const MODULE_NAME = 'token-decoder'

/*
   JSON Web Token (JWT) is a compact, URL-safe means of representing
   claims to be transferred between two parties.  The claims in a JWT
   are encoded as a JSON object that is used as the payload of a JSON
   Web Signature (JWS) structure or as the plaintext of a JSON Web
   Encryption (JWE) structure, enabling the claims to be digitally
   signed or integrity protected with a Message Authentication Code
   (MAC) and/or encrypted.
*/

const JSONWebToken = require('jsonwebtoken') // A library to deal with JSON Web Tokens.
const webTokenLibrary = require('jwks-rsa')   // A library to retrieve RSA signing keys from a JWKS (JSON Web Key Set) endpoint.

const decoder = webTokenLibrary({
  cache: true,
  rateLimit: true,
  jwksRequestsPerMinute: 1,
  jwksUri: `https://${process.env.AUTH0_DOMAIN}/.well-known/jwks.json`
})

function decodeToken (token, callBackFunction) {
  try {
    if (process.env.INFO_LOG === true) { console.log('[INFO] ' + MODULE_NAME + ' -> decodeToken -> Entering function.') }

    const decoded = JSONWebToken.decode(token, { complete: true })
    const header = decoded.header
    const payload = decoded.payload

    if (
      header === null ||
      header.kid === null ||
      payload === null
    ) {
      if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> Invalid Token. ') }
      if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> token = ' + token) }
      callBackFunction(global.DEFAULT_FAIL_RESPONSE)
      return
    }

    decoder.getSigningKey(header.kid, onKeyReady)

    function onKeyReady (err, key) {
      if (process.env.INFO_LOG === true) { console.log('[INFO] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> Entering function.') }

      if (err) {
        if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> Error getting the key. ') }
        if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> key = ' + key) }
        if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> err = ' + err) }
        callBackFunction(global.DEFAULT_FAIL_RESPONSE)
        return
      }

      JSONWebToken.verify(
        token,
        key.publicKey,
        { algorithms: ['RS256'] },
        onVerified)

      function onVerified (err, decoded) {
        if (process.env.INFO_LOG === true) { console.log('[INFO] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> onVerified -> Entering function.') }

        if (err) {
          if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> onVerified -> Error verifying. ') }
          if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> onVerified -> decoded = ' + decoded) }
          if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> onKeyReady -> onVerified -> err = ' + err) }
          callBackFunction(global.DEFAULT_FAIL_RESPONSE)
          return
        }

        callBackFunction(global.DEFAULT_OK_RESPONSE, decoded)
      }
    }
  } catch (err) {
    if (process.env.ERROR_LOG === true) { console.log('[ERROR] ' + MODULE_NAME + ' -> decodeToken -> err = ' + err) }
    callBackFunction(global.DEFAULT_FAIL_RESPONSE)
  }
}

module.exports = decodeToken