import os
import sys
import pty
import fcntl
import subprocess
import logging
import os.path
import struct
import termios
from fcntl import ioctl
from itertools import chain, imap
from subprocess import Popen, PIPE, STDOUT

from sjrpc.utils import pass_connection, threadless
from sjrpc.core.protocols import TunnelProtocol

from cloudcontrol.node.tags import Tag, tag_inspector
from cloudcontrol.node.plugins import Base as BasePlugin
from cloudcontrol.node.host import tags


logger = logging.getLogger(__name__)


def disk_tag_value(disk_name):
    def size():
        s = open(os.path.join('/sys/block', disk_name, 'size')).read().strip()
        try:
            s = int(s)
            if s > 0:
                return s * 512
            else:
                return None
        except ValueError:
            return None

    return size


class FakePtySocket(object):
    """A fake socket object wrapping a :class:`subprocess.Popen` object
    standard input/output.

    """
    def __init__(self, fd):
        self._fd = fd

    def recv(self, size):
        return os.read(self._fd, size)

    def send(self, data):
        return os.write(self._fd, data)

    def fileno(self):
        return self._fd

    def setblocking(self, blocking):
        if not blocking:
            # Disable blocking mode on stdin:
            current_flags = fcntl.fcntl(self._fd, fcntl.F_GETFL)
            fcntl.fcntl(self._fd, fcntl.F_SETFL, current_flags | os.O_NONBLOCK)
            pass
        else:
            raise NotImplementedError('Not implemented')

    def close(self):
        pass


class RemoteShell(object):
    """Handles basic operations on remote shell."""
    def __init__(self, ev_loop, conn, exec_='/bin/bash'):
        """
        :param ev_loop: pyev loop instance
        :param conn: sjRPC connection
        :param exec_: binary path

        .. warning:: constructor must be called inside the thread runnig libev
            loop, this is necessary in order to create and start watcher and to
            close file descriptors
        """
        # handles close when waiting process to end from an other thread
        self.watcher = ev_loop.async(self.close_cb)
        self.watcher.start()
        self.master, self.slave = pty.openpty()
        self.endpoint = FakePtySocket(self.master)
        self.proto = conn.create_tunnel(endpoint=self.endpoint)
        self.conn = conn
        try:
            self.process = subprocess.Popen(
                [exec_], stdout=self.slave,
                bufsize=0, stdin=self.slave,
                stderr=self.slave,
                preexec_fn=os.setsid,
                close_fds=True,
                cwd=os.environ.get('HOME', '/'),
            )
        except OSError:
            logger.exception('Error while executing remote shell')
            # close opened fds
            self.close_cb()
            raise

    @property
    def label(self):
        return self.proto.label

    def resize(self, row, col, xpixel, ypixel):
        ioctl(self.master, termios.TIOCSWINSZ,
              struct.pack('HHHH', row, col, xpixel, ypixel))

    def close(self):
        # async
        self.watcher.send()

    def terminate(self):
        self.process.terminate()

    def kill(self):
        self.process.kill()

    def close_cb(self, *args):
        if self.watcher is not None:
            self.watcher.stop()
            self.watcher = None
        if self.master is not None:
            try:
                os.close(self.master)
            except OSError:
                logger.error('Error when closing file descriptor for pty')
            self.master = None
        if self.slave is not None:
            try:
                os.close(self.slave)
            except OSError:
                logger.error('Error when closing slave file descriptor for pty')
            self.slave = None
        if self.proto is not None:
            try:
                self.proto.close()
            except Exception:
                logger.error('Error while trying to close RPC tunnel')
            self.proto = None

    def wait(self):
        return self.process.wait()

    def wait_n_close(self):
        ret_code = self.wait()
        self.close()
        return ret_code


class Handler(BasePlugin):
    """Handler for host role."""
    def __init__(self, *args, **kwargs):
        BasePlugin.__init__(self, *args, **kwargs)

        # add plugin tags
        self.tag_db.add_tags(tag_inspector(tags))

        # disk related tags
        self.tag_db.add_tags(imap(
            lambda d: Tag('disk%s_size' % d, disk_tag_value(d), 60),
            self.tag_db['__main__']['disk']._calculate_value().split(),
        ))

        # rpc handler
        self.rpc_handler.update(dict(
            execute_command=self.execute_command,
            node_shutdown=self.node_shutdown,
            rshell=self.rshell,
            rshell_resize=self.rshell_resize,
            rshell_wait=self.rshell_wait,
        ))
        # running shells
        self.shells = dict()

    def execute_command(self, command):
        """Execute an arbitrary shell command on the host.

        :param string command: shell command to run
        """
        # return stdout and stderr mixed in
        try:
            return Popen(command, shell=True, bufsize=-1, stdin=PIPE, stdout=PIPE,
                         stderr=STDOUT).communicate()[0] or None
        except Exception:
            logger.exception('Error while executing a remote command')
            raise

    def node_shutdown(self, reboot=True, gracefull=True):
        """Halt/Reboot the node.

        :param bool reboot: halt/reboot the system
        :param bool gracefull: force the operation (gracefull == not force)
        """
        args = ['/sbin/shutdown']
        if reboot:
            args.append('-r')
            if gracefull:
                logger.info('Going to reboot the host...')
                args.append('-f')
            else:
                logger.info('Going to force the reboot of the host...')
                args.append('-n')
        else:
            # halt
            args.append('-h -P')
            if not gracefull:
                logger.info('Going to halt the host...')
                args.append('-n')
            else:
                logger.info('Going to force the halt of the host...')

        args.append('0')

        return self.execute_command(' '.join(args))

    @threadless
    @pass_connection
    def rshell(self, conn, shell='/bin/bash'):
        """Create a shell tunnel and return the label of the created tunnel.

        """
        remote_shell = RemoteShell(self.main.evloop, conn, shell)
        self.shells[remote_shell.label] = remote_shell
        return remote_shell.label

    @threadless
    def rshell_resize(self, label, row, col, xpixel, ypixel):
        """Resize the rshell."""
        self.shells[label].resize(row, col, xpixel, ypixel)

    def rshell_wait(self, label):
        """Wait for a tunnel termination."""
        return self.shells[label].wait_n_close()