(Swift 2) Get GMail IMAP OAuth2 Access Token for Desktop App

Demonstrates how to get a GMail IMAP OAuth2 access token from a desktop application or script, which can be used with the XOAUTH2 authentication method.

This example requires a browser window to be displayed to allow the GMail account owner to authorize the access. The code for displaying the web browser is omitted. Suggestions for a few programming languages are provided in code comments. You'll need to find out how to display a web browser and navigate to the URL returned by the call to oauth2.StartAuth.

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

    // For Google OAuth2, set the listen port equal to the port used
    // in the Authorized Redirect URL for the Client ID.
    // For example, in this case the Authorized Redirect URL would be http://localhost:3017/
    // Your app should choose a port not likely not used by any other application.
    oauth2.ListenPort = 3017

    oauth2.AuthorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth"
    oauth2.TokenEndpoint = "https://www.googleapis.com/oauth2/v4/token"

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

    oauth2.CodeChallenge = true
    oauth2.CodeChallengeMethod = "S256"

    // This is the full-permissions scope for GMail, which would allow full IMAP read/write access.
    oauth2.Scope = "https://mail.google.com/"

    // 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
    }

    // 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 Google 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...
    // System.Diagnostics.Process.Start(url);

    // Now wait for the authorization.
    // We'll wait for a max of 30 seconds.
    var numMsWaited: Int = 0
    while (numMsWaited < 30000) && (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
    }

    // Save the full JSON access token response to a file.
    let sbJson = CkoStringBuilder()
    sbJson.Append(oauth2.AccessTokenResponse)
    sbJson.WriteFile("qa_data/tokens/_gmailFullAccess.json", charset: "utf-8", emitBom: false)

    // The saved JSON response looks like this:

    // 	{
    // 	 "access_token": "ya39.Ci-XA_C5bGgRDC3UaD-h0_NeL-DVIQnI2gHtABCHkZzrwlARkwX6R3O0PCDEzRlfaQ",
    // 	 "token_type": "Bearer",
    // 	 "expires_in": 3600,
    // 	 "refresh_token": "1/r_2c_7jddspcdfesrrfKqfXtqo08D6Q-gUU0DsdfVMsx0c"
    // 	}
    // 
    print("OAuth2 authorization granted!")
    print("Access Token: \(oauth2.AccessToken)")

}