|
| 1 | +"""ZAP (Zero-latency Agent Protocol) Server for hanzo-mcp. |
| 2 | +
|
| 3 | +Allows Hanzo browser extensions to discover this MCP server |
| 4 | +and call tools directly over a binary WebSocket protocol. |
| 5 | +
|
| 6 | +Protocol: 9-byte header + JSON payload |
| 7 | + [0x5A 0x41 0x50 0x01] magic "ZAP\x01" |
| 8 | + [type] 1 byte message type |
| 9 | + [length] 4 bytes big-endian payload length |
| 10 | + [payload] UTF-8 JSON |
| 11 | +""" |
| 12 | + |
| 13 | +from __future__ import annotations |
| 14 | + |
| 15 | +import asyncio |
| 16 | +import json |
| 17 | +import logging |
| 18 | +import struct |
| 19 | +import time |
| 20 | +from typing import Any, Callable, Awaitable |
| 21 | + |
| 22 | +logger = logging.getLogger(__name__) |
| 23 | + |
| 24 | +# ── Protocol Constants ────────────────────────────────────────────────── |
| 25 | +ZAP_MAGIC = b"\x5a\x41\x50\x01" # "ZAP\x01" |
| 26 | +MSG_HANDSHAKE = 0x01 |
| 27 | +MSG_HANDSHAKE_OK = 0x02 |
| 28 | +MSG_REQUEST = 0x10 |
| 29 | +MSG_RESPONSE = 0x11 |
| 30 | +MSG_PING = 0xFE |
| 31 | +MSG_PONG = 0xFF |
| 32 | + |
| 33 | +ZAP_PORTS = [9999, 9998, 9997, 9996, 9995] |
| 34 | +HEADER_SIZE = 9 # 4 (magic) + 1 (type) + 4 (length) |
| 35 | + |
| 36 | + |
| 37 | +# ── Encode / Decode ───────────────────────────────────────────────────── |
| 38 | + |
| 39 | +def encode(msg_type: int, payload: Any) -> bytes: |
| 40 | + """Encode a ZAP message: magic + type + length + JSON payload.""" |
| 41 | + data = json.dumps(payload).encode("utf-8") |
| 42 | + header = ZAP_MAGIC + struct.pack("!BL", msg_type, len(data)) |
| 43 | + return header + data |
| 44 | + |
| 45 | + |
| 46 | +def decode(buf: bytes) -> tuple[int, Any] | None: |
| 47 | + """Decode a ZAP message. Returns (type, payload) or None.""" |
| 48 | + if len(buf) < HEADER_SIZE: |
| 49 | + return None |
| 50 | + |
| 51 | + if buf[:4] != ZAP_MAGIC: |
| 52 | + # Not ZAP binary — try plain JSON fallback |
| 53 | + try: |
| 54 | + payload = json.loads(buf.decode("utf-8")) |
| 55 | + return (MSG_REQUEST, payload) |
| 56 | + except (json.JSONDecodeError, UnicodeDecodeError): |
| 57 | + return None |
| 58 | + |
| 59 | + msg_type = buf[4] |
| 60 | + length = struct.unpack("!L", buf[5:9])[0] |
| 61 | + if len(buf) < HEADER_SIZE + length: |
| 62 | + return None |
| 63 | + |
| 64 | + try: |
| 65 | + payload = json.loads(buf[HEADER_SIZE : HEADER_SIZE + length].decode("utf-8")) |
| 66 | + return (msg_type, payload) |
| 67 | + except (json.JSONDecodeError, UnicodeDecodeError): |
| 68 | + return None |
| 69 | + |
| 70 | + |
| 71 | +# ── Client tracking ───────────────────────────────────────────────────── |
| 72 | + |
| 73 | +class ZapClient: |
| 74 | + __slots__ = ("writer", "client_id", "browser", "version", "connected_at") |
| 75 | + |
| 76 | + def __init__( |
| 77 | + self, |
| 78 | + writer: asyncio.StreamWriter, |
| 79 | + client_id: str = "unknown", |
| 80 | + browser: str = "unknown", |
| 81 | + version: str = "0", |
| 82 | + ): |
| 83 | + self.writer = writer |
| 84 | + self.client_id = client_id |
| 85 | + self.browser = browser |
| 86 | + self.version = version |
| 87 | + self.connected_at = time.time() |
| 88 | + |
| 89 | + |
| 90 | +# ── WebSocket-like framing over raw TCP ───────────────────────────────── |
| 91 | +# We use asyncio websockets for the actual WS server. |
