feat: add signal handling for graceful shutdown in main execution (#86)

* feat: enhance argument parsing and validation with environment variable support

* feat: add signal handling for graceful shutdown in main execution

wyoming_microsoft_tts/__main__.py

@@ -2,6 +2,9 @@
 import asyncio
 import contextlib
 import logging
+import os
+import re
+import signal
 from functools import partial
 from typing import Any
 
@@ -14,18 +17,26 @@
 
 _LOGGER = logging.getLogger(__name__)
 
+stop_event = asyncio.Event()
 
-async def main() -> None:
-    """Start Wyoming Microsoft TTS server."""
+
+def handle_stop_signal(*args):
+    """Handle shutdown signal and set the stop event."""
+    _LOGGER.info("Received stop signal. Shutting down...")
+    stop_event.set()
+
+
+def parse_arguments():
+    """Parse command-line arguments."""
     parser = argparse.ArgumentParser()
     parser.add_argument(
         "--service-region",
-        required=True,
+        default=os.getenv("AZURE_SERVICE_REGION"),
         help="Microsoft Azure region (e.g., westus2)",
     )
     parser.add_argument(
         "--subscription-key",
-        required=True,
+        default=os.getenv("AZURE_SUBSCRIPTION_KEY"),
         help="Microsoft Azure subscription key",
     )
     parser.add_argument(
@@ -59,9 +70,30 @@ async def main() -> None:
     )
     #
     parser.add_argument("--debug", action="store_true", help="Log DEBUG messages")
-    args = parser.parse_args()
+    return parser.parse_args()
+
 
+def validate_args(args):
+    """Validate command-line arguments."""
+    if not args.service_region or not args.subscription_key:
+        raise ValueError(
+            "Both --service-region and --subscription-key must be provided either as command-line arguments or environment variables."
+        )
+    # Reinstate key validation with more flexibility to accommodate complex keys
+    if not re.match(r"^[A-Za-z0-9\-_]{40,}$", args.subscription_key):
+        _LOGGER.warning(
+            "The subscription key does not match the expected format but will attempt to initialize."
+        )
+
+
+async def main() -> None:
+    """Start Wyoming Microsoft TTS server."""
+    args = parse_arguments()
+    validate_args(args)
+
+    # setup logging
     logging.basicConfig(level=logging.DEBUG if args.debug else logging.INFO)
+    _LOGGER.debug("Arguments parsed successfully.")
 
     # Load voice info
     voices_info = get_voices(
@@ -80,7 +112,8 @@ async def main() -> None:
     # Make sure default voice is in the list
     if args.voice not in voices_info:
         raise ValueError(
-            f"Voice {args.voice} not found in voices.json, please look up the correct voice name here\nhttps://learn.microsoft.com/en-us/azure/ai-services/speech-service/language-support?tabs=tts"
+            f"Voice {args.voice} not found in voices.json, please look up the correct voice name here"
+            + "\nhttps://learn.microsoft.com/en-us/azure/ai-services/speech-service/language-support?tabs=tts"
         )
 
     voices_info.update(aliases_info)
@@ -157,5 +190,9 @@ def get_description(voice_info: dict[str, Any]):
 # -----------------------------------------------------------------------------
 
 if __name__ == "__main__":
+    # Set up signal handling for graceful shutdown
+    signal.signal(signal.SIGTERM, handle_stop_signal)
+    signal.signal(signal.SIGINT, handle_stop_signal)
+
     with contextlib.suppress(KeyboardInterrupt):
         asyncio.run(main())