const fs = require('fs')
const path = require('path')
const jwt = require('jsonwebtoken')
const request = require('request')

// settings
const basePath = 'https://identityhomolog.acesso.io'

// entry point
let options = {
    serviceAccount: 'svcapp1',
    tenant: "9ea3c3bd-4447-4c3b-ae2e-504b795d3733"
}

requestAnAccessToken(createServiceAccountToken(options), (err, accessToken) => {
    let payload = jwt.decode(accessToken.access_token)
    console.log('Response:')
    console.log(' Access Token: ', accessToken.access_token)
    console.log(' ID: ', payload.jti)
    console.log(' Issuer: ', payload.iss)
    console.log(' Subject: ', payload.sub)
    console.log(' expires_in: ', accessToken.expires_in)
    console.log(' Expiration Date: ', new Date(payload.exp))
    console.log(' Creation Date: ', new Date(payload.iat))
})

// functions
function createServiceAccountToken({tenant, serviceAccount, account = ''}) {
    // Reads the service account private key
    let privateKey = fs.readFileSync(path.resolve(`${serviceAccount}.key.pem`))

    // Prepare the request
    let payload = {
        iss: `${serviceAccount}@${tenant}.iam.acesso.io`,
        aud: basePath,
        scope: '*',
        exp: Math.floor(Date.now() / 1000) + 3600,
        iat: Math.floor(Date.now() / 1000)
    }
    // Service account is requesting an access token for another user?
    if (account) {
        payload.sub = account
    }

    // Create JWS
    return jwt.sign(payload, privateKey, { algorithm: 'RS256' })
}

function requestAnAccessToken(serviceToken, callback) {
    // Prepare the request
    let options = {
        method: 'POST',
        url: `${basePath}/oauth2/token`,
        headers: {'content-type': 'application/x-www-form-urlencoded'},
        form: {
            grant_type: 'urn:ietf:params:oauth:grant-type:jwt-bearer' ,
            assertion: serviceToken
        }
    }
    console.log('Requesting Access Token with self created token:' )
    console.log('', serviceToken)

    // Ask identity and authorization server for an access token
    request(options, (error, response, body) => {
        if (error) {
            callback(new Error(error))
        }

        body = JSON.parse(body)

        if (body.error) {
            callback(new Error(`${body.error}: ${body.error_description}`))
        }

        callback(null, body)
    })
}