# Copyright (c) 2012, 2023, Oracle and/or its affiliates.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License, version 2.0, as
# published by the Free Software Foundation.
#
# This program is also distributed with certain software (including
# but not limited to OpenSSL) that is licensed under separate terms,
# as designated in a particular file or component or in included license
# documentation.  The authors of MySQL hereby grant you an
# additional permission to link the program and your derivative works
# with the separately licensed software that they have included with
# MySQL.
#
# Without limiting anything contained in the foregoing, this file,
# which is part of MySQL Connector/Python, is also subject to the
# Universal FOSS Exception, version 1.0, a copy of which can be found at
# http://oss.oracle.com/licenses/universal-foss-exception.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the GNU General Public License, version 2.0, for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

"""Module implementing low-level socket communication with MySQL servers.
"""

import socket
import struct
import warnings
import zlib

from abc import ABC, abstractmethod
from collections import deque
from typing import Any, Deque, List, Optional, Tuple, Union

try:
    import ssl

    TLS_VERSIONS = {
        "TLSv1": ssl.PROTOCOL_TLSv1,
        "TLSv1.1": ssl.PROTOCOL_TLSv1_1,
        "TLSv1.2": ssl.PROTOCOL_TLSv1_2,
        "TLSv1.3": ssl.PROTOCOL_TLS,
    }
    TLS_V1_3_SUPPORTED = hasattr(ssl, "HAS_TLSv1_3") and ssl.HAS_TLSv1_3
except ImportError:
    # If import fails, we don't have SSL support.
    TLS_V1_3_SUPPORTED = False
    ssl = None

from .errors import (
    InterfaceError,
    NotSupportedError,
    OperationalError,
    ProgrammingError,
)

MIN_COMPRESS_LENGTH = 50
MAX_PAYLOAD_LENGTH = 2**24 - 1
PACKET_HEADER_LENGTH = 4
COMPRESSED_PACKET_HEADER_LENGTH = 7


def _strioerror(err: IOError) -> str:
    """Reformat the IOError error message.

    This function reformats the IOError error message.
    """
    return str(err) if not err.errno else f"{err.errno} {err.strerror}"


class NetworkBroker(ABC):
    """Broker class interface.

    The network object is a broker used as a delegate by a socket object. Whenever the
    socket wants to deliver or get packets to or from the MySQL server it needs to rely
    on its network broker (netbroker).

    The netbroker sends `payloads` and receives `packets`.

    A packet is a bytes sequence, it has a header and body (referred to as payload).
    The first `PACKET_HEADER_LENGTH` or `COMPRESSED_PACKET_HEADER_LENGTH`
    (as appropriate) bytes correspond to the `header`, the remaining ones represent the
    `payload`.

    The maximum payload length allowed to be sent per packet to the server is
    `MAX_PAYLOAD_LENGTH`. When  `send` is called with a payload whose length is greater
    than `MAX_PAYLOAD_LENGTH` the netbroker breaks it down into packets, so the caller
    of `send` can provide payloads of arbitrary length.

    Finally, data received by the netbroker comes directly from the server, expect to
    get a packet for each call to `recv`. The received packet contains a header and
    payload, the latter respecting `MAX_PAYLOAD_LENGTH`.
    """

    @abstractmethod
    def send(
        self,
        sock: socket.socket,
        address: str,
        payload: bytes,
        packet_number: Optional[int] = None,
        compressed_packet_number: Optional[int] = None,
    ) -> None:
        """Send `payload` to the MySQL server.

        If provided a payload whose length is greater than `MAX_PAYLOAD_LENGTH`, it is
        broken down into packets.

        Args:
            sock: Object holding the socket connection.
            address: Socket's location.
            payload: Packet's body to send.
            packet_number: Sequence id (packet ID) to attach to the header when sending
                           plain packets.
            compressed_packet_number: Same as `packet_number` but used when sending
                                      compressed packets.

        Raises:
            :class:`OperationalError`: If something goes wrong while sending packets to
                                       the MySQL server.
        """

    @abstractmethod
    def recv(self, sock: socket.socket, address: str) -> bytearray:
        """Get the next available packet from the MySQL server.

        Args:
            sock: Object holding the socket connection.
            address: Socket's location.

