(C++) PayPal -- Get an OAuth 2.0 Access Token

Demonstrates how to send a request to get a PayPal OAuth2 access token. Sends an HTTP request equivalent to the following:

curl https://api.sandbox.paypal.com/v1/oauth2/token \
  -H "Accept: application/json" \
  -H "Accept-Language: en_US" \
  -u "Client-Id:Secret" \
  -d "grant_type=client_credentials"

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#include <CkRest.h>
#include <CkJsonObject.h>
#include <CkDateTime.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    // Note: Requires Chilkat v9.5.0.64 or greater.

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

    CkRest rest;

    // Make the initial connection.
    // A single REST object, once connected, can be used for many PayPal REST API calls.
    // The auto-reconnect indicates that if the already-established HTTPS connection is closed,
    // then it will be automatically re-established as needed.
    bool bAutoReconnect = true;
    bool success = rest.Connect("api.sandbox.paypal.com",443,true,bAutoReconnect);
    if (success != true) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    // Duplicate this request:

    // 	curl https://api.sandbox.paypal.com/v1/oauth2/token \
    // 	  -H "Accept: application/json" \
    // 	  -H "Accept-Language: en_US" \
    // 	  -u "Client-Id:Secret" \
    // 	  -d "grant_type=client_credentials"

    rest.AddHeader("Accept","application/json");
    rest.AddHeader("Accept-Language","en_US");

    // For additional help on where to find  your client ID and API secret, see PayPal Client_ID and API_Secret
    rest.SetAuthBasic("PAYPAL_REST_API_CLIENT_ID","PAYPAL_REST_API_SECRET");

    rest.AddQueryParam("grant_type","client_credentials");

    const char *responseStr = rest.fullRequestFormUrlEncoded("POST","/v1/oauth2/token");
    if (rest.get_LastMethodSuccess() != true) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    std::cout << rest.lastRequestHeader() << "\r\n";

    // A sample response:

    // 	{
    // 	  "scope": "https://api.paypal.com/v1/payments/.* https://api.paypal.com/v1/vault/credit-card https://api.paypal.com/v1/vault/credit-card/.*",
    // 	  "access_token": "EEwJ6tF9x5WCIZDYzyZGaz6Khbw7raYRIBV_WxVvgmsG",
    // 	  "token_type": "Bearer",
    // 	  "app_id": "APP-6XR95014BA15863X",
    // 	  "expires_in": 28800
    // 	}

    CkJsonObject json;
    json.Load(responseStr);
    json.put_EmitCompact(false);

    // Check the response status code.  A 200 indicates success..
    if (rest.get_ResponseStatusCode() != 200) {
        std::cout << json.emit() << "\r\n";
        std::cout << "Failed." << "\r\n";
        return;
    }

    // Given that the access token expires in approx 8 hours,
    // let's record the date/time this token was created.
    // This will allow us to know beforehand if the token
    // is expired (and we can then fetch a new token).
    CkDateTime dateTime;
    bool bLocalTime = false;
    int dtNow = dateTime.GetAsUnixTime(bLocalTime);
    json.AppendInt("tokenCreateTimeUtc",dtNow);

    // Examine the access token and save to a file.
    std::cout << "Access Token: " << json.stringOf("access_token") << "\r\n";
    std::cout << "Full JSON Response:" << "\r\n";
    std::cout << json.emit() << "\r\n";

    CkStringBuilder sbResponse;
    sbResponse.Append(json.emit());
    bool bEmitBom = false;
    sbResponse.WriteFile("qa_data/tokens/paypal.json","utf-8",bEmitBom);
    }