deferredcommand.py

# validated: 2024-01-24 DS 192a28af4731 DeferredCommand.java
from typing import Callable

from wpiutil import SendableBuilder

from .command import Command
from .commandscheduler import CommandScheduler
from .printcommand import PrintCommand
from .subsystem import Subsystem


class DeferredCommand(Command):
    """
    Defers Command construction to runtime. Runs the command returned by the supplier when this
    command is initialized, and ends when it ends. Useful for performing runtime tasks before
    creating a new command. If this command is interrupted, it will cancel the command.

    Note that the supplier *must* create a new Command each call. For selecting one of a
    preallocated set of commands, use :class:`commands2.SelectCommand`.
    """

    def __init__(self, supplier: Callable[[], Command], *requirements: Subsystem):
        """
        :param supplier:     The command supplier
        :param requirements: The command requirements.
        """
        super().__init__()

        assert callable(supplier)

        self._null_command = PrintCommand(
            f"[DeferredCommand] Supplied command (from {supplier!r} was None!"
        )
        self._supplier = supplier
        self._command = self._null_command
        self.addRequirements(*requirements)

    def initialize(self):
        cmd = self._supplier()
        if cmd is not None:
            self._command = cmd
            CommandScheduler.getInstance().registerComposedCommands([self._command])
        self._command.initialize()

    def execute(self):
        self._command.execute()

    def isFinished(self):
        return self._command.isFinished()

    def end(self, interrupted):
        self._command.end(interrupted)
        self._command = self._null_command

    def initSendable(self, builder: SendableBuilder):
        super().initSendable(builder)
        builder.addStringProperty(
            "deferred",
            lambda: "null"
            if self._command is self._null_command
            else self._command.getName(),
            lambda _: None,
        )