(Objective-C) Google Drive - Build a Local Cache of Metadata

This example demonstrates how to download the metadata for all files in a Google Drive account to create a local filesystem cache with the information. The cache can be used to fetch information without having to query Google Drive.

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#import <CkoAuthGoogle.h>
#import <CkoRest.h>
#import <CkoCache.h>
#import <CkoDateTime.h>
#import <NSString.h>
#import <CkoJsonObject.h>
#import <CkoJsonArray.h>
#import <CkoHashtable.h>
#import <CkoStringBuilder.h>
#import <CkoStringArray.h>

BOOL success = YES;

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

// This example uses a previously obtained access token having permission for the 
// Google Drive scope.

CkoAuthGoogle *gAuth = [[CkoAuthGoogle alloc] init];
gAuth.AccessToken = @"GOOGLE_DRIVE_ACCESS_TOKEN";

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

// Connect using TLS.
BOOL bAutoReconnect = YES;
success = [rest Connect: @"www.googleapis.com" port: [NSNumber numberWithInt: 443] tls: YES autoReconnect: bAutoReconnect];

// Provide the authentication credentials (i.e. the access token)
[rest SetAuthGoogle: gAuth];

// -------------------------------------------------------------------
// Initialize our cache object.  Indicate the location of the root cache directory, and how many cache levels are to exist.
// For small caches (level 0) all cache files are in the root directory.
// For medium caches (level 1) cache files are located in 256 sub-directories from the root.
// For large caches (level 2) cache files are located in 256x256 sub-directories two levels down from the root.
CkoCache *gdCache = [[CkoCache alloc] init];
gdCache.Level = [NSNumber numberWithInt:0];
// Use a root directory that makes sense on your operating system..
[gdCache AddRoot: @"C:/ckCache/googleDrive"];

// If we are re-building the cache, we can first delete the entire contents of the cache.
int numCacheFilesDeleted = [[gdCache DeleteAll] intValue];

// Create a date/time object with an time 7 days from the current date/time.
CkoDateTime *dtExpire = [[CkoDateTime alloc] init];
[dtExpire SetFromCurrentSystemTime];
[dtExpire AddDays: [NSNumber numberWithInt: 7]];

// Indicate that we want ALL possible fields.
// If no fields are indicated, then only the basic fields are returned.
NSString *allFields = @"appProperties,capabilities,contentHints,createdTime,description,explicitlyTrashed,fileExtension,folderColorRgb,fullFileExtension,headRevisionId,iconLink,id,imageMediaMetadata,isAppAuthorized,kind,lastModifyingUser,md5Checksum,mimeType,modifiedByMeTime,modifiedTime,name,originalFilename,ownedByMe,owners,parents,permissions,properties,quotaBytesUsed,shared,sharedWithMeTime,sharingUser,size,spaces,starred,thumbnailLink,trashed,version,videoMediaMetadata,viewedByMe,viewedByMeTime,viewersCanCopyContent,webContentLink,webViewLink,writersCanShare";

// We're going to keep a master list of fileId's as we iterate over all the files in this Google Drive account.
// This master list will also be saved to the cache under the key "AllGoogleDriveFileIds".
CkoJsonObject *jsonMaster = [[CkoJsonObject alloc] init];
CkoJsonArray *jsonMasterArr = [jsonMaster AppendArray: @"fileIds"];
// Also keep a list of file paths.
CkoJsonArray *jsonMasterPaths = [jsonMaster AppendArray: @"filePaths"];

// The default page size is 100, with a max of 1000.
[rest AddQueryParam: @"pageSize" value: @"200"];

CkoJsonObject *json = [[CkoJsonObject alloc] init];
CkoJsonObject *jsonFileMetadata = 0;
int i;
int numFiles;

