import paramiko
import queue
import urllib.parse
import requests.adapters
import logging
import os
import signal
import socket
import subprocess

from docker.transport.basehttpadapter import BaseHTTPAdapter
from .. import constants

import urllib3
import urllib3.connection

RecentlyUsedContainer = urllib3._collections.RecentlyUsedContainer


class SSHSocket(socket.socket):
    def __init__(self, host):
        super().__init__(
            socket.AF_INET, socket.SOCK_STREAM)
        self.host = host
        self.port = None
        self.user = None
        if ':' in self.host:
            self.host, self.port = self.host.split(':')
        if '@' in self.host:
            self.user, self.host = self.host.split('@')

        self.proc = None

    def connect(self, **kwargs):
        args = ['ssh']
        if self.user:
            args = args + ['-l', self.user]

        if self.port:
            args = args + ['-p', self.port]

        args = args + ['--', self.host, 'docker system dial-stdio']

        preexec_func = None
        if not constants.IS_WINDOWS_PLATFORM:
            def f():
                signal.signal(signal.SIGINT, signal.SIG_IGN)
            preexec_func = f

        env = dict(os.environ)

        # drop LD_LIBRARY_PATH and SSL_CERT_FILE
        env.pop('LD_LIBRARY_PATH', None)
        env.pop('SSL_CERT_FILE', None)

        self.proc = subprocess.Popen(
            args,
            env=env,
            stdout=subprocess.PIPE,
            stdin=subprocess.PIPE,
            preexec_fn=preexec_func)

    def _write(self, data):
        if not self.proc or self.proc.stdin.closed:
            raise Exception('SSH subprocess not initiated.'
                            'connect() must be called first.')
        written = self.proc.stdin.write(data)
        self.proc.stdin.flush()
        return written

    def sendall(self, data):
        self._write(data)

    def send(self, data):
        return self._write(data)

    def recv(self, n):
        if not self.proc:
            raise Exception('SSH subprocess not initiated.'
                            'connect() must be called first.')
        return self.proc.stdout.read(n)

    def makefile(self, mode):
        if not self.proc:
            self.connect()
        self.proc.stdout.channel = self

        return self.proc.stdout

    def close(self):
        if not self.proc or self.proc.stdin.closed:
            return
        self.proc.stdin.write(b'\n\n')
        self.proc.stdin.flush()
        self.proc.terminate()


class SSHConnection(urllib3.connection.HTTPConnection):
    def __init__(self, ssh_transport=None, timeout=60, host=None):
        super().__init__(
            'localhost', timeout=timeout
        )
        self.ssh_transport = ssh_transport
        self.timeout = timeout
        self.ssh_host = host

    def connect(self):
        if self.ssh_transport:
            sock = self.ssh_transport.open_session()
            sock.settimeout(self.timeout)
            sock.exec_command('docker system dial-stdio')
        else:
            sock = SSHSocket(self.ssh_host)
            sock.settimeout(self.timeout)
            sock.connect()

        self.sock = sock


class SSHConnectionPool(urllib3.connectionpool.HTTPConnectionPool):
    scheme = 'ssh'

    def __init__(self, ssh_client=None, timeout=60, maxsize=10, host=None):
        super().__init__(
            'localhost', timeout=timeout, maxsize=maxsize
        )
        self.ssh_transport = None
        self.timeout = timeout
        if ssh_client:
            self.ssh_transport = ssh_client.get_transport()
        self.ssh_host = host

    def _new_conn(self):
        return SSHConnection(self.ssh_transport, self.timeout, self.ssh_host)

    # When re-using connections, urllib3 calls fileno() on our
    # SSH channel instance, quickly overloading our fd limit. To avoid this,
    # we override _get_conn
    def _get_conn(self, timeout):
        conn = None
        try:
            conn = self.pool.get(block=self.block, timeout=timeout)

        except AttributeError:  # self.pool is None
            raise urllib3.exceptions.ClosedPoolError(self, "Pool is closed.")

        except queue.Empty:
            if self.block:
                raise urllib3.exceptions.EmptyPoolError(
                    self,
                    "Pool reached maximum size and no more "
                    "connections are allowed."
                )
            # Oh well, we'll create a new connection then

        return conn or self._new_conn()


class SSHHTTPAdapter(BaseHTTPAdapter):

    __attrs__ = requests.adapters.HTTPAdapter.__attrs__ + [
        'pools', 'timeout', 'ssh_client', 'ssh_params', 'max_pool_size'
    ]

    def __init__(self, base_url, timeout=60,
                 pool_connections=constants.DEFAULT_NUM_POOLS,
                 max_pool_size=constants.DEFAULT_MAX_POOL_SIZE,
                 shell_out=False):
        self.ssh_client = None
        if not shell_out:
            self._create_paramiko_client(base_url)
            self._connect()

        self.ssh_host = base_url
        if base_url.startswith('ssh://'):
            self.ssh_host = base_url[len('ssh://'):]

        self.timeout = timeout
        self.max_pool_size = max_pool_size
        self.pools = RecentlyUsedContainer(
            pool_connections, dispose_func=lambda p: p.close()
        )
        super().__init__()

    def _create_paramiko_client(self, base_url):
        logging.getLogger("paramiko").setLevel(logging.WARNING)
        self.ssh_client = paramiko.SSHClient()
        base_url = urllib.parse.urlparse(base_url)
        self.ssh_params = {
            "hostname": base_url.hostname,
            "port": base_url.port,
            "username": base_url.username
            }
        ssh_config_file = os.path.expanduser("~/.ssh/config")
        if os.path.exists(ssh_config_file):
            conf = paramiko.SSHConfig()
            with open(ssh_config_file) as f:
                conf.parse(f)
            host_config = conf.lookup(base_url.hostname)
            if 'proxycommand' in host_config:
                self.ssh_params["sock"] = paramiko.ProxyCommand(
                    host_config['proxycommand']
                )
            if 'hostname' in host_config:
                self.ssh_params['hostname'] = host_config['hostname']
            if base_url.port is None and 'port' in host_config:
                self.ssh_params['port'] = host_config['port']
            if base_url.username is None and 'user' in host_config:
                self.ssh_params['username'] = host_config['user']
            if 'identityfile' in host_config:
                self.ssh_params['key_filename'] = host_config['identityfile']

        self.ssh_client.load_system_host_keys()
        self.ssh_client.set_missing_host_key_policy(paramiko.RejectPolicy())

    def _connect(self):
        if self.ssh_client:
            self.ssh_client.connect(**self.ssh_params)

    def get_connection(self, url, proxies=None):
        if not self.ssh_client:
            return SSHConnectionPool(
                ssh_client=self.ssh_client,
                timeout=self.timeout,
                maxsize=self.max_pool_size,
                host=self.ssh_host
            )
        with self.pools.lock:
            pool = self.pools.get(url)
            if pool:
                return pool

            # Connection is closed try a reconnect
            if self.ssh_client and not self.ssh_client.get_transport():
                self._connect()

            pool = SSHConnectionPool(
                ssh_client=self.ssh_client,
                timeout=self.timeout,
                maxsize=self.max_pool_size,
                host=self.ssh_host
            )
            self.pools[url] = pool

        return pool

    def close(self):
        super().close()
        if self.ssh_client:
            self.ssh_client.close()
