# Copyright 2015-present MongoDB, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Internal network layer helper methods."""

import datetime
import errno
import socket
import struct
import time

from bson import _decode_all_selective
from pymongo import _csot, helpers, message, ssl_support
from pymongo.common import MAX_MESSAGE_SIZE
from pymongo.compression_support import _NO_COMPRESSION, decompress
from pymongo.errors import (
    NotPrimaryError,
    OperationFailure,
    ProtocolError,
    _OperationCancelled,
)
from pymongo.message import _UNPACK_REPLY, _OpMsg
from pymongo.monitoring import _is_speculative_authenticate
from pymongo.socket_checker import _errno_from_exception

_UNPACK_HEADER = struct.Struct("<iiii").unpack


def command(
    sock_info,
    dbname,
    spec,
    is_mongos,
    read_preference,
    codec_options,
    session,
    client,
    check=True,
    allowable_errors=None,
    address=None,
    listeners=None,
    max_bson_size=None,
    read_concern=None,
    parse_write_concern_error=False,
    collation=None,
    compression_ctx=None,
    use_op_msg=False,
    unacknowledged=False,
    user_fields=None,
    exhaust_allowed=False,
    write_concern=None,
):
    """Execute a command over the socket, or raise socket.error.

    :Parameters:
      - `sock`: a raw socket instance
      - `dbname`: name of the database on which to run the command
      - `spec`: a command document as an ordered dict type, eg SON.
      - `is_mongos`: are we connected to a mongos?
      - `read_preference`: a read preference
      - `codec_options`: a CodecOptions instance
      - `session`: optional ClientSession instance.
      - `client`: optional MongoClient instance for updating $clusterTime.
      - `check`: raise OperationFailure if there are errors
      - `allowable_errors`: errors to ignore if `check` is True
      - `address`: the (host, port) of `sock`
      - `listeners`: An instance of :class:`~pymongo.monitoring.EventListeners`
      - `max_bson_size`: The maximum encoded bson size for this server
      - `read_concern`: The read concern for this command.
      - `parse_write_concern_error`: Whether to parse the ``writeConcernError``
        field in the command response.
      - `collation`: The collation for this command.
      - `compression_ctx`: optional compression Context.
      - `use_op_msg`: True if we should use OP_MSG.
      - `unacknowledged`: True if this is an unacknowledged command.
      - `user_fields` (optional): Response fields that should be decoded
        using the TypeDecoders from codec_options, passed to
        bson._decode_all_selective.
      - `exhaust_allowed`: True if we should enable OP_MSG exhaustAllowed.
    """
    name = next(iter(spec))
    ns = dbname + ".$cmd"
    speculative_hello = False

    # Publish the original command document, perhaps with lsid and $clusterTime.
    orig = spec
    if is_mongos and not use_op_msg:
        spec = message._maybe_add_read_preference(spec, read_preference)
    if read_concern and not (session and session.in_transaction):
        if read_concern.level:
            spec["readConcern"] = read_concern.document
        if session:
            session._update_read_concern(spec, sock_info)
    if collation is not None:
        spec["collation"] = collation

    publish = listeners is not None and listeners.enabled_for_commands
    if publish:
        start = datetime.datetime.now()
        speculative_hello = _is_speculative_authenticate(name, spec)

    if compression_ctx and name.lower() in _NO_COMPRESSION:
        compression_ctx = None

    if client and client._encrypter and not client._encrypter._bypass_auto_encryption:
        spec = orig = client._encrypter.encrypt(dbname, spec, codec_options)

    # Support CSOT
    if client:
        sock_info.apply_timeout(client, spec)
    _csot.apply_write_concern(spec, write_concern)

    if use_op_msg:
        flags = _OpMsg.MORE_TO_COME if unacknowledged else 0
        flags |= _OpMsg.EXHAUST_ALLOWED if exhaust_allowed else 0
        request_id, msg, size, max_doc_size = message._op_msg(
            flags, spec, dbname, read_preference, codec_options, ctx=compression_ctx
        )
        # If this is an unacknowledged write then make sure the encoded doc(s)
        # are small enough, otherwise rely on the server to return an error.
        if unacknowledged and max_bson_size is not None and max_doc_size > max_bson_size:
            message._raise_document_too_large(name, size, max_bson_size)
    else:
        request_id, msg, size = message._query(
            0, ns, 0, -1, spec, None, codec_options, compression_ctx
        )

    if max_bson_size is not None and size > max_bson_size + message._COMMAND_OVERHEAD:
        message._raise_document_too_large(name, size, max_bson_size + message._COMMAND_OVERHEAD)

    if publish:
        encoding_duration = datetime.datetime.now() - start
        listeners.publish_command_start(
            orig, dbname, request_id, address, service_id=sock_info.service_id
        )
        start = datetime.datetime.now()

    try:
        sock_info.sock.sendall(msg)
        if use_op_msg and unacknowledged:
            # Unacknowledged, fake a successful command response.
            reply = None
            response_doc = {"ok": 1}
        else:
            reply = receive_message(sock_info, request_id)
            sock_info.more_to_come = reply.more_to_come
            unpacked_docs = reply.unpack_response(
                codec_options=codec_options, user_fields=user_fields
            )

