(Objective-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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#import <CkoJsonObject.h>
#import <CkoHttpCurl.h>
#import <NSString.h>

BOOL success = NO;

// 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 = NO;

// --------------------------------------------------------------------------------------------------------
// 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.
CkoJsonObject *jsonAuth = [[CkoJsonObject alloc] init];

// 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.EnableSecrets = YES;

success = [jsonAuth UpdateString: @"oauth2.client_id" value: @"!!sharepoint|oauth2|client_id"];
if (success == YES) {
    success = [jsonAuth UpdateString: @"oauth2.client_secret" value: @"!!sharepoint|oauth2|client_secret"];
}

if (success == YES) {
    success = [jsonAuth UpdateString: @"oauth2.token_endpoint" value: @"!!sharepoint|oauth2|token_endpoint"];
}

if (success == NO) {
    NSLog(@"%@",jsonAuth.LastErrorText);
    return;
}

// Request Microsoft Graph permissions that were granted to the application.
[jsonAuth UpdateString: @"oauth2.scope" value: @"https://graph.microsoft.com/.default"];

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

CkoHttpCurl *curl = [[CkoHttpCurl alloc] init];

// 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" varValue: @"example.sharepoint.com"];
[curl SetVar: @"site_name" varValue: @"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" curl: @"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" jsonPath: @"id" varName: @"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" curl: @"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" arrayPath: @"value" wherePath: @"name" whereValue: @"Documents" caseSensitive: YES subPath: @"id" varName: @"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.
NSString *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 == NO) {
    NSLog(@"%@",curl.LastErrorText);
    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.StatusCode intValue];
if (statusCode != 200) {
    NSLog(@"%@",curl.ResponseBodyStr);
    NSLog(@"%@%d",@"status code = ",statusCode);
    return;
}

// The file has been downloaded successfully and written to:
// 
//   c:/temp/qa_output/starfish.jpg
// 
NSLog(@"%@",@"Success.");