import argparse


def create_parser():
    # Create the top-level parser
    parser = argparse.ArgumentParser(description="Time tracker.")
    subparsers = parser.add_subparsers(dest="command", help="Sub-command help")

    # Create the parser for the "ls" command
    _ = subparsers.add_parser("ls", help="List all events.")

    # Create the parser for the "ps" command
    _ = subparsers.add_parser("ps", help="Show the currently running event.")

    # Create the parser for the "add" command
    parser_add = subparsers.add_parser("add", help="Adding a new event.")
    parser_add.add_argument("name", help="Name of the event")
    parser_add.add_argument("-s", "--start", required=True, help="Start datetime (default now)")
    parser_add.add_argument("-e", "--end", required=True, help="End datetime")

    # Create the parser for the "start" command
    parser_start = subparsers.add_parser("start", help="Starting a new event.")
    parser_start.add_argument("name", help="Name of the event")
    parser_start.add_argument("-s", "--start", help="Start datetime (default now)")

    # Create the parser for the "end" command
    parser_end = subparsers.add_parser("end", help="Ending the current event.")
    parser_end.add_argument("-e", "--end", help="End datetime")

    return parser