(Swift 3,4,5...) Azure AD Service-to-service access token request

Send an Azure AD service-to-service token request to get an access token using a shared secret.

For more information, see https://docs.microsoft.com/en-us/azure/active-directory/develop/v1-oauth2-client-creds-grant-flow#service-to-service-access-token-request

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

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

    let http = CkoHttp()!

    // To see the exact HTTP request sent and the response, set the SessionLogFilename property:
    http.sessionLogFilename = "qa_output/chilkatHttpLog.txt"

    let req = CkoHttpRequest()!

    // Set the following request params:
    // grant_type 	required 	Specifies the requested grant type. In a Client Credentials Grant flow, the value must be client_credentials.
    // 
    // client_id 	required 	Specifies the Azure AD client id of the calling web service. 
    //     To find the calling application's client ID, in the Azure portal, click Azure Active Directory, click App registrations, click the application. 
    //     The client_id is the Application ID
    // 
    // client_secret 	required 	Enter a key registered for the calling web service or daemon application in Azure AD. 
    //     To create a key, in the Azure portal, click Azure Active Directory, click App registrations, click the application, click Settings, click Keys, and add a Key.
    //     URL-encode this secret when providing it.
    // 
    // resource 	required 	Enter the App ID URI of the receiving web service. To find the App ID URI, in the Azure portal, click Azure Active Directory, 
    //     click App registrations, click the service application, and then click Settings and Properties.

    req.addParam("grant_type", value: "client_credentials")
    req.addParam("client_id", value: "MY_CLIENT_ID")
    req.addParam("client_secret", value: "MY_CLIENT_SECRET")
    req.addParam("resource", value: "https://service.contoso.com/")

    // The URL passed to PostUrlEncoded has this form:   https://login.microsoftonline.com/<tenant_id>/oauth2/token
    var resp: CkoHttpResponse? = http.postUrlEncoded("https://login.microsoftonline.com/<tenant_id>/oauth2/token", req: req)
    if http.lastMethodSuccess == false {
        print("\(http.lastErrorText!)")
        return
    }

    var respStatusCode: Int = resp!.statusCode.intValue
    print("Response Status Code = \(respStatusCode)")

    let json = CkoJsonObject()!
    json.emitCompact = false
    json.load(resp!.bodyStr)
    print("Response JSON:")
    print("\(json.emit()!)")

    if respStatusCode >= 400 {
        print("Response Header:")
        print("\(resp!.header!)")
        print("Failed.")
        resp = nil
        return
    }

    // Sample response:

    // {
    //   "token_type": "Bearer",
    //   "expires_in": "3599",
    //   "ext_expires_in": "3599",
    //   "expires_on": "1570059833",
    //   "not_before": "1570055933",
    //   "resource": "https://adminchilkatsoft.onmicrosoft.com/eb1b8ced-76b7-4845-aec5-d3e91776e345",
    //   "access_token": "eyJ0eXAiO ... pmgw"
    // }

    // To get the items from the JSON....
    var token_type: String? = json.string(of: "token_type")
    var expires_in: String? = json.string(of: "expires_in")
    var ext_expires_in: String? = json.string(of: "ext_expires_in")
    var expires_on: String? = json.string(of: "expires_on")
    var not_before: String? = json.string(of: "not_before")
    var resource: String? = json.string(of: "resource")
    var access_token: String? = json.string(of: "access_token")

    resp = nil

}