from __future__ import annotations

import logging
import math
import socket

import dask
from dask.sizeof import sizeof
from dask.utils import parse_bytes

from distributed import protocol
from distributed.utils import get_ip, get_ipv6, nbytes, offload

logger = logging.getLogger(__name__)


# Offload (de)serializing large frames to improve event loop responsiveness.
OFFLOAD_THRESHOLD = dask.config.get("distributed.comm.offload")
if isinstance(OFFLOAD_THRESHOLD, str):
    OFFLOAD_THRESHOLD = parse_bytes(OFFLOAD_THRESHOLD)


# Find the function, `host_array()`, to use when allocating new host arrays
try:
    # Use NumPy, when available, to avoid memory initialization cost.
    # A `bytearray` is zero-initialized using `calloc`, which we don't need.
    # `np.empty` both skips the zero-initialization, and
    # uses hugepages when available ( https://github.com/numpy/numpy/pull/14216 ).
    import numpy

    def numpy_host_array(n: int) -> memoryview:
        return numpy.empty((n,), dtype="u1").data

    host_array = numpy_host_array
except ImportError:

    def builtin_host_array(n: int) -> memoryview:
        return memoryview(bytearray(n))

    host_array = builtin_host_array


async def to_frames(
    msg,
    allow_offload=True,
    **kwargs,
):
    """
    Serialize a message into a list of Distributed protocol frames.
    Any kwargs are forwarded to protocol.dumps().
    """

    def _to_frames():
        try:
            return list(protocol.dumps(msg, **kwargs))
        except Exception as e:
            logger.info("Unserializable Message: %s", msg)
            logger.exception(e)
            raise

    if OFFLOAD_THRESHOLD and allow_offload:
        try:
            msg_size = sizeof(msg)
        except RecursionError:
            msg_size = math.inf
    else:
        msg_size = 0

    if allow_offload and OFFLOAD_THRESHOLD and msg_size > OFFLOAD_THRESHOLD:
        return await offload(_to_frames)
    else:
        return _to_frames()


async def from_frames(frames, deserialize=True, deserializers=None, allow_offload=True):
    """
    Unserialize a list of Distributed protocol frames.
    """
    size = False

    def _from_frames():
        try:
            return protocol.loads(
                frames, deserialize=deserialize, deserializers=deserializers
            )
        except EOFError:
            if size > 1000:
                datastr = "[too large to display]"
            else:
                datastr = frames
            # Aid diagnosing
            logger.error("truncated data stream (%d bytes): %s", size, datastr)
            raise

    if allow_offload and deserialize and OFFLOAD_THRESHOLD:
        size = sum(map(nbytes, frames))
    if allow_offload and deserialize and OFFLOAD_THRESHOLD and size > OFFLOAD_THRESHOLD:
        res = await offload(_from_frames)
    else:
        res = _from_frames()

    return res


def get_tcp_server_addresses(tcp_server):
    """
    Get all bound addresses of a started Tornado TCPServer.
    """
    sockets = list(tcp_server._sockets.values())
    if not sockets:
        raise RuntimeError(f"TCP Server {tcp_server!r} not started yet?")

    def _look_for_family(fam):
        socks = []
        for sock in sockets:
            if sock.family == fam:
                socks.append(sock)
        return socks

    # If listening on both IPv4 and IPv6, prefer IPv4 as defective IPv6
    # is common (e.g. Travis-CI).
    socks = _look_for_family(socket.AF_INET)
    if not socks:
        socks = _look_for_family(socket.AF_INET6)
    if not socks:
        raise RuntimeError("No Internet socket found on TCPServer??")

    return [sock.getsockname() for sock in socks]


def get_tcp_server_address(tcp_server):
    """
    Get the first bound address of a started Tornado TCPServer.
    """
    return get_tcp_server_addresses(tcp_server)[0]


def ensure_concrete_host(host, default_host=None):
    """
    Ensure the given host string (or IP) denotes a concrete host, not a
    wildcard listening address.
    """
    if host in ("0.0.0.0", ""):
        return default_host or get_ip()
    elif host == "::":
        return default_host or get_ipv6()
    else:
        return host
