_jsonrpc.py

"""
Minimal async JSON-RPC 2.0 client for stdio transport

This uses threading to handle blocking IO in an async-friendly way.
Much simpler and more reliable than pure asyncio subprocess.
"""

import asyncio
import inspect
import json
import logging
import threading
import time
import uuid
from collections.abc import Awaitable, Callable
from typing import Any

from ._diagnostics import elapsed_ms

logger = logging.getLogger(__name__)


class JsonRpcError(Exception):
    """JSON-RPC error response"""

    def __init__(self, code: int, message: str, data: Any = None):
        self.code = code
        self.message = message
        self.data = data
        super().__init__(f"JSON-RPC Error {code}: {message}")


class ProcessExitedError(Exception):
    """Error raised when the CLI process exits unexpectedly"""

    pass


RequestHandler = Callable[[dict], dict | Awaitable[dict]]


def _log_request_timing(
    level: int,
    start: float,
    method: str,
    request_id: str,
    status: str,
    *,
    exc_info: bool = False,
) -> None:
    if logger.isEnabledFor(level):
        logger.log(
            level,
            "JsonRpcClient.request JSON-RPC request finished",
            extra={
                "elapsed_ms": elapsed_ms(start),
                "method": method,
                "request_id": request_id,
                "status": status,
            },
            exc_info=exc_info,
        )


class JsonRpcClient:
    """
    Minimal async JSON-RPC 2.0 client for stdio transport

    Uses threads for blocking IO but provides async interface.
    """

    def __init__(self, process):
        """
        Create client from subprocess.Popen with stdin/stdout pipes

        Args:
            process: subprocess.Popen with stdin=PIPE, stdout=PIPE
        """
        self.process = process
        self.pending_requests: dict[str, asyncio.Future] = {}
        self._pending_inline_callbacks: dict[str, Callable[[Any], None]] = {}
        self.notification_handler: Callable[[str, dict], None] | None = None
        self.notification_method_handlers: dict[str, Callable[[dict], Any]] = {}
        self.request_handlers: dict[str, RequestHandler] = {}
        self._running = False
        self._read_thread: threading.Thread | None = None
        self._stderr_thread: threading.Thread | None = None
        self._loop: asyncio.AbstractEventLoop | None = None
        self._write_lock = threading.Lock()
        self._pending_lock = threading.Lock()
        self._process_exit_error: str | None = None
        self._stderr_output: list[str] = []
        self._stderr_lock = threading.Lock()
        self.on_close: Callable[[], None] | None = None

    def start(self, loop: asyncio.AbstractEventLoop | None = None):
        """Start listening for messages in background thread"""
        if not self._running:
            self._running = True
            # Always use the provided loop or get the running loop
            self._loop = loop or asyncio.get_running_loop()
            self._read_thread = threading.Thread(target=self._read_loop, daemon=True)
            self._read_thread.start()
            # Start stderr reader thread if process has stderr
            if hasattr(self.process, "stderr") and self.process.stderr:
                self._stderr_thread = threading.Thread(target=self._stderr_loop, daemon=True)
                self._stderr_thread.start()

    def _stderr_loop(self):
        """Read stderr in background to capture error messages"""
        try:
            while self._running:
                if not self.process.stderr:
                    break
                line = self.process.stderr.readline()
                if not line:
                    break
                stderr_line = line.decode("utf-8") if isinstance(line, bytes) else line
                logger.warning("[CLI] %s", stderr_line.rstrip())
                with self._stderr_lock:
                    self._stderr_output.append(stderr_line)
        except Exception:
            logger.debug("Error reading Copilot CLI stderr", exc_info=True)

    def get_stderr_output(self) -> str:
        """Get captured stderr output"""
        with self._stderr_lock:
            return "".join(self._stderr_output).strip()

    async def stop(self):
        """Stop listening and clean up"""
        self._running = False
        if self._read_thread:
            self._read_thread.join(timeout=1.0)
        if self._stderr_thread:
            self._stderr_thread.join(timeout=1.0)

    async def request(
        self,
        method: str,
        params: dict | None = None,
        timeout: float | None = None,
        *,
        on_response_inline: Callable[[Any], None] | None = None,
    ) -> Any:
        """
        Send a JSON-RPC request and wait for the response.

        Args:
            method: Method name
            params: Optional parameters
            timeout: Optional request timeout in seconds. If None (default),
                waits indefinitely for the server to respond.
            on_response_inline: Optional synchronous callback invoked from the
                reader thread the instant a successful response is parsed,
                before the awaiter's future is scheduled on the event loop.
                Use this to perform state mutations (for example, registering
                a server-assigned session id) that must be visible before any
                subsequent notification on the same connection is dispatched.
                The callback receives the parsed JSON result. If the callback
                raises, the exception is propagated to the awaiter.

