OpenGait/opengait/demo/output.py

"""
Output publishers for OpenGait demo results.

Provides pluggable result publishing:
- ConsolePublisher: JSONL to stdout
- NatsPublisher: NATS message broker integration
"""

from __future__ import annotations

import asyncio
import json
import logging
import sys
import threading
import time
from typing import TYPE_CHECKING, Protocol, TextIO, cast, runtime_checkable

if TYPE_CHECKING:
    from types import TracebackType

logger = logging.getLogger(__name__)


@runtime_checkable
class ResultPublisher(Protocol):
    """Protocol for result publishers."""

    def publish(self, result: dict[str, object]) -> None:
        """
        Publish a result dictionary.

        Parameters
        ----------
        result : dict[str, object]
            Result data with keys: frame, track_id, label, confidence, window, timestamp_ns
        """
        ...


class ConsolePublisher:
    """Publisher that outputs JSON Lines to stdout."""

    _output: TextIO

    def __init__(self, output: TextIO = sys.stdout) -> None:
        """
        Initialize console publisher.

        Parameters
        ----------
        output : TextIO
            File-like object to write to (default: sys.stdout)
        """
        self._output = output

    def publish(self, result: dict[str, object]) -> None:
        """
        Publish result as JSON line.

        Parameters
        ----------
        result : dict[str, object]
            Result data with keys: frame, track_id, label, confidence, window, timestamp_ns
        """
        try:
            json_line = json.dumps(result, ensure_ascii=False, default=str)
            _ = self._output.write(json_line + "\n")
            self._output.flush()
        except Exception as e:
            logger.warning(f"Failed to publish to console: {e}")

    def close(self) -> None:
        """Close the publisher (no-op for console)."""
        pass

    def __enter__(self) -> ConsolePublisher:
        """Context manager entry."""
        return self

    def __exit__(
        self,
        exc_type: type[BaseException] | None,
        exc_val: BaseException | None,
        exc_tb: TracebackType | None,
    ) -> None:
        """Context manager exit."""
        self.close()


class _NatsClient(Protocol):
    """Protocol for connected NATS client."""

    async def publish(self, subject: str, payload: bytes) -> object: ...

    async def close(self) -> object: ...

    async def flush(self) -> object: ...


class NatsPublisher:
    """
    Publisher that sends results to NATS message broker.

    This is a sync-friendly wrapper around the async nats-py client.
    Uses a background thread with dedicated event loop to bridge sync
    publish calls to async NATS operations, making it safe to use in
    both sync and async contexts.
    """

    _nats_url: str
    _subject: str
    _nc: _NatsClient | None
    _connected: bool
    _loop: asyncio.AbstractEventLoop | None
    _thread: threading.Thread | None
    _lock: threading.Lock

    def __init__(self, nats_url: str, subject: str = "scoliosis.result") -> None:
        """
        Initialize NATS publisher.

        Parameters
        ----------
        nats_url : str
            NATS server URL (e.g., "nats://localhost:4222")
        subject : str
            NATS subject to publish to (default: "scoliosis.result")
        """
        self._nats_url = nats_url
        self._subject = subject
        self._nc = None
        self._connected = False
        self._loop = None
        self._thread = None
        self._lock = threading.Lock()

    def _start_background_loop(self) -> bool:
        """
        Start background thread with event loop for async operations.

        Returns
        -------
        bool
            True if loop is running, False otherwise
        """
        with self._lock:
            if self._loop is not None and self._loop.is_running():
                return True

            try:
                loop = asyncio.new_event_loop()
                self._loop = loop

                def run_loop() -> None:
                    asyncio.set_event_loop(loop)
                    loop.run_forever()

                self._thread = threading.Thread(target=run_loop, daemon=True)
                self._thread.start()
                return True
            except Exception as e:
                logger.warning(f"Failed to start background event loop: {e}")
                return False

    def _stop_background_loop(self) -> None:
        """Stop the background event loop and thread."""
        with self._lock:
            if self._loop is not None and self._loop.is_running():
                _ = self._loop.call_soon_threadsafe(self._loop.stop)
            if self._thread is not None and self._thread.is_alive():
                self._thread.join(timeout=2.0)
            self._loop = None
            self._thread = None

    def _ensure_connected(self) -> bool:
        """
        Ensure connection to NATS server.

