94 lines
2.8 KiB
Python
94 lines
2.8 KiB
Python
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#!/usr/bin/env python3
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"""
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LSP WebSocket bridge: stdin/stdout (LSP Content-Length framed) <-> WebSocket.
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websocat reads stdin line-by-line and holds the JSON body until a trailing \\n
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arrives -- causing a deadlock on the first LSP message. This script solves that
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by reading complete Content-Length-framed messages from stdin before sending.
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Usage:
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lsp_bridge.py <wss://host/path>
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The bridge is transparent: it reads exactly one LSP message from stdin (header +
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body), sends it as a single binary WebSocket frame, and writes any incoming
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frames straight to stdout.
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"""
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import asyncio
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import ssl
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import sys
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import websockets
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def _parse_header(buf: bytes) -> tuple[int, int]:
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"""Return (content_length, body_start_offset) or (-1, -1) if header incomplete."""
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end = buf.find(b"\r\n\r\n")
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if end == -1:
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return -1, -1
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content_length = 0
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for line in buf[:end].split(b"\r\n"):
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if line.lower().startswith(b"content-length:"):
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content_length = int(line.split(b":")[1].strip())
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return content_length, end + 4
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async def _read_stdin_lsp(reader: asyncio.StreamReader) -> bytes | None:
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"""Read one complete LSP-framed message from the async stdin reader."""
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buf = b""
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content_length = -1
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body_start = -1
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while True:
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chunk = await reader.read(4096)
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if not chunk:
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return None
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buf += chunk
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if content_length == -1:
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content_length, body_start = _parse_header(buf)
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if content_length != -1 and len(buf) >= body_start + content_length:
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return buf[: body_start + content_length]
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async def main(uri: str) -> None:
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ssl_ctx = ssl.create_default_context() if uri.startswith("wss://") else None
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loop = asyncio.get_event_loop()
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stdin_reader = asyncio.StreamReader()
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await loop.connect_read_pipe(
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lambda: asyncio.StreamReaderProtocol(stdin_reader), sys.stdin.buffer
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)
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async with websockets.connect(uri, ssl=ssl_ctx) as ws:
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async def stdin_to_ws() -> None:
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try:
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while True:
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msg = await _read_stdin_lsp(stdin_reader)
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if msg is None:
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break
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await ws.send(msg)
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except Exception:
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pass
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async def ws_to_stdout() -> None:
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try:
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async for frame in ws:
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data = frame if isinstance(frame, bytes) else frame.encode()
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sys.stdout.buffer.write(data)
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sys.stdout.buffer.flush()
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except Exception:
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pass
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await asyncio.gather(stdin_to_ws(), ws_to_stdout())
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if __name__ == "__main__":
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if len(sys.argv) < 2:
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print("Usage: lsp_bridge.py <wss://...>", file=sys.stderr)
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sys.exit(1)
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asyncio.run(main(sys.argv[1]))
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