(Lianja) Get Google API Access Token using JSON Private Key using NIST Time Server Date/Time

Demonstrates how to get a Google API access token using a JSON service account private key, using the NIST time server date/time rather than the local system date/time.

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

// First, let's get the current date/time from time-c.nist.gov
loSocket = createobject("CkSocket")

// Connect to an NIST time server and read the current date/time
lnMaxWaitMs = 8000
llUseTls = .F.
llSuccess = loSocket.Connect("time-c.nist.gov",37,llUseTls,lnMaxWaitMs)
if (llSuccess <> .T.) then
    ? loSocket.LastErrorText
    release loSocket
    return
endif

// The time server will send a big-endian 32-bit integer representing
// the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
// The ReceiveInt32 method will receive a 4-byte integer, but returns
// .T. or .F. to indicate success.  If successful, the integer
// is obtained via the ReceivedInt property.
llBigEndian = .T.
llSuccess = loSocket.ReceiveInt32(llBigEndian)
if (llSuccess <> .T.) then
    ? loSocket.LastErrorText
    release loSocket
    return
endif

loDt = createobject("CkDateTime")
loDt.SetFromNtpTime(loSocket.ReceivedInt)

// Show the current local date/time
llBLocalTime = .T.
? "Current local date/time: " + loDt.GetAsRfc822(llBLocalTime)

lnMaxWaitMs = 10
loSocket.Close(lnMaxWaitMs)

// ------------------------------------------------------------------------
// OK, we have the current date/time.  We'll use it to set the IAT property
// in the code below.

// First load the JSON key into a string.
loFac = createobject("CkFileAccess")
lcJsonKey = loFac.ReadEntireTextFile("qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8")
if (loFac.LastMethodSuccess <> .T.) then
    ? loFac.LastErrorText
    release loSocket
    release loDt
    release loFac
    return
endif

// A JSON private key should look 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"
// 	}

loGAuth = createobject("CkAuthGoogle")
loGAuth.JsonKey = lcJsonKey

// Choose a scope.
loGAuth.Scope = "https://www.googleapis.com/auth/cloud-platform"

// 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 = ""

// ------------------------------------------------------------------------
// Set the IAT using the date/time from the NIST time server.
lnUnixTime = loDt.GetAsUnixTime(.F.)
? "unixTime = " + str(lnUnixTime)
loGAuth.Iat = lnUnixTime

// 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.
loTlsSock = createobject("CkSocket")
llSuccess = loTlsSock.Connect("www.googleapis.com",443,.T.,5000)
if (llSuccess <> .T.) then
    ? loTlsSock.LastErrorText
    release loSocket
    release loDt
    release loFac
    release loGAuth
    release loTlsSock
    return
endif

// Send the request to obtain the access token.
llSuccess = loGAuth.ObtainAccessToken(loTlsSock)
if (llSuccess <> .T.) then
    ? loGAuth.LastErrorText
    release loSocket
    release loDt
    release loFac
    release loGAuth
    release loTlsSock
    return
endif

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


release loSocket
release loDt
release loFac
release loGAuth
release loTlsSock