(Tcl) Google Photos Refresh Access Token

Demonstrates how to refresh a Google Access Token. Refreshing an oauth2 access token does not need to display an interactive browser like when originally getting the OAuth2 access token for the 1st time. Your application can do it automatically without user interaction.

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load ./chilkat.dll

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

# It is assumed we previously obtained an OAuth2 access token.
# This example loads the JSON access token file 
# saved by this example: Get Google Photos OAuth2 Access Token

set jsonToken [new_CkJsonObject]

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

# The access token JSON looks like this:

# {
#   "access_token": "ya29.GlamBqWR6cp8lEfJMmTHVEua45912XLKoq4djyHl_Z3CEIzsPLIZkJSGie5oOrbaggy1rjJHn1zW5bjqSesGr5MEYIp9Hx-0CuvjVYf8srg2jeaDMwMACvzemp43",
#   "expires_in": 3600,
#   "refresh_token": "1/rl6k16nysDl9Bp1EhRH9F1WyRIoiSQAvko49Z4yY694MT5V1QXLj2ibNZGaRgek0",
#   "scope": "https://www.googleapis.com/auth/photoslibrary",
#   "token_type": "Bearer"
# }

set oauth2 [new_CkOAuth2]

CkOAuth2_put_TokenEndpoint $oauth2 "https://www.googleapis.com/oauth2/v4/token"

# Replace these with actual values.
CkOAuth2_put_ClientId $oauth2 "GOOGLE-CLIENT-ID"
CkOAuth2_put_ClientSecret $oauth2 "GOOGLE-CLIENT-SECRET"

# Get the "refresh_token"
CkOAuth2_put_RefreshToken $oauth2 [CkJsonObject_stringOf $jsonToken "refresh_token"]

# Send the HTTP POST to refresh the access token..
set success [CkOAuth2_RefreshAccessToken $oauth2]
if {$success != 1} then {
    puts [CkOAuth2_lastErrorText $oauth2]
    delete_CkJsonObject $jsonToken
    delete_CkOAuth2 $oauth2
    exit
}

# The response contains a new access token, but we must keep
# our existing refresh token for when we need to refresh again in the future.
CkJsonObject_UpdateString $jsonToken "access_token" [CkOAuth2_accessToken $oauth2]

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

CkJsonObject_put_EmitCompact $jsonToken 0
CkJsonObject_EmitSb $jsonToken $sbJson
CkStringBuilder_WriteFile $sbJson "qa_data/tokens/googlePhotos.json" "utf-8" 0

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

delete_CkJsonObject $jsonToken
delete_CkOAuth2 $oauth2
delete_CkStringBuilder $sbJson