| 92 | + |
| 93 | + |
| 94 | +class ZapServer: |
| 95 | + """ZAP WebSocket server for browser extension discovery.""" |
| 96 | + |
| 97 | + def __init__( |
| 98 | + self, |
| 99 | + tools: list[dict[str, Any]], |
| 100 | + call_tool: Callable[[str, dict[str, Any]], Awaitable[Any]], |
| 101 | + name: str = "hanzo-mcp", |
| 102 | + ): |
| 103 | + self.tools = tools |
| 104 | + self.call_tool = call_tool |
| 105 | + self.name = name |
| 106 | + self.server_id = f"mcp-{int(time.time()):x}" |
| 107 | + self.clients: dict[Any, ZapClient] = {} |
| 108 | + self._server: Any = None |
| 109 | + self.port: int | None = None |
| 110 | + |
| 111 | + self.tool_manifest = [ |
| 112 | + { |
| 113 | + "name": t.get("name", ""), |
| 114 | + "description": t.get("description", ""), |
| 115 | + "inputSchema": t.get("inputSchema", t.get("input_schema", {})), |
| 116 | + } |
| 117 | + for t in self.tools |
| 118 | + ] |
| 119 | + |
| 120 | + async def _handle_connection(self, websocket: Any) -> None: |
| 121 | + """Handle a single WebSocket connection.""" |
| 122 | + client: ZapClient | None = None |
| 123 | + try: |
| 124 | + async for raw in websocket: |
| 125 | + if isinstance(raw, str): |
| 126 | + raw = raw.encode("utf-8") |
| 127 | + |
| 128 | + result = decode(raw) |
| 129 | + if result is None: |
| 130 | + continue |
| 131 | + |
| 132 | + msg_type, payload = result |
| 133 | + |
| 134 | + if msg_type == MSG_HANDSHAKE: |
| 135 | + client_id = payload.get("clientId", "unknown") |
| 136 | + browser = payload.get("browser", "unknown") |
| 137 | + version = payload.get("version", "0") |
| 138 | + client = ZapClient( |
| 139 | + writer=websocket, |
| 140 | + client_id=client_id, |
| 141 | + browser=browser, |
| 142 | + version=version, |
| 143 | + ) |
| 144 | + self.clients[websocket] = client |
| 145 | + logger.info( |
| 146 | + f"[ZAP] Client connected: {client_id} ({browser} v{version})" |
| 147 | + ) |
| 148 | + await websocket.send( |
| 149 | + encode( |
| 150 | + MSG_HANDSHAKE_OK, |
| 151 | + { |
| 152 | + "serverId": self.server_id, |
| 153 | + "name": self.name, |
| 154 | + "tools": self.tool_manifest, |
| 155 | + }, |
| 156 | + ) |
| 157 | + ) |
| 158 | + |
| 159 | + elif msg_type == MSG_REQUEST: |
| 160 | + req_id = payload.get("id", "") |
| 161 | + method = payload.get("method", "") |
| 162 | + params = payload.get("params", {}) |
| 163 | + await self._handle_request(websocket, req_id, method, params) |
| 164 | + |
| 165 | + elif msg_type == MSG_PING: |
| 166 | + await websocket.send(encode(MSG_PONG, {})) |
| 167 | + |
| 168 | + except Exception as e: |
| 169 | + logger.debug(f"[ZAP] Connection error: {e}") |
| 170 | + finally: |
| 171 | + if websocket in self.clients: |
| 172 | + client = self.clients.pop(websocket) |
| 173 | + logger.info(f"[ZAP] Client disconnected: {client.client_id}") |
| 174 | + |
| 175 | + async def _handle_request( |
| 176 | + self, websocket: Any, req_id: str, method: str, params: Any |
| 177 | + ) -> None: |
| 178 | + """Handle a ZAP RPC request.""" |
| 179 | + try: |
| 180 | + if method == "tools/list": |
| 181 | + result = {"tools": self.tool_manifest} |
| 182 | + |
| 183 | + elif method == "tools/call": |
| 184 | + tool_name = (params or {}).get("name", "") |
| 185 | + args = (params or {}).get("arguments", {}) |
