(Objective-C) OneDrive -- Streaming REST Download to File

Downloads the contents of a DriveItem directly to a file in the local filesystem using the Chilkat REST class.

Note: This example requires Chilkat v9.5.0.69 or greater.

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#import <CkoRest.h>
#import <CkoOAuth2.h>
#import <NSString.h>
#import <CkoBinData.h>
#import <CkoUrl.h>
#import <CkoStringBuilder.h>
#import <CkoJsonObject.h>
#import <CkoStream.h>

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoRest *rest = [[CkoRest alloc] init];

// Use your previously obtained access token here:
// See the following examples for getting an access token:
//    Get Microsoft Graph OAuth2 Access Token (Azure AD v2.0 Endpoint).
//    Get Microsoft Graph OAuth2 Access Token (Azure AD Endpoint).
//    Refresh Access Token (Azure AD v2.0 Endpoint).
//    Refresh Access Token (Azure AD Endpoint).

// First connect to graph.microsoft.com.  If there's a connectivity problem, we'll find out here.
BOOL success = [rest Connect: @"graph.microsoft.com" port: [NSNumber numberWithInt: 443] tls: YES autoReconnect: YES];
if (success != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// (Make sure your token was obtained with the FilesRead or Files.ReadWrite scope.)
CkoOAuth2 *oauth2 = [[CkoOAuth2 alloc] init];
oauth2.AccessToken = @"MICROSOFT_GRAPH_ACCESS_TOKEN";
[rest SetAuthOAuth2: oauth2];

// Send the GET request to download the file.
NSString *uriPath = @"/v1.0/me/drive/root:/Misc/wildlife/penguins.jpg:/content";
success = [rest SendReqNoBody: @"GET" uriPath: uriPath];
if (rest.LastMethodSuccess != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// NOTE: This way of doing the HTTP GET (i.e. download) may be more cumbersome, but it 
// allows for finer control of handling errors.  The connection establishment, the sending of the
// request, the reading of the response header, and the reading of the response body (i.e. the file data)
// are handled by separate method calls.  If the response header indicates an error, we can read
// the response body and treat it differently than if reading the file data.

// Read the response header.
int statusCode = [[rest ReadResponseHeader] intValue];
NSLog(@"%@%d",@"Response Status Code = ",statusCode);
if (statusCode == 302) {
    // This is a redirect.  Read the response body, if any, and then follow the redirect.
    // Usually the response body will be empty for a redirect, but we need to be sure to read
    // the response body just in case it exists.
    CkoBinData *discard = [[CkoBinData alloc] init];
    [rest ReadRespBd: discard];
    [rest Disconnect: [NSNumber numberWithInt: 10]];

    // For OneDrive, the redirect URL does not need authorization because the only way
    // to have obtained the direct download URL is from an authenticated request.
    // In fact, if we leave the authentication present, the GET request to the redirect URL will fail.

    // Note: The ClearAuth method is introduced in v9.5.0.69.
    [rest ClearAuth];

    // Follow the redirect URL...
    CkoUrl *redirectUrl = [rest RedirectUrl];
    NSLog(@"%@%@",@"Redirect Host: ",redirectUrl.Host);
    NSLog(@"%@%@",@"Redirect URI Path: ",redirectUrl.PathWithQueryParams);

    success = [rest Connect: redirectUrl.Host port: redirectUrl.Port tls: redirectUrl.Ssl autoReconnect: YES];
    if (success != YES) {
        NSLog(@"%@",rest.LastErrorText);
        return;
    }

    // Send the request..
    success = [rest SendReqNoBody: @"GET" uriPath: redirectUrl.Path];

    if (rest.LastMethodSuccess != YES) {
        NSLog(@"%@",rest.LastErrorText);
        return;
    }

    statusCode = [[rest ReadResponseHeader] intValue];
    NSLog(@"%@",rest.LastErrorText);
    NSLog(@"%@%d",@"Redirect Response Status Code = ",statusCode);

}

if (statusCode >= 300) {

    // Read the error response body.
    CkoStringBuilder *sbJson = [[CkoStringBuilder alloc] init];
    success = [rest ReadRespSb: sbJson];
    if (success != YES) {
        NSLog(@"%@",rest.LastErrorText);
        return;
    }

    CkoJsonObject *jsonErr = [[CkoJsonObject alloc] init];
    jsonErr.EmitCompact = NO;
    [jsonErr LoadSb: sbJson];
    NSLog(@"%@",[jsonErr Emit]);

    return;
}

// Stream the response body directly to a local file.
NSString *localPath = @"qa_output/penguins.jpg";

CkoStream *stream = [[CkoStream alloc] init];
stream.SinkFile = localPath;

success = [rest ReadRespBodyStream: stream autoSetStreamCharset: YES];
if (success != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

NSLog(@"%@",@"Successfully streamed a OneDrive file to the local filesystem.");