(Swift 2) HMRC OAuth2 Access Token

Demonstrates how to get an HMRC OAuth2 access token from a desktop (installed) application or script. This example gets an HMRC MTD VAT read/write access token.

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 oauth2 = CkoOAuth2()
    var success: Bool

    // This should be the port in the localhost callback URL for your app.
    // Important: Make sure the callback URI in your HMRC developer app 
    // is exactly "http://localhost:3017/".  Don't forget the ending "/" char.
    // The callback URL would look like "http://localhost:3017/" if the port number is 3017.

    // IMPORTANT: Don't forget to setup your HMRC application to use the Redirect URI "http://localhost:3017/" as shown
    // here: Configure Redirect URI for HMRC application
    oauth2.ListenPort = 3017

    oauth2.AuthorizationEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/authorize"
    oauth2.TokenEndpoint = "https://test-api.service.hmrc.gov.uk/oauth/token"

    // Replace these with actual values.
    oauth2.ClientId = "HMRC-CLIENT-ID"
    oauth2.ClientSecret = "HMRC-CLIENT-SECRET"

    // The scopes are documented in the HMRC reference documentation for each API.
    // This example gets a read/write access token for the HMRC MTD VAT API.
    oauth2.Scope = "read:vat write:vat"

    // Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
    var url: String? = oauth2.StartAuth()
    if oauth2.LastMethodSuccess != true {
        print("\(oauth2.LastErrorText)")
        return
    }

    let http = CkoHttp()

    // At this point, your application should load the URL in a browser.
    // For example, 
    // in C#: System.Diagnostics.Process.Start(url);
    // in Java: Desktop.getDesktop().browse(new URI(url));
    // in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
    //              wsh.Run url
    // in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
    // in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
    // The GitHub account owner would interactively accept or deny the authorization request.

    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...
    // Add the code to load the url in a web browser here...

    // Now wait for the authorization.
    // We'll wait for a max of 120 seconds.
    var numMsWaited: Int = 0
    while (numMsWaited < 120000) && (oauth2.AuthFlowState.intValue < 3) {
        oauth2.SleepMs(100)
        numMsWaited = numMsWaited + 100
    }

    // If there was no response from the browser within 30 seconds, then 
    // the AuthFlowState will be equal to 1 or 2.
    // 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
    // 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
    // In that case, cancel the background task started in the call to StartAuth.
    if oauth2.AuthFlowState.intValue < 3 {
        oauth2.Cancel()
        print("No response from the browser!")
        return
    }

    // Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
    // The possible AuthFlowState values are:
    // 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
    // 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
    // 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
    if oauth2.AuthFlowState.intValue == 5 {
        print("OAuth2 failed to complete.")
        print("\(oauth2.FailureInfo)")
        return
    }

    if oauth2.AuthFlowState.intValue == 4 {
        print("OAuth2 authorization was denied.")
        print("\(oauth2.AccessTokenResponse)")
        return
    }

    if oauth2.AuthFlowState.intValue != 3 {
        print("Unexpected AuthFlowState:\(oauth2.AuthFlowState.intValue)")
        return
    }

    print("OAuth2 authorization granted!")
    print("Access Token = \(oauth2.AccessToken)")

    // Get the full JSON response:
    let json = CkoJsonObject()
    json.Load(oauth2.AccessTokenResponse)
    json.EmitCompact = false
    print("\(json.Emit())")

    // The JSON response looks like this:

    // {
    //   "token_type": "Bearer",
    //   "scope": "user_impersonation",
    //   "expires_in": "3599",
    //   "ext_expires_in": "0",
    //   "expires_on": "1524783438",
    //   "not_before": "1524779538",
    //   "resource": "https://mydomain.api.crm.dynamics.com",
    //   "access_token": "...",
    //   "refresh_token": "...",
    //   "id_token": "..."
    // }

    // If an "expires_on" member does not exist, then add the JSON member by
    // getting the current system date/time and adding the "expires_in" seconds.
    // This way we'll know when the token expires.
    if json.HasMember("expires_on") != true {
        let dtExpire = CkoDateTime()
        dtExpire.SetFromCurrentSystemTime()
        dtExpire.AddSeconds(json.IntOf("expires_in").intValue)
        json.AppendString("expires_on", value: dtExpire.GetAsUnixTimeStr(false))
    }

    print("\(json.Emit())")

    // Save the JSON to a file for future requests.
    let fac = CkoFileAccess()
    fac.WriteEntireTextFile("qa_data/tokens/hmrc.json", fileData: json.Emit(), charset: "utf-8", includePreamble: false)

}