(Delphi ActiveX) 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.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
gAuth: TChilkatAuthGoogle;
rest: TChilkatRest;
bAutoReconnect: Integer;
gdCache: TChilkatCache;
numCacheFilesDeleted: Integer;
dtExpire: TCkDateTime;
allFields: WideString;
jsonMaster: TChilkatJsonObject;
jsonMasterArr: TChilkatJsonArray;
jsonMasterPaths: TChilkatJsonArray;
json: TChilkatJsonObject;
jsonFileMetadata: IChilkatJsonObject;
i: Integer;
numFiles: Integer;
jsonResponse: WideString;
pageNumber: Integer;
pageToken: WideString;
bContinueLoop: Integer;
bHasMorePages: Integer;
hashTable: TChilkatHashtable;
sbPathForFileId: TChilkatStringBuilder;
saFileInfo: TCkStringArray;
fileId: WideString;
sbPath: TChilkatStringBuilder;
bFinished: Integer;
strJsonMaster: WideString;

begin
success := 0;

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.

gAuth := TChilkatAuthGoogle.Create(Self);
gAuth.AccessToken := 'GOOGLE_DRIVE_ACCESS_TOKEN';

rest := TChilkatRest.Create(Self);

// Connect using TLS.
bAutoReconnect := 1;
success := rest.Connect('www.googleapis.com',443,1,bAutoReconnect);

// Provide the authentication credentials (i.e. the access token)
rest.SetAuthGoogle(gAuth.ControlInterface);

// -------------------------------------------------------------------
// 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.
gdCache := TChilkatCache.Create(Self);
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.
numCacheFilesDeleted := gdCache.DeleteAll();

// Create a date/time object with an time 7 days from the current date/time.
dtExpire := TCkDateTime.Create(Self);
dtExpire.SetFromCurrentSystemTime();
dtExpire.AddDays(7);

// Indicate that we want ALL possible fields.
// If no fields are indicated, then only the basic fields are returned.
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".
jsonMaster := TChilkatJsonObject.Create(Self);

jsonMasterArr := TChilkatJsonArray.Create(Self);
jsonMaster.AppendArray2('fileIds',jsonMasterArr.ControlInterface);

// Also keep a list of file paths.
jsonMasterPaths := TChilkatJsonArray.Create(Self);
jsonMaster.AppendArray2('filePaths',jsonMasterPaths.ControlInterface);

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

json := TChilkatJsonObject.Create(Self);

// Send the request for the 1st page.
jsonResponse := rest.FullRequestNoBody('GET','/drive/v3/files');

pageNumber := 1;

bContinueLoop := rest.LastMethodSuccess and (rest.ResponseStatusCode = 200);

while bContinueLoop = 1 do
  begin

    Memo1.Lines.Add('---- Page ' + IntToStr(pageNumber) + ' ----');
    json.Load(jsonResponse);

    numFiles := json.SizeOfArray('files');
    i := 0;
    while i < numFiles do
      begin
        // Add this file ID to the master list.
        json.I := i;
        jsonMasterArr.AddStringAt(-1,json.StringOf('files[i].id'));

        i := i + 1;
      end;

    // 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 := 0;
    bHasMorePages := json.LastMethodSuccess;
    if (bHasMorePages = 1) then
      begin
        rest.ClearAllQueryParams();
        rest.AddQueryParam('pageSize','200');
        rest.AddQueryParam('pageToken',pageToken);
        jsonResponse := rest.FullRequestNoBody('GET','/drive/v3/files');
        bContinueLoop := rest.LastMethodSuccess and (rest.ResponseStatusCode = 200);
        pageNumber := pageNumber + 1;
      end;

  end;

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// 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
  begin
    Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode));
    Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText);
    Memo1.Lines.Add('response header: ' + rest.ResponseHeader);
    Memo1.Lines.Add('response JSON: ' + jsonResponse);
    Exit;
  end;

// 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.)
hashTable := TChilkatHashtable.Create(Self);
// Set the capacity of the hash table to something reasonable for the number of files
// to be hashed.
hashTable.ClearWithNewCapacity(521);

sbPathForFileId := TChilkatStringBuilder.Create(Self);

// Used for storing the file name and parents[0] in the hashTable.
saFileInfo := TCkStringArray.Create(Self);
saFileInfo.Unique := 0;

numFiles := jsonMaster.SizeOfArray('fileIds');
i := 0;
while i < numFiles do
  begin
    jsonMaster.I := i;
    fileId := jsonMaster.StringOf('fileIds[i]');
    sbPathForFileId.SetString('/drive/v3/files/');
    sbPathForFileId.Append(fileId);

    rest.ClearAllQueryParams();
    rest.AddQueryParam('fields',allFields);
    jsonResponse := rest.FullRequestNoBody('GET',sbPathForFileId.GetAsString());
    if ((rest.LastMethodSuccess <> 1) or (rest.ResponseStatusCode <> 200)) then
      begin
        // Force an exit of this loop..
        numFiles := 0;
      end;

    // Save this file's metadata to the local cache.
    // The lookup key is the fileId.
    gdCache.SaveTextDt(fileId,dtExpire.ControlInterface,'',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());

    Memo1.Lines.Add(json.StringOf('name') + ', ' + json.StringOf('parents[0]'));

    i := i + 1;
  end;

// Check to see if the above loop exited with errors...
if (rest.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// 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
  begin
    Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode));
    Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText);
    Memo1.Lines.Add('response header: ' + rest.ResponseHeader);
    Memo1.Lines.Add('response JSON: ' + jsonResponse);
    Exit;
  end;

// 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"
// 

Memo1.Lines.Add('---- building paths ----');

sbPath := TChilkatStringBuilder.Create(Self);
numFiles := jsonMaster.SizeOfArray('fileIds');
i := 0;
while i < numFiles do
  begin
    jsonMaster.I := i;

    sbPath.Clear();

    fileId := jsonMaster.StringOf('fileIds[i]');
    bFinished := 0;
    while (bFinished = 0) do
      begin
        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) = 0) then
          begin
            bFinished := 1;
          end
        else
          begin
            sbPath.Prepend('/');
          end;
      end;

    Memo1.Lines.Add(IntToStr(i) + ': ' + sbPath.GetAsString());

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

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

    i := i + 1;
  end;

// Save the master list of file IDs and file paths to the local cache.
jsonMaster.EmitCompact := 0;
strJsonMaster := jsonMaster.Emit();
gdCache.SaveTextNoExpire('AllGoogleDriveFileIds','',strJsonMaster);
Memo1.Lines.Add('JSON Master Record:');
Memo1.Lines.Add(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",
//   ]
// }

Memo1.Lines.Add('Entire cache rebuilt...');
end;