        Returns:
            packet: A packet from the MySQL server.

        Raises:
            :class:`OperationalError`: If something goes wrong while receiving packets
                                       from the MySQL server.
            :class:`InterfaceError`: If something goes wrong while receiving packets
                                     from the MySQL server.
        """


class NetworkBrokerPlain(NetworkBroker):
    """Broker class for MySQL socket communication."""

    def __init__(self) -> None:
        self._pktnr: int = -1  # packet number

    def _set_next_pktnr(self) -> None:
        """Increment packet id."""
        self._pktnr = (self._pktnr + 1) % 256

    def _send_pkt(self, sock: socket.socket, address: str, pkt: bytes) -> None:
        """Write packet to the comm channel."""
        try:
            sock.sendall(pkt)
        except IOError as err:
            raise OperationalError(
                errno=2055, values=(address, _strioerror(err))
            ) from err
        except AttributeError as err:
            raise OperationalError(errno=2006) from err

    def _recv_chunk(self, sock: socket.socket, size: int = 0) -> bytearray:
        """Read `size` bytes from the comm channel."""
        pkt = bytearray(size)
        pkt_view = memoryview(pkt)
        while size:
            read = sock.recv_into(pkt_view, size)
            if read == 0 and size > 0:
                raise InterfaceError(errno=2013)
            pkt_view = pkt_view[read:]
            size -= read
        return pkt

    def send(
        self,
        sock: socket.socket,
        address: str,
        payload: bytes,
        packet_number: Optional[int] = None,
        compressed_packet_number: Optional[int] = None,
    ) -> None:
        """Send payload to the MySQL server.

        If provided a payload whose length is greater than `MAX_PAYLOAD_LENGTH`, it is
        broken down into packets.
        """
        if packet_number is None:
            self._set_next_pktnr()
        else:
            self._pktnr = packet_number

        # If the payload is larger than or equal to MAX_PAYLOAD_LENGTH
        # the length is set to 2^24 - 1 (ff ff ff) and additional
        # packets are sent with the rest of the payload until the
        # payload of a packet is less than MAX_PAYLOAD_LENGTH.
        if len(payload) >= MAX_PAYLOAD_LENGTH:
            offset = 0
            for _ in range(len(payload) // MAX_PAYLOAD_LENGTH):
                # payload_len, sequence_id, payload
                self._send_pkt(
                    sock,
                    address,
                    b"\xff\xff\xff"
                    + struct.pack("<B", self._pktnr)
                    + payload[offset : offset + MAX_PAYLOAD_LENGTH],
                )
                self._set_next_pktnr()
                offset += MAX_PAYLOAD_LENGTH
            payload = payload[offset:]
        self._send_pkt(
            sock,
            address,
            struct.pack("<I", len(payload))[0:3]
            + struct.pack("<B", self._pktnr)
            + payload,
        )

    def recv(self, sock: socket.socket, address: str) -> bytearray:
        """Receive `one` packet from the MySQL server."""
        try:
            # Read the header of the MySQL packet
            header = self._recv_chunk(sock, size=PACKET_HEADER_LENGTH)

            # Pull the payload length and sequence id
            payload_len, self._pktnr = (
                struct.unpack("<I", header[0:3] + b"\x00")[0],
                header[3],
            )

            # Read the payload, and return packet
            return header + self._recv_chunk(sock, size=payload_len)
        except IOError as err:
            raise OperationalError(
                errno=2055, values=(address, _strioerror(err))
            ) from err


class NetworkBrokerCompressed(NetworkBrokerPlain):
    """Broker class for MySQL socket communication."""

    def __init__(self) -> None:
        super().__init__()
        self._compressed_pktnr = -1
        self._queue_read: Deque[bytearray] = deque()

    @staticmethod
    def _prepare_packets(payload: bytes, pktnr: int) -> List[bytes]:
        """Prepare a payload for sending to the MySQL server."""
        pkts = []