// Send the request for the 1st page.
NSString *jsonResponse = [rest FullRequestNoBody: @"GET" uriPath: @"/drive/v3/files"];

int pageNumber = 1;
NSString *pageToken = 0;
BOOL bContinueLoop = rest.LastMethodSuccess && ([rest.ResponseStatusCode intValue] == 200);

while (bContinueLoop == YES) {

    NSLog(@"%@%d%@",@"---- Page ",pageNumber,@" ----");
    [json Load: jsonResponse];

    numFiles = [[json SizeOfArray: @"files"] intValue];
    i = 0;
    while (i < numFiles) {
        // Add this file ID to the master list.
        json.I = [NSNumber numberWithInt: i];
        [jsonMasterArr AddStringAt: [NSNumber numberWithInt: -1] value: [json StringOf: @"files[i].id"]];

        i = i + 1;
    }

    // Get the next page of files.
    // If the "nextPageToken" is present in the JSON response, then use it in the "pageToken" parameter
    // for the next request.   If no "nextPageToken" was present, then this was the last page of files.
    pageToken = [json StringOf: @"nextPageToken"];
    bContinueLoop = NO;
    BOOL bHasMorePages = json.LastMethodSuccess;
    if (bHasMorePages == YES) {
        [rest ClearAllQueryParams];
        [rest AddQueryParam: @"pageSize" value: @"200"];
        [rest AddQueryParam: @"pageToken" value: pageToken];
        jsonResponse = [rest FullRequestNoBody: @"GET" uriPath: @"/drive/v3/files"];
        bContinueLoop = rest.LastMethodSuccess && ([rest.ResponseStatusCode intValue] == 200);
        pageNumber = pageNumber + 1;
    }

}

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// Check to see if the above loop exited with errors...
// A successful response will have a status code equal to 200.
if ([rest.ResponseStatusCode intValue] != 200) {
    NSLog(@"%@%d",@"response status code = ",[rest.ResponseStatusCode intValue]);
    NSLog(@"%@%@",@"response status text = ",rest.ResponseStatusText);
    NSLog(@"%@%@",@"response header: ",rest.ResponseHeader);
    NSLog(@"%@%@",@"response JSON: ",jsonResponse);
    return;
}

// Iterate over the file IDs and download the metadata for each, saving each to the cache...
// Also, keep in-memory hash entries of the name and parent[0] so we can quickly 
// build the path-->fileId cache entries. (Given that the Google Drive REST API uses
// fileIds, this gives us an easy way to lookup a fileId based on a filePath.)
CkoHashtable *hashTable = [[CkoHashtable alloc] init];
// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
[hashTable ClearWithNewCapacity: [NSNumber numberWithInt: 521]];

CkoStringBuilder *sbPathForFileId = [[CkoStringBuilder alloc] init];

// Used for storing the file name and parents[0] in the hashTable.
CkoStringArray *saFileInfo = [[CkoStringArray alloc] init];
saFileInfo.Unique = NO;

NSString *fileId = 0;
numFiles = [[jsonMaster SizeOfArray: @"fileIds"] intValue];
i = 0;
while (i < numFiles) {
    jsonMaster.I = [NSNumber numberWithInt: i];
    fileId = [jsonMaster StringOf: @"fileIds[i]"];
    [sbPathForFileId SetString: @"/drive/v3/files/"];
    [sbPathForFileId Append: fileId];

    [rest ClearAllQueryParams];
    [rest AddQueryParam: @"fields" value: allFields];
    jsonResponse = [rest FullRequestNoBody: @"GET" uriPath: [sbPathForFileId GetAsString]];
    if ((rest.LastMethodSuccess != YES) || ([rest.ResponseStatusCode intValue] != 200)) {
        // Force an exit of this loop..
        numFiles = 0;
    }

    // Save this file's metadata to the local cache.
    // The lookup key is the fileId.
    [gdCache SaveTextDt: fileId expire: dtExpire eTag: @"" strData: jsonResponse];

    // Get this file's name and parent[0], and put this information
    // in our in-memory hashtable to be used below..
    [json Load: jsonResponse];

    [saFileInfo Clear];
    [saFileInfo Append: [json StringOf: @"name"]];
    [saFileInfo Append: [json StringOf: @"parents[0]"]];
    [hashTable AddStr: fileId value: [saFileInfo Serialize]];

    NSLog(@"%@%@%@",[json StringOf: @"name"],@", ",[json StringOf: @"parents[0]"]);

    i = i + 1;
}

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// Check to see if the above loop exited with errors...
// A successful response will have a status code equal to 200.
if ([rest.ResponseStatusCode intValue] != 200) {
    NSLog(@"%@%d",@"response status code = ",[rest.ResponseStatusCode intValue]);
    NSLog(@"%@%@",@"response status text = ",rest.ResponseStatusText);
    NSLog(@"%@%@",@"response header: ",rest.ResponseHeader);
    NSLog(@"%@%@",@"response JSON: ",jsonResponse);
    return;
}

// Now that all the fileId's are in the cache, let's build the directory path
// for each fileID.  

