"""
Unix socket client — sends commands to the native host relay socket.
Used by both the CLI and the public Python API.

Profile selection order:
  1. Explicit `profile` argument to send_command()
  2. BROWSER_CLI_PROFILE environment variable
  3. First entry in /tmp/browser-cli-registry.json
  4. Fallback: /tmp/browser-cli-default.sock
"""
import json
import os
import socket
import struct
import uuid
from pathlib import Path
from typing import Any

REGISTRY_PATH = Path("/tmp/browser-cli-registry.json")
DEFAULT_SOCKET = "/tmp/browser-cli-default.sock"


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


def _resolve_socket(profile: str | None = None) -> str:
    """Return the socket path for the given profile (or auto-detect)."""
    target = profile or os.environ.get("BROWSER_CLI_PROFILE")

    if target:
        if REGISTRY_PATH.exists():
            try:
                reg = json.loads(REGISTRY_PATH.read_text())
                if target in reg:
                    return reg[target]
            except Exception:
                pass
        safe = target.replace(" ", "_").replace("/", "_")
        return f"/tmp/browser-cli-{safe}.sock"

    # Auto-detect: use first registered entry
    if REGISTRY_PATH.exists():
        try:
            reg = json.loads(REGISTRY_PATH.read_text())
            if reg:
                return next(iter(reg.values()))
        except Exception:
            pass

    return DEFAULT_SOCKET


def send_command(command: str, args: dict | None = None, profile: str | None = None) -> Any:
    """Send a command to the browser and return the response data."""
    sock_path = _resolve_socket(profile)
    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(sock_path)
            sock.sendall(framed)
            response = _recv_all(sock)
    except (FileNotFoundError, ConnectionRefusedError, OSError):
        profile_hint = f" (profile: {profile})" if profile else ""
        raise BrowserNotConnected(
            f"Cannot connect to browser{profile_hint}.\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\n"
            "  Tip: use BROWSER_CLI_PROFILE=<name> to select a specific profile"
        )

    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