        Returns:
            The result from the response

        Raises:
            JsonRpcError: If the server returns an error
            asyncio.TimeoutError: If the request times out (only when timeout is set)
        """
        request_start = time.perf_counter()
        request_id = str(uuid.uuid4())

        # Use the stored loop to ensure consistency with the reader thread
        if not self._loop:
            raise RuntimeError("Client not started. Call start() first.")

        future = self._loop.create_future()
        with self._pending_lock:
            self.pending_requests[request_id] = future
            if on_response_inline is not None:
                self._pending_inline_callbacks[request_id] = on_response_inline

        message = {
            "jsonrpc": "2.0",
            "id": request_id,
            "method": method,
            "params": params or {},
        }

        try:
            await self._send_message(message)
            if timeout is not None:
                result = await asyncio.wait_for(future, timeout=timeout)
            else:
                result = await future
        except asyncio.CancelledError:
            _log_request_timing(logging.DEBUG, request_start, method, request_id, "canceled")
            raise
        except Exception:
            _log_request_timing(
                logging.WARNING,
                request_start,
                method,
                request_id,
                "failed",
                exc_info=True,
            )
            raise
        else:
            _log_request_timing(logging.DEBUG, request_start, method, request_id, "succeeded")
            return result
        finally:
            with self._pending_lock:
                self.pending_requests.pop(request_id, None)
                self._pending_inline_callbacks.pop(request_id, None)

    async def notify(self, method: str, params: dict | None = None):
        """
        Send a JSON-RPC notification (no response expected).

        Args:
            method: Method name
            params: Optional parameters
        """
        message = {
            "jsonrpc": "2.0",
            "method": method,
            "params": params or {},
        }
        await self._send_message(message)

    def set_notification_handler(self, handler: Callable[[str, dict], None]):
        """Set the handler for incoming notifications from the server."""
        self.notification_handler = handler

    def set_notification_method_handler(self, method: str, handler: Callable[[dict], Any] | None):
        """Register a handler for a specific server-to-client notification method.

        Notifications carry no ``id`` and expect no response, so they are
        dispatched separately from request handlers. A registered method
        handler takes precedence over the generic notification handler. The
        handler may be a coroutine function; its result is awaited.
        """
        if handler is None:
            self.notification_method_handlers.pop(method, None)
        else:
            self.notification_method_handlers[method] = handler

    def set_request_handler(self, method: str, handler: RequestHandler):
        if handler is None:
            self.request_handlers.pop(method, None)
        else:
            self.request_handlers[method] = handler

    async def _send_message(self, message: dict):
        """Send a JSON-RPC message with a Content-Length header."""
        loop = self._loop or asyncio.get_event_loop()

        def write():
            content = json.dumps(message, separators=(",", ":"))
            content_bytes = content.encode("utf-8")
            header = f"Content-Length: {len(content_bytes)}\r\n\r\n"
            with self._write_lock:
                self.process.stdin.write(header.encode("utf-8"))
                self.process.stdin.write(content_bytes)
                self.process.stdin.flush()

        # Run in thread pool to avoid blocking
        await loop.run_in_executor(None, write)

    def _read_loop(self):
        """Read messages from the stream (runs in thread)"""
        try:
            while self._running:
                message = self._read_message()
                if message:
                    self._handle_message(message)
                else:
                    # No message means stream closed - process likely exited
                    break
        except EOFError:
            # Stream closed - check if process exited
            pass
        except Exception as e:
            if self._running:
                logger.warning("Failed to parse incoming JSON-RPC message", exc_info=True)
                # Store error for pending requests
                self._process_exit_error = str(e)

        # Process exited or read failed - fail all pending requests
        if self._running:
            logger.debug("JSON-RPC read loop ended")
            self._fail_pending_requests()
            if self.on_close is not None:
                self.on_close()

    def _fail_pending_requests(self):
        """Fail all pending requests when process exits"""
        # Build error message with stderr output
        stderr_output = self.get_stderr_output()
        return_code = None
        if hasattr(self.process, "poll"):
            return_code = self.process.poll()

        if stderr_output:
            error_msg = f"CLI process exited with code {return_code}\nstderr: {stderr_output}"
        elif return_code is not None:
            error_msg = f"CLI process exited with code {return_code}"
        else:
            error_msg = "CLI process exited unexpectedly"

        # Fail all pending requests
        with self._pending_lock:
            for request_id, future in list(self.pending_requests.items()):
                if not future.done():
                    exc = ProcessExitedError(error_msg)
                    loop = future.get_loop()
                    loop.call_soon_threadsafe(future.set_exception, exc)

    def _read_exact(self, num_bytes: int) -> bytes:
        """
        Read exactly num_bytes, handling partial/short reads from pipes.

        Args:
            num_bytes: Number of bytes to read

        Returns:
            Bytes read from stream

        Raises:
            EOFError: If stream ends before reading all bytes
        """
        chunks = []
        remaining = num_bytes
        while remaining > 0:
            chunk = self.process.stdout.read(remaining)
            if not chunk:
                raise EOFError("Unexpected end of stream while reading JSON-RPC message")
            chunks.append(chunk)
            remaining -= len(chunk)
        return b"".join(chunks)

    def _read_message(self) -> dict | None:
        """
        Read a single JSON-RPC message with a Content-Length header (blocking).