        # If the payload is larger than or equal to MAX_PAYLOAD_LENGTH
        # the length is set to 2^24 - 1 (ff ff ff) and additional
        # packets are sent with the rest of the payload until the
        # payload of a packet is less than MAX_PAYLOAD_LENGTH.
        if len(payload) >= MAX_PAYLOAD_LENGTH:
            offset = 0
            for _ in range(len(payload) // MAX_PAYLOAD_LENGTH):
                # payload length + sequence id + payload
                pkts.append(
                    b"\xff\xff\xff"
                    + struct.pack("<B", pktnr)
                    + payload[offset : offset + MAX_PAYLOAD_LENGTH]
                )
                pktnr = (pktnr + 1) % 256
                offset += MAX_PAYLOAD_LENGTH
            payload = payload[offset:]
        pkts.append(
            struct.pack("<I", len(payload))[0:3] + struct.pack("<B", pktnr) + payload
        )
        return pkts

    def _set_next_compressed_pktnr(self) -> None:
        """Increment packet id."""
        self._compressed_pktnr = (self._compressed_pktnr + 1) % 256

    def _send_pkt(self, sock: socket.socket, address: str, pkt: bytes) -> None:
        """Compress packet and write it to the comm channel."""
        compressed_pkt = zlib.compress(pkt)
        pkt = (
            struct.pack("<I", len(compressed_pkt))[0:3]
            + struct.pack("<B", self._compressed_pktnr)
            + struct.pack("<I", len(pkt))[0:3]
            + compressed_pkt
        )
        return super()._send_pkt(sock, address, pkt)

    def send(
        self,
        sock: socket.socket,
        address: str,
        payload: bytes,
        packet_number: Optional[int] = None,
        compressed_packet_number: Optional[int] = None,
    ) -> None:
        """Send `payload` as compressed packets to the MySQL server.

        If provided a payload whose length is greater than `MAX_PAYLOAD_LENGTH`, it is
        broken down into packets.
        """
        # get next packet numbers
        if packet_number is None:
            self._set_next_pktnr()
        else:
            self._pktnr = packet_number
        if compressed_packet_number is None:
            self._set_next_compressed_pktnr()
        else:
            self._compressed_pktnr = compressed_packet_number

        payload_prep = bytearray(b"").join(self._prepare_packets(payload, self._pktnr))
        if len(payload) >= MAX_PAYLOAD_LENGTH - PACKET_HEADER_LENGTH:
            # sending a MySQL payload of the size greater or equal to 2^24 - 5
            # via compression leads to at least one extra compressed packet
            # WHY? let's say len(payload) is MAX_PAYLOAD_LENGTH - 3; when preparing
            # the payload, a header of size PACKET_HEADER_LENGTH is pre-appended
            # to the payload. This means that len(payload_prep) is
            # MAX_PAYLOAD_LENGTH - 3 + PACKET_HEADER_LENGTH = MAX_PAYLOAD_LENGTH + 1
            # surpassing the maximum allowed payload size per packet.
            offset = 0

            # send several MySQL packets
            for _ in range(len(payload_prep) // MAX_PAYLOAD_LENGTH):
                self._send_pkt(
                    sock, address, payload_prep[offset : offset + MAX_PAYLOAD_LENGTH]
                )
                self._set_next_compressed_pktnr()
                offset += MAX_PAYLOAD_LENGTH
            self._send_pkt(sock, address, payload_prep[offset:])
        else:
            # send one MySQL packet
            # For small packets it may be too costly to compress the packet.
            # Usually payloads less than 50 bytes (MIN_COMPRESS_LENGTH)
            # aren't compressed (see MySQL source code Documentation).
            if len(payload) > MIN_COMPRESS_LENGTH:
                # perform compression
                self._send_pkt(sock, address, payload_prep)
            else:
                # skip compression
                super()._send_pkt(
                    sock,
                    address,
                    struct.pack("<I", len(payload_prep))[0:3]
                    + struct.pack("<B", self._compressed_pktnr)
                    + struct.pack("<I", 0)[0:3]
                    + payload_prep,
                )

    def _recv_compressed_pkt(
        self, sock: socket.socket, compressed_pll: int, uncompressed_pll: int
    ) -> None:
        """Handle reading of a compressed packet."""
        # compressed_pll stands for compressed payload length.
        # Recalling that if uncompressed payload length == 0, the packet
        # comes in uncompressed, so no decompression is needed.
        compressed_pkt = super()._recv_chunk(sock, size=compressed_pll)
        pkt = (
            compressed_pkt
            if uncompressed_pll == 0
            else bytearray(zlib.decompress(compressed_pkt))
        )

