"""
uart_bridge.launch.py — FC↔Orin UART bridge (Issue #362)

Launches serial_bridge_node configured for Jetson Orin UART port.
Bridges Flight Controller (STM32F722) telemetry from /dev/ttyTHS1 into ROS2.

Published topics (same as USB CDC bridge):
  /saltybot/imu              sensor_msgs/Imu         — pitch/roll/yaw as angular velocity
  /saltybot/balance_state    std_msgs/String (JSON)  — full PID diagnostics
  /diagnostics              diagnostic_msgs/DiagnosticArray — system health

Usage:
    ros2 launch saltybot_bridge uart_bridge.launch.py

    # Override UART port (Orin has THS0–THS3):
    ros2 launch saltybot_bridge uart_bridge.launch.py uart_port:=/dev/ttyTHS0

    # Override baud rate:
    ros2 launch saltybot_bridge uart_bridge.launch.py baud_rate:=115200

Prerequisites:
  - Flight Controller connected to /dev/ttyTHS1 @ 921600 baud
  - STM32 firmware transmitting JSON telemetry frames (50 Hz)
  - ROS2 environment sourced (source install/setup.bash)

Note:
  /dev/ttyTHS1 is the native UART1 on Jetson Orin. Verify connectivity:
    $ cat /dev/ttyTHS1 | head -5
    {"p":123,"r":-45,"e":0,"ig":0,"m":0,"s":1,"y":0}
    ...

Troubleshooting:
  - "Permission denied" → run with sudo or add user to dialout group
  - No frames received → check Flight Controller baud rate, verify UART cable
  - Garbled output → check baud rate mismatch, check cable shield/termination
"""

from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node


def generate_launch_description():
    return LaunchDescription([
        # ── Launch arguments ───────────────────────────────────────────────────
        DeclareLaunchArgument(
            "uart_port",
            default_value="/dev/ttyTHS1",
            description="Jetson Orin UART device (THS0–THS3)",
        ),
        DeclareLaunchArgument(
            "baud_rate",
            default_value="921600",
            description="Serial baud rate (Flight Controller standard)",
        ),
        DeclareLaunchArgument(
            "timeout",
            default_value="0.1",
            description="Serial read timeout in seconds",
        ),
        DeclareLaunchArgument(
            "reconnect_delay",
            default_value="2.0",
            description="Delay before reconnect attempt on serial error (seconds)",
        ),

        # ── Serial bridge node ─────────────────────────────────────────────────
        Node(
            package="saltybot_bridge",
            executable="serial_bridge_node",
            name="fc_uart_bridge",
            output="screen",
            parameters=[
                {
                    "serial_port": LaunchConfiguration("uart_port"),
                    "baud_rate": LaunchConfiguration("baud_rate"),
                    "timeout": LaunchConfiguration("timeout"),
                    "reconnect_delay": LaunchConfiguration("reconnect_delay"),
                },
            ],
        ),
    ])