(Tcl) Get a Xero OAuth2 Access Token via PKCE

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Gets a Xero OAuth2 access token via PKCE.

For more information, see https://github.com/XeroAPI/Xero-Postman-Tutorial-PKCE-Edition

Chilkat Tcl Extension Downloads Chilkat Tcl Extension Downloads

load ./chilkat.dll

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

set oauth2 [new_CkOAuth2]

# For Xero OAuth2, set the listen port equal to the port used
# in the Authorized Redirect URL for the Client ID.
# For example, in this case the Authorized Redirect URL would be http://localhost:55568/
# (The final "/" char is important to include in your Authorized Redirect URL in the Xero application settings in the Xero developer portal.)
# Your app should choose a port not likely not used by any other application.
# See Xero OAuth2 for Desktop Apps for more information.
CkOAuth2_put_ListenPort $oauth2 55568

CkOAuth2_put_AuthorizationEndpoint $oauth2 "https://login.xero.com/identity/connect/authorize"
CkOAuth2_put_TokenEndpoint $oauth2 "https://identity.xero.com/connect/token"

# Replace this with your actual Client ID.
CkOAuth2_put_ClientId $oauth2 "XERO_APP_OAUTH2_CLIENT_ID"

# To use PKCE, enable code challenge and set the code challenge method to "S256".
CkOAuth2_put_CodeChallenge $oauth2 1
CkOAuth2_put_CodeChallengeMethod $oauth2 "S256"

# See https://developer.xero.com/documentation/oauth2/scopes for a complete list of scopes.
# You will need to change the scopes depending on what access is needed..
CkOAuth2_put_Scope $oauth2 "openid profile email accounting.transactions accounting.attachments accounting.settings payroll.employees offline_access"

# 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
}

puts "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        
# in dBASE: run(false, 'rundll32 url.dll,FileProtocolHandler "' + lcUrl + '"')
# 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 60 seconds.
set numMsWaited 0
while {expr [$numMsWaited < 60000]  &&  [[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
}

# Save the full JSON access token response to a file.
set sbJson [new_CkStringBuilder]

CkStringBuilder_Append $sbJson [CkOAuth2_accessTokenResponse $oauth2]
CkStringBuilder_WriteFile $sbJson "qa_data/tokens/xero-access-token.json" "utf-8" 0

# The saved JSON response looks like this:

# 	{
# 	 "access_token": "...",
# 	 "token_type": "Bearer",
# 	 "expires_in": 3600,
# 	 "refresh_token": "..."
# 	}
# 
puts "OAuth2 authorization granted!"
puts "Access Token = [CkOAuth2_accessToken $oauth2]"

delete_CkOAuth2 $oauth2
delete_CkStringBuilder $sbJson