        Returns
        -------
        bool
            True if connected, False otherwise
        """
        with self._lock:
            if self._connected and self._nc is not None:
                return True

        if not self._start_background_loop():
            return False

        try:
            import nats

            async def _connect() -> _NatsClient:
                nc = await nats.connect(self._nats_url)  # pyright: ignore[reportUnknownMemberType]
                return cast(_NatsClient, nc)

            # Run connection in background loop
            future = asyncio.run_coroutine_threadsafe(
                _connect(),
                self._loop,  # pyright: ignore[reportArgumentType]
            )
            self._nc = future.result(timeout=10.0)
            self._connected = True
            logger.info(f"Connected to NATS at {self._nats_url}")
            return True
        except ImportError:
            logger.warning(
                "nats-py package not installed. Install with: pip install nats-py"
            )
            return False
        except Exception as e:
            logger.warning(f"Failed to connect to NATS at {self._nats_url}: {e}")
            return False

    def publish(self, result: dict[str, object]) -> None:
        """
        Publish result to NATS subject.

        Parameters
        ----------
        result : dict[str, object]
            Result data with keys: frame, track_id, label, confidence, window, timestamp_ns
        """
        if not self._ensure_connected():
            # Graceful degradation: log warning but don't crash
            logger.debug(
                f"NATS unavailable, dropping result: {result.get('track_id', 'unknown')}"
            )
            return

        try:

            async def _publish() -> None:
                if self._nc is not None:
                    payload = json.dumps(
                        result, ensure_ascii=False, default=str
                    ).encode("utf-8")
                    _ = await self._nc.publish(self._subject, payload)
                    _ = await self._nc.flush()
            # Run publish in background loop
            future = asyncio.run_coroutine_threadsafe(
                _publish(),
                self._loop,  # pyright: ignore[reportArgumentType]
            )
            future.result(timeout=5.0)  # Wait for publish to complete
        except Exception as e:
            logger.warning(f"Failed to publish to NATS: {e}")
            self._connected = False  # Mark for reconnection on next publish

    def close(self) -> None:
        """Close NATS connection."""
        with self._lock:
            if self._nc is not None and self._connected and self._loop is not None:
                try:

                    async def _close() -> None:
                        if self._nc is not None:
                            _ = await self._nc.close()

                    future = asyncio.run_coroutine_threadsafe(
                        _close(),
                        self._loop,
                    )
                    future.result(timeout=5.0)
                except Exception as e:
                    logger.debug(f"Error closing NATS connection: {e}")
                finally:
                    self._nc = None
                    self._connected = False

        self._stop_background_loop()

    def __enter__(self) -> NatsPublisher:
        """Context manager entry."""
        return self

    def __exit__(
        self,
        exc_type: type[BaseException] | None,
        exc_val: BaseException | None,
        exc_tb: TracebackType | None,
    ) -> None:
        """Context manager exit."""
        self.close()


def create_publisher(
    nats_url: str | None,
    subject: str = "scoliosis.result",
) -> ResultPublisher:
    """
    Factory function to create appropriate publisher.

    Parameters
    ----------
    nats_url : str | None
        NATS server URL. If None or empty, returns ConsolePublisher.
    subject : str
        NATS subject to publish to (default: "scoliosis.result")

    Returns
    -------
    ResultPublisher
        NatsPublisher if nats_url provided, otherwise ConsolePublisher

    Examples
    --------
    >>> # Console output (default)
    >>> pub = create_publisher(None)
    >>> pub.publish({"frame": 1, "track_id": 42, "label": "normal", "confidence": 0.95, "window": 30, "timestamp_ns": 1234567890})
    >>>
    >>> # NATS output
    >>> pub = create_publisher("nats://localhost:4222")
    >>> pub.publish({"frame": 1, "track_id": 42, "label": "normal", "confidence": 0.95, "window": 30, "timestamp_ns": 1234567890})
    >>>
    >>> # Context manager usage
    >>> with create_publisher("nats://localhost:4222") as pub:
    ...     pub.publish(result)
    """
    if nats_url:
        return NatsPublisher(nats_url, subject)
    return ConsolePublisher()


def create_result(
    frame: int,
    track_id: int,
    label: str,
    confidence: float,
    window: int | tuple[int, int],
    timestamp_ns: int | None = None,
) -> dict[str, object]:
    """
    Create a standardized result dictionary.

    Parameters
    ----------
    frame : int
        Frame number
    track_id : int
        Track/person identifier
    label : str
        Classification label (e.g., "normal", "scoliosis")
    confidence : float
        Confidence score (0.0 to 1.0)
    window : int | tuple[int, int]
        Frame window as int (end frame) or tuple [start, end] that produced this result
        Frame window [start, end] that produced this result
    timestamp_ns : int | None
        Timestamp in nanoseconds. If None, uses current time.

    Returns
    -------
    dict[str, object]
        Standardized result dictionary
    """
    return {
        "frame": frame,
        "track_id": track_id,
        "label": label,
        "confidence": confidence,
        "window": window if isinstance(window, int) else window[1],
        "timestamp_ns": timestamp_ns
        if timestamp_ns is not None
        else time.monotonic_ns(),
    }