#!/usr/bin/env python3
from dotenv import load_dotenv
import os
import secrets
import subprocess
import threading
import shutil
import time
from pathlib import Path
from flask import Flask, request
import logging
import atexit

# Setup Flask and load environment variables
app = Flask(__name__)
application = app  # WSGI servers like gunicorn look for 'application'
load_dotenv()

# Configuration
INGEST_PSK = os.environ.get('OBS_STREAM_KEY') or os.environ.get('STREAM_PSK')
INGEST_RTMP_HOST = os.environ.get('INGEST_RTMP_HOST', '127.0.0.1')
try:
    INGEST_RTMP_PORT = int(os.environ.get('INGEST_RTMP_PORT', '1936'))
except ValueError as exc:
    raise ValueError('INGEST_RTMP_PORT must be an integer') from exc
INGEST_THREAD_QUEUE_SIZE = int(os.environ.get('INGEST_THREAD_QUEUE_SIZE', '4096'))
HLS_SEGMENT_TIME = float(os.environ.get('HLS_SEGMENT_TIME', '2'))
HLS_PLAYLIST_SIZE = int(os.environ.get('HLS_PLAYLIST_SIZE', '3'))
HLS_DELETE_THRESHOLD = int(os.environ.get('HLS_DELETE_THRESHOLD', '20'))
HLS_PLAYLIST_TIMEOUT = float(os.environ.get('HLS_PLAYLIST_TIMEOUT', '5'))
HLS_PLAYLIST_POLL_INTERVAL = float(os.environ.get('HLS_PLAYLIST_POLL_INTERVAL', '0.1'))
BASE_DIR = Path(os.environ.get('STREAM_DIR', '/var/www/streams'))
SERVER_DOMAIN = os.environ.get('SERVER_DOMAIN', 'yummers.b-cdn.net')
STREAM_HEX = secrets.token_hex(16)
STREAM_PATH = BASE_DIR / 'live' / STREAM_HEX
HLS_ROUTE_PREFIX = f"/hls/{STREAM_HEX}"
# Media output settings tuned for VRChat playback
AUDIO_BITRATE = '256k'
AUDIO_CHANNELS = 2
AUDIO_SAMPLE_RATE = 48000

# Setup logging
logging.basicConfig(
    level=getattr(logging, os.environ.get('LOG_LEVEL', 'INFO')),
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
)
logger = logging.getLogger('obs_proxy')

# Global state
ffmpeg_process = None
ffmpeg_worker_thread = None
ffmpeg_stop_event = threading.Event()


def _worker_running() -> bool:
    """Return True if the ffmpeg worker thread is currently active."""
    return ffmpeg_worker_thread is not None and ffmpeg_worker_thread.is_alive()

# Validate configuration
if not INGEST_PSK:
    logger.error("OBS_STREAM_KEY/STREAM_PSK is not set")
    exit(1)

# Create required directories
BASE_DIR.mkdir(parents=True, exist_ok=True)
STREAM_PATH.mkdir(parents=True, exist_ok=True)

def reset_stream_path():
    """Ensure the live stream directory is empty and ready."""
    shutil.rmtree(STREAM_PATH, ignore_errors=True)
    STREAM_PATH.mkdir(parents=True, exist_ok=True)


def _safe_reset_stream_path(context: str) -> bool:
    """Reset the stream directory and log any failure."""
    try:
        reset_stream_path()
        return True
    except Exception as exc:  # pragma: no cover - best effort logging
        logger.error("Error resetting stream directory %s: %s", context, exc)
        return False


def _verify_stream_path_writable() -> None:
    """Ensure the stream directory is writable before launching FFmpeg."""
    test_file = STREAM_PATH / "write_test.txt"
    try:
        with open(test_file, "w", encoding="utf-8") as probe:
            probe.write("ok")
    except Exception as exc:  # pragma: no cover - best effort logging
        logger.error("Could not write to stream directory: %s", exc)
    finally:
        if test_file.exists():
            test_file.unlink()


def _wait_for_playlist(process: subprocess.Popen[str], attempt: int):
    """Block until the playlist appears or we hit the configured timeout."""
    playlist_path = STREAM_PATH / 'stream.m3u8'
    start = time.monotonic()

    while True:
        if playlist_path.exists():
            elapsed = time.monotonic() - start
            segments = sorted(seg.name for seg in playlist_path.parent.glob('segment-*.ts'))
            logger.info(
                "HLS playlist materialized after %.2fs at %s; segments=%s",
                elapsed,
                playlist_path,
                segments,
            )
            return True, 'ready'

        if ffmpeg_stop_event.is_set():
            return False, 'stop_requested'

        if process.poll() is not None:
            return False, 'ffmpeg_exited'

        elapsed = time.monotonic() - start
        if elapsed >= HLS_PLAYLIST_TIMEOUT:
            logger.warning(
                "HLS playlist still missing after %.2fs on attempt %s; recycling FFmpeg",
                elapsed,
                attempt,
            )
            return False, 'timeout'

        if ffmpeg_stop_event.wait(HLS_PLAYLIST_POLL_INTERVAL):
            return False, 'stop_requested'


def _start_pipe_logger(pipe, level):
    """Drain an ffmpeg pipe on a background thread to avoid deadlocks."""

