(C) OAuth2 for a GMail using a JSON Service Account Key

Demonstrates how get an OAuth2 access token for GMail (Google Service Account) using a JSON private key.

After the access token is obtained, it may be used to send email. When the access token expires, a new access token needs to be obtained (using this same procedure).

Note: This is for OAuth2 using Google Service account keys.

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#include <C_CkFileAccess.h>
#include <C_CkAuthGoogle.h>
#include <C_CkSocket.h>
#include <C_CkMailMan.h>
#include <C_CkEmail.h>

void ChilkatSample(void)
    {
    HCkFileAccess fac;
    const char *jsonKey;
    HCkAuthGoogle gAuth;
    HCkSocket tlsSock;
    BOOL success;
    HCkMailMan mailman;
    HCkEmail email;

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

    // First load the JSON key into a string.
    fac = CkFileAccess_Create();
    jsonKey = CkFileAccess_readEntireTextFile(fac,"qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8");
    if (CkFileAccess_getLastMethodSuccess(fac) != TRUE) {
        printf("%s\n",CkFileAccess_lastErrorText(fac));
        CkFileAccess_Dispose(fac);
        return;
    }

    // A JSON private key should look like this:

    // 	{
    // 	  "type": "service_account",
    // 	  "project_id": "chilkattest-1350",
    // 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
    // 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
    // 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
    // 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
    // 	  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    // 	  "token_uri": "https://accounts.google.com/o/oauth2/token",
    // 	  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    // 	  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
    // 	}

    gAuth = CkAuthGoogle_Create();
    CkAuthGoogle_putJsonKey(gAuth,jsonKey);

    // Choose a scope.
    CkAuthGoogle_putScope(gAuth,"https://mail.google.com/");

    // Request an access token that is valid for this many seconds.
    CkAuthGoogle_putExpireNumSeconds(gAuth,3600);

    // If the application is requesting delegated access:
    // The email address of the user for which the application is requesting delegated access,
    // then set the email address here. (Otherwise leave it empty.)
    CkAuthGoogle_putSubEmailAddress(gAuth,"");

    // Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
    // The Chilkat socket object is used so that the connection can be established
    // through proxies or an SSH tunnel if desired.
    tlsSock = CkSocket_Create();
    success = CkSocket_Connect(tlsSock,"www.googleapis.com",443,TRUE,5000);
    if (success != TRUE) {
        printf("%s\n",CkSocket_lastErrorText(tlsSock));
        CkFileAccess_Dispose(fac);
        CkAuthGoogle_Dispose(gAuth);
        CkSocket_Dispose(tlsSock);
        return;
    }

    // Send the request to obtain the access token.
    success = CkAuthGoogle_ObtainAccessToken(gAuth,tlsSock);
    if (success != TRUE) {
        printf("%s\n",CkAuthGoogle_lastErrorText(gAuth));
        CkFileAccess_Dispose(fac);
        CkAuthGoogle_Dispose(gAuth);
        CkSocket_Dispose(tlsSock);
        return;
    }

    // Examine the access token:
    printf("Access Token: %s\n",CkAuthGoogle_accessToken(gAuth));

    // Now that we have the access token, it may be used to send email
    // while it remains valid.  Once the access token expires, a new access token 
    // should be obtained using the same code as above.

    // -----------------------------------------------------------------------
    mailman = CkMailMan_Create();

    // Set the properties for the GMail SMTP server:
    CkMailMan_putSmtpHost(mailman,"smtp.gmail.com");
    CkMailMan_putSmtpPort(mailman,587);
    CkMailMan_putStartTLS(mailman,TRUE);

    CkMailMan_putSmtpUsername(mailman,"YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS");
    CkMailMan_putOAuth2AccessToken(mailman,CkAuthGoogle_accessToken(gAuth));

    // Create a new email object
    email = CkEmail_Create();

    CkEmail_putSubject(email,"This is a test");
    CkEmail_putBody(email,"This is a test");
    CkEmail_putFrom(email,"YOUR NAME <YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS>");
    success = CkEmail_AddTo(email,"Chilkat Admin","admin@chilkatsoft.com");
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    // Call SendEmail to connect to the SMTP server and send.
    // The connection (i.e. session) to the SMTP server remains
    // open so that subsequent SendEmail calls may use the
    // same connection.  
    success = CkMailMan_SendEmail(mailman,email);
    if (success != TRUE) {
        printf("%s\n",CkMailMan_lastErrorText(mailman));
        CkFileAccess_Dispose(fac);
        CkAuthGoogle_Dispose(gAuth);
        CkSocket_Dispose(tlsSock);
        CkMailMan_Dispose(mailman);
        CkEmail_Dispose(email);
        return;
    }

    // You may close the connection here.  If the connection is kept open, 
    // the next call to mailman.SendEmail will continue using the already-established connection
    // (and automatically re-connect if needed).
    success = CkMailMan_CloseSmtpConnection(mailman);
    if (success != TRUE) {
        printf("Connection to SMTP server not closed cleanly.\n");
    }

    printf("Email Sent via GMail using an OAuth2 Service Account Key.\n");


    CkFileAccess_Dispose(fac);
    CkAuthGoogle_Dispose(gAuth);
    CkSocket_Dispose(tlsSock);
    CkMailMan_Dispose(mailman);
    CkEmail_Dispose(email);

    }