        offset = 0
        while offset < len(pkt):
            # pll stands for payload length
            pll = struct.unpack(
                "<I", pkt[offset : offset + PACKET_HEADER_LENGTH - 1] + b"\x00"
            )[0]
            if PACKET_HEADER_LENGTH + pll > len(pkt) - offset:
                # More bytes need to be consumed
                # Read the header of the next MySQL packet
                header = super()._recv_chunk(sock, size=COMPRESSED_PACKET_HEADER_LENGTH)

                # compressed payload length, sequence id, uncompressed payload length
                (
                    compressed_pll,
                    self._compressed_pktnr,
                    uncompressed_pll,
                ) = (
                    struct.unpack("<I", header[0:3] + b"\x00")[0],
                    header[3],
                    struct.unpack("<I", header[4:7] + b"\x00")[0],
                )
                compressed_pkt = super()._recv_chunk(sock, size=compressed_pll)

                # recalling that if uncompressed payload length == 0, the packet
                # comes in uncompressed, so no decompression is needed.
                pkt += (
                    compressed_pkt
                    if uncompressed_pll == 0
                    else zlib.decompress(compressed_pkt)
                )

            self._queue_read.append(pkt[offset : offset + PACKET_HEADER_LENGTH + pll])
            offset += PACKET_HEADER_LENGTH + pll

    def recv(self, sock: socket.socket, address: str) -> bytearray:
        """Receive `one` or `several` packets from the MySQL server, enqueue them, and
        return the packet at the head.
        """
        if not self._queue_read:
            try:
                # Read the header of the next MySQL packet
                header = super()._recv_chunk(sock, size=COMPRESSED_PACKET_HEADER_LENGTH)

                # compressed payload length, sequence id, uncompressed payload length
                (
                    compressed_pll,
                    self._compressed_pktnr,
                    uncompressed_pll,
                ) = (
                    struct.unpack("<I", header[0:3] + b"\x00")[0],
                    header[3],
                    struct.unpack("<I", header[4:7] + b"\x00")[0],
                )
                self._recv_compressed_pkt(sock, compressed_pll, uncompressed_pll)
            except IOError as err:
                raise OperationalError(
                    errno=2055, values=(address, _strioerror(err))
                ) from err

        if not self._queue_read:
            return None

        pkt = self._queue_read.popleft()
        self._pktnr = pkt[3]

        return pkt


class MySQLSocket(ABC):
    """MySQL socket communication interface.

    Examples:
        Subclasses: network.MySQLTCPSocket and network.MySQLUnixSocket.
    """

    def __init__(self) -> None:
        """Network layer where transactions are made with plain (uncompressed) packets
        is enabled by default.
        """
        # holds the socket connection
        self.sock: Optional[socket.socket] = None
        self._connection_timeout: Optional[int] = None
        self.server_host: Optional[str] = None
        self._netbroker: NetworkBroker = NetworkBrokerPlain()

    def switch_to_compressed_mode(self) -> None:
        """Enable network layer where transactions are made with compressed packets."""
        self._netbroker = NetworkBrokerCompressed()

    def shutdown(self) -> None:
        """Shut down the socket before closing it."""
        try:
            self.sock.shutdown(socket.SHUT_RDWR)
            self.sock.close()
        except (AttributeError, OSError):
            pass

    def close_connection(self) -> None:
        """Close the socket."""
        try:
            self.sock.close()
        except (AttributeError, OSError):
            pass

    def __del__(self) -> None:
        self.shutdown()

    def set_connection_timeout(self, timeout: Optional[int]) -> None:
        """Set the connection timeout."""
        self._connection_timeout = timeout
        if self.sock:
            self.sock.settimeout(timeout)

    def switch_to_ssl(self, ssl_context: Any, host: str) -> None:
        """Upgrade an existing connection to TLS.

        Args:
            ssl_context (ssl.SSLContext): The SSL Context to be used.
            host (str): Server host name.

        Returns:
            None.

