(Excel) Get Google Cloud SQL Access Token using Service Account JSON Private Key

Demonstrates how to get a Google Cloud SQL access token using a JSON service account private key. Obtaining an access token for a service account requires no user interaction (it does not require a browser, nor callback URI's, etc.).

When an access token expires, an application can be (and should be) designed to automatically fetch a new access token.

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

' First load the JSON key into a string.
Dim fac As Chilkat.FileAccess
Set fac = Chilkat.NewFileAccess

jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatCloud-13a07a2e8b3f.json","utf-8")
If (fac.LastMethodSuccess <> True) Then
    Debug.Print fac.LastErrorText
    Exit Sub
End If

' A JSON private key should look something like this:

' 	{
' 	  "type": "service_account",
' 	  "project_id": "chilkattest-1350",
' 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
' 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
' 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
' 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
' 	  "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/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
' 	}

Dim gAuth As Chilkat.AuthGoogle
Set gAuth = Chilkat.NewAuthGoogle
gAuth.JsonKey = jsonKey

' Choose a scope.
' Here's the OAuth 2.0 scope information for the Cloud SQL Admin API:
' https://www.googleapis.com/auth/sqlservice.admin 	(Read/write access to Cloud SQL.)
' https://www.googleapis.com/auth/cloud-platform 	(Instances.import and Instances.export need this additional scope.)
gAuth.Scope = "https://www.googleapis.com/auth/sqlservice.admin"

' Request an access token that is valid for this many seconds.
gAuth.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.)
gAuth.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.
Dim tlsSock As Chilkat.Socket
Set tlsSock = Chilkat.NewSocket

success = tlsSock.Connect("www.googleapis.com",443,True,5000)
If (success <> True) Then
    Debug.Print tlsSock.LastErrorText
    Exit Sub
End If

' Send the request to obtain the access token.
success = gAuth.ObtainAccessToken(tlsSock)
If (success <> True) Then
    Debug.Print gAuth.LastErrorText
    Exit Sub
End If

' Examine the access token:
Debug.Print "Access Token: "; gAuth.AccessToken

' Access token looks like this:  ya29.c.Ko4Bwwe3nG5rUvoBmJwadi ... Br4Ogz0B6qLAjg

' We're going to save this access token to a file to be used
' by other examples.
Dim sbToken As Chilkat.StringBuilder
Set sbToken = Chilkat.NewStringBuilder
Dim success As Boolean
success = sbToken.Append(gAuth.AccessToken)
success = sbToken.WriteFile("qa_data/tokens/google_cloud_sql_access_token.txt","utf-8",False)