1) {
      const part = parts[i]
      let next = tmp?.[part]
      if (!next && part && tmp[PARAM_PART]) {
        const param = tmp[PARAM]
        params[param] = safeDecodeUriComponent(part)
        next = tmp[PARAM_PART]
      }
      if (tmp[WILDCARD]) {
        wildcard = tmp[WILDCARD]
      }
      if (!next) {
        tmp = wildcard
        break
      }
      tmp = next
    }

    const handler = getHandler(tmp, method) || getHandler(wildcard, method)
    if (!handler) {
      return
    }
    this._cache?.set(method + path, { handler, params, path })
    return { handler, params, path }
  }
}

const getHandler = (tmp, method) =>
  tmp?.[METHODS]?.[method] || tmp?.[METHODS]?.ALL