on-modify.py

#!/usr/bin/env python3

import json
import sys
import subprocess


def stop_running_task():
    subprocess.run(['timetrap', 'out'])


def start_task(task):
    sheet = task.get('sheet', 'default')
    subprocess.run(['timetrap', 'sheet', sheet])
    subprocess.run(['timetrap', 'in', task['description']])


def main():
    old = json.loads(sys.stdin.readline())
    new = json.loads(sys.stdin.readline())
    print(json.dumps(new))

    if 'start' in new and 'start' not in old:
        # Start task
        start_task(new)
    elif 'start' not in new and 'start' in old:
        # Stop task
        stop_running_task()


if __name__ == '__main__':
    main()