"""
Unix socket client — sends commands to the native host relay socket.
Used by both the CLI and the public Python API.
"""
import json
import socket
import struct
import uuid
from typing import Any

SOCKET_PATH = "/tmp/browser-cli.sock"


class BrowserNotConnected(Exception):
    """Raised when the native host socket is not available."""


def send_command(command: str, args: dict | None = None) -> Any:
    """Send a command to the browser and return the response data."""
    msg = {
        "id": str(uuid.uuid4()),
        "command": command,
        "args": args or {},
    }
    payload = json.dumps(msg).encode("utf-8")
    framed = struct.pack("<I", len(payload)) + payload

    try:
        with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as sock:
            sock.connect(SOCKET_PATH)
            sock.sendall(framed)
            response = _recv_all(sock)
    except (FileNotFoundError, ConnectionRefusedError, OSError):
        raise BrowserNotConnected(
            "Cannot connect to browser.\n"
            "Make sure:\n"
            "  1. The browser-cli extension is installed and enabled\n"
            "  2. The native host is registered: uv run browser-cli install chrome\n"
            "  3. Your browser is running"
        )

    result = json.loads(response)
    if not result.get("success", True):
        raise RuntimeError(result.get("error", "unknown error from browser"))
    return result.get("data")


def _recv_all(sock: socket.socket) -> bytes:
    raw_len = _recv_exact(sock, 4)
    msg_len = struct.unpack("<I", raw_len)[0]
    return _recv_exact(sock, msg_len)


def _recv_exact(sock: socket.socket, n: int) -> bytes:
    buf = b""
    while len(buf) < n:
        chunk = sock.recv(n - len(buf))
        if not chunk:
            raise ConnectionError("Socket closed before full message received")
        buf += chunk
    return buf