(Go) Constant Contact (v3) OAuth2 Access Token

Gets an OAuth2 access token for ConstantContact.

For more information, see https://v3.developer.constantcontact.com/api_guide/server_flow.html

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

    oauth2 := chilkat.NewOAuth2()
    var success bool

    // This should be the port in the localhost callback URL for your app.  
    // The callback URL would look like "http://localhost:3017/" if the port number is 3017.
    // Make sure when defining your application (i.e. "My Applications" at  https://app.constantcontact.com/pages/dma/portal/)
    // that the Redirect URI is exactly this:  "http://localhost:3017/".   You may use any port number as long as it agrees
    // with the ListenPort here.  It is important to use "http" and not "https" in the callback URI.  The trailing "/" is also important.
    oauth2.SetListenPort(3017)

    oauth2.SetAuthorizationEndpoint("https://api.cc.email/v3/idfed")
    oauth2.SetTokenEndpoint("https://idfed.constantcontact.com/as/token.oauth2")

    // Replace these with actual values.
    oauth2.SetClientId("CLIENT_KEY")
    oauth2.SetClientSecret("CLIENT_SECRET")

    // Add one or more SPACE separated scopes
    oauth2.SetScope("account_read account_update contact_data campaign_data")

    // Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
    url := oauth2.StartAuth()
    if oauth2.LastMethodSuccess() != true {
        fmt.Println(oauth2.LastErrorText())
        oauth2.DisposeOAuth2()
        return
    }

    fmt.Println(*url)

    // 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 Microsoft 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 30 seconds.
    numMsWaited := 0
    for (numMsWaited < 30000) && (oauth2.AuthFlowState() < 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() < 3 {
        oauth2.Cancel()
        fmt.Println("No response from the browser!")
        oauth2.DisposeOAuth2()
        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() == 5 {
        fmt.Println("OAuth2 failed to complete.")
        fmt.Println(oauth2.FailureInfo())
        oauth2.DisposeOAuth2()
        return
    }

    if oauth2.AuthFlowState() == 4 {
        fmt.Println("OAuth2 authorization was denied.")
        fmt.Println(oauth2.AccessTokenResponse())
        oauth2.DisposeOAuth2()
        return
    }

    if oauth2.AuthFlowState() != 3 {
        fmt.Println("Unexpected AuthFlowState:", oauth2.AuthFlowState())
        oauth2.DisposeOAuth2()
        return
    }

    fmt.Println("OAuth2 authorization granted!")
    fmt.Println("Access Token = ", oauth2.AccessToken())

    // Get the full JSON response:
    json := chilkat.NewJsonObject()
    json.Load(oauth2.AccessTokenResponse())
    json.SetEmitCompact(false)

    // The JSON response looks like this:

    // {
    //   "access_token": "aEr4czHReESHUGcc2LRknzsMxUbW",
    //   "refresh_token": "s2qH27ikM7r3Ia0LrZGDOIgKw0bubUotBdJ7fTtc7y",
    //   "token_type": "Bearer"
    // }

    fmt.Println(*json.Emit())

    // Save the JSON to a file for future requests.
    fac := chilkat.NewFileAccess()
    fac.WriteEntireTextFile("qa_data/tokens/constantContact.json",*json.Emit(),"utf-8",false)

    oauth2.DisposeOAuth2()
    json.DisposeJsonObject()
    fac.DisposeFileAccess()