"""
pubsub_launch.py —— 同时启动 4 个 pub/sub 节点(2 Python + 2 C++)。

节点:
    - talker_py     (py_pubsub)
    - listener_py   (py_pubsub)
    - talker_cpp    (cpp_pubsub)
    - listener_cpp  (cpp_pubsub)

全部订阅同一个 topic 'chatter',验证跨语言互通。
"""

from launch import LaunchDescription
from launch_ros.actions import Node


def generate_launch_description():
    return LaunchDescription([
        Node(
            package='py_pubsub',
            executable='talker',
            name='talker_py',
            output='screen',
            parameters=[{'period_ms': 500, 'topic': 'chatter'}],
        ),
        Node(
            package='py_pubsub',
            executable='listener',
            name='listener_py',
            output='screen',
            parameters=[{'topic': 'chatter'}],
        ),
        Node(
            package='cpp_pubsub',
            executable='talker',
            name='talker_cpp',
            output='screen',
            parameters=[{'period_ms': 500, 'topic': 'chatter'}],
        ),
        Node(
            package='cpp_pubsub',
            executable='listener',
            name='listener_cpp',
            output='screen',
            parameters=[{'topic': 'chatter'}],
        ),
    ])