            response_doc = unpacked_docs[0]
            if client:
                client._process_response(response_doc, session)
            if check:
                helpers._check_command_response(
                    response_doc,
                    sock_info.max_wire_version,
                    allowable_errors,
                    parse_write_concern_error=parse_write_concern_error,
                )
    except Exception as exc:
        if publish:
            duration = (datetime.datetime.now() - start) + encoding_duration
            if isinstance(exc, (NotPrimaryError, OperationFailure)):
                failure = exc.details
            else:
                failure = message._convert_exception(exc)
            listeners.publish_command_failure(
                duration, failure, name, request_id, address, service_id=sock_info.service_id
            )
        raise
    if publish:
        duration = (datetime.datetime.now() - start) + encoding_duration
        listeners.publish_command_success(
            duration,
            response_doc,
            name,
            request_id,
            address,
            service_id=sock_info.service_id,
            speculative_hello=speculative_hello,
        )

    if client and client._encrypter and reply:
        decrypted = client._encrypter.decrypt(reply.raw_command_response())
        response_doc = _decode_all_selective(decrypted, codec_options, user_fields)[0]

    return response_doc


_UNPACK_COMPRESSION_HEADER = struct.Struct("<iiB").unpack


def receive_message(sock_info, request_id, max_message_size=MAX_MESSAGE_SIZE):
    """Receive a raw BSON message or raise socket.error."""
    if _csot.get_timeout():
        deadline = _csot.get_deadline()
    else:
        timeout = sock_info.sock.gettimeout()
        if timeout:
            deadline = time.monotonic() + timeout
        else:
            deadline = None
    # Ignore the response's request id.
    length, _, response_to, op_code = _UNPACK_HEADER(
        _receive_data_on_socket(sock_info, 16, deadline)
    )
    # No request_id for exhaust cursor "getMore".
    if request_id is not None:
        if request_id != response_to:
            raise ProtocolError(f"Got response id {response_to!r} but expected {request_id!r}")
    if length <= 16:
        raise ProtocolError(
            f"Message length ({length!r}) not longer than standard message header size (16)"
        )
    if length > max_message_size:
        raise ProtocolError(
            "Message length ({!r}) is larger than server max "
            "message size ({!r})".format(length, max_message_size)
        )
    if op_code == 2012:
        op_code, _, compressor_id = _UNPACK_COMPRESSION_HEADER(
            _receive_data_on_socket(sock_info, 9, deadline)
        )
        data = decompress(_receive_data_on_socket(sock_info, length - 25, deadline), compressor_id)
    else:
        data = _receive_data_on_socket(sock_info, length - 16, deadline)

    try:
        unpack_reply = _UNPACK_REPLY[op_code]
    except KeyError:
        raise ProtocolError(f"Got opcode {op_code!r} but expected {_UNPACK_REPLY.keys()!r}")
    return unpack_reply(data)


_POLL_TIMEOUT = 0.5


def wait_for_read(sock_info, deadline):
    """Block until at least one byte is read, or a timeout, or a cancel."""
    context = sock_info.cancel_context
    # Only Monitor connections can be cancelled.
    if context:
        sock = sock_info.sock
        timed_out = False
        while True:
            # SSLSocket can have buffered data which won't be caught by select.
            if hasattr(sock, "pending") and sock.pending() > 0:
                readable = True
            else:
                # Wait up to 500ms for the socket to become readable and then
                # check for cancellation.
                if deadline:
                    remaining = deadline - time.monotonic()
                    # When the timeout has expired perform one final check to
                    # see if the socket is readable. This helps avoid spurious
                    # timeouts on AWS Lambda and other FaaS environments.
                    if remaining <= 0:
                        timed_out = True
                    timeout = max(min(remaining, _POLL_TIMEOUT), 0)
                else:
                    timeout = _POLL_TIMEOUT
                readable = sock_info.socket_checker.select(sock, read=True, timeout=timeout)
            if context.cancelled:
                raise _OperationCancelled("hello cancelled")
            if readable:
                return
            if timed_out:
                raise socket.timeout("timed out")


# Errors raised by sockets (and TLS sockets) when in non-blocking mode.
BLOCKING_IO_ERRORS = (BlockingIOError, *ssl_support.BLOCKING_IO_ERRORS)


def _receive_data_on_socket(sock_info, length, deadline):
    buf = bytearray(length)
    mv = memoryview(buf)
    bytes_read = 0
    while bytes_read < length:
        try:
            wait_for_read(sock_info, deadline)
            # CSOT: Update timeout. When the timeout has expired perform one
            # final non-blocking recv. This helps avoid spurious timeouts when
            # the response is actually already buffered on the client.
            if _csot.get_timeout():
                sock_info.set_socket_timeout(max(deadline - time.monotonic(), 0))
            chunk_length = sock_info.sock.recv_into(mv[bytes_read:])
        except BLOCKING_IO_ERRORS:
            raise socket.timeout("timed out")
        except OSError as exc:  # noqa: B014
            if _errno_from_exception(exc) == errno.EINTR:
                continue
            raise
        if chunk_length == 0:
            raise OSError("connection closed")

        bytes_read += chunk_length

    return mv
