(Lianja) POP3 Auto-Refresh Office365 Access Token

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Demonstrates how to automatically recover from an expired OAuth2 access token when OAuth2 authentication fails in the POP3 protocol. If the server responds with "-ERR Authentication failure: unknown user name or bad password.", then we refresh the access token and retry.

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

loMailman = createobject("CkMailMan")

loMailman.MailHost = "outlook.office365.com"
loMailman.MailPort = 995
loMailman.PopSsl = .T.

// Use your O365 email address here.
loMailman.PopUsername = "OFFICE365_EMAIL_ADDRESS"

// When using OAuth2 authentication, leave the password empty.
loMailman.PopPassword = ""

// Load our previously obtained OAuth2 access token.
loJsonToken = createobject("CkJsonObject")
llSuccess = loJsonToken.LoadFile("qa_data/tokens/office365.json")
if (llSuccess = .F.) then
    ? loJsonToken.LastErrorText
    release loMailman
    release loJsonToken
    return
endif

loMailman.OAuth2AccessToken = loJsonToken.StringOf("access_token")

// Make the TLS connection to the outlook.office365.com POP3 server.
llSuccess = loMailman.Pop3Connect()
if (llSuccess <> .T.) then
    ? loMailman.LastErrorText
    release loMailman
    release loJsonToken
    return
endif

// Authenticate using XOAUTH2
llSuccess = loMailman.Pop3Authenticate()
if (llSuccess <> .T.) then
    // If we're still connected to the mail server, then it means the server sent a non-success response,
    // Such as:  -ERR Authentication failure: unknown user name or bad password.
    if (loMailman.IsPop3Connected = .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 loMailman
            release loJsonToken
            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

        // Update the mailman with the new access token.
        loMailman.OAuth2AccessToken = loOauth2.AccessToken

        // Retry the authentication.
        llSuccess = loMailman.Pop3Authenticate()
        if (llSuccess = .F.) then
            ? loMailman.LastErrorText
            release loMailman
            release loJsonToken
            release loOauth2
            release loSbJson
            return
        endif

    else
        ? loMailman.LastErrorText
        release loMailman
        release loJsonToken
        release loOauth2
        release loSbJson
        return
    endif

endif

// Find out how many emails are on the server..
lnNumEmails = loMailman.CheckMail()
if (lnNumEmails < 0) then
    ? loMailman.LastErrorText
    release loMailman
    release loJsonToken
    release loOauth2
    release loSbJson
    return
endif

// Examine the POP3 session log:
? loMailman.Pop3SessionLog

// The POP3 session log will look something like this:

// **** Connected to outlook.office365.com:995
// < +OK The Microsoft Exchange POP3 service is ready. [QwBIADIAUABSADEANgBDAEEAMAAwADEAMgAuAG4AYQBtAHAAcgBkADEANgAuAHAAcgBvAGQALgBvAHUAdABsAG8AbwBrAC4AYwBvAG0A]
// > AUTH XOAUTH2
// < + 
// > <base64 string in XOAUTH2 format>
// < -ERR Authentication failure: unknown user name or bad password.
// > AUTH XOAUTH2
// < + 
// > <base64 string in XOAUTH2 format>
// < +OK User successfully authenticated.
// > STAT
// < +OK 248 46637086

// End the POP3 session and close the connection to the GMail server.
llSuccess = loMailman.Pop3EndSession()
if (llSuccess <> .T.) then
    ? loMailman.LastErrorText
    release loMailman
    release loJsonToken
    release loOauth2
    release loSbJson
    return
endif

? "Finished."


release loMailman
release loJsonToken
release loOauth2
release loSbJson