(Tcl) Facebook OAuth2 Access Token

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

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load ./chilkat.dll

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

set oauth2 [new_CkOAuth2]

# This should match the Site URL configured for your Facebook APP, such as "http://localhost:3017/"
CkOAuth2_put_ListenPort $oauth2 3017

CkOAuth2_put_AuthorizationEndpoint $oauth2 "https://www.facebook.com/dialog/oauth"
CkOAuth2_put_TokenEndpoint $oauth2 "https://graph.facebook.com/oauth/access_token"

# Replace these with actual values.
CkOAuth2_put_ClientId $oauth2 "FACEBOOK-CLIENT-ID"
CkOAuth2_put_ClientSecret $oauth2 "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.
CkOAuth2_put_Scope $oauth2 "public_profile,user_friends,email,user_posts,user_likes,user_photos,publish_actions"

CkOAuth2_put_CodeChallenge $oauth2 1
CkOAuth2_put_CodeChallengeMethod $oauth2 "S256"

# Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
set url [CkOAuth2_startAuth $oauth2]
if {[CkOAuth2_get_LastMethodSuccess $oauth2] != 1} then {
    puts [CkOAuth2_lastErrorText $oauth2]
    delete_CkOAuth2 $oauth2
    exit
}

# 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.
set numMsWaited 0
while {expr [$numMsWaited < 30000]  &&  [[CkOAuth2_get_AuthFlowState $oauth2] < 3]} {
    CkOAuth2_SleepMs $oauth2 100
    set numMsWaited [expr $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 {[CkOAuth2_get_AuthFlowState $oauth2] < 3} then {
    CkOAuth2_Cancel $oauth2
    puts "No response from the browser!"
    delete_CkOAuth2 $oauth2
    exit
}

# 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 {[CkOAuth2_get_AuthFlowState $oauth2] == 5} then {
    puts "OAuth2 failed to complete."
    puts [CkOAuth2_failureInfo $oauth2]
    delete_CkOAuth2 $oauth2
    exit
}

if {[CkOAuth2_get_AuthFlowState $oauth2] == 4} then {
    puts "OAuth2 authorization was denied."
    puts [CkOAuth2_accessTokenResponse $oauth2]
    delete_CkOAuth2 $oauth2
    exit
}

if {[CkOAuth2_get_AuthFlowState $oauth2] != 3} then {
    puts "Unexpected AuthFlowState:[CkOAuth2_get_AuthFlowState $oauth2]"
    delete_CkOAuth2 $oauth2
    exit
}

puts "OAuth2 authorization granted!"
puts "Access Token = [CkOAuth2_accessToken $oauth2]"

delete_CkOAuth2 $oauth2