(VB.NET UWP/WinRT) MercadoLibre OAuth2 Access Token

Demonstrates how to get a MercadoLibre OAuth2 access token from a desktop application or script.

Important: This example requires that you add a line of code (or a few lines of code) to launch a web browser that navigates to the URL returned by the StartAuth method. The MercadoLibre account owner interactively authorizes the access just for the 1st time in getting the access token. Once the access token is obtained, it can be refreshed with no user interaction.

Also, you must define your app in the MercadoLibre web portal. You would need to add a Redirect URL such as "http://localhost:3017/". The port number in the Redirect URI must match the Chilkat OAuth2's ListenPort and the format of the URL should be exactly "http://localhost:3017/". Do not use "https://" because the redirect from the browser to your app (listening on a background thread in Chilkat) is a localhost-to-localhost connection.

For more information, see https://developers.mercadolibre.com.ar/es_ar/autenticacion-y-autorizacion

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

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

Dim oauth2 As New Chilkat.OAuth2
Dim success As Boolean

' This should be the port in the localhost Redirect URI for your app defined in the MercadoLibre developer portal.  
' The Redirect URI would look like "http://localhost:3017/" if the port number is 3017.
oauth2.ListenPort = 3017

oauth2.AuthorizationEndpoint = "https://auth.mercadolibre.com.ar/authorization"
oauth2.TokenEndpoint = "https://api.mercadolibre.com/oauth/token"

' Replace these with actual values.
oauth2.ClientId = "MY_MERCADOLIBRE_APP_ID"
oauth2.ClientSecret = "MY_MERCADOLIBRE_APP_SECRET"

oauth2.Scope = "read write offline_access"

' Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
Dim url As String = oauth2.StartAuth()
If (oauth2.LastMethodSuccess <> True) Then
    Debug.WriteLine(oauth2.LastErrorText)
    Exit Sub
End If


' 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.
Dim numMsWaited As Integer = 0
While (numMsWaited < 30000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs(100)
    numMsWaited = numMsWaited + 100
End While

' 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) Then
    oauth2.Cancel()
    Debug.WriteLine("No response from the browser!")
    Exit Sub
End If



' 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) Then
    Debug.WriteLine("OAuth2 failed to complete.")
    Debug.WriteLine(oauth2.FailureInfo)
    Exit Sub
End If


If (oauth2.AuthFlowState = 4) Then
    Debug.WriteLine("OAuth2 authorization was denied.")
    Debug.WriteLine(oauth2.AccessTokenResponse)
    Exit Sub
End If


If (oauth2.AuthFlowState <> 3) Then
    Debug.WriteLine("Unexpected AuthFlowState:" & oauth2.AuthFlowState)
    Exit Sub
End If


Debug.WriteLine("OAuth2 authorization granted!")
Debug.WriteLine("Access Token = " & oauth2.AccessToken)

' Get the full JSON response:
Dim json As New Chilkat.JsonObject
json.Load(oauth2.AccessTokenResponse)
json.EmitCompact = False
Debug.WriteLine(json.Emit())

' The JSON response looks like this:

' {
'   "access_token": "APP_USR-8133606632685744-060115-93e1fd8b5e767c51c238df347bd0b288-577628017",
'   "token_type": "bearer",
'   "expires_in": 21600,
'   "scope": "offline_access read write",
'   "user_id": 577625107,
'   "refresh_token": "TG-5ad522a286f1200006ac4ed1-577625007"
' }


' Save the JSON to a file for future requests.
Dim fac As New Chilkat.FileAccess
fac.WriteEntireTextFile("qa_data/tokens/mercadolibre.json",json.Emit(),"utf-8",False)