import * as jwt from 'jsonwebtoken'

import { Response, Body } from './types'

export const verifyJwt = (token, authKey) => {
  try {
    const decoded = jwt.verify(token, authKey) as jwt.JwtPayload

    if (!('exp' in decoded) || !decoded.exp) {
      throw new Error('No expiry data for provided jwt.')
    }

    return {
      jwt: jwt.verify(token, authKey),
      success: (Date.now() / 1000) < decoded.exp!,
    }
  } catch (e) {
    return {
      e,
      success: false,
    }
  }
}

const validateBody = (body: Body) => {
  if (!body.authKeys || !body.authKeys.current || !body.authKeys.previous) {
    throw new Error('Failed to validate body. Improper authkeys provided.')
  }

  if (!body.jwt) {
    throw new Error('Failed to validate body. Improper jwt provided.')
  }
}

export async function ServerUtils_IsUserAuthorised(body: Body) {
  const response: Response = {
    access: true,
  }

  try {
    // Check the JWT using the authKey
    // Check the authKey against the last 2 cached on the server.

    validateBody(body)
    const decodedCurrent = verifyJwt(body.jwt, body.authKeys.current)
    const decodedPrevious = verifyJwt(body.jwt, body.authKeys.previous)

    if (!decodedCurrent.success && !decodedPrevious.success) {
      response.error = 'Not Authorised, Log In'
      response.access = false
      return response
    }

    const decoded = (decodedCurrent.success
      ? decodedCurrent.jwt : decodedPrevious.jwt) as jwt.JwtPayload
    const encoded = body.jwt
    return { ...response, ...decoded, encoded }
  } catch (err) {
    return new Promise((resolve) => {
      response.error = 'Fatal error in ServerUtils_IsUserAuthorised. Investigate.'
      response.errorMessage = err.message
      response.success = false
      response.access = false
      return resolve(response)
    })
  }
}