local-transcription/backend/main_headless.py

#!/usr/bin/env python3
"""Headless entry point for the Local Transcription backend.

Runs the transcription engine + API server without any GUI (no PySide6).
Designed to be launched as a Tauri sidecar or run standalone for development.

Usage:
    python -m backend.main_headless [--port PORT] [--host HOST]

The backend prints the actual port to stdout as JSON on startup:
    {"event": "ready", "port": 8080}

This allows the Tauri shell to discover which port the backend bound to.
"""

import argparse
import json
import multiprocessing
import os
import signal
import sys
from pathlib import Path

# Must be called before anything else for PyInstaller compatibility
multiprocessing.freeze_support()

if __name__ == "__main__":
    try:
        multiprocessing.set_start_method('spawn', force=True)
    except RuntimeError:
        pass

# Add project root to path
project_root = Path(__file__).resolve().parent.parent
sys.path.insert(0, str(project_root))
os.chdir(project_root)

from client.instance_lock import InstanceLock


def main():
    parser = argparse.ArgumentParser(description="Local Transcription headless backend")
    parser.add_argument("--host", default="127.0.0.1", help="API server host (default: 127.0.0.1)")
    parser.add_argument("--port", type=int, default=8080, help="API server port (default: 8080)")
    args = parser.parse_args()

    instance_lock = InstanceLock()
    if not instance_lock.acquire():
        print(json.dumps({"event": "error", "message": "Another instance is already running"}),
              flush=True)
        sys.exit(1)

    def handle_shutdown(signum, frame):
        print(json.dumps({"event": "shutdown"}), flush=True)
        if controller:
            controller.shutdown()
        instance_lock.release()
        sys.exit(0)

    signal.signal(signal.SIGTERM, handle_shutdown)
    signal.signal(signal.SIGINT, handle_shutdown)

    controller = None

    try:
        from backend.app_controller import AppController
        from backend.api_server import APIServer

        # Override web server port from CLI arg
        from client.config import Config
        config = Config()
        config.set('web_server.host', args.host)
        config.set('web_server.port', args.port)

        # Create controller and initialize
        controller = AppController(config=config)

        # Wire a state callback that prints the ready event
        def on_state_changed(state, message):
            event = {"event": "state", "state": state, "message": message}
            print(json.dumps(event), flush=True)

        controller.on_state_changed = on_state_changed

        # Initialize engine + web server
        controller.initialize()

        # Create API server wrapping the controller
        api_server = APIServer(controller)

        # Determine actual port (web server may have shifted if port was in use)
        actual_port = controller.actual_web_port or args.port

        # Print ready event so Tauri can discover the port
        print(json.dumps({"event": "ready", "port": actual_port}), flush=True)

        # Run the API server (blocks)
        import uvicorn
        import logging

        logging.getLogger("uvicorn").setLevel(logging.ERROR)
        logging.getLogger("uvicorn.access").setLevel(logging.ERROR)

        uvicorn.run(
            api_server.app,
            host=args.host,
            port=actual_port + 1,  # API on port+1, OBS display on the main port
            log_level="error",
            access_log=False,
        )

    except KeyboardInterrupt:
        print(json.dumps({"event": "shutdown", "reason": "keyboard_interrupt"}), flush=True)
    except Exception as e:
        print(json.dumps({"event": "error", "message": str(e)}), flush=True)
        import traceback
        traceback.print_exc()
        sys.exit(1)
    finally:
        if controller:
            controller.shutdown()
        instance_lock.release()


if __name__ == "__main__":
    main()