MyJsonAPI TypeScript

MyJsonAPI.ts

class MyJsonAPI<T = any> {
  key: string

  constructor(key?: string) {
    if (validKey(key)) {
      this.key = key
    }
  }

  get isReady() {
    return validKey(this.key)
  }

  get apiURL() {
    return `${MyJsonAPI.BASE_URL}/${this.key}`
  }

  get(): Promise<T> {
    if (!this.isReady) {
      return Promise.reject(new Error(`Invalid key: ${this.key}`))
    }
    else {
      return fetch(this.apiURL).then(toJSON)
    }
  }

  set(value: T): Promise<{ key: string, url: string, data: T }> {
    if (!validKey(this.key)) {
      return this.create(value)
    }
    else {
      return this.update(value)
    }
  }

  private update(value: T): Promise<{ key: string, url: string, data: T }> {
    return fetch(this.apiURL, {
      body: value,
      method: 'POST',
    })
      .then(response => {
        if (response.ok) {
          return ({
            key: this.key,
            url: this.apiURL,
            data: value
          })
        }
        else {
          throw new Error(`API Error: ${response.statusText} (${response.status})`)
        }
      })
  }

  private create(value: T): Promise<{ key: string, url: string, data: T }> {
    return fetch(MyJsonAPI.BASE_URL, {
      body: value,
      method: 'POST',
    })
      .then(toJSON)
      .then(result => {
        const urlParts = result.uri.split('/')
        const key = urlParts[urlParts.length - 1]

        this.key = key

        return { key, url: this.apiURL, data: value }
      })
  }

  static BASE_URL = 'https://api.myjson.com/bins'
}

function validKey(key: string | undefined): key is string {
  if (typeof key !== 'string') {
    return false
  }
  else if (key.length === 0) {
    return false
  }
  else {
    return true
  }
}

function toJSON<T = any>(response: Response): Promise<T> {
  return response.json()
}