(Swift 2) 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 Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    var success: Bool = 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.

    let gAuth = CkoAuthGoogle()
    gAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

    let rest = CkoRest()

    // Connect using TLS.
    var bAutoReconnect: Bool = true
    success = rest.Connect("www.googleapis.com", port: 443, tls: true, autoReconnect: 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.
    let gdCache = CkoCache()
    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.
    var numCacheFilesDeleted: Int = gdCache.DeleteAll().intValue

    // Create a date/time object with an time 7 days from the current date/time.
    let dtExpire = CkoDateTime()
    dtExpire.SetFromCurrentSystemTime()
    dtExpire.AddDays(7)

    // Indicate that we want ALL possible fields.
    // If no fields are indicated, then only the basic fields are returned.
    var allFields: String? = "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".
    let jsonMaster = CkoJsonObject()
    var jsonMasterArr: CkoJsonArray? = jsonMaster.AppendArray("fileIds")
    // Also keep a list of file paths.
    var jsonMasterPaths: CkoJsonArray? = jsonMaster.AppendArray("filePaths")

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

    let json = CkoJsonObject()
    var jsonFileMetadata: CkoJsonObject?
    var i: Int
    var numFiles: Int

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

    var pageNumber: Int = 1
    var pageToken: String?
    var bContinueLoop: Bool = rest.LastMethodSuccess && (rest.ResponseStatusCode.intValue == 200)

    while bContinueLoop == true {

        print("---- Page \(pageNumber) ----")
        json.Load(jsonResponse)

        numFiles = json.SizeOfArray("files").intValue
        i = 0
        while i < numFiles {
            // Add this file ID to the master list.
            json.I = i
            jsonMasterArr!.AddStringAt(-1, value: 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
        var bHasMorePages: Bool = json.LastMethodSuccess
        if bHasMorePages == true {
            rest.ClearAllQueryParams()
            rest.AddQueryParam("pageSize", value: "200")
            rest.AddQueryParam("pageToken", value: pageToken)
            jsonResponse = rest.FullRequestNoBody("GET", uriPath: "/drive/v3/files")
            bContinueLoop = rest.LastMethodSuccess && (rest.ResponseStatusCode.intValue == 200)
            pageNumber = pageNumber + 1
        }

    }

    jsonMasterArr = nil

    // Check to see if the above loop exited with errors...
    if rest.LastMethodSuccess != true {
        print("\(rest.LastErrorText)")
        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.intValue != 200 {
        print("response status code = \(rest.ResponseStatusCode.intValue)")
        print("response status text = \(rest.ResponseStatusText)")
        print("response header: \(rest.ResponseHeader)")
        print("response JSON: \(jsonResponse!)")
        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.)
    let hashTable = CkoHashtable()
    // Set the capacity of the hash table to something reasonable for the number of files
    // to be hashed.
    hashTable.ClearWithNewCapacity(521)

    let sbPathForFileId = CkoStringBuilder()

    // Used for storing the file name and parents[0] in the hashTable.
    let saFileInfo = CkoStringArray()
    saFileInfo.Unique = false

    var fileId: String?
    numFiles = jsonMaster.SizeOfArray("fileIds").intValue
    i = 0
    while i < numFiles {
        jsonMaster.I = i
        fileId = jsonMaster.StringOf("fileIds[i]")
        sbPathForFileId.SetString("/drive/v3/files/")
        sbPathForFileId.Append(fileId)

        rest.ClearAllQueryParams()
        rest.AddQueryParam("fields", value: allFields)
        jsonResponse = rest.FullRequestNoBody("GET", uriPath: sbPathForFileId.GetAsString())
        if (rest.LastMethodSuccess != true) || (rest.ResponseStatusCode.intValue != 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, expire: dtExpire, eTag: "", strData: 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, value: saFileInfo.Serialize())

        print("\(json.StringOf("name")), \(json.StringOf("parents[0]"))")

        i = i + 1
    }

    // Check to see if the above loop exited with errors...
    if rest.LastMethodSuccess != true {
        print("\(rest.LastErrorText)")
        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.intValue != 200 {
        print("response status code = \(rest.ResponseStatusCode.intValue)")
        print("response status text = \(rest.ResponseStatusText)")
        print("response header: \(rest.ResponseHeader)")
        print("response JSON: \(jsonResponse!)")
        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"
    // 

    print("---- building paths ----")

    let sbPath = CkoStringBuilder()
    numFiles = jsonMaster.SizeOfArray("fileIds").intValue
    i = 0
    while i < numFiles {
        jsonMaster.I = i

        sbPath.Clear()

        fileId = jsonMaster.StringOf("fileIds[i]")
        var bFinished: Bool = false
        while (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("/")
            }

        }

        print("\(i): \(sbPath.GetAsString())")

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

        jsonMasterPaths!.AddStringAt(-1, value: sbPath.GetAsString())

        i = i + 1
    }

    jsonMasterPaths = nil

    // Save the master list of file IDs and file paths to the local cache.
    jsonMaster.EmitCompact = false
    var strJsonMaster: String? = jsonMaster.Emit()
    gdCache.SaveTextNoExpire("AllGoogleDriveFileIds", eTag: "", strData: strJsonMaster)
    print("JSON Master Record:")
    print("\(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",
    //   ]
    // }

    print("Entire cache rebuilt...")

}