import os
import subprocess as sp
import logging
import socket
import json
import tempfile
import time

from contextlib import suppress
from multiprocessing import Process
from os.path import join as join_path
from os.path import isdir

logger = logging.getLogger(__name__)


class VMQMPHandles:
    def __init__(self, path):
        self.path = path
        self.sock = socket.socket(socket.AF_UNIX)
        self.file = self.sock.makefile()

    def __enter__(self):
        self.sock.connect(self.path)

        # eat qmp greetings
        self.file.readline()

        # init qmp
        self.sock.sendall(b'{ "execute": "qmp_capabilities" }')
        self.file.readline()

        return self.sock, self.file

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.file.close()
        self.sock.close()

        if exc_type:
            logger.error('Couldn\'t get handle for VM.', exc_type, exc_val, exc_tb)
            raise exc_type("Couldn't get handle for VM.") from exc_type


class TransferVM(Process):
    def __init__(self, src_uuid, dest_uuid, host, socket_dir):
        self.src_uuid = src_uuid
        self.dest_uuid = dest_uuid
        self.host = host
        self.src_sock_path = os.path.join(socket_dir, self.src_uuid)
        self.dest_sock_path = os.path.join(socket_dir, self.dest_uuid)

        super().__init__()

    def run(self):
        with suppress(FileNotFoundError):
            os.remove(self.src_sock_path)

        command = ['ssh', '-nNT', '-L', '{}:{}'.format(self.src_sock_path, self.dest_sock_path),
                   'root@{}'.format(self.host)]

        try:
            p = sp.Popen(command)
        except Exception as e:
            logger.error('Couldn\' forward unix socks over ssh.', exc_info=e)
        else:
            time.sleep(2)
            vmm = VMM()
            logger.debug('Executing: ssh forwarding command: %s', command)
            vmm.execute_command(self.src_uuid, command='migrate',
                                arguments={'uri': 'unix:{}'.format(self.src_sock_path)})

            while p.poll() is None:
                success, output = vmm.execute_command(self.src_uuid, command='query-migrate')
                if success:
                    status = output['return']['status']
                    if status != 'active':
                        print('Migration Status: ', status)
                        return
                    else:
                        print('Migration Status: ', status)
                else:
                    return
                time.sleep(0.2)


class VMM:
    # Virtual Machine Manager
    def __init__(self, qemu_path='/usr/bin/qemu-system-x86_64',
                 vmm_backend=os.path.expanduser('~/ucloud/vmm/')):
        self.qemu_path = qemu_path
        self.vmm_backend = vmm_backend
        self.socket_dir = os.path.join(self.vmm_backend, 'sock')

    def is_running(self, uuid):
        sock_path = os.path.join(self.vmm_backend, uuid)
        try:
            sock = socket.socket(socket.AF_UNIX)
            sock.connect(sock_path)
            recv = sock.recv(4096)
        except Exception as err:
            # unix sock doesn't exists or it is closed
            logger.info('VM %s sock either don\' exists or it is closed.', uuid,
                        'It mean VM is stopped.', exc_info=err)
        else:
            # if we receive greetings from qmp it mean VM is running
            if len(recv) > 0:
                return True

        with suppress(FileNotFoundError):
            os.remove(sock_path)

        return False

    def start(self, *args, uuid, migration=False):
        # start --> sucess?
        migration_args = ()
        if migration:
            migration_args = ('-incoming', 'unix:{}'.format(os.path.join(self.socket_dir, uuid)))

        if self.is_running(uuid):
            logger.warning('Cannot start VM. It is already running.')
        else:
            qmp_arg = ('-qmp', 'unix:{}/{},server,nowait'.format(self.vmm_backend, uuid))
            vnc_arg = ('-vnc', 'unix:{}'.format(tempfile.NamedTemporaryFile().name))

            command = [self.qemu_path, *args, *qmp_arg, *migration_args, *vnc_arg, '-daemonize']
            try:
                sp.check_output(command, stderr=sp.PIPE)
            except sp.CalledProcessError as err:
                logger.exception('Error occurred while starting VM.\nDetail %s', err.stderr.decode('utf-8'))
            else:
                time.sleep(2)

    def execute_command(self, uuid, command, **kwargs):
        # execute_command -> sucess?, output
        try:
            with VMQMPHandles(os.path.join(self.vmm_backend, uuid)) as (sock_handle, file_handle):
                command_to_execute = {
                    'execute': command,
                    **kwargs
                }
                sock_handle.sendall(json.dumps(command_to_execute).encode('utf-8'))
                output = file_handle.readline()
        except Exception as err:
            logger.exception('Error occurred while executing command and getting valid output from qmp')
        else:
            try:
                output = json.loads(output)
            except:
                logger.exception('QMP Output isn\'t valid JSON. %s', output)
            else:
                return 'return' in output, output
        return False, None

    def stop(self, uuid):
        success, output = self.execute_command(command='quit', uuid=uuid)
        return success

    def get_status(self, uuid):
        success, output = self.execute_command(command='query-status', uuid=uuid)
        if success:
            return output['return']['status']
        else:
            return 'STOPPED'

    def discover(self):
        vms = [
            uuid for uuid in os.listdir(self.vmm_backend)
            if not isdir(join_path(self.vmm_backend, uuid))
        ]
        return vms

    def get_vnc(self, uuid):
        success, output = self.execute_command(uuid, command='query-vnc')
        if success:
            return output['return']['service']
        return None

    def transfer(self, src_uuid, dest_uuid, host):
        p = TransferVM(src_uuid, dest_uuid, socket_dir=self.socket_dir, host=host)
        p.start()