#
# Copyright (C) 2015 GNS3 Technologies Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# 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 for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
Interface for Dynamips hypervisor management module ("hypervisor")
http://github.com/GNS3/dynamips/blob/master/README.hypervisor#L46
"""

import re
import time
import logging
import asyncio

from .dynamips_error import DynamipsError

log = logging.getLogger(__name__)


class DynamipsHypervisor:

    """
    Creates a new connection to a Dynamips server (also called hypervisor)

    :param working_dir: working directory
    :param host: the hostname or ip address string of the Dynamips server
    :param port: the tcp port integer (defaults to 7200)
    :param timeout: timeout integer for how long to wait for a response to commands sent to the
    hypervisor (defaults to 30 seconds)
    """

    # Used to parse Dynamips response codes
    error_re = re.compile(r"""^2[0-9]{2}-""")
    success_re = re.compile(r"""^1[0-9]{2}\s{1}""")

    def __init__(self, working_dir, host, port=7200, timeout=30.0):

        self._host = host
        self._port = port

        self._devices = []
        self._working_dir = working_dir
        self._version = "N/A"
        self._timeout = timeout
        self._reader = None
        self._writer = None
        self._io_lock = asyncio.Lock()

    async def connect(self, timeout=10):
        """
        Connects to the hypervisor.
        """

        # connect to a local address by default
        # if listening to all addresses (IPv4 or IPv6)
        if self._host == "0.0.0.0":
            host = "127.0.0.1"
        elif self._host == "::":
            host = "::1"
        else:
            host = self._host

        begin = time.time()
        connection_success = False
        last_exception = None
        while time.time() - begin < timeout:
            await asyncio.sleep(0.01)
            try:
                self._reader, self._writer = await asyncio.wait_for(
                    asyncio.open_connection(host, self._port), timeout=1
                )
            except (asyncio.TimeoutError, OSError) as e:
                last_exception = e
                continue
            connection_success = True
            break

        if not connection_success:
            raise DynamipsError(f"Couldn't connect to hypervisor on {host}:{self._port} :{last_exception}")
        else:
            log.info(f"Connected to Dynamips hypervisor on {host}:{self._port} after {time.time() - begin:.4f} seconds")

        try:
            version = await self.send("hypervisor version")
            self._version = version[0].split("-", 1)[0]
        except IndexError:
            self._version = "Unknown"

        # this forces to send the working dir to Dynamips
        await self.set_working_dir(self._working_dir)

    @property
    def version(self):
        """
        Returns Dynamips version.

        :returns: version string
        """

        return self._version

    async def close(self):
        """
        Closes the connection to this hypervisor (but leave it running).
        """

        await self.send("hypervisor close")
        self._writer.close()
        self._reader, self._writer = None

    async def stop(self):
        """
        Stops this hypervisor (will no longer run).
        """

        try:
            # try to properly stop the hypervisor
            await self.send("hypervisor stop")
        except DynamipsError:
            pass
        try:
            if self._writer is not None:
                await self._writer.drain()
                self._writer.close()
        except OSError as e:
            log.debug(f"Stopping hypervisor {self._host}:{self._port} {e}")
        self._reader = self._writer = None

    async def reset(self):
        """
        Resets this hypervisor (used to get an empty configuration).
        """

        await self.send("hypervisor reset")

    async def set_working_dir(self, working_dir):
        """
        Sets the working directory for this hypervisor.

        :param working_dir: path to the working directory
        """

        # encase working_dir in quotes to protect spaces in the path
        await self.send(f'hypervisor working_dir "{working_dir}"')
        self._working_dir = working_dir
        log.debug(f"Working directory set to {self._working_dir}")

    @property
    def working_dir(self):
        """
        Returns current working directory

        :returns: path to the working directory
        """

        return self._working_dir

    @property
    def devices(self):
        """
        Returns the list of devices managed by this hypervisor instance.

        :returns: a list of device instances
        """

        return self._devices

    @property
    def port(self):
        """
        Returns the port used to start the hypervisor.

