(C) Dropbox: OAuth2 Authorization to Obtain an Access Token

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This example runs the OAuth 2.0 authorization flow that lets the user sign in to Dropbox and authorize your app.

Note: This example requires Chilkat v10.1.2 or greater.

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#include <C_CkOAuth2.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    HCkOAuth2 oauth2;
    const char *url;
    BOOL success;
    int numMsWaited;
    HCkJsonObject json;

    // For more information about the OAuth2, see OAuth 2.0 Authorization Flow

    oauth2 = CkOAuth2_Create();

    // The port should match the Authorized Redirect URL in your Dropbox app, 
    // which would look like "http://localhost:3017/"
    CkOAuth2_putListenPort(oauth2,3017);

    // IMPORTANT: One of the OAuth2 redirect URIs for your Dropbox app must be
    // exactly this string:  http://localhost:3017/

    CkOAuth2_putAuthorizationEndpoint(oauth2,"https://www.dropbox.com/oauth2/authorize");
    CkOAuth2_putTokenEndpoint(oauth2,"https://api.dropboxapi.com/oauth2/token");

    // Replace this with your actual Dropbox App Key
    CkOAuth2_putClientId(oauth2,"DROPBOX_APP_KEY");

    // This is for Require Proof Key for Code Exchange (PKCE)
    // See OAuth2 PKCE Explained
    CkOAuth2_putCodeChallenge(oauth2,TRUE);
    CkOAuth2_putCodeChallengeMethod(oauth2,"S256");

    // Add token_access_type=offline to also get a refresh token in the response
    CkOAuth2_AddAuthQueryParam(oauth2,"token_access_type","offline");

    // Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
    url = CkOAuth2_startAuth(oauth2);
    if (CkOAuth2_getLastMethodSuccess(oauth2) != TRUE) {
        printf("%s\n",CkOAuth2_lastErrorText(oauth2));
        CkOAuth2_Dispose(oauth2);
        return;
    }

    printf("url = %s\n",url);

    // Launch the default browser on the system and navigate to the url.
    // The LaunchBrowser method was added in Chilkat v10.1.2.
    success = CkOAuth2_LaunchBrowser(oauth2,url);
    if (success == FALSE) {
        printf("%s\n",CkOAuth2_lastErrorText(oauth2));
        CkOAuth2_Dispose(oauth2);
        return;
    }

    // Wait for the user to approve or deny authorization in the browser.
    numMsWaited = 0;
    while ((numMsWaited < 90000) && (CkOAuth2_getAuthFlowState(oauth2) < 3)) {
        CkOAuth2_SleepMs(oauth2,100);
        numMsWaited = numMsWaited + 100;
    }

    // If the browser does not respond within the specified time, AuthFlowState will be:
    // 
    // 1: Waiting for Redirect - The OAuth2 background thread is waiting for the browser's redirect request.
    // 2: Waiting for Final Response - The thread is awaiting the final access token response.
    // In either case, cancel the background task initiated by StartAuth.

    if (CkOAuth2_getAuthFlowState(oauth2) < 3) {
        CkOAuth2_Cancel(oauth2);
        printf("No response from the browser!\n");
        CkOAuth2_Dispose(oauth2);
        return;
    }

    // Check AuthFlowState to determine if authorization was granted, denied, or failed:
    // 
    // 3: Success - OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
    // 4: Access Denied - OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
    // 5: Failure - OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

    if (CkOAuth2_getAuthFlowState(oauth2) == 5) {
        printf("OAuth2 failed to complete.\n");
        printf("%s\n",CkOAuth2_failureInfo(oauth2));
        CkOAuth2_Dispose(oauth2);
        return;
    }

    if (CkOAuth2_getAuthFlowState(oauth2) == 4) {
        printf("OAuth2 authorization was denied.\n");
        printf("%s\n",CkOAuth2_accessTokenResponse(oauth2));
        CkOAuth2_Dispose(oauth2);
        return;
    }

    if (CkOAuth2_getAuthFlowState(oauth2) != 3) {
        printf("Unexpected AuthFlowState:%d\n",CkOAuth2_getAuthFlowState(oauth2));
        CkOAuth2_Dispose(oauth2);
        return;
    }

    printf("OAuth2 authorization granted!\n");

    json = CkJsonObject_Create();
    CkJsonObject_Load(json,CkOAuth2_accessTokenResponse(oauth2));
    CkJsonObject_putEmitCompact(json,FALSE);

    printf("Access Token Response = %s\n",CkJsonObject_emit(json));

    // A sample access token response:

    // {
    //   "access_token": "...",
    //   "token_type": "bearer",
    //   "expires_in": 14399,
    //   "refresh_token": "...",
    //   "scope": "account_info.read",
    //   "uid": "562542581",
    //   "account_id": "dbid:AACQhDS0E3_Vb72Ynd0F-GxGWdTI2qcTHzA"
    // }

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

    // Save the JSON access token response to a file for subsequent use..
    CkJsonObject_WriteFile(json,"qa_data/tokens/dropbox.json");


    CkOAuth2_Dispose(oauth2);
    CkJsonObject_Dispose(json);

    }