    def pipe_logger():
        with pipe:
            for line in iter(pipe.readline, ''):
                line = line.strip()
                if line:
                    logger.log(level, "ffmpeg: %s", line)

    threading.Thread(target=pipe_logger, daemon=True).start()


def _terminate_ffmpeg_process(process: subprocess.Popen[str], *, timeout: float = 5.0, log_errors: bool = True) -> None:
    """Terminate an ffmpeg process, falling back to kill if needed."""
    try:
        process.terminate()
        process.wait(timeout=timeout)
    except Exception as exc:  # pragma: no cover - best effort logging
        if log_errors:
            logger.error(f"Error stopping FFmpeg: {exc}")
        try:
            process.kill()
        except Exception:  # pragma: no cover
            pass


def _build_ffmpeg_command() -> list[str]:
    """Construct the ffmpeg command line we execute for each attempt."""

    return [
        'ffmpeg',
        '-nostdin',
        '-hide_banner',
        '-loglevel', os.environ.get('FFMPEG_LOGLEVEL', 'warning'),
        '-fflags', '+genpts',
        '-thread_queue_size', str(INGEST_THREAD_QUEUE_SIZE),
        '-i', f'rtmp://{INGEST_RTMP_HOST}:{INGEST_RTMP_PORT}/live/{INGEST_PSK}',
        '-map', '0:v:0?',
        '-map', '0:a:0?',
        '-c:v', 'copy',
        '-c:a', 'aac',
        '-b:a', AUDIO_BITRATE,
        '-ac', str(AUDIO_CHANNELS),
        '-ar', str(AUDIO_SAMPLE_RATE),
        '-f', 'hls',
        '-hls_time', str(HLS_SEGMENT_TIME),
        '-hls_list_size', str(HLS_PLAYLIST_SIZE),
        '-hls_flags', 'delete_segments+independent_segments',
        '-hls_delete_threshold', str(HLS_DELETE_THRESHOLD),
        '-hls_segment_filename', str(STREAM_PATH / 'segment-%05d.ts'),
        str(STREAM_PATH / 'stream.m3u8'),
    ]


def _run_ffmpeg_once(attempt: int) -> bool:
    """Start ffmpeg, wait for it to exit, and report whether it ran cleanly."""
    global ffmpeg_process

    logger.info("Starting FFmpeg for live stream (attempt %s)", attempt)

    try:
        process = subprocess.Popen(
            _build_ffmpeg_command(),
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            text=True,
            bufsize=1,
        )
    except Exception as exc:  # pragma: no cover - best effort logging
        logger.error("Failed to start FFmpeg: %s", exc)
        return False

    ffmpeg_process = process
    start_time = time.monotonic()

    logger.info("FFmpeg process started with PID %s", process.pid)
    logger.info('Stream active; waiting for playlist to appear')

    _start_pipe_logger(process.stderr, logging.WARNING)
    _start_pipe_logger(process.stdout, logging.DEBUG)

    playlist_ready, playlist_reason = _wait_for_playlist(process, attempt)

    if not playlist_ready and not ffmpeg_stop_event.is_set():
        if playlist_reason == 'timeout' and process.poll() is None:
            logger.info("Terminating FFmpeg attempt %s after playlist timeout", attempt)
            _terminate_ffmpeg_process(process, log_errors=False)
        elif playlist_reason == 'ffmpeg_exited':
            logger.debug("FFmpeg exited before playlist became available on attempt %s", attempt)

    exit_code = process.wait()
    elapsed = time.monotonic() - start_time

    ffmpeg_process = None

    if ffmpeg_stop_event.is_set():
        logger.info(
            "FFmpeg stop requested; process exited with code %s after %.2fs",
            exit_code,
            elapsed,
        )
        return True

    if not playlist_ready:
        logger.error(
            "FFmpeg attempt %s ended (exit %s) before playlist became available (reason=%s)",
            attempt,
            exit_code,
            playlist_reason,
        )
        return False

    if exit_code != 0:
        logger.error("FFmpeg exited with code %s after %.2fs", exit_code, elapsed)
        return False

    logger.info("FFmpeg process completed successfully after %.2fs", elapsed)
    return True


def _ffmpeg_worker_loop() -> None:
    """Keep spawning FFmpeg until it runs cleanly or a stop is requested."""
    attempt = 0