        :returns: port number (integer)
        """

        return self._port

    @port.setter
    def port(self, port):
        """
        Sets the port used to start the hypervisor.

        :param port: port number (integer)
        """

        self._port = port

    @property
    def host(self):
        """
        Returns the host (binding) used to start the hypervisor.

        :returns: host/address (string)
        """

        return self._host

    @host.setter
    def host(self, host):
        """
        Sets the host (binding) used to start the hypervisor.

        :param host: host/address (string)
        """

        self._host = host

    async def send(self, command):
        """
        Sends commands to this hypervisor.

        :param command: a Dynamips hypervisor command

        :returns: results as a list
        """

        # Dynamips responses are of the form:
        #   1xx yyyyyy\r\n
        #   1xx yyyyyy\r\n
        #   ...
        #   100-yyyy\r\n
        # or
        #   2xx-yyyy\r\n
        #
        # Where 1xx is a code from 100-199 for a success or 200-299 for an error
        # The result might be multiple lines and might be less than the buffer size
        # but still have more data. The only thing we know for sure is the last line
        # will begin with '100-' or a '2xx-' and end with '\r\n'

        async with self._io_lock:
            if self._writer is None or self._reader is None:
                raise DynamipsError("Not connected")

            try:
                command = command.strip() + "\n"
                log.debug(f"sending {command}")
                self._writer.write(command.encode())
                await self._writer.drain()
            except OSError as e:
                raise DynamipsError(
                    "Could not send Dynamips command '{command}' to {host}:{port}: {error}, process running: {run}".format(
                        command=command.strip(), host=self._host, port=self._port, error=e, run=self.is_running()
                    )
                )

            # Now retrieve the result
            data = []
            buf = ""
            retries = 0
            max_retries = 10
            while True:
                try:
                    try:
                        # line = await self._reader.readline()  # this can lead to ValueError: Line is too long
                        chunk = await self._reader.read(1024)  # match to Dynamips' buffer size
                    except asyncio.CancelledError:
                        # task has been canceled but continue to read
                        # any remaining data sent by the hypervisor
                        continue
                    except ConnectionResetError as e:
                        # Sometimes WinError 64 (ERROR_NETNAME_DELETED) is returned here on Windows.
                        # These happen if connection reset is received before IOCP could complete
                        # a previous operation. Ignore and try again....
                        log.warning(f"Connection reset received while reading Dynamips response: {e}")
                        continue
                    if not chunk:
                        if retries > max_retries:
                            raise DynamipsError(
                                "No data returned from {host}:{port}, Dynamips process running: {run}".format(
                                    host=self._host, port=self._port, run=self.is_running()
                                )
                            )
                        else:
                            retries += 1
                            await asyncio.sleep(0.1)
                            continue
                    retries = 0
                    buf += chunk.decode("utf-8", errors="ignore")
                except OSError as e:
                    raise DynamipsError(
                        "Could not read response for '{command}' from {host}:{port}: {error}, process running: {run}".format(
                            command=command.strip(), host=self._host, port=self._port, error=e, run=self.is_running()
                        )
                    )

                # If the buffer doesn't end in '\n' then we can't be done
                try:
                    if buf[-1] != "\n":
                        continue
                except IndexError:
                    raise DynamipsError(
                        "Could not communicate with {host}:{port}, Dynamips process running: {run}".format(
                            host=self._host, port=self._port, run=self.is_running()
                        )
                    )

                data += buf.split("\r\n")
                if data[-1] == "":
                    data.pop()
                buf = ""

                # Does it contain an error code?
                if self.error_re.search(data[-1]):
                    raise DynamipsError(f"Dynamips error when running command '{command}': {data[-1][4:]}")

                # Or does the last line begin with '100-'? Then we are done!
                if data[-1][:4] == "100-":
                    data[-1] = data[-1][4:]
                    if data[-1] == "OK":
                        data.pop()
                    break

            # Remove success responses codes
            for index in range(len(data)):
                if self.success_re.search(data[index]):
                    data[index] = data[index][4:]

            log.debug(f"returned result {data}")
            return data