        Raises:
            ProgrammingError: If the transport does not expose the socket instance.
            NotSupportedError: If Python installation has no SSL support.
        """
        # Ensure that self.sock is already created
        assert self.sock is not None

        if self.sock.family == 1:  # socket.AF_UNIX
            raise ProgrammingError("SSL is not supported when using Unix sockets")

        if ssl is None:
            raise NotSupportedError("Python installation has no SSL support")

        try:
            self.sock = ssl_context.wrap_socket(self.sock, server_hostname=host)
        except NameError as err:
            raise NotSupportedError("Python installation has no SSL support") from err
        except (ssl.SSLError, IOError) as err:
            raise InterfaceError(
                errno=2055, values=(self.address, _strioerror(err))
            ) from err
        except ssl.CertificateError as err:
            raise InterfaceError(str(err)) from err
        except NotImplementedError as err:
            raise InterfaceError(str(err)) from err

    def build_ssl_context(
        self,
        ssl_ca: Optional[str] = None,
        ssl_cert: Optional[str] = None,
        ssl_key: Optional[str] = None,
        ssl_verify_cert: Optional[bool] = False,
        ssl_verify_identity: Optional[bool] = False,
        tls_versions: Optional[List[str]] = None,
        tls_cipher_suites: Optional[List[str]] = None,
    ) -> Any:
        """Build a SSLContext.

        Args:
            ssl_ca: Certificate authority, opptional.
            ssl_cert: SSL certificate, optional.
            ssl_key: Private key, optional.
            ssl_verify_cert: Verify the SSL certificate if `True`.
            ssl_verify_identity: Verify host identity if `True`.
            tls_versions: TLS protocol versions, optional.
            tls_cipher_suites: Set of steps that helps to establish a secure connection.

        Returns:
            ssl_context (ssl.SSLContext): An SSL Context ready be used.

        Raises:
            NotSupportedError: Python installation has no SSL support.
            InterfaceError: Socket undefined or invalid ssl data.
        """
        if not self.sock:
            raise InterfaceError(errno=2048)

        if ssl is None:
            raise NotSupportedError("Python installation has no SSL support")

        if tls_versions is None:
            tls_versions = []

        if tls_cipher_suites is None:
            tls_cipher_suites = []

        try:
            if tls_versions:
                tls_versions.sort(reverse=True)
                tls_version = tls_versions[0]
                ssl_protocol = TLS_VERSIONS[tls_version]
                context = ssl.SSLContext(ssl_protocol)

                if tls_version == "TLSv1.3":
                    if "TLSv1.2" not in tls_versions:
                        context.options |= ssl.OP_NO_TLSv1_2
                    if "TLSv1.1" not in tls_versions:
                        context.options |= ssl.OP_NO_TLSv1_1
                    if "TLSv1" not in tls_versions:
                        context.options |= ssl.OP_NO_TLSv1
            else:
                # `check_hostname` is True by default
                context = ssl.create_default_context()

            context.check_hostname = ssl_verify_identity

            if ssl_verify_cert:
                context.verify_mode = ssl.CERT_REQUIRED
            elif ssl_verify_identity:
                context.verify_mode = ssl.CERT_OPTIONAL
            else:
                context.verify_mode = ssl.CERT_NONE

            context.load_default_certs()

            if ssl_ca:
                try:
                    context.load_verify_locations(ssl_ca)
                except (IOError, ssl.SSLError) as err:
                    raise InterfaceError(f"Invalid CA Certificate: {err}") from err
            if ssl_cert:
                try:
                    context.load_cert_chain(ssl_cert, ssl_key)
                except (IOError, ssl.SSLError) as err:
                    raise InterfaceError(f"Invalid Certificate/Key: {err}") from err

            if tls_cipher_suites:
                context.set_ciphers(":".join(tls_cipher_suites))

            return context
        except NameError as err:
            raise NotSupportedError("Python installation has no SSL support") from err
        except (
            IOError,
            NotImplementedError,
            ssl.CertificateError,
            ssl.SSLError,
        ) as err:
            raise InterfaceError(str(err)) from err

    def send(
        self,
        payload: bytes,
        packet_number: Optional[int] = None,
        compressed_packet_number: Optional[int] = None,
    ) -> None:
        """Send `payload` to the MySQL server.

