# traffic_line_task

This package owns the competition phase that starts after navigation has
stopped at the LED sign point. It does not start a camera or base driver.

Route policy:

- `STOP` and `NONE`: remain stationary and keep recognising.
- `LEFT` or `RIGHT`: execute the calibrated first junction maneuver, reacquire
  the lane, then finish after the final lane has continuously disappeared.
- `STRAIGHT`: enter the centre route, use odometry only to arm the expected
  second-junction region, drive straight for a configured duration after
  confirmed lane loss, trigger its fixed right maneuver, then continue
  following until the final lane has continuously disappeared.

With `use_finish_distance_limits: false`, odometry does not terminate either
finish segment. Final lane loss stops the vehicle immediately and is confirmed
for `finish_lane_loss_confirm_time` before entering `FINISHED`. A stable lane
that returns during confirmation resumes the same segment. Junction maneuvers
still retain their calibrated odometry limits and safety checks.

On `FINISHED`, the state machine publishes `任务完成` exactly once on
`/speech_command/announce`. The separately started `speech_command` node owns
the actual TTS playback; this package never starts a second speech node.

For endpoint inspection, `stop_after_second_maneuver: true` makes the state
machine enter `FINISHED` immediately after that fixed right maneuver and keeps
line following disabled. Set it back to `false` after the turn endpoint has
been verified.

Route distances live in `config/traffic_line_task.yaml`. The state machine
reports `CONFIG_INVALID` and cannot move if any required value is zero or
negative.

## Route-distance calibration

The calibration node only reads `/odom`; it never opens the camera, starts the
base driver, or publishes `/cmd_vel`. Start it beside the already-running base:

```bash
source ~/ucar_ws/devel/setup.bash
roslaunch traffic_line_task route_distance_calibration.launch
```

At the beginning of one segment, reset the measurement, move the vehicle with
the same low-speed maneuver or line-follow controller that will be used in the
task, and then mark the endpoint. For example:

```bash
rosservice call /route_distance_calibrator/reset "{}"
rosservice call /route_distance_calibrator/mark \
  "label: 'first_left_turn_distance_m'"
```

The response contains path distance and accumulated yaw. Repeat the segment at
least three times and put a conservative repeatable value in
`config/traffic_line_task.yaml`. Valid labels are exactly the seven distance
keys in that file.

The single-boundary fallback remains implemented by `line_follow_debug.py`.
If no valid lane target remains, this state machine disables line control,
stops in place, and waits up to two seconds for a stable target before entering
`FAULT`.

After calibration, start the already-shared camera and base driver, stop every
other `/cmd_vel` source, and run:

```bash
source ~/ucar_ws/devel/setup.bash
roslaunch traffic_line_task traffic_line_task.launch
```

Monitor:

```bash
rostopic echo /traffic_line_task/state
rostopic echo /traffic_line_task/segment_distance
```

Abort or reset:

```bash
rosservice call /traffic_line_task/abort "{}"
rosservice call /traffic_line_task/reset "{}"
```