(VB.NET 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)

Dim success As Boolean = 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.

Dim gAuth As New Chilkat.AuthGoogle
gAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

Dim rest As New Chilkat.Rest

' Connect using TLS.
Dim bAutoReconnect As Boolean = 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.
Dim gdCache As 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.
Dim numCacheFilesDeleted As Integer = gdCache.DeleteAll()

' Create a date/time object with an time 7 days from the current date/time.
Dim dtExpire As 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.
Dim allFields As String = "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".
Dim jsonMaster As New Chilkat.JsonObject
Dim jsonMasterArr As Chilkat.JsonArray = jsonMaster.AppendArray("fileIds")
' Also keep a list of file paths.
Dim jsonMasterPaths As Chilkat.JsonArray = jsonMaster.AppendArray("filePaths")

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

Dim json As New Chilkat.JsonObject
Dim jsonFileMetadata As Chilkat.JsonObject
Dim i As Integer
Dim numFiles As Integer

' Send the request for the 1st page.
Dim jsonResponse As String = Await rest.FullRequestNoBodyAsync("GET","/drive/v3/files")

Dim pageNumber As Integer = 1
Dim pageToken As String
Dim bContinueLoop As Boolean = rest.LastMethodSuccess And (rest.ResponseStatusCode = 200)

While bContinueLoop = True

    Debug.WriteLine("---- Page " & 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
    End While

    ' 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
    Dim bHasMorePages As Boolean = json.LastMethodSuccess
    If (bHasMorePages = True) Then
        rest.ClearAllQueryParams()
        rest.AddQueryParam("pageSize","200")
        rest.AddQueryParam("pageToken",pageToken)
        jsonResponse = Await rest.FullRequestNoBodyAsync("GET","/drive/v3/files")
        bContinueLoop = rest.LastMethodSuccess And (rest.ResponseStatusCode = 200)
        pageNumber = pageNumber + 1
    End If


End While



' Check to see if the above loop exited with errors...
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If

' 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) Then
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)
    Debug.WriteLine("response JSON: " & jsonResponse)
    Exit Sub
End If


' 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.)
Dim hashTable As New Chilkat.Hashtable
' Set the capacity of the hash table to something reasonable for the number of files
' to be hashed.
hashTable.ClearWithNewCapacity(521)


Dim sbPathForFileId As New Chilkat.StringBuilder

' Used for storing the file name and parents[0] in the hashTable.
Dim saFileInfo As New Chilkat.StringArray
saFileInfo.Unique = False

Dim fileId As String
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) Or (rest.ResponseStatusCode <> 200)) Then
        ' Force an exit of this loop..
        numFiles = 0
    End If


    ' 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
End While

' Check to see if the above loop exited with errors...
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If

' 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) Then
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)
    Debug.WriteLine("response JSON: " & jsonResponse)
    Exit Sub
End If


' 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 ----")

Dim sbPath As New Chilkat.StringBuilder
numFiles = jsonMaster.SizeOfArray("fileIds")
i = 0
While i < numFiles
    jsonMaster.I = i

    sbPath.Clear()

    fileId = jsonMaster.StringOf("fileIds[i]")
    Dim bFinished As Boolean = 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) Then
            bFinished = True
        Else
            sbPath.Prepend("/")
        End If

    End While

    Debug.WriteLine(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
End While



' Save the master list of file IDs and file paths to the local cache.
jsonMaster.EmitCompact = False
Dim strJsonMaster As String = 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...")