(PowerBuilder) 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

integer li_rc
integer li_Success
oleobject loo_GAuth
oleobject loo_Rest
integer li_BAutoReconnect
oleobject loo_GdCache
integer li_NumCacheFilesDeleted
oleobject loo_DtExpire
string ls_AllFields
oleobject loo_JsonMaster
oleobject loo_JsonMasterArr
oleobject loo_JsonMasterPaths
oleobject loo_Json
oleobject loo_JsonFileMetadata
integer i
integer li_NumFiles
string ls_JsonResponse
integer li_PageNumber
string ls_PageToken
integer li_BContinueLoop
integer li_BHasMorePages
oleobject loo_HashTable
oleobject loo_SbPathForFileId
oleobject loo_SaFileInfo
string ls_FileId
oleobject loo_SbPath
integer li_BFinished
string ls_StrJsonMaster

li_Success = 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.

loo_GAuth = create oleobject
li_rc = loo_GAuth.ConnectToNewObject("Chilkat_9_5_0.AuthGoogle")
if li_rc < 0 then
    destroy loo_GAuth
    MessageBox("Error","Connecting to COM object failed")
    return
end if
loo_GAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

loo_Rest = create oleobject
li_rc = loo_Rest.ConnectToNewObject("Chilkat_9_5_0.Rest")

// Connect using TLS.
li_BAutoReconnect = 1
li_Success = loo_Rest.Connect("www.googleapis.com",443,1,li_BAutoReconnect)

// Provide the authentication credentials (i.e. the access token)
loo_Rest.SetAuthGoogle(loo_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.
loo_GdCache = create oleobject
li_rc = loo_GdCache.ConnectToNewObject("Chilkat_9_5_0.Cache")

loo_GdCache.Level = 0
// Use a root directory that makes sense on your operating system..
loo_GdCache.AddRoot("C:/ckCache/googleDrive")

// If we are re-building the cache, we can first delete the entire contents of the cache.
li_NumCacheFilesDeleted = loo_GdCache.DeleteAll()

// Create a date/time object with an time 7 days from the current date/time.
loo_DtExpire = create oleobject
li_rc = loo_DtExpire.ConnectToNewObject("Chilkat_9_5_0.CkDateTime")

loo_DtExpire.SetFromCurrentSystemTime()
loo_DtExpire.AddDays(7)

// Indicate that we want ALL possible fields.
// If no fields are indicated, then only the basic fields are returned.
ls_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".
loo_JsonMaster = create oleobject
li_rc = loo_JsonMaster.ConnectToNewObject("Chilkat_9_5_0.JsonObject")

loo_JsonMasterArr = loo_JsonMaster.AppendArray("fileIds")
// Also keep a list of file paths.
loo_JsonMasterPaths = loo_JsonMaster.AppendArray("filePaths")

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

loo_Json = create oleobject
li_rc = loo_Json.ConnectToNewObject("Chilkat_9_5_0.JsonObject")

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

li_PageNumber = 1

li_BContinueLoop = loo_Rest.LastMethodSuccess AND (loo_Rest.ResponseStatusCode = 200)

do while li_BContinueLoop = 1

    Write-Debug "---- Page " + string(li_PageNumber) + " ----"
    loo_Json.Load(ls_JsonResponse)

    li_NumFiles = loo_Json.SizeOfArray("files")
    i = 0
    do while i < li_NumFiles
        // Add this file ID to the master list.
        loo_Json.I = i
        loo_JsonMasterArr.AddStringAt(-1,loo_Json.StringOf("files[i].id"))

        i = i + 1
    loop

    // 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.
    ls_PageToken = loo_Json.StringOf("nextPageToken")
    li_BContinueLoop = 0
    li_BHasMorePages = loo_Json.LastMethodSuccess
    if li_BHasMorePages = 1 then
        loo_Rest.ClearAllQueryParams()
        loo_Rest.AddQueryParam("pageSize","200")
        loo_Rest.AddQueryParam("pageToken",ls_PageToken)
        ls_JsonResponse = loo_Rest.FullRequestNoBody("GET","/drive/v3/files")
        li_BContinueLoop = loo_Rest.LastMethodSuccess AND (loo_Rest.ResponseStatusCode = 200)
        li_PageNumber = li_PageNumber + 1
    end if

loop

destroy loo_JsonMasterArr

// Check to see if the above loop exited with errors...
if loo_Rest.LastMethodSuccess <> 1 then
    Write-Debug loo_Rest.LastErrorText
    destroy loo_GAuth
    destroy loo_Rest
    destroy loo_GdCache
    destroy loo_DtExpire
    destroy loo_JsonMaster
    destroy loo_Json
    return
end if

// Check to see if the above loop exited with errors...
// A successful response will have a status code equal to 200.
if loo_Rest.ResponseStatusCode <> 200 then
    Write-Debug "response status code = " + string(loo_Rest.ResponseStatusCode)
    Write-Debug "response status text = " + loo_Rest.ResponseStatusText
    Write-Debug "response header: " + loo_Rest.ResponseHeader
    Write-Debug "response JSON: " + ls_JsonResponse
    destroy loo_GAuth
    destroy loo_Rest
    destroy loo_GdCache
    destroy loo_DtExpire
    destroy loo_JsonMaster
    destroy loo_Json
    return
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.)
loo_HashTable = create oleobject
li_rc = loo_HashTable.ConnectToNewObject("Chilkat_9_5_0.Hashtable")

// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
loo_HashTable.ClearWithNewCapacity(521)

loo_SbPathForFileId = create oleobject
li_rc = loo_SbPathForFileId.ConnectToNewObject("Chilkat_9_5_0.StringBuilder")

// Used for storing the file name and parents[0] in the hashTable.
loo_SaFileInfo = create oleobject
li_rc = loo_SaFileInfo.ConnectToNewObject("Chilkat_9_5_0.StringArray")

loo_SaFileInfo.Unique = 0

li_NumFiles = loo_JsonMaster.SizeOfArray("fileIds")
i = 0
do while i < li_NumFiles
    loo_JsonMaster.I = i
    ls_FileId = loo_JsonMaster.StringOf("fileIds[i]")
    loo_SbPathForFileId.SetString("/drive/v3/files/")
    loo_SbPathForFileId.Append(ls_FileId)

    loo_Rest.ClearAllQueryParams()
    loo_Rest.AddQueryParam("fields",ls_AllFields)
    ls_JsonResponse = loo_Rest.FullRequestNoBody("GET",loo_SbPathForFileId.GetAsString())
    if (loo_Rest.LastMethodSuccess <> 1) OR (loo_Rest.ResponseStatusCode <> 200) then
        // Force an exit of this loop..
        li_NumFiles = 0
    end if

    // Save this file's metadata to the local cache.
    // The lookup key is the fileId.
    loo_GdCache.SaveTextDt(ls_FileId,loo_DtExpire,"",ls_JsonResponse)

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

    loo_SaFileInfo.Clear()
    loo_SaFileInfo.Append(loo_Json.StringOf("name"))
    loo_SaFileInfo.Append(loo_Json.StringOf("parents[0]"))
    loo_HashTable.AddStr(ls_FileId,loo_SaFileInfo.Serialize())

    Write-Debug loo_Json.StringOf("name") + ", " + loo_Json.StringOf("parents[0]")

    i = i + 1
loop

// Check to see if the above loop exited with errors...
if loo_Rest.LastMethodSuccess <> 1 then
    Write-Debug loo_Rest.LastErrorText
    destroy loo_GAuth
    destroy loo_Rest
    destroy loo_GdCache
    destroy loo_DtExpire
    destroy loo_JsonMaster
    destroy loo_Json
    destroy loo_HashTable
    destroy loo_SbPathForFileId
    destroy loo_SaFileInfo
    return
end if

// Check to see if the above loop exited with errors...
// A successful response will have a status code equal to 200.
if loo_Rest.ResponseStatusCode <> 200 then
    Write-Debug "response status code = " + string(loo_Rest.ResponseStatusCode)
    Write-Debug "response status text = " + loo_Rest.ResponseStatusText
    Write-Debug "response header: " + loo_Rest.ResponseHeader
    Write-Debug "response JSON: " + ls_JsonResponse
    destroy loo_GAuth
    destroy loo_Rest
    destroy loo_GdCache
    destroy loo_DtExpire
    destroy loo_JsonMaster
    destroy loo_Json
    destroy loo_HashTable
    destroy loo_SbPathForFileId
    destroy loo_SaFileInfo
    return
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"
// 

Write-Debug "---- building paths ----"

loo_SbPath = create oleobject
li_rc = loo_SbPath.ConnectToNewObject("Chilkat_9_5_0.StringBuilder")

li_NumFiles = loo_JsonMaster.SizeOfArray("fileIds")
i = 0
do while i < li_NumFiles
    loo_JsonMaster.I = i

    loo_SbPath.Clear()

    ls_FileId = loo_JsonMaster.StringOf("fileIds[i]")
    li_BFinished = 0
    do while (li_BFinished = 0)
        loo_SaFileInfo.Clear()
        loo_SaFileInfo.AppendSerialized(loo_HashTable.LookupStr(ls_FileId))
        // Append this file or directory name.
        loo_SbPath.Prepend(loo_SaFileInfo.GetString(0))
        // Get the parent fileId
        ls_FileId = loo_SaFileInfo.GetString(1)
        // If this fileId is not in the hashtable, then it's the fileId for "My Drive", and we are finished.
        if loo_HashTable.Contains(ls_FileId) = 0 then
            li_BFinished = 1
        else
            loo_SbPath.Prepend("/")
        end if

    loop

    Write-Debug string(i) + ": " + loo_SbPath.GetAsString()

    // Store the filePath --> fileId mapping in our local cache.
    ls_FileId = loo_JsonMaster.StringOf("fileIds[i]")
    loo_GdCache.SaveTextDt(loo_SbPath.GetAsString(),loo_DtExpire,"",ls_FileId)

    loo_JsonMasterPaths.AddStringAt(-1,loo_SbPath.GetAsString())

    i = i + 1
loop

destroy loo_JsonMasterPaths

// Save the master list of file IDs and file paths to the local cache.
loo_JsonMaster.EmitCompact = 0
ls_StrJsonMaster = loo_JsonMaster.Emit()
loo_GdCache.SaveTextNoExpire("AllGoogleDriveFileIds","",ls_StrJsonMaster)
Write-Debug "JSON Master Record:"
Write-Debug ls_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",
//   ]
// }

Write-Debug "Entire cache rebuilt..."


destroy loo_GAuth
destroy loo_Rest
destroy loo_GdCache
destroy loo_DtExpire
destroy loo_JsonMaster
destroy loo_Json
destroy loo_HashTable
destroy loo_SbPathForFileId
destroy loo_SaFileInfo
destroy loo_SbPath