(C) 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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#include <C_CkMailMan.h>
#include <C_CkJsonObject.h>
#include <C_CkOAuth2.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    HCkMailMan mailman;
    HCkJsonObject jsonToken;
    BOOL success;
    HCkOAuth2 oauth2;
    HCkStringBuilder sbJson;
    int numEmails;

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

    mailman = CkMailMan_Create();

    CkMailMan_putMailHost(mailman,"outlook.office365.com");
    CkMailMan_putMailPort(mailman,995);
    CkMailMan_putPopSsl(mailman,TRUE);

    // Use your O365 email address here.
    CkMailMan_putPopUsername(mailman,"OFFICE365_EMAIL_ADDRESS");

    // When using OAuth2 authentication, leave the password empty.
    CkMailMan_putPopPassword(mailman,"");

    // Load our previously obtained OAuth2 access token.
    jsonToken = CkJsonObject_Create();
    success = CkJsonObject_LoadFile(jsonToken,"qa_data/tokens/office365.json");
    if (success == FALSE) {
        printf("%s\n",CkJsonObject_lastErrorText(jsonToken));
        CkMailMan_Dispose(mailman);
        CkJsonObject_Dispose(jsonToken);
        return;
    }

    CkMailMan_putOAuth2AccessToken(mailman,CkJsonObject_stringOf(jsonToken,"access_token"));

    // Make the TLS connection to the outlook.office365.com POP3 server.
    success = CkMailMan_Pop3Connect(mailman);
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        CkMailMan_Dispose(mailman);
        CkJsonObject_Dispose(jsonToken);
        return;
    }

    // Authenticate using XOAUTH2
    success = CkMailMan_Pop3Authenticate(mailman);
    if (success != TRUE) {
        // 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 (CkMailMan_getIsPop3Connected(mailman) == TRUE) {

            // Refresh the OAuth2 access token, and if successful, save the new (refreshed) access token and try authenticating again.
            oauth2 = CkOAuth2_Create();

            // Use your actual Directory (tenant) ID instead of "112d7ed6-71bf-4eba-a866-738364321bfc"
            CkOAuth2_putTokenEndpoint(oauth2,"https://login.microsoftonline.com/112d7ed6-71bf-4eba-a866-738364321bfc/oauth2/v2.0/token");

            // Replace these with your Azure App Registration's actual values.
            CkOAuth2_putClientId(oauth2,"CLIENT_ID");
            CkOAuth2_putClientSecret(oauth2,"CLIENT_SECRET");

            // Get the "refresh_token"
            CkOAuth2_putRefreshToken(oauth2,CkJsonObject_stringOf(jsonToken,"refresh_token"));

            // Send the HTTP POST to refresh the access token..
            success = CkOAuth2_RefreshAccessToken(oauth2);
            if (success != TRUE) {
                printf("%s\n",CkOAuth2_lastErrorText(oauth2));
                CkMailMan_Dispose(mailman);
                CkJsonObject_Dispose(jsonToken);
                CkOAuth2_Dispose(oauth2);
                return;
            }

            printf("New access token: %s\n",CkOAuth2_accessToken(oauth2));
            printf("New refresh token: %s\n",CkOAuth2_refreshToken(oauth2));

            // Update the JSON with the new tokens.
            CkJsonObject_UpdateString(jsonToken,"access_token",CkOAuth2_accessToken(oauth2));
            CkJsonObject_UpdateString(jsonToken,"refresh_token",CkOAuth2_refreshToken(oauth2));

            // Save the new JSON access token response to a file.
            sbJson = CkStringBuilder_Create();
            CkJsonObject_putEmitCompact(jsonToken,FALSE);
            CkJsonObject_EmitSb(jsonToken,sbJson);
            CkStringBuilder_WriteFile(sbJson,"qa_data/tokens/office365.json","utf-8",FALSE);

            printf("New Access Token = %s\n",CkOAuth2_accessToken(oauth2));

            // Update the mailman with the new access token.
            CkMailMan_putOAuth2AccessToken(mailman,CkOAuth2_accessToken(oauth2));

            // Retry the authentication.
            success = CkMailMan_Pop3Authenticate(mailman);
            if (success == FALSE) {
                printf("%s\n",CkMailMan_lastErrorText(mailman));
                CkMailMan_Dispose(mailman);
                CkJsonObject_Dispose(jsonToken);
                CkOAuth2_Dispose(oauth2);
                CkStringBuilder_Dispose(sbJson);
                return;
            }

        }
        else {
            printf("%s\n",CkMailMan_lastErrorText(mailman));
            CkMailMan_Dispose(mailman);
            CkJsonObject_Dispose(jsonToken);
            CkOAuth2_Dispose(oauth2);
            CkStringBuilder_Dispose(sbJson);
            return;
        }

    }

    // Find out how many emails are on the server..
    numEmails = CkMailMan_CheckMail(mailman);
    if (numEmails < 0) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        CkMailMan_Dispose(mailman);
        CkJsonObject_Dispose(jsonToken);
        CkOAuth2_Dispose(oauth2);
        CkStringBuilder_Dispose(sbJson);
        return;
    }

    // Examine the POP3 session log:
    printf("%s\n",CkMailMan_pop3SessionLog(mailman));

    // 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.
    success = CkMailMan_Pop3EndSession(mailman);
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        CkMailMan_Dispose(mailman);
        CkJsonObject_Dispose(jsonToken);
        CkOAuth2_Dispose(oauth2);
        CkStringBuilder_Dispose(sbJson);
        return;
    }

    printf("Finished.\n");


    CkMailMan_Dispose(mailman);
    CkJsonObject_Dispose(jsonToken);
    CkOAuth2_Dispose(oauth2);
    CkStringBuilder_Dispose(sbJson);

    }