(Ruby) Facebook OAuth2 Access Token

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

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

# It requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

oauth2 = Chilkat::CkOAuth2.new()

# This should match the Site URL configured for your Facebook APP, such as "http://localhost:3017/"
oauth2.put_ListenPort(3017)

oauth2.put_AuthorizationEndpoint("https://www.facebook.com/dialog/oauth")
oauth2.put_TokenEndpoint("https://graph.facebook.com/oauth/access_token")

# Replace these with actual values.
oauth2.put_ClientId("FACEBOOK-CLIENT-ID")
oauth2.put_ClientSecret("FACEBOOK-CLIENT-SECRET")

# Set the Scope to a comma-separated list of permissions the app wishes to request.
# See https://developers.facebook.com/docs/facebook-login/permissions/ for a full list of permissions.
oauth2.put_Scope("public_profile,user_friends,email,user_posts,user_likes,user_photos,publish_actions")

oauth2.put_CodeChallenge(true)
oauth2.put_CodeChallengeMethod("S256")

# Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
url = oauth2.startAuth()
if (oauth2.get_LastMethodSuccess() != true)
    print oauth2.lastErrorText() + "\n";
    exit
end

# 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 Facebook 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
while (numMsWaited < 30000) and (oauth2.get_AuthFlowState() < 3)
    oauth2.SleepMs(100)
    numMsWaited = numMsWaited + 100
end

# 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.get_AuthFlowState() < 3)
    oauth2.Cancel()
    print "No response from the browser!" + "\n";
    exit
end

# 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.get_AuthFlowState() == 5)
    print "OAuth2 failed to complete." + "\n";
    print oauth2.failureInfo() + "\n";
    exit
end

if (oauth2.get_AuthFlowState() == 4)
    print "OAuth2 authorization was denied." + "\n";
    print oauth2.accessTokenResponse() + "\n";
    exit
end

if (oauth2.get_AuthFlowState() != 3)
    print "Unexpected AuthFlowState:" + oauth2.get_AuthFlowState().to_s() + "\n";
    exit
end

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