# Setting Up a Google Drive to GCS Migration Flow
## **1. Start the Flow**
You can start the flow by selecting **New API Request** as the trigger.
### Initiate Your Flow Variables
When the flow starts, the following important variables are initialized:
{% hint style="info" %}
You also define MIME handling for Docs, Sheets, Slides, and Drawings so that Google-native files can be exported in the correct format during migration.
{% endhint %}
***
## **2. Configure Drive and GCS Settings**
### Map Get Configs
The next step maps values from your [**DriveConfigFlow** ](https://docs.fastn.ai/flows/tutorials/setting-up-a-google-drive-to-gcs-migration-widget#configuration-flow-drive_to_gcs)so the flow has all required tenant and bucket details.
### Create Bucket for Tenant
Once these values are ready, you can use the Google Cloud Storage connector to create a **bucket for the tenant** if it doesn’t already exist.
***
## **3. Set the File Path Rules**
You will then hit a **Switch** step that determines how the `filePath` variable is set:
* If `baseFilePath` is provided → set `filePath` = `{{var.baseFilePath}}`
* If `separateFoldersForUsers` is `true` → set `filePath` per tenant/user
* Else → set `filePath` = `"Google Drive"`
From here, you move into the **Loop Over Input** step.
***
## **4. Loop Over Input Items**
For each item in your incoming list of file IDs:
* Use the Google Drive connector with **getFile**
* `File ID` = `{{steps.loopOverInput.loopOverItem.value}}`
* `param.fields` = `id,name,mimeType,modifiedTime`
* Initialize `fileObject` from `loopOverItem`
* Append this file object to the `files` array using the advanced action **insertItem**.
{% hint style="info" %}
You can click the three-dots next to your variable to setup or edit the advanced action selected.
{% endhint %}
***
## **5. Loop Over Files**
After the Loop Over Input ends, the next step will be a loop that runs until all files are processed.
**i. Initialize Loop Counters and Variables**
* **Data Mapper:** `fileLength = arrayLength(var.files)` ; total files in the queue.
#### Switch Statement
* If no files remain, exit the loop.
* Else, set:
* `currentFile = {{var.files[0]}}` , the file you’ll process now.
* Remove the first item from `var.files` using `removeItem`.
**ii. Switch Statement to Check If Current File is a Folder**
* If `currentFile.mimeType` indicates a folder:
* Call **Google Drive Connector** with action to **getFilesFromFolder** with:
* `param.q = '{{var.currentFile.file.id}}' in parents`
* `param.fields = files(id,name,mimeType,modifiedTime)`
* Append each returned file to `var.files` so they’re picked up in the same loop.
**Non-Folder Files**
* Build a **state key** for this file:
* **Read State** for `stateKey` to check if the file is already processed or unchanged.
#### iii. Switch Step to Check if Files are Updated
Next Step is a switch statement that checks if files are updated, and ends the flow if there is no update.
If the file is updated,
* Run **gettingMimeType** JS step → detect MIME type and extension.
```
function handler(params) {
const mimeTypes = params?.data.var.mimeTypes;
const fileMimeTypes = params?.data.var.currentFile.file.metadata?.mimeType;
for (let i = 0; i < mimeTypes.length; i++) {
if (mimeTypes[i].googleMimeType === fileMimeTypes) {
return {
mimeType: mimeTypes[i].exportableMimeTypes,
extension: mimeTypes[i].exportablExtension
};
}
}
```
* Run **preparingParams** JS step → prepare download/export URLs.
```
function handler(params) {
const fileId = params?.data.var.currentFile.file.value;
let fileNamePrefix = '';
if (params?.data.input.overrideFiles === false) {
fileNamePrefix = Date.now() + '_';
}
return {
googleUrl: 'https://www.googleapis.com/drive/v3/files/' + fileId + '/export?mimeType=' + params?.data.steps.gettingMimeType.output.mimeType,
nonGoogleUrl: 'https://www.googleapis.com/drive/v3/files/' + fileId + '?alt=media',
fileNamePrefix
};
}
```
* Get access token from **Fastn Connector** using the action **getConnectorToken**.
**iv. Decide How to Download (Switch Step)**
* **If Google-native file (Docs, Sheets, Slides, Drawings):**
* **Else (non-Google file):**
**v. Download from Drive**
* For both types of files, the variables that are initialized will connect to the flow component **Download file** where you can download these files.
**vi. Upload to Google Cloud Storage**
* In the next step, you will use the **Google Cloud Storage** connector with the action **uploadFileToGCS** with your target bucket and `fileName`.
**vii. Update File State**
* In the next step, you will use the State component to overwrite the State for StateKey depending on the updates.
* Loop picks up next `currentFile` and continues until `var.files` is empty.
***
## **6. Finish the Migration**
The loop continues until all files are processed.\
When complete, the main flow returns a success message confirming the migration.
