import os
import xml.etree.ElementTree as ET
import requests

# Global variables for API access - These variables do not change and are set once when the app starts.
API_URL = os.getenv('SYNCTHING_API_URL', 'http://127.0.0.1:8384')
API_KEY = None

def get_api_key(config_file):
    """ Retrieve the API key from the local Syncthing configuration XML file. """
    try:
        tree = ET.parse(config_file)
        root = tree.getroot()
        return root.find('.//apikey').text
    except FileNotFoundError:
        raise Exception("Configuration file not found.")
    except AttributeError:
        raise Exception("API key not found in the configuration file.")
   

def syncthing_request(url):
    """ Generic function for Syncthing API GET requests. """
    headers = {'X-Api-Key': API_KEY}
    response = requests.get(url, headers=headers)
    response.raise_for_status()
    return response.json()
   

def check_folder_idle(folder_id):
    """ Check if the specified folder is idle. """
    status_url = f"{API_URL}/rest/db/status?folder={folder_id}"
    status = syncthing_request(status_url)
    return status['state'] == 'idle'
    
def long_poll_events(last_event_id, folder_id):
    """ Long poll the events endpoint filtering by the last known event ID and specific events. """
    events_url = f"{API_URL}/rest/events?since={last_event_id}&events=StateChanged&timeout=60"
    events = syncthing_request(events_url)
    return [event for event in events if event['data']['folder'] == folder_id]
    
def main():
    global API_KEY
    folder_id = os.getenv('SYNCTHING_FOLDER_ID')
    config_file = os.getenv('SYNCTHING_CONFIG_FILE')

    if not folder_id:
        raise ValueError("Folder ID must be provided as an environment variable.")

    API_KEY = get_api_key(config_file)

    # Start by getting the latest event ID
    current_events = syncthing_request(f"{API_URL}/rest/events?limit=1")
    last_event_id = current_events[0]['id'] if current_events else 0

    # Check initial state
    is_idle = check_folder_idle(folder_id)

    while not is_idle:
        events = long_poll_events(last_event_id, folder_id)
        for event in events:
            last_event_id = event['id']
            is_idle = event['data']['to'] == 'idle'
            if is_idle:
                print("Folder transitioned to idle.")
                break
    

if __name__ == '__main__':
    main()