(Objective-C) Download a File from a SharePoint Documents Library

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This example shows how to use Chilkat's HttpCurl class to download a file from the root of a SharePoint Documents document library. The example demonstrates how HttpCurl automatically resolves the SharePoint site name to a site ID, finds the drive ID for the Documents library, locates the file by name, and then downloads the file content using Microsoft Graph.

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#import <CkoJsonObject.h>
#import <CkoHttpCurl.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

BOOL success = NO;

// This example downloads a file named "hamlet.json" from the root of the SharePoint
// Documents document library.
// 
// The example demonstrates how HttpCurl can automatically resolve all of the
// information needed to locate and download a file:
// 
//   site_name            -> site_id
//   site_id              -> document_library_id
//   document_library_id  -> file_id
//   file_id              -> file content
// 
// The application only provides the SharePoint site name and the desired
// filename.  HttpCurl automatically executes the required Microsoft Graph
// requests to obtain the remaining values.

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 first step is to obtain the Microsoft Graph site ID.
// 
// The application only knows the SharePoint site name, so define
// a 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 next step is to find 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"];

// Now list the contents of the Documents document library.
[curl AddFunction: @"getFiles" curl: @"GET https://graph.microsoft.com/v1.0/sites/{{site_id}}/drives/{{document_library_id}}/root/children"];

// Search the returned files for an item named "hamlet.json"
// and save its Microsoft Graph item ID in the file_id variable.
[curl AddOutput2: @"getFiles" arrayPath: @"value" wherePath: @"name" whereValue: @"hamlet.json" caseSensitive: YES subPath: @"id" varName: @"file_id"];

// This is the target request.
// 
// GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content
// 
// The /content endpoint returns the actual contents of the file.
// 
// The -L option instructs HttpCurl to follow the redirect returned by
// Microsoft Graph.  The Graph API typically responds with a redirect
// to the actual file download URL.
NSString *curlCommand = @"GET -L https://graph.microsoft.com/v1.0/drives/{{document_library_id}}/items/{{file_id}}/content";

// Execute the request.
// 
// HttpCurl examines the target request and determines that both
// document_library_id and file_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) getFiles     -> file_id
//   4) download     -> file content
// 
// The final response returned by DoYourThing is the downloaded
// file content from the target request.
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 response body contains the contents of the downloaded file.
CkoStringBuilder *sbFileContents = [[CkoStringBuilder alloc] init];
[curl GetResponseSb: sbFileContents];

// Optionally save the downloaded content to a local file.
// 
// The third argument controls whether the file is appended.
// Passing ckfalse causes the file to be overwritten if it already exists.
success = [sbFileContents WriteFile: @"c:/temp/hamlet.json" charset: @"utf-8" emitBom: NO];
if (success == NO) {
    NSLog(@"%@",sbFileContents.LastErrorText);
    return;
}

NSLog(@"%@",@"Success.");