import * as crypto from 'crypto'

export default class ValidateTelegramWebAppData {
  /**
     * Creates ValidateTelegramWebAppData instance.
     * @constructor
     * @param {string} telegramBotToken - your Telegram bot's token
     */
  telegramBotToken: string

  constructor (telegramBotToken: string) {
    this.telegramBotToken = telegramBotToken
  }

  /**
     * @param {string} initData - initData received from Telegram
     * @param {number} secondsToExpire - number of seconds to expire from auth_date; enter 0 to ignore expiry check
     * @returns {ValidateDataResponse} - Returns an object with keys 'isValid' and 'data'.
     * - Value of 'isValid' will be true if data is valid; false if data is invalid/has expired.
     * - Value of 'data' contains the parsed initData in object
     */
  ValidateData (initData: any, secondsToExpire: number): ValidateDataResponse {
    const params = new URLSearchParams(initData as string)
    const data: WebAppInitData = {}
    let hash = ''
    for (const [key, value] of params.entries()) {
      key === 'hash' ? hash = value : data[key] = value
    };
    const dataCheckString = Object.keys(data)
      .sort()
      .map(key => `${key}=${data[key]}`)
      .join('\n')
    const secretKey = crypto.createHmac('sha256', 'WebAppData').update(this.telegramBotToken).digest()
    const hmac = crypto.createHmac('sha256', secretKey).update(dataCheckString).digest('hex')
    const currentTime = Date.now() / 1000
    const currentAndAuthTimeDiff = currentTime - data.auth_date!
    if (secondsToExpire === 0) {
      return {
        isValid: hmac === hash,
        data
      }
    } else {
      return {
        isValid: !!(currentAndAuthTimeDiff < secondsToExpire && hmac === hash),
        data
      }
    }
  }
}

interface ValidateDataResponse {
  isValid: boolean
  data: WebAppInitData
}

interface WebAppUser {
  id: number
  is_bot?: boolean
  first_name: string
  last_name?: string
  username?: string
  language_code?: string
  is_premium?: true
  added_to_attachment_menu?: true
  allows_write_to_pm?: true
  photo_url?: string
};

interface WebAppChat {
  id: number
  type: string
  title: string
  username?: string
  photo_url?: string
};

interface WebAppInitData {
  [key: string]: any
  query_id?: string
  user?: WebAppUser
  receiver?: WebAppUser
  chat?: WebAppChat
  chat_type?: string
  chat_instance?: string
  start_param?: string
  can_send_after?: number
  auth_date?: number
  hash?: string
};