first commit

backend/app/voice/tunnel.py

@@ -0,0 +1,66 @@
+"""Transparent WebSocket frame relay — no parse, no audio processing."""
+
+import asyncio
+import logging
+
+import websockets
+from fastapi import WebSocket, WebSocketDisconnect
+from websockets.exceptions import ConnectionClosed
+
+logger = logging.getLogger(__name__)
+
+
+async def relay_text_websockets(left: WebSocket, right: WebSocket) -> None:
+    stop = asyncio.Event()
+
+    async def forward(source: WebSocket, destination: WebSocket) -> None:
+        try:
+            while not stop.is_set():
+                message = await source.receive_text()
+                await destination.send_text(message)
+        except (WebSocketDisconnect, RuntimeError):
+            stop.set()
+
+    await asyncio.gather(forward(left, right), forward(right, left))
+
+
+async def relay_provider_to_upstream(
+    provider: WebSocket,
+    upstream_url: str,
+    *,
+    initial_frames: list[str] | None = None,
+    additional_headers: dict[str, str] | None = None,
+) -> None:
+    """Raw carrier ↔ customer upstream tunnel."""
+    logger.info("Opening upstream tunnel to %s", upstream_url)
+    async with websockets.connect(
+        upstream_url,
+        open_timeout=10,
+        close_timeout=5,
+        additional_headers=additional_headers,
+        ping_interval=20,
+        ping_timeout=20,
+        max_queue=16,
+    ) as upstream:
+        for frame in initial_frames or []:
+            await upstream.send(frame)
+
+        async def provider_to_upstream() -> None:
+            try:
+                while True:
+                    raw = await provider.receive_text()
+                    await upstream.send(raw)
+            except (WebSocketDisconnect, RuntimeError):
+                return
+
+        async def upstream_to_provider() -> None:
+            try:
+                while True:
+                    raw = await upstream.recv()
+                    if isinstance(raw, bytes):
+                        raw = raw.decode("utf-8")
+                    await provider.send_text(raw)
+            except (ConnectionClosed, WebSocketDisconnect, RuntimeError):
+                return
+
+        await asyncio.gather(provider_to_upstream(), upstream_to_provider())