(C++) Download a SharePoint File by Path using HttpCurl

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This example shows how to use Chilkat's HttpCurl class to download a file from SharePoint when the file path within the document library is already known. The example uses Microsoft Graph to automatically resolve the SharePoint site name to a site ID, find the drive ID for the Documents document library, and then download the file directly by path using the Graph root:/path:/content syntax.

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#include <CkJsonObject.h>
#include <CkHttpCurl.h>

void ChilkatSample(void)
    {
    bool success = false;

    // This example downloads a file from a SharePoint Documents document library
    // when the file's path within the library is already known.
    // 
    // The file downloaded in this example is:
    // 
    //   images/sea_creatures/starfish.jpg
    // 
    // Unlike the previous example  that searched for a file by name and obtained
    // its Microsoft Graph item ID, this example uses the Graph path-based API.
    // 
    // The example demonstrates how HttpCurl automatically resolves:
    // 
    //   site_name  -> site_id
    //   site_id    -> document_library_id
    // 
    // and then uses the known file path to download the file directly.

    success = false;

    // --------------------------------------------------------------------------------------------------------
    // Before running this example, create an Azure App Registration and grant it
    // the Microsoft Graph permissions required to access SharePoint.
    // 
    // The application will authenticate using OAuth2 Client Credentials.
    // See:
    // How to Create SharePoint App Registration for OAuth 2.0 Client Credentials
    // --------------------------------------------------------------------------------------------------------

    // Build a JSON authentication configuration.
    // HttpCurl will use this information to automatically obtain OAuth2 access tokens.
    CkJsonObject jsonAuth;

    // Enable secret lookup.
    // 
    // Instead of hard-coding sensitive values such as the client ID,
    // client secret, and token endpoint, secret specification strings
    // are used.  Chilkat automatically retrieves the actual values from
    // Windows Credential Manager (Windows) or Apple Keychain (macOS).
    // 
    // See:
    // Secret Specification Strings
    jsonAuth.put_EnableSecrets(true);

    success = jsonAuth.UpdateString("oauth2.client_id","!!sharepoint|oauth2|client_id");
    if (success == true) {
        success = jsonAuth.UpdateString("oauth2.client_secret","!!sharepoint|oauth2|client_secret");
    }

    if (success == true) {
        success = jsonAuth.UpdateString("oauth2.token_endpoint","!!sharepoint|oauth2|token_endpoint");
    }

    if (success == false) {
        std::cout << jsonAuth.lastErrorText() << "\r\n";
        return;
    }

    // Request Microsoft Graph permissions that were granted to the application.
    jsonAuth.UpdateString("oauth2.scope","https://graph.microsoft.com/.default");

    // ---------------------------------------------------------------------------------------------------

    CkHttpCurl curl;

    // Associate the OAuth2 configuration with HttpCurl.
    // 
    // When the request is executed, Chilkat automatically obtains an access token
    // if needed and adds the Authorization: Bearer header to the HTTP request.
    curl.SetAuth(jsonAuth);

    // Define values that are already known.
    // 
    // These variables are referenced in curl commands using
    // {{variable_name}} substitution syntax.
    curl.SetVar("sharepoint_hostname","example.sharepoint.com");
    curl.SetVar("site_name","test");

    // The download request requires a Microsoft Graph site ID.
    // 
    // Because the application only knows the SharePoint site name,
    // define a helper function that can retrieve the site information.
    curl.AddFunction("getSite","GET https://graph.microsoft.com/v1.0/sites/root:/sites/{{site_name}}");

    // Extract the site's ID and store it in the HttpCurl variable named site_id.
    curl.AddOutput("getSite","id","site_id");

    // The download request also requires the drive ID of the Documents
    // document library.
    // 
    // Microsoft Graph refers to document libraries as "drives".
    curl.AddFunction("getDrives","GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives");

    // Search the returned drives for the one named "Documents"
    // and save its drive ID in the document_library_id variable.
    curl.AddOutput2("getDrives","value","name","Documents",true,"id","document_library_id");

    // This is the target Microsoft Graph request.
    // 
    // GET /sites/{site-id}/drives/{drive-id}/root:/{path-to-file}:/content
    // 
    // The path-based API allows a file to be downloaded directly when its
    // location within the document library is known.
    // 
    // The -L option causes HttpCurl to follow redirects.
    // Microsoft Graph typically returns a redirect to the actual download URL.
    // 
    // The -o option specifies the output filename.
    // The --output-dir option specifies the directory where the downloaded
    // file will be saved.
    const char *curlCommand = "GET -L --output-dir c:/temp/qa_output -o starfish.jpg https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root:/images/sea_creatures/starfish.jpg:/content";

    // Execute the request.
    // 
    // HttpCurl examines the target request and determines that both
    // site_id and document_library_id are required.
    // 
    // To obtain these values, it automatically builds and executes
    // the following dependency chain:
    // 
    //   1) getSite    -> site_id
    //   2) getDrives  -> document_library_id
    //   3) download   -> file content
    // 
    // The file is streamed directly to the output file specified by
    // the curl command.
    success = curl.DoYourThing(curlCommand);
    if (success == false) {
        std::cout << curl.lastErrorText() << "\r\n";
        return;
    }

    // A successful Graph response should return HTTP 200.
    // Any other status code typically indicates an authentication,
    // permission, site lookup, document library lookup, or file lookup error.
    int statusCode = curl.get_StatusCode();
    if (statusCode != 200) {
        std::cout << curl.responseBodyStr() << "\r\n";
        std::cout << "status code = " << statusCode << "\r\n";
        return;
    }

    // The file has been downloaded successfully and written to:
    // 
    //   c:/temp/qa_output/starfish.jpg
    // 
    std::cout << "Success." << "\r\n";
    }