インクリメンタルなデシリアライザ

deserialize.ts

class Stack<T> {
  private _intenal: T[]
  private _pointer: number = -1

  constructor(size: number = 0) {
    this._intenal = new Array(size)
  }

  get top(): T | undefined {
    return this._intenal[this._pointer]
  }

  get empty(): boolean {
    return this._pointer === -1
  }

  push(value: T): void {
    this._pointer++
    if (this._intenal.length > this._pointer) {
      this._intenal[this._pointer] = value
    } else {
      this._intenal.push(value)
    }
  }

  pop(): T | undefined {
    return this._intenal[this._pointer--]
  }

  clear(): void {
    this._pointer = -1
  }
}

type StackItem =
  | {
      type: 'ARRAY'
      position: number
      size: number
      array: Array<unknown>
    }
  | {
      type: 'MAP_KEY' | 'MAP_VALUE'
      remains: number
      key: string | null
      map: Record<string, unknown>
    }

class Deserializer {
  private stack: Stack<StackItem>
  private value: unknown

  constructor(depth: number = 8) {
    this.stack = new Stack(depth)
  }

  getResult(): unknown {
    if (!this.stack.empty) throw new Error('Cannot get result when processing')
    return this.value
  }

  setValue(value: unknown) {
    this.value = value
    let item: StackItem | undefined
    while ((item = this.stack.top)) {
      switch (item.type) {
        case 'ARRAY':
          item.array[item.position++] = this.value
          if (item.position !== item.array.length) return
          this.value = item.array
          this.stack.pop()
          continue
        case 'MAP_KEY':
          if (typeof this.value !== 'string') throw new Error('The type of key must be string')
          item.key = this.value
          item.type = 'MAP_VALUE'
          return
        case 'MAP_VALUE':
          item.map[item.key!] = this.value
          if (--item.remains !== 0) {
            item.type = 'MAP_KEY'
            return
          } else {
            this.value = item.map
            this.stack.pop()
            continue
          }
        default:
          return
      }
    }
  }

  enterArray(size: number) {
    this.stack.push({ type: 'ARRAY', position: 0, size: size | 0, array: new Array(size) })
  }

  enterMap(size: number) {
    if (size === 0) {
      this.value = {}
      return
    }
    this.stack.push({ type: 'MAP_KEY', remains: size | 0, key: null, map: {} })
  }
}

const d = new Deserializer()

d.enterMap(4)
d.setValue('id')
d.setValue(1)
d.setValue('text')
d.setValue('hogehoge')
d.setValue('user')
d.enterMap(2)
d.setValue('id')
d.setValue(1)
d.setValue('name')
d.setValue('admin')
d.setValue('array')
d.enterArray(3)
d.setValue(1)
d.setValue(2)
d.setValue(3)

console.log(d.getResult())

yea