(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 <C_CkRest.h>
#include <C_CkJsonObject.h>
#include <C_CkDateTime.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    HCkRest rest;
    BOOL bAutoReconnect;
    BOOL success;
    const char *responseStr;
    HCkJsonObject json;
    HCkDateTime dateTime;
    BOOL bLocalTime;
    int dtNow;
    HCkStringBuilder sbResponse;
    BOOL bEmitBom;

    // 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.

    rest = CkRest_Create();

    // 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.
    bAutoReconnect = TRUE;
    success = CkRest_Connect(rest,"api.sandbox.paypal.com",443,TRUE,bAutoReconnect);
    if (success != TRUE) {
        printf("%s\n",CkRest_lastErrorText(rest));
        CkRest_Dispose(rest);
        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"

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

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

    CkRest_AddQueryParam(rest,"grant_type","client_credentials");

    responseStr = CkRest_fullRequestFormUrlEncoded(rest,"POST","/v1/oauth2/token");
    if (CkRest_getLastMethodSuccess(rest) != TRUE) {
        printf("%s\n",CkRest_lastErrorText(rest));
        CkRest_Dispose(rest);
        return;
    }

    printf("%s\n",CkRest_lastRequestHeader(rest));

    // 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
    // 	}

    json = CkJsonObject_Create();
    CkJsonObject_Load(json,responseStr);
    CkJsonObject_putEmitCompact(json,FALSE);

    // Check the response status code.  A 200 indicates success..
    if (CkRest_getResponseStatusCode(rest) != 200) {
        printf("%s\n",CkJsonObject_emit(json));
        printf("Failed.\n");
        CkRest_Dispose(rest);
        CkJsonObject_Dispose(json);
        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).
    dateTime = CkDateTime_Create();
    bLocalTime = FALSE;
    dtNow = CkDateTime_GetAsUnixTime(dateTime,bLocalTime);
    CkJsonObject_AppendInt(json,"tokenCreateTimeUtc",dtNow);

    // Examine the access token and save to a file.
    printf("Access Token: %s\n",CkJsonObject_stringOf(json,"access_token"));
    printf("Full JSON Response:\n");
    printf("%s\n",CkJsonObject_emit(json));

    sbResponse = CkStringBuilder_Create();
    CkStringBuilder_Append(sbResponse,CkJsonObject_emit(json));
    bEmitBom = FALSE;
    CkStringBuilder_WriteFile(sbResponse,"qa_data/tokens/paypal.json","utf-8",bEmitBom);


    CkRest_Dispose(rest);
    CkJsonObject_Dispose(json);
    CkDateTime_Dispose(dateTime);
    CkStringBuilder_Dispose(sbResponse);

    }