(Visual FoxPro) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loGAuth
LOCAL loRest
LOCAL lnBAutoReconnect
LOCAL loGdCache
LOCAL lnNumCacheFilesDeleted
LOCAL loDtExpire
LOCAL lcAllFields
LOCAL loJsonMaster
LOCAL loJsonMasterArr
LOCAL loJsonMasterPaths
LOCAL loJson
LOCAL loJsonFileMetadata
LOCAL i
LOCAL lnNumFiles
LOCAL lcJsonResponse
LOCAL lnPageNumber
LOCAL lcPageToken
LOCAL lnBContinueLoop
LOCAL lnBHasMorePages
LOCAL loHashTable
LOCAL loSbPathForFileId
LOCAL loSaFileInfo
LOCAL lcFileId
LOCAL loSbPath
LOCAL lnBFinished
LOCAL lcStrJsonMaster

lnSuccess = 1

* 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.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.AuthGoogle')
loGAuth = CreateObject('Chilkat.AuthGoogle')
loGAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Rest')
loRest = CreateObject('Chilkat.Rest')

* Connect using TLS.
lnBAutoReconnect = 1
lnSuccess = loRest.Connect("www.googleapis.com",443,1,lnBAutoReconnect)

* Provide the authentication credentials (i.e. the access token)
loRest.SetAuthGoogle(loGAuth)

* -------------------------------------------------------------------
* 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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cache')
loGdCache = CreateObject('Chilkat.Cache')
loGdCache.Level = 0
* Use a root directory that makes sense on your operating system..
loGdCache.AddRoot("C:/ckCache/googleDrive")

* If we are re-building the cache, we can first delete the entire contents of the cache.
lnNumCacheFilesDeleted = loGdCache.DeleteAll()

* Create a date/time object with an time 7 days from the current date/time.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.CkDateTime')
loDtExpire = CreateObject('Chilkat.CkDateTime')
loDtExpire.SetFromCurrentSystemTime()
loDtExpire.AddDays(7)

* Indicate that we want ALL possible fields.
* If no fields are indicated, then only the basic fields are returned.
lcAllFields = "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".
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJsonMaster = CreateObject('Chilkat.JsonObject')
loJsonMasterArr = loJsonMaster.AppendArray("fileIds")
* Also keep a list of file paths.
loJsonMasterPaths = loJsonMaster.AppendArray("filePaths")

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

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.JsonObject')
loJson = CreateObject('Chilkat.JsonObject')

* Send the request for the 1st page.
lcJsonResponse = loRest.FullRequestNoBody("GET","/drive/v3/files")

lnPageNumber = 1

lnBContinueLoop = loRest.LastMethodSuccess AND (loRest.ResponseStatusCode = 200)

DO WHILE lnBContinueLoop = 1

    ? "---- Page " + STR(lnPageNumber) + " ----"
    loJson.Load(lcJsonResponse)

    lnNumFiles = loJson.SizeOfArray("files")
    i = 0
    DO WHILE i < lnNumFiles
        * Add this file ID to the master list.
        loJson.I = i
        loJsonMasterArr.AddStringAt(-1,loJson.StringOf("files[i].id"))

        i = i + 1
    ENDDO

    * 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.
    lcPageToken = loJson.StringOf("nextPageToken")
    lnBContinueLoop = 0
    lnBHasMorePages = loJson.LastMethodSuccess
    IF (lnBHasMorePages = 1) THEN
        loRest.ClearAllQueryParams()
        loRest.AddQueryParam("pageSize","200")
        loRest.AddQueryParam("pageToken",lcPageToken)
        lcJsonResponse = loRest.FullRequestNoBody("GET","/drive/v3/files")
        lnBContinueLoop = loRest.LastMethodSuccess AND (loRest.ResponseStatusCode = 200)
        lnPageNumber = lnPageNumber + 1
    ENDIF

ENDDO

RELEASE loJsonMasterArr

* Check to see if the above loop exited with errors...
IF (loRest.LastMethodSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loGAuth
    RELEASE loRest
    RELEASE loGdCache
    RELEASE loDtExpire
    RELEASE loJsonMaster
    RELEASE loJson
    CANCEL
ENDIF

* Check to see if the above loop exited with errors...
* A successful response will have a status code equal to 200.
IF (loRest.ResponseStatusCode <> 200) THEN
    ? "response status code = " + STR(loRest.ResponseStatusCode)
    ? "response status text = " + loRest.ResponseStatusText
    ? "response header: " + loRest.ResponseHeader
    ? "response JSON: " + lcJsonResponse
    RELEASE loGAuth
    RELEASE loRest
    RELEASE loGdCache
    RELEASE loDtExpire
    RELEASE loJsonMaster
    RELEASE loJson
    CANCEL
ENDIF

* 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.)
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Hashtable')
loHashTable = CreateObject('Chilkat.Hashtable')
* Set the capacity of the hash table to something reasonable for the number of files
* to be hashed.
loHashTable.ClearWithNewCapacity(521)

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbPathForFileId = CreateObject('Chilkat.StringBuilder')

