(CkPython) Refresh GMail SMTP OAuth2 Access Token

Demonstrates how to refresh an access token for sending email via GMail (SMTP).

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import sys
import chilkat

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

# See Get GMail SMTP Access Token 
# for sample code showing how to obtain a GMail SMTP access token for desktop apps.

# It is assumed we previously obtained an OAuth2 access token for GMail (one with a scope for sending email).

jsonToken = chilkat.CkJsonObject()
success = jsonToken.LoadFile("qa_data/tokens/_gmailSmtp.json")
if (success != True):
    print("Failed to load _gmailSmtp.json")
    sys.exit()

# The access token JSON looks something like this:

# 	{ 
# 	 "access_token": "abac.Ci-ZabcdF37-NUrmSzxbHxTsMbtlN-uPfabcdAQN_2ekzj0s5ofCzRabcdTDMGaa2Q",
# 	 "token_type": "Bearer",
# 	 "expires_in": 3600,
# 	 "refresh_token": "1/lEe5abcdNJ77eOSDBabcdkQGVmDalkwabcdR2Hatbo"
# 	}
# 

oauth2 = chilkat.CkOAuth2()

oauth2.put_TokenEndpoint("https://www.googleapis.com/oauth2/v4/token")

# Replace these with actual values.
oauth2.put_ClientId("GOOGLE-CLIENT-ID")
oauth2.put_ClientSecret("GOOGLE-CLIENT-SECRET")

# Get the "refresh_token"
oauth2.put_RefreshToken(jsonToken.stringOf("refresh_token"))

# Send the HTTP POST to refresh the access token..
success = oauth2.RefreshAccessToken()
if (success != True):
    print(oauth2.lastErrorText())
    sys.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.
jsonToken.UpdateString("access_token",oauth2.accessToken())

# Save the new JSON access token response to a file.
sbJson = chilkat.CkStringBuilder()
jsonToken.put_EmitCompact(False)
jsonToken.EmitSb(sbJson)
sbJson.WriteFile("qa_data/tokens/_gmailSmtp.json","utf-8",False)

print("OAuth2 authorization granted!")
print("New Access Token = " + oauth2.accessToken())