Add flow to monitor transect start/end info updates

[leewujung]

On the Lasker now Kevin Stierhoff has set up a mechanism to update transect_start_end_time.csv that contains the start and end time of individual transect segment. This file will be overwritten each day at 0700, and then usually manually after a new transect or transect segment is processed in Echoview. Therefore, we need to watch the filesystem for update of this file. The watchdog library mentioned in #159 seems also a good candidate for doing this.

What we need for this flow would be:

• A utility function that watches update for updates of transect_start_end_time.csv
• Hooking this watchdog event to an event emission in Prefect to trigger a flow run -- this flow will ultimately be the flow that compute NASC for the new transect(s), but for now this can just be a mock flow for testing

[leewujung]

For the second part i was curious so did a quick google... Gemini said below haha 😅:

import time
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
from prefect.deployments import run_deployment

class PrefectTriggerHandler(FileSystemEventHandler):
    def on_created(self, event):
        if event.is_directory:
            return
        
        print(f"New file detected: {event.src_path}. Triggering Prefect...")
        
        # Trigger your Prefect deployment
        run_deployment(
            name="your-flow-name/your-deployment-name",
            parameters={"file_path": event.src_path}
        )

if __name__ == "__main__":
    path_to_watch = "./watched_folder"
    
    event_handler = PrefectTriggerHandler()
    observer = Observer()
    observer.schedule(event_handler, path=path_to_watch, recursive=False)
    
    observer.start()
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()