| 186 | + if not tool_name: |
| 187 | + raise ValueError("Missing tool name") |
| 188 | + result = await self.call_tool(tool_name, args) |
| 189 | + |
| 190 | + elif method == "notifications/elementSelected": |
| 191 | + result = {"acknowledged": True} |
| 192 | + |
| 193 | + else: |
| 194 | + raise ValueError(f"Unknown method: {method}") |
| 195 | + |
| 196 | + await websocket.send(encode(MSG_RESPONSE, {"id": req_id, "result": result})) |
| 197 | + |
| 198 | + except Exception as e: |
| 199 | + await websocket.send( |
| 200 | + encode( |
| 201 | + MSG_RESPONSE, |
| 202 | + { |
| 203 | + "id": req_id, |
| 204 | + "error": {"code": -1, "message": str(e)}, |
| 205 | + }, |
| 206 | + ) |
| 207 | + ) |
| 208 | + |
| 209 | + async def start(self, preferred_port: int | None = None) -> bool: |
| 210 | + """Start the ZAP server on the first available port.""" |
| 211 | + try: |
| 212 | + import websockets |
| 213 | + except ImportError: |
| 214 | + logger.warning( |
| 215 | + "[ZAP] websockets package not installed. " |
| 216 | + "Install with: pip install websockets" |
| 217 | + ) |
| 218 | + return False |
| 219 | + |
| 220 | + ports = ( |
| 221 | + [preferred_port, *[p for p in ZAP_PORTS if p != preferred_port]] |
| 222 | + if preferred_port |
| 223 | + else ZAP_PORTS |
| 224 | + ) |
| 225 | + |
| 226 | + for port in ports: |
| 227 | + try: |
| 228 | + self._server = await websockets.serve( |
| 229 | + self._handle_connection, |
| 230 | + "127.0.0.1", |
| 231 | + port, |
| 232 | + ) |
| 233 | + self.port = port |
| 234 | + logger.info( |
| 235 | + f"[ZAP] Server listening on ws://127.0.0.1:{port} " |
| 236 | + f"({len(self.tool_manifest)} tools)" |
| 237 | + ) |
| 238 | + return True |
| 239 | + except OSError: |
| 240 | + continue |
| 241 | + |
| 242 | + logger.warning( |
| 243 | + "[ZAP] Could not bind to any port (9999-9995). ZAP discovery disabled." |
| 244 | + ) |
| 245 | + return False |
| 246 | + |
| 247 | + def stop(self) -> None: |
| 248 | + """Stop the ZAP server.""" |
| 249 | + if self._server: |
| 250 | + self._server.close() |
| 251 | + self._server = None |
| 252 | + self.port = None |
| 253 | + for ws in list(self.clients.keys()): |
| 254 | + try: |
| 255 | + asyncio.ensure_future(ws.close()) |
| 256 | + except Exception: |
| 257 | + pass |
| 258 | + self.clients.clear() |
| 259 | + |
| 260 | + |
| 261 | +async def start_zap_server( |
| 262 | + tools: list[dict[str, Any]], |
| 263 | + call_tool: Callable[[str, dict[str, Any]], Awaitable[Any]], |
| 264 | + name: str = "hanzo-mcp", |
| 265 | + preferred_port: int | None = None, |
| 266 | +) -> ZapServer | None: |
| 267 | + """Create and start a ZAP server. |
| 268 | +
|
| 269 | + Args: |
| 270 | + tools: List of tool dicts with name, description, inputSchema. |
| 271 | + call_tool: Async callable (name, args) -> result to route tool calls. |
| 272 | + name: Server name for handshake. |
| 273 | + preferred_port: Preferred port to try first. |
| 274 | +
|
| 275 | + Returns: |
| 276 | + ZapServer instance if started, None otherwise. |
| 277 | + """ |
| 278 | + server = ZapServer(tools=tools, call_tool=call_tool, name=name) |
| 279 | + ok = await server.start(preferred_port=preferred_port) |
| 280 | + return server if ok else None |
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