(Tcl) Refresh Expiring OAuth2 Access Token for Azure Registered App

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load ./chilkat.dll

# We previously obtained an access token and saved the JSON to a file using this example:
# Get OAuth2 Access Token for Azure Registered App

# This example will examine the JSON and expiration date, and if near expiration will
# refresh the access token.

set json [new_CkJsonObject]

set success [CkJsonObject_LoadFile $json "qa_data/tokens/_myAzureApp.json"]
if {$success != 1} then {
    puts "Failed to load the access token."
    delete_CkJsonObject $json
    exit
}

# The contents of the JSON look like this:
# {
#   "token_type": "Bearer",
#   "scope": "User.Read Mail.ReadWrite Mail.Send",
#   "expires_in": 3600,
#   "ext_expires_in": 0,
#   "access_token": "EwBAA8l6B...",
#   "refresh_token": "MCRMdbe6Cd...",
#   "id_token": "eyJ0eXAiOiJ...",
#   "expires_on": "1494112119"
# }

# The "expires_on" value is a Unix time.
set dtExpire [new_CkDateTime]

CkDateTime_SetFromUnixTime $dtExpire 0 [CkJsonObject_IntOf $json "expires_on"]

# If this date/time expires within 10 minutes of the current system time, refresh the token.
if {[CkDateTime_ExpiresWithin $dtExpire 10 "minutes"] != 1} then {
    puts "No need to refresh, the access token won't expire within the next 10 minutes."
    delete_CkJsonObject $json
    delete_CkDateTime $dtExpire
    exit
}

# OK, we need to refresh the access token..
set oauth2 [new_CkOAuth2]

# Note: The endpoint depends on the Azure App Registration.
# See How to Choose the Correct Endpoints for your Azure App Registration
CkOAuth2_put_TokenEndpoint $oauth2 "https://login.microsoftonline.com/common/oauth2/v2.0/token"

# Use your client ID.
CkOAuth2_put_ClientId $oauth2 "CLIENT_ID"

# Get the existing refresh token.
CkOAuth2_put_RefreshToken $oauth2 [CkJsonObject_stringOf $json "refresh_token"]

# Send the HTTP POST to refresh the access token.
set success [CkOAuth2_RefreshAccessToken $oauth2]
if {$success == 0} then {
    puts [CkOAuth2_lastErrorText $oauth2]
    delete_CkJsonObject $json
    delete_CkDateTime $dtExpire
    delete_CkOAuth2 $oauth2
    exit
}

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

# Get the full JSON response:
CkJsonObject_Load $json [CkOAuth2_accessTokenResponse $oauth2]
CkJsonObject_put_EmitCompact $json 0

# If an "expires_on" member does not exist, then add the JSON member by
# getting the current system date/time and adding the "expires_in" seconds.
# This way we'll know when the token expires.
if {[CkJsonObject_HasMember $json "expires_on"] != 1} then {
    CkDateTime_SetFromCurrentSystemTime $dtExpire
    CkDateTime_AddSeconds $dtExpire [CkJsonObject_IntOf $json "expires_in"]
    CkJsonObject_AppendString $json "expires_on" [CkDateTime_getAsUnixTimeStr $dtExpire 0]
}

puts [CkJsonObject_emit $json]

# Save the new access token JSON to a file for future requests.
set fac [new_CkFileAccess]

CkFileAccess_WriteEntireTextFile $fac "qa_data/tokens/_myAzureApp.json" [CkJsonObject_emit $json] "utf-8" 0

delete_CkJsonObject $json
delete_CkDateTime $dtExpire
delete_CkOAuth2 $oauth2
delete_CkFileAccess $fac