(Swift 3,4,5...) Shopify OAuth2 Authentication

Demonstrates obtaining an access token for a Shopify application using OAuth2 authentication. This example is for non-web-apps, and requires that a browser window be displayed to get authorization from the user.

A web-based application would not obtain an OAuth2 token in this way, because the redirect URL would route back to the web application.

Note: Once an access token is in hand, the remainder of the Chilkat examples, which use an already-obtained access token, apply to both web and non-web apps.

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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.  
    // The callback URL would look like "http://localhost:3017/" if the port number is 3017.
    // Make sure that "http://localhost:3017/" is listed in your Whitelisted Redirection URLs for your Shopify app.
    oauth2.listenPort = 3017

    // The full content of the Authorization Endpoin for Shopify looks like this:
    // https://{shop}.myshopify.com/admin/oauth/authorize?client_id={api_key}&scope={scopes}&redirect_uri={redirect_uri}&state={nonce}&grant_options[]={option}

    // Replace "chilkat" with your shop name.
    oauth2.authorizationEndpoint = "https://chilkat.myshopify.com/admin/oauth/authorize"
    oauth2.tokenEndpoint = "https://chilkat.myshopify.com/admin/oauth/access_token"

    // Replace these with actual values.
    oauth2.clientId = "SHOPIFY_API_KEY"
    oauth2.clientSecret = "SHOPIFY_API_SECRET_KEY"

    oauth2.codeChallenge = true
    oauth2.codeChallengeMethod = "S256"

    // Set requested scopes.  See https://help.shopify.com/api/getting-started/authentication/oauth
    oauth2.scope = "read_product_listings,read_customers,read_orders,read_draft_orders"

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

    print("url: \(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 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
    }

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

    // Save the full JSON access token response to a file.
    let sbJson = CkoStringBuilder()!
    sbJson.append(oauth2.accessTokenResponse)
    sbJson.writeFile("qa_data/tokens/shopify-access-token.json", charset: "utf-8", emitBom: false)

    // The saved JSON response looks like this:

    // {
    //   "access_token": "1364e43a5332583188cb27bc85469b1f",
    //   "scope": "read_product_listings,read_customers,read_orders,read_draft_orders"
    // }

}