(C# UWP/WinRT) 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.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

bool success = true;

// 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.

Chilkat.AuthGoogle gAuth = new Chilkat.AuthGoogle();
gAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN";

Chilkat.Rest rest = new Chilkat.Rest();

// Connect using TLS.
bool bAutoReconnect = true;
success = await rest.ConnectAsync("www.googleapis.com",443,true,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.
Chilkat.Cache gdCache = new Chilkat.Cache();
gdCache.Level = 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();

// Create a date/time object with an time 7 days from the current date/time.
Chilkat.CkDateTime dtExpire = new Chilkat.CkDateTime();
dtExpire.SetFromCurrentSystemTime();
dtExpire.AddDays(7);

// Indicate that we want ALL possible fields.
// If no fields are indicated, then only the basic fields are returned.
string 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".
Chilkat.JsonObject jsonMaster = new Chilkat.JsonObject();
Chilkat.JsonArray jsonMasterArr = jsonMaster.AppendArray("fileIds");
// Also keep a list of file paths.
Chilkat.JsonArray jsonMasterPaths = jsonMaster.AppendArray("filePaths");

// The default page size is 100, with a max of 1000.
rest.AddQueryParam("pageSize","200");

Chilkat.JsonObject json = new Chilkat.JsonObject();
Chilkat.JsonObject jsonFileMetadata = null;
int i;
int numFiles;

// Send the request for the 1st page.
string jsonResponse = await rest.FullRequestNoBodyAsync("GET","/drive/v3/files");

int pageNumber = 1;
string pageToken;
bool bContinueLoop = rest.LastMethodSuccess && (rest.ResponseStatusCode == 200);

while (bContinueLoop == true) {

    Debug.WriteLine("---- Page " + Convert.ToString(pageNumber) + " ----");
    json.Load(jsonResponse);

    numFiles = json.SizeOfArray("files");
    i = 0;
    while (i < numFiles) {
        // Add this file ID to the master list.
        json.I = i;
        jsonMasterArr.AddStringAt(-1,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 = false;
    bool bHasMorePages = json.LastMethodSuccess;
    if (bHasMorePages == true) {
        rest.ClearAllQueryParams();
        rest.AddQueryParam("pageSize","200");
        rest.AddQueryParam("pageToken",pageToken);
        jsonResponse = await rest.FullRequestNoBodyAsync("GET","/drive/v3/files");
        bContinueLoop = rest.LastMethodSuccess && (rest.ResponseStatusCode == 200);
        pageNumber = pageNumber + 1;
    }

}

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(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 != 200) {
    Debug.WriteLine("response status code = " + Convert.ToString(rest.ResponseStatusCode));
    Debug.WriteLine("response status text = " + rest.ResponseStatusText);
    Debug.WriteLine("response header: " + rest.ResponseHeader);
    Debug.WriteLine("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.)
Chilkat.Hashtable hashTable = new Chilkat.Hashtable();
// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
hashTable.ClearWithNewCapacity(521);

Chilkat.StringBuilder sbPathForFileId = new Chilkat.StringBuilder();

// Used for storing the file name and parents[0] in the hashTable.
Chilkat.StringArray saFileInfo = new Chilkat.StringArray();
saFileInfo.Unique = false;

string fileId;
numFiles = jsonMaster.SizeOfArray("fileIds");
i = 0;
while (i < numFiles) {
    jsonMaster.I = i;
    fileId = jsonMaster.StringOf("fileIds[i]");
    sbPathForFileId.SetString("/drive/v3/files/");
    sbPathForFileId.Append(fileId);

    rest.ClearAllQueryParams();
    rest.AddQueryParam("fields",allFields);
    jsonResponse = await rest.FullRequestNoBodyAsync("GET",sbPathForFileId.GetAsString());
    if ((rest.LastMethodSuccess != true) || (rest.ResponseStatusCode != 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,dtExpire,"",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,saFileInfo.Serialize());

    Debug.WriteLine(json.StringOf("name") + ", " + json.StringOf("parents[0]"));

    i = i + 1;
}

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess != true) {
    Debug.WriteLine(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 != 200) {
    Debug.WriteLine("response status code = " + Convert.ToString(rest.ResponseStatusCode));
    Debug.WriteLine("response status text = " + rest.ResponseStatusText);
    Debug.WriteLine("response header: " + rest.ResponseHeader);
    Debug.WriteLine("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"
// 

Debug.WriteLine("---- building paths ----");

Chilkat.StringBuilder sbPath = new Chilkat.StringBuilder();
numFiles = jsonMaster.SizeOfArray("fileIds");
i = 0;
while (i < numFiles) {
    jsonMaster.I = i;

    sbPath.Clear();

    fileId = jsonMaster.StringOf("fileIds[i]");
    bool bFinished = false;
    while ((bFinished == false)) {
        saFileInfo.Clear();
        saFileInfo.AppendSerialized(hashTable.LookupStr(fileId));
        // Append this file or directory name.
        sbPath.Prepend(saFileInfo.GetString(0));
        // Get the parent fileId
        fileId = saFileInfo.GetString(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) == false) {
            bFinished = true;
        }
        else {
            sbPath.Prepend("/");
        }

    }

    Debug.WriteLine(Convert.ToString(i) + ": " + sbPath.GetAsString());

    // Store the filePath --> fileId mapping in our local cache.
    fileId = jsonMaster.StringOf("fileIds[i]");
    gdCache.SaveTextDt(sbPath.GetAsString(),dtExpire,"",fileId);

    jsonMasterPaths.AddStringAt(-1,sbPath.GetAsString());

    i = i + 1;
}

// Save the master list of file IDs and file paths to the local cache.
jsonMaster.EmitCompact = false;
string strJsonMaster = jsonMaster.Emit();
gdCache.SaveTextNoExpire("AllGoogleDriveFileIds","",strJsonMaster);
Debug.WriteLine("JSON Master Record:");
Debug.WriteLine(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",
//   ]
// }

Debug.WriteLine("Entire cache rebuilt...");