        Returns:
            Parsed JSON message, or None if the connection is closed.
        """
        # Read header line
        header_line = self.process.stdout.readline()
        if not header_line:
            return None

        # Parse Content-Length
        header = header_line.decode("utf-8").strip()
        if not header.startswith("Content-Length:"):
            return None

        content_length = int(header.split(":")[1].strip())

        # Read empty line
        self.process.stdout.readline()

        # Read exact content using loop to handle short reads
        content_bytes = self._read_exact(content_length)
        content = content_bytes.decode("utf-8")

        return json.loads(content)

    def _handle_message(self, message: dict):
        """Handle an incoming message (response or notification)"""
        # Check if it's a response to our request
        if "id" in message:
            with self._pending_lock:
                future = self.pending_requests.get(message["id"])
                inline_cb = self._pending_inline_callbacks.pop(message["id"], None)

            if future is not None:
                loop = future.get_loop()

                if "error" in message:
                    error = message["error"]
                    exc = JsonRpcError(
                        error.get("code", -1),
                        error.get("message", "Unknown error"),
                        error.get("data"),
                    )
                    loop.call_soon_threadsafe(future.set_exception, exc)
                elif "result" in message:
                    result = message["result"]
                    # Invoke the inline callback synchronously in the reader
                    # thread so any state it mutates is visible before the next
                    # message (e.g. a session.event notification) is dispatched.
                    if inline_cb is not None:
                        try:
                            inline_cb(result)
                        except Exception as exc:  # pylint: disable=broad-except
                            logger.warning(
                                "Inline response callback for request %s raised",
                                message["id"],
                                exc_info=True,
                            )
                            loop.call_soon_threadsafe(future.set_exception, exc)
                            return
                    loop.call_soon_threadsafe(future.set_result, result)
                else:
                    exc = ValueError("Invalid JSON-RPC response")
                    loop.call_soon_threadsafe(future.set_exception, exc)
                return

        # Check if it's a notification from the server
        if "method" in message and "id" not in message:
            method = message["method"]
            params = message.get("params", {})
            handler = self.notification_method_handlers.get(method)
            if handler is not None and self._loop:
                # Method-specific notification handler takes precedence.
                self._loop.call_soon_threadsafe(self._dispatch_notification, handler, params)
                return
            if self.notification_handler and self._loop:
                # Schedule notification handler on the event loop for thread safety
                self._loop.call_soon_threadsafe(self.notification_handler, method, params)
            return

        # Otherwise handle as incoming request (tool.call, etc.)
        if "method" in message and "id" in message:
            self._handle_request(message)

    def _handle_request(self, message: dict):
        method = message.get("method", "")
        handler = self.request_handlers.get(method)
        if not handler:
            if self._loop:
                asyncio.run_coroutine_threadsafe(
                    self._send_error_response(
                        message["id"], -32601, f"Method not found: {message['method']}", None
                    ),
                    self._loop,
                )
            return
        if not self._loop:
            return
        asyncio.run_coroutine_threadsafe(
            self._dispatch_request(message, handler),
            self._loop,
        )

    def _dispatch_notification(self, handler: Callable[[dict], Any], params: dict):
        """Invoke a method-specific notification handler. Runs on the event loop;
        coroutine results are scheduled and any error is logged (notifications
        carry no response, so failures never propagate to the server)."""
        try:
            outcome = handler(params)
        except Exception:  # pylint: disable=broad-except
            logger.warning("Notification handler raised", exc_info=True)
            return
        if inspect.isawaitable(outcome):

            async def _await_outcome():
                try:
                    await outcome
                except Exception:  # pylint: disable=broad-except
                    logger.warning("Notification handler raised", exc_info=True)

            asyncio.create_task(_await_outcome())

    async def _dispatch_request(self, message: dict, handler: RequestHandler):
        try:
            params = message.get("params", {})
            outcome = handler(params)
            if inspect.isawaitable(outcome):
                outcome = await outcome
            if outcome is not None and not isinstance(
                outcome, dict | list | str | int | float | bool
            ):
                raise ValueError(
                    "Request handler must return a JSON-serializable value, "
                    f"got {type(outcome).__name__}"
                )
            await self._send_response(message["id"], outcome)
        except JsonRpcError as exc:
            logger.debug(
                "Error handling JSON-RPC method %s: %s", message.get("method", ""), exc.message
            )
            await self._send_error_response(message["id"], exc.code, exc.message, exc.data)
        except Exception as exc:  # pylint: disable=broad-except
            logger.debug(
                "Error handling JSON-RPC method %s: %s",
                message.get("method", ""),
                str(exc),
                exc_info=True,
            )
            await self._send_error_response(message["id"], -32603, str(exc), None)

    async def _send_response(self, request_id: str, result: Any):
        response = {
            "jsonrpc": "2.0",
            "id": request_id,
            "result": result,
        }
        await self._send_message(response)

    async def _send_error_response(
        self, request_id: str, code: int, message: str, data: dict | None
    ):
        response = {
            "jsonrpc": "2.0",
            "id": request_id,
            "error": {
                "code": code,
                "message": message,
                "data": data,
            },
        }
        await self._send_message(response)