    while not ffmpeg_stop_event.is_set():
        attempt += 1
        if _run_ffmpeg_once(attempt):
            break

        if ffmpeg_stop_event.is_set():
            break

        _safe_reset_stream_path("between FFmpeg attempts")

    logger.debug("FFmpeg worker exiting")


def start_ffmpeg_process():
    """Start FFmpeg to convert RTMP ingest into HLS."""
    global ffmpeg_worker_thread

    if _worker_running():
        logger.warning("FFmpeg worker already running; skipping duplicate start")
        return True

    if _safe_reset_stream_path("before FFmpeg start"):
        logger.info(f"Stream directory ready at {STREAM_PATH}")
    _verify_stream_path_writable()

    ffmpeg_stop_event.clear()

    try:
        ffmpeg_worker_thread = threading.Thread(
            target=_ffmpeg_worker_loop,
            daemon=True,
            name="ffmpeg-worker",
        )
        ffmpeg_worker_thread.start()
        return True
    except Exception as exc:  # pragma: no cover - defensive logging
        logger.error(f"Failed to start FFmpeg worker thread: {exc}")
        ffmpeg_worker_thread = None
        return False


def cleanup_stream():
    """Stop FFmpeg and purge any cached HLS segments."""
    global ffmpeg_process, ffmpeg_worker_thread

    ffmpeg_stop_event.set()

    if ffmpeg_process:
        _terminate_ffmpeg_process(ffmpeg_process)
        ffmpeg_process = None

    worker = ffmpeg_worker_thread
    if worker and worker.is_alive():
        worker.join(timeout=5)
        if worker.is_alive():  # pragma: no cover - diagnostic
            logger.warning("FFmpeg worker thread did not exit cleanly")
    ffmpeg_worker_thread = None

    _safe_reset_stream_path("during cleanup")

    ffmpeg_stop_event.clear()


# Routes
@app.route('/rtmp_callbacks/on_publish', methods=['POST'])
def on_publish():
    """Callback when a stream starts"""
    stream_key = request.form.get('name')
    logger.info("on_publish received for key=%s", stream_key)

    if not stream_key or stream_key != INGEST_PSK:
        logger.warning("Unauthorized stream key attempted to publish: %s", stream_key)
        return "Unauthorized", 403

    if ffmpeg_process or _worker_running():
        logger.info("Stream already active, recycling existing session")
        cleanup_stream()

    if not start_ffmpeg_process():
        return "Failed to start stream", 500

    playlist_path = STREAM_PATH / 'stream.m3u8'
    if playlist_path.exists():
        logger.info("Existing playlist found at %s", playlist_path)

    return "OK"


@app.route('/rtmp_callbacks/on_publish_done', methods=['POST'])
def on_publish_done():
    """Callback when a stream ends"""
    stream_key = request.form.get('name')
    logger.info("on_publish_done received for key=%s", stream_key)

    if not stream_key or stream_key != INGEST_PSK:
        logger.warning("on_publish_done received for unknown key: %s", stream_key)
        return "Bad request", 400

    if ffmpeg_process or _worker_running():
        cleanup_stream()

    logger.info("Stream publishing ended")
    return "OK"


@app.route('/health')
def health_check():
    """Health check endpoint"""
    return {
        "status": "healthy",
        "streaming": ffmpeg_process is not None
    }


def print_instructions():
    """Print usage instructions"""
    obs_url = f"rtmps://{SERVER_DOMAIN}:1935/live"
    hls_url = f"https://{SERVER_DOMAIN}{HLS_ROUTE_PREFIX}/stream.m3u8"

    print("\n" + "="*80)
    print(f"{'OBS TO VRCHAT STREAMING PROXY':^80}")
    print("="*80)

    print("\n[URLS]")
    print(f"  OBS ingest: {obs_url}")
    print(f"  HLS:        {hls_url}")

    print("\n[STATUS]")
    print(f"  Stream is {'ACTIVE' if ffmpeg_process else 'INACTIVE'}")
    print(f"  Session ID: {STREAM_HEX}")
    print(f"  On-disk path: {STREAM_PATH}")
    print("="*80 + "\n")

# Register cleanup once the module is imported so any WSGI server benefits.
atexit.register(cleanup_stream)


def main():
    """Entry point for running with a production WSGI server."""
    try:
        from waitress import serve
    except ImportError as exc:  # pragma: no cover - defensive guardrail
        raise RuntimeError(
            "Waitress is required to run this service. Install it with 'pip install waitress'."
        ) from exc

    print_instructions()
    host = os.environ.get('HOST', '0.0.0.0')
    port = int(os.environ.get('PORT', 5000))
    logger.info("Starting Waitress on %s:%s", host, port)
    serve(app, host=host, port=port)


if __name__ == '__main__':
    main()