(Tcl) Refresh GMail OAuth2 Access Token

Demonstrates how to refresh an expired or soon-to-expire GMail OAuth2 access token.

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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 GMail OAuth2 Access Token

set jsonToken [new_CkJsonObject]

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

# The access token JSON looks like this:

# 	{ 
# 	 "access_token": "abac.Ci-ZabcdF37-VUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5osCzRabcdTDMGaa2Q",
# 	 "token_type": "Bearer",
# 	 "expires_in": 3600,
# 	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
# 	}
# 

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/gmail.json" "utf-8" 0

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

delete_CkJsonObject $jsonToken
delete_CkOAuth2 $oauth2
delete_CkStringBuilder $sbJson