        NOTE: if `payload` is an instance of `bytearray`, then `payload` might be
        changed by this method - `bytearray` is similar to passing a variable by
        reference.

        If you're sure you won't read `payload` after invoking `send()`,
        then you can use `bytearray.` Otherwise, you must use `bytes`.
        """
        return self._netbroker.send(
            self.sock,
            self.address,
            payload,
            packet_number=packet_number,
            compressed_packet_number=compressed_packet_number,
        )

    def recv(self) -> bytearray:
        """Get packet from the MySQL server comm channel."""
        return self._netbroker.recv(self.sock, self.address)

    @abstractmethod
    def open_connection(self) -> None:
        """Open the socket."""

    @property
    @abstractmethod
    def address(self) -> str:
        """Get the location of the socket."""


class MySQLUnixSocket(MySQLSocket):
    """MySQL socket class using UNIX sockets.

    Opens a connection through the UNIX socket of the MySQL Server.
    """

    def __init__(self, unix_socket: str = "/tmp/mysql.sock") -> None:
        super().__init__()
        self.unix_socket: str = unix_socket
        self._address: str = unix_socket

    @property
    def address(self) -> str:
        return self._address

    def open_connection(self) -> None:
        try:
            self.sock = socket.socket(
                # pylint: disable=no-member
                socket.AF_UNIX,
                socket.SOCK_STREAM,
            )
            self.sock.settimeout(self._connection_timeout)
            self.sock.connect(self.unix_socket)
        except IOError as err:
            raise InterfaceError(
                errno=2002, values=(self.address, _strioerror(err))
            ) from err
        except Exception as err:
            raise InterfaceError(str(err)) from err

    def switch_to_ssl(
        self, *args: Any, **kwargs: Any  # pylint: disable=unused-argument
    ) -> None:
        """Switch the socket to use SSL."""
        warnings.warn(
            "SSL is disabled when using unix socket connections",
            Warning,
        )


class MySQLTCPSocket(MySQLSocket):
    """MySQL socket class using TCP/IP.

    Opens a TCP/IP connection to the MySQL Server.
    """

    def __init__(
        self,
        host: str = "127.0.0.1",
        port: int = 3306,
        force_ipv6: bool = False,
    ) -> None:
        super().__init__()
        self.server_host: str = host
        self.server_port: int = port
        self.force_ipv6: bool = force_ipv6
        self._family: int = 0
        self._address: str = f"{host}:{port}"

    @property
    def address(self) -> str:
        return self._address

    def open_connection(self) -> None:
        """Open the TCP/IP connection to the MySQL server."""
        # pylint: disable=no-member
        # Get address information
        addrinfo: Union[
            Tuple[None, None, None, None, None],
            Tuple[
                socket.AddressFamily,
                socket.SocketKind,
                int,
                str,
                Union[Tuple[str, int], Tuple[str, int, int, int]],
            ],
        ] = (None, None, None, None, None)
        try:
            addrinfos = socket.getaddrinfo(
                self.server_host,
                self.server_port,
                0,
                socket.SOCK_STREAM,
                socket.SOL_TCP,
            )
            # If multiple results we favor IPv4, unless IPv6 was forced.
            for info in addrinfos:
                if self.force_ipv6 and info[0] == socket.AF_INET6:
                    addrinfo = info
                    break
                if info[0] == socket.AF_INET:
                    addrinfo = info
                    break
            if self.force_ipv6 and addrinfo[0] is None:
                raise InterfaceError(f"No IPv6 address found for {self.server_host}")
            if addrinfo[0] is None:
                addrinfo = addrinfos[0]
        except IOError as err:
            raise InterfaceError(
                errno=2003, values=(self.address, _strioerror(err))
            ) from err

        (self._family, socktype, proto, _, sockaddr) = addrinfo

        # Instanciate the socket and connect
        try:
            self.sock = socket.socket(self._family, socktype, proto)
            self.sock.settimeout(self._connection_timeout)
            self.sock.connect(sockaddr)
        except IOError as err:
            raise InterfaceError(
                errno=2003,
                values=(
                    self.server_host,
                    self.server_port,
                    _strioerror(err),
                ),
            ) from err
        except Exception as err:
            raise OperationalError(str(err)) from err
