(Lianja) 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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llSuccess = .T.

// 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.

loGAuth = createobject("CkAuthGoogle")
loGAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

loRest = createobject("CkRest")

// Connect using TLS.
llBAutoReconnect = .T.
llSuccess = loRest.Connect("www.googleapis.com",443,.T.,llBAutoReconnect)

// 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.
loGdCache = createobject("CkCache")
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.
loDtExpire = createobject("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".
loJsonMaster = createobject("CkJsonObject")
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")

loJson = createobject("CkJsonObject")

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

lnPageNumber = 1

llBContinueLoop = loRest.LastMethodSuccess and (loRest.ResponseStatusCode = 200)

do while llBContinueLoop = .T.

    ? "---- 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")
    llBContinueLoop = .F.
    llBHasMorePages = loJson.LastMethodSuccess
    if (llBHasMorePages = .T.) then
        loRest.ClearAllQueryParams()
        loRest.AddQueryParam("pageSize","200")
        loRest.AddQueryParam("pageToken",lcPageToken)
        lcJsonResponse = loRest.FullRequestNoBody("GET","/drive/v3/files")
        llBContinueLoop = 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 <> .T.) then
    ? loRest.LastErrorText
    release loGAuth
    release loRest
    release loGdCache
    release loDtExpire
    release loJsonMaster
    release loJson
    return
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
    return
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.)
loHashTable = createobject("CkHashtable")
// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
loHashTable.ClearWithNewCapacity(521)

loSbPathForFileId = createobject("CkStringBuilder")

// Used for storing the file name and parents[0] in the hashTable.
loSaFileInfo = createobject("CkStringArray")
loSaFileInfo.Unique = .F.

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 <> .T.) 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 <> .T.) then
    ? loRest.LastErrorText
    release loGAuth
    release loRest
    release loGdCache
    release loDtExpire
    release loJsonMaster
    release loJson
    release loHashTable
    release loSbPathForFileId
    release loSaFileInfo
    return
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
    return
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 ----"

loSbPath = createobject("CkStringBuilder")
lnNumFiles = loJsonMaster.SizeOfArray("fileIds")
i = 0
do while i < lnNumFiles
    loJsonMaster.I = i

    loSbPath.Clear()

    lcFileId = loJsonMaster.StringOf("fileIds[i]")
    llBFinished = .F.
    do while (llBFinished = .F.)
        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) = .F.) then
            llBFinished = .T.
        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 = .F.
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