(Go) 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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    success := 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.

    gAuth := chilkat.NewAuthGoogle()
    gAuth.SetAccessToken("GOOGLE_DRIVE_ACCESS_TOKEN")

    rest := chilkat.NewRest()

    // Connect using TLS.
    bAutoReconnect := true
    success = rest.Connect("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.
    gdCache := chilkat.NewCache()
    gdCache.SetLevel(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 := chilkat.NewCkDateTime()
    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 := chilkat.NewJsonObject()
    jsonMasterArr := jsonMaster.AppendArray("fileIds")
    // Also keep a list of file paths.
    jsonMasterPaths := jsonMaster.AppendArray("filePaths")

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

    json := chilkat.NewJsonObject()
    // jsonFileMetadata is a JsonObject
    var i int
    var numFiles int

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

    pageNumber := 1
    var pageToken *string = new(string)
    bContinueLoop := rest.LastMethodSuccess() && (rest.ResponseStatusCode() == 200)

    for bContinueLoop == true {

        fmt.Println("---- Page ", pageNumber, " ----")
        json.Load(*jsonResponse)

        numFiles = json.SizeOfArray("files")
        i = 0
        for i < numFiles {
            // Add this file ID to the master list.
            json.SetI(i)
            jsonMasterArr.AddStringAt(-1,*json.StringOf("files[i].id"))

            i = i + 1
        }

        // 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
        bHasMorePages := json.LastMethodSuccess()
        if bHasMorePages == true {
            rest.ClearAllQueryParams()
            rest.AddQueryParam("pageSize","200")
            rest.AddQueryParam("pageToken",*pageToken)
            jsonResponse = *rest.FullRequestNoBody("GET","/drive/v3/files")
            bContinueLoop = rest.LastMethodSuccess() && (rest.ResponseStatusCode() == 200)
            pageNumber = pageNumber + 1
        }

    }

    jsonMasterArr.DisposeJsonArray()

    // Check to see if the above loop exited with errors...
    if rest.LastMethodSuccess() != true {
        fmt.Println(rest.LastErrorText())
        gAuth.DisposeAuthGoogle()
        rest.DisposeRest()
        gdCache.DisposeCache()
        dtExpire.DisposeCkDateTime()
        jsonMaster.DisposeJsonObject()
        json.DisposeJsonObject()
        return
    }

    // 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 {
        fmt.Println("response status code = ", rest.ResponseStatusCode())
        fmt.Println("response status text = ", rest.ResponseStatusText())
        fmt.Println("response header: ", rest.ResponseHeader())
        fmt.Println("response JSON: ", *jsonResponse)
        gAuth.DisposeAuthGoogle()
        rest.DisposeRest()
        gdCache.DisposeCache()
        dtExpire.DisposeCkDateTime()
        jsonMaster.DisposeJsonObject()
        json.DisposeJsonObject()
        return
    }

    // 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 := chilkat.NewHashtable()
    // Set the capacity of the hash table to something reasonable for the number of files
    // to be hashed.
    hashTable.ClearWithNewCapacity(521)

    sbPathForFileId := chilkat.NewStringBuilder()

    // Used for storing the file name and parents[0] in the hashTable.
    saFileInfo := chilkat.NewStringArray()
    saFileInfo.SetUnique(false)

    var fileId *string = new(string)
    numFiles = jsonMaster.SizeOfArray("fileIds")
    i = 0
    for i < numFiles {
        jsonMaster.SetI(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() != true) || (rest.ResponseStatusCode() != 200) {
            // Force an exit of this loop..
            numFiles = 0
        }

        // 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())

        fmt.Println(*json.StringOf("name"), ", ", *json.StringOf("parents[0]"))

        i = i + 1
    }

    // Check to see if the above loop exited with errors...
    if rest.LastMethodSuccess() != true {
        fmt.Println(rest.LastErrorText())
        gAuth.DisposeAuthGoogle()
        rest.DisposeRest()
        gdCache.DisposeCache()
        dtExpire.DisposeCkDateTime()
        jsonMaster.DisposeJsonObject()
        json.DisposeJsonObject()
        hashTable.DisposeHashtable()
        sbPathForFileId.DisposeStringBuilder()
        saFileInfo.DisposeStringArray()
        return
    }

    // 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 {
        fmt.Println("response status code = ", rest.ResponseStatusCode())
        fmt.Println("response status text = ", rest.ResponseStatusText())
        fmt.Println("response header: ", rest.ResponseHeader())
        fmt.Println("response JSON: ", *jsonResponse)
        gAuth.DisposeAuthGoogle()
        rest.DisposeRest()
        gdCache.DisposeCache()
        dtExpire.DisposeCkDateTime()
        jsonMaster.DisposeJsonObject()
        json.DisposeJsonObject()
        hashTable.DisposeHashtable()
        sbPathForFileId.DisposeStringBuilder()
        saFileInfo.DisposeStringArray()
        return
    }

    // 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"
    // 

    fmt.Println("---- building paths ----")

    sbPath := chilkat.NewStringBuilder()
    numFiles = jsonMaster.SizeOfArray("fileIds")
    i = 0
    for i < numFiles {
        jsonMaster.SetI(i)

        sbPath.Clear()

        fileId = *jsonMaster.StringOf("fileIds[i]")
        bFinished := false
        for (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 {
                bFinished = true
            }
            else {
                sbPath.Prepend("/")
            }

        }

        fmt.Println(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
    }

    jsonMasterPaths.DisposeJsonArray()

    // Save the master list of file IDs and file paths to the local cache.
    jsonMaster.SetEmitCompact(false)
    strJsonMaster := jsonMaster.Emit()
    gdCache.SaveTextNoExpire("AllGoogleDriveFileIds","",*strJsonMaster)
    fmt.Println("JSON Master Record:")
    fmt.Println(*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",
    //   ]
    // }

    fmt.Println("Entire cache rebuilt...")

    gAuth.DisposeAuthGoogle()
    rest.DisposeRest()
    gdCache.DisposeCache()
    dtExpire.DisposeCkDateTime()
    jsonMaster.DisposeJsonObject()
    json.DisposeJsonObject()
    hashTable.DisposeHashtable()
    sbPathForFileId.DisposeStringBuilder()
    saFileInfo.DisposeStringArray()
    sbPath.DisposeStringBuilder()