(Visual FoxPro) Get Firebase Access Token from JSON Service Account Private Key

Demonstrates how to get a Firebase access token using a JSON service account private key. Your Firebase service account can be used to authenticate multiple Firebase features, such as Database, Storage and Auth, programmatically.

A Firebase JSON service account private key can be created in the Firebase settings/admin portion of the console.firebase.google.com site as shown here:

Scroll down to see the example code...

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loFac
LOCAL lcJsonKey
LOCAL loGAuth
LOCAL loTlsSock
LOCAL lnSuccess

* This example requires the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* First load the Firebase JSON private key into a string.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.FileAccess')
loFac = CreateObject('Chilkat.FileAccess')
lcJsonKey = loFac.ReadEntireTextFile("qa_data/firebase/firebase-chilkat-firebase-adminsdk-n28n4-1b664ee163.json","utf-8")
IF (loFac.LastMethodSuccess <> 1) THEN
    ? loFac.LastErrorText
    RELEASE loFac
    CANCEL
ENDIF

* A Firebase JSON private key should look something like this:

* { 
*   "type": "service_account",
*   "project_id": "firebase-chilkat",
*   "private_key_id": "1c664ee164907413c91ddefcf5b765ecba8779e2",
*   "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvQIBA ... Ya2UZii/lXn73/ZOK8=\n-----END PRIVATE KEY-----\n",
*   "client_email": "firebase-adminsdk-n28n4@firebase-chilkat.iam.gserviceaccount.com",
*   "client_id": "134846322329335418431",
*   "auth_uri": "https://accounts.google.com/o/oauth2/auth",
*   "token_uri": "https://accounts.google.com/o/oauth2/token",
*   "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
*   "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/firebase-adminsdk-n28n4%40firebase-chilkat.iam.gserviceaccount.com"
* } 
* 

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.AuthGoogle')
loGAuth = CreateObject('Chilkat.AuthGoogle')
loGAuth.JsonKey = lcJsonKey

* Choose a scope.
* The scope could be "https://www.googleapis.com/auth/firebase.database"
* or a space-delimited list of scopes:
* "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email"

loGAuth.Scope = "https://www.googleapis.com/auth/firebase.database https://www.googleapis.com/auth/userinfo.email"

* Request an access token that is valid for this many seconds.
loGAuth.ExpireNumSeconds = 3600

* If the application is requesting delegated access:
* The email address of the user for which the application is requesting delegated access,
* then set the email address here. (Otherwise leave it empty.)
loGAuth.SubEmailAddress = ""

* Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
* The Chilkat socket object is used so that the connection can be established
* through proxies or an SSH tunnel if desired.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Socket')
loTlsSock = CreateObject('Chilkat.Socket')
lnSuccess = loTlsSock.Connect("www.googleapis.com",443,1,5000)
IF (lnSuccess <> 1) THEN
    ? loTlsSock.LastErrorText
    RELEASE loFac
    RELEASE loGAuth
    RELEASE loTlsSock
    CANCEL
ENDIF

* Send the request to obtain the access token.
lnSuccess = loGAuth.ObtainAccessToken(loTlsSock)
IF (lnSuccess <> 1) THEN
    ? loGAuth.LastErrorText
    RELEASE loFac
    RELEASE loGAuth
    RELEASE loTlsSock
    CANCEL
ENDIF

* Examine the access token:
? "Firebase Access Token: " + loGAuth.AccessToken

* Save the token to a file (or wherever desired).  This token is valid for 1 hour.
loFac.WriteEntireTextFile("qa_data/tokens/firebaseToken.txt",loGAuth.AccessToken,"utf-8",0)

RELEASE loFac
RELEASE loGAuth
RELEASE loTlsSock