hono/deno_dist/router/reg-exp-router/trie.ts

import type { ParamMap, Context } from './node.ts'
import { Node } from './node.ts'

export type { ParamMap } from './node.ts'
export type ReplacementMap = number[]

export class Trie {
  context: Context = { varIndex: 0 }
  root: Node = new Node()

  insert(path: string, index: number, pathErrorCheckOnly: boolean): ParamMap {
    const paramMap: ParamMap = []

    const groups: [string, string][] = [] // [mark, original string]
    for (let i = 0; ; ) {
      let replaced = false
      path = path.replace(/\{[^}]+\}/g, (m) => {
        const mark = `@\\${i}`
        groups[i] = [mark, m]
        i++
        replaced = true
        return mark
      })
      if (!replaced) {
        break
      }
    }

    /**
     *  - pattern (:label, :label{0-9]+}, ...)
     *  - /* wildcard
     *  - character
     */
    const tokens = path.match(/(?::[^\/]+)|(?:\/\*$)|./g) || []
    for (let i = groups.length - 1; i >= 0; i--) {
      const [mark] = groups[i]
      for (let j = tokens.length - 1; j >= 0; j--) {
        if (tokens[j].indexOf(mark) !== -1) {
          tokens[j] = tokens[j].replace(mark, groups[i][1])
          break
        }
      }
    }

    this.root.insert(tokens, index, paramMap, this.context, pathErrorCheckOnly)

    return paramMap
  }

  buildRegExp(): [RegExp, ReplacementMap, ReplacementMap] {
    let regexp = this.root.buildRegExpStr()
    if (regexp === '') {
      return [/^$/, [], []] // never match
    }

    let captureIndex = 0
    const indexReplacementMap: ReplacementMap = []
    const paramReplacementMap: ReplacementMap = []

    regexp = regexp.replace(/#(\d+)|@(\d+)|\.\*\$/g, (_, handlerIndex, paramIndex) => {
      if (typeof handlerIndex !== 'undefined') {
        indexReplacementMap[++captureIndex] = Number(handlerIndex)
        return '$()'
      }
      if (typeof paramIndex !== 'undefined') {
        paramReplacementMap[Number(paramIndex)] = ++captureIndex
        return ''
      }

      return ''
    })

    return [new RegExp(`^${regexp}`), indexReplacementMap, paramReplacementMap]
  }
}