* Used for storing the file name and parents[0] in the hashTable.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringArray')
loSaFileInfo = CreateObject('Chilkat.StringArray')
loSaFileInfo.Unique = 0

lnNumFiles = loJsonMaster.SizeOfArray("fileIds")
i = 0
DO WHILE i < lnNumFiles
    loJsonMaster.I = i
    lcFileId = loJsonMaster.StringOf("fileIds[i]")
    loSbPathForFileId.SetString("/drive/v3/files/")
    loSbPathForFileId.Append(lcFileId)

    loRest.ClearAllQueryParams()
    loRest.AddQueryParam("fields",lcAllFields)
    lcJsonResponse = loRest.FullRequestNoBody("GET",loSbPathForFileId.GetAsString())
    IF ((loRest.LastMethodSuccess <> 1) OR (loRest.ResponseStatusCode <> 200)) THEN
        * Force an exit of this loop..
        lnNumFiles = 0
    ENDIF

    * Save this file's metadata to the local cache.
    * The lookup key is the fileId.
    loGdCache.SaveTextDt(lcFileId,loDtExpire,"",lcJsonResponse)

    * Get this file's name and parent[0], and put this information
    * in our in-memory hashtable to be used below..
    loJson.Load(lcJsonResponse)

    loSaFileInfo.Clear()
    loSaFileInfo.Append(loJson.StringOf("name"))
    loSaFileInfo.Append(loJson.StringOf("parents[0]"))
    loHashTable.AddStr(lcFileId,loSaFileInfo.Serialize())

    ? loJson.StringOf("name") + ", " + loJson.StringOf("parents[0]")

    i = i + 1
ENDDO

* Check to see if the above loop exited with errors...
IF (loRest.LastMethodSuccess <> 1) THEN
    ? loRest.LastErrorText
    RELEASE loGAuth
    RELEASE loRest
    RELEASE loGdCache
    RELEASE loDtExpire
    RELEASE loJsonMaster
    RELEASE loJson
    RELEASE loHashTable
    RELEASE loSbPathForFileId
    RELEASE loSaFileInfo
    CANCEL
ENDIF

* Check to see if the above loop exited with errors...
* A successful response will have a status code equal to 200.
IF (loRest.ResponseStatusCode <> 200) THEN
    ? "response status code = " + STR(loRest.ResponseStatusCode)
    ? "response status text = " + loRest.ResponseStatusText
    ? "response header: " + loRest.ResponseHeader
    ? "response JSON: " + lcJsonResponse
    RELEASE loGAuth
    RELEASE loRest
    RELEASE loGdCache
    RELEASE loDtExpire
    RELEASE loJsonMaster
    RELEASE loJson
    RELEASE loHashTable
    RELEASE loSbPathForFileId
    RELEASE loSaFileInfo
    CANCEL
ENDIF

* 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"
* 

? "---- building paths ----"

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.StringBuilder')
loSbPath = CreateObject('Chilkat.StringBuilder')
lnNumFiles = loJsonMaster.SizeOfArray("fileIds")
i = 0
DO WHILE i < lnNumFiles
    loJsonMaster.I = i

    loSbPath.Clear()

    lcFileId = loJsonMaster.StringOf("fileIds[i]")
    lnBFinished = 0
    DO WHILE (lnBFinished = 0)
        loSaFileInfo.Clear()
        loSaFileInfo.AppendSerialized(loHashTable.LookupStr(lcFileId))
        * Append this file or directory name.
        loSbPath.Prepend(loSaFileInfo.GetString(0))
        * Get the parent fileId
        lcFileId = loSaFileInfo.GetString(1)
        * If this fileId is not in the hashtable, then it's the fileId for "My Drive", and we are finished.
        IF (loHashTable.Contains(lcFileId) = 0) THEN
            lnBFinished = 1
        ELSE
            loSbPath.Prepend("/")
        ENDIF

    ENDDO

    ? STR(i) + ": " + loSbPath.GetAsString()

    * Store the filePath --> fileId mapping in our local cache.
    lcFileId = loJsonMaster.StringOf("fileIds[i]")
    loGdCache.SaveTextDt(loSbPath.GetAsString(),loDtExpire,"",lcFileId)

    loJsonMasterPaths.AddStringAt(-1,loSbPath.GetAsString())

    i = i + 1
ENDDO

RELEASE loJsonMasterPaths

* Save the master list of file IDs and file paths to the local cache.
loJsonMaster.EmitCompact = 0
lcStrJsonMaster = loJsonMaster.Emit()
loGdCache.SaveTextNoExpire("AllGoogleDriveFileIds","",lcStrJsonMaster)
? "JSON Master Record:"
? lcStrJsonMaster

* 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",
*   ]
* }

? "Entire cache rebuilt..."

RELEASE loGAuth
RELEASE loRest
RELEASE loGdCache
RELEASE loDtExpire
RELEASE loJsonMaster
RELEASE loJson
RELEASE loHashTable
RELEASE loSbPathForFileId
RELEASE loSaFileInfo
RELEASE loSbPath