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Facebook OAuth2 Access Token

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

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Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

# To further clarify, see OAuth 2.0 Authorization Flow

$oauth2 = New-Object Chilkat.OAuth2

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

$oauth2.AuthorizationEndpoint = "https://www.facebook.com/dialog/oauth"
$oauth2.TokenEndpoint = "https://graph.facebook.com/oauth/access_token"

# Replace this with your actual App ID
$oauth2.ClientId = "APP_ID"

# 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.Scope = "public_profile,user_friends,email,user_posts,user_likes,user_photos"

# This is for Require Proof Key for Code Exchange (PKCE)
# See OAuth2 PKCE Explained
$oauth2.CodeChallenge = $true
$oauth2.CodeChallengeMethod = "S256"

# Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
$url = $oauth2.StartAuth()
if ($oauth2.LastMethodSuccess -ne $true) {
    $($oauth2.LastErrorText)
    exit
}

$("url = " + $url)

# Launch the default browser on the system and navigate to the url.
# The LaunchBrowser method was added in Chilkat v10.1.2.
$success = $oauth2.LaunchBrowser($url)
if ($success -eq $false) {
    $($oauth2.LastErrorText)
    exit
}

# Wait for the user to approve or deny authorization in the browser.
$numMsWaited = 0
while (($numMsWaited -lt 90000) -and ($oauth2.AuthFlowState -lt 3)) {
    $oauth2.SleepMs(100)
    $numMsWaited = $numMsWaited + 100
}

# If the browser does not respond within the specified time, AuthFlowState will be:
# 
# 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
# 2: Waiting for Final Response – The thread is awaiting the final access token response.
# In either case, cancel the background task initiated by StartAuth.

if ($oauth2.AuthFlowState -lt 3) {
    $oauth2.Cancel()
    $("No response from the browser!")
    exit
}

# Check AuthFlowState to determine if authorization was granted, denied, or failed:
# 
# 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
# 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
# 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

if ($oauth2.AuthFlowState -eq 5) {
    $("OAuth2 failed to complete.")
    $($oauth2.FailureInfo)
    exit
}

if ($oauth2.AuthFlowState -eq 4) {
    $("OAuth2 authorization was denied.")
    $($oauth2.AccessTokenResponse)
    exit
}

if ($oauth2.AuthFlowState -ne 3) {
    $("Unexpected AuthFlowState:" + $oauth2.AuthFlowState)
    exit
}

$("OAuth2 authorization granted!")
$("Access Token = " + $oauth2.AccessToken)