// (Technically, a fileId can have multiple parents, which means it can be in multiple directories
// at once.  This is only going to build directory paths following the 0'th parent ID in the parents list.)

// The directory path for files in "My Drive" will be just the filename.
// For files in sub-directories, the path will be relative, such as "subdir1/subdir2/something.pdf"
// 

NSLog(@"%@",@"---- building paths ----");

CkoStringBuilder *sbPath = [[CkoStringBuilder alloc] init];
numFiles = [[jsonMaster SizeOfArray: @"fileIds"] intValue];
i = 0;
while (i < numFiles) {
    jsonMaster.I = [NSNumber numberWithInt: i];

    [sbPath Clear];

    fileId = [jsonMaster StringOf: @"fileIds[i]"];
    BOOL bFinished = NO;
    while ((bFinished == NO)) {
        [saFileInfo Clear];
        [saFileInfo AppendSerialized: [hashTable LookupStr: fileId]];
        // Append this file or directory name.
        [sbPath Prepend: [saFileInfo GetString: [NSNumber numberWithInt: 0]]];
        // Get the parent fileId
        fileId = [saFileInfo GetString: [NSNumber numberWithInt: 1]];
        // If this fileId is not in the hashtable, then it's the fileId for "My Drive", and we are finished.
        if ([hashTable Contains: fileId] == NO) {
            bFinished = YES;
        }
        else {
            [sbPath Prepend: @"/"];
        }

    }

    NSLog(@"%d%@%@",i,@": ",[sbPath GetAsString]);

    // Store the filePath --> fileId mapping in our local cache.
    fileId = [jsonMaster StringOf: @"fileIds[i]"];
    [gdCache SaveTextDt: [sbPath GetAsString] expire: dtExpire eTag: @"" strData: fileId];

    [jsonMasterPaths AddStringAt: [NSNumber numberWithInt: -1] value: [sbPath GetAsString]];

    i = i + 1;
}

// Save the master list of file IDs and file paths to the local cache.
jsonMaster.EmitCompact = NO;
NSString *strJsonMaster = [jsonMaster Emit];
[gdCache SaveTextNoExpire: @"AllGoogleDriveFileIds" eTag: @"" strData: strJsonMaster];
NSLog(@"%@",@"JSON Master Record:");
NSLog(@"%@",strJsonMaster);

// The JSON Master Cache Record looks something like this:
// An application can load the JSON master record and iterate over all the files
// in Google Drive by file ID, or by path.  
// {
//   "fileIds": [
//     "0B53Q6OSTWYolQlExSlBQT1phZXM",
//     "0B53Q6OSTWYolVHRPVkxtYWFtZkk",
//     "0B53Q6OSTWYolRGZEV3ZGUTZfNFk",
//     "0B53Q6OSTWYolS2FXSjliMXQxSU0",
//     "0B53Q6OSTWYolZUhxckMzb0dRMzg",
//     "0B53Q6OSTWYolbUF6WS1Gei1oalk",
//     "0B53Q6OSTWYola296ODZUSm5GYU0",
//     "0B53Q6OSTWYolbTE3c3J5RHBUcHM",
//     "0B53Q6OSTWYolTmhybWJSUGd5Q2c",
//     "0B53Q6OSTWYolY2tPU1BnYW02T2c",
//     "0B53Q6OSTWYolTTBBR2NvUE81Zzg",
//   ],
//   "filePaths": [
//     "testFolder/abc/123/pigs.json",
//     "testFolder/starfish20.jpg",
//     "testFolder/penguins2.jpg",
//     "testFolder/starfish.jpg",
//     "testFolder/abc/123/starfish.jpg",
//     "testFolder/abc/123/penguins.jpg",
//     "testFolder/abc/123",
//     "testFolder/abc",
//     "testFolder/testHello.txt",
//     "testFolder",
//     "helloWorld.txt",
//   ]
// }

NSLog(@"%@",@"Entire cache rebuilt...");