(Lianja) IMAP Auto-Refresh Office365 Access Token

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Demonstrates how to automatically recover from an expired access token when OAuth2 authentication fails in the IMAP protocol. If the server responds with "NO AUTHENTICATE failed.", then we refresh the access token and retry.

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// An Office365 OAuth2 access token must first be obtained prior
// to running this code.

// Getting the OAuth2 access token for the 1st time requires the O365 account owner's 
// interactive authorizaition via a web browser.  Afterwards, the access token
// can be repeatedly refreshed automatically.

// See the following examples for getting and refreshing an OAuth2 access token

// Get Office365 SMTP/IMAP/POP3 OAuth2 Access Token
// Refresh Office365 SMTP/IMAP/POP3 OAuth2 Access Token

// First get our previously obtained OAuth2 access token.
loJsonToken = createobject("CkJsonObject")
llSuccess = loJsonToken.LoadFile("qa_data/tokens/office365.json")
if (llSuccess = .F.) then
    ? "Failed to open the office365 OAuth JSON file."
    release loJsonToken
    return
endif

loImap = createobject("CkImap")

loImap.Ssl = .T.
loImap.Port = 993

// Connect to the Office365 IMAP server.
llSuccess = loImap.Connect("outlook.office365.com")
if (llSuccess <> .T.) then
    ? loImap.LastErrorText
    release loJsonToken
    release loImap
    return
endif

// Use OAuth2 authentication.
loImap.AuthMethod = "XOAUTH2"

// Login using our username (i.e. email address) and the access token for the password.
llSuccess = loImap.Login("OFFICE365_EMAIL_ADDRESS",loJsonToken.StringOf("access_token"))
if (llSuccess <> .T.) then
    lcLoginLastErrorText = loImap.LastErrorText

    // If we're still connected to the mail server, then it means the server sent a non-success response,
    // Such as:  NO AUTHENTICATE failed.
    if (loImap.IsConnected() = .T.) then

        // Refresh the OAuth2 access token, and if successful, save the new (refreshed) access token and try authenticating again.
        loOauth2 = createobject("CkOAuth2")

        // Use your actual Directory (tenant) ID instead of "112d7ed6-71bf-4eba-a866-738364321bfc"
        loOauth2.TokenEndpoint = "https://login.microsoftonline.com/112d7ed6-71bf-4eba-a866-738364321bfc/oauth2/v2.0/token"

        // Replace these with your Azure App Registration's actual values.
        loOauth2.ClientId = "CLIENT_ID"
        loOauth2.ClientSecret = "CLIENT_SECRET"

        // Get the "refresh_token"
        loOauth2.RefreshToken = loJsonToken.StringOf("refresh_token")

        // Send the HTTP POST to refresh the access token..
        llSuccess = loOauth2.RefreshAccessToken()
        if (llSuccess <> .T.) then
            ? loOauth2.LastErrorText
            release loJsonToken
            release loImap
            release loOauth2
            return
        endif

        ? "New access token: " + loOauth2.AccessToken
        ? "New refresh token: " + loOauth2.RefreshToken

        // Update the JSON with the new tokens.
        loJsonToken.UpdateString("access_token",loOauth2.AccessToken)
        loJsonToken.UpdateString("refresh_token",loOauth2.RefreshToken)

        // Save the new JSON access token response to a file.
        loSbJson = createobject("CkStringBuilder")
        loJsonToken.EmitCompact = .F.
        loJsonToken.EmitSb(loSbJson)
        loSbJson.WriteFile("qa_data/tokens/office365.json","utf-8",.F.)

        ? "New Access Token = " + loOauth2.AccessToken

        // Retry the login.
        llSuccess = loImap.Login("OFFICE365_EMAIL_ADDRESS",loJsonToken.StringOf("access_token"))
        if (llSuccess = .F.) then
            ? loImap.LastErrorText
            release loJsonToken
            release loImap
            release loOauth2
            release loSbJson
            return
        endif

    else
        // Show the last error text for the call to Login
        ? lcLoginLastErrorText
        release loJsonToken
        release loImap
        release loOauth2
        release loSbJson
        return
    endif

else
    ? "O365 OAuth authentication is successful."
endif

// Do something...
llSuccess = loImap.SelectMailbox("Inbox")
if (llSuccess <> .T.) then
    ? loImap.LastErrorText
    release loJsonToken
    release loImap
    release loOauth2
    release loSbJson
    return
endif

// Your application can continue to do other things in the IMAP session....

// When finished, logout and close the connection.
llSuccess = loImap.Logout()
llSuccess = loImap.Disconnect()

? "Finished."


release loJsonToken
release loImap
release loOauth2
release loSbJson