import ast
import greenlet
import logging
import neovim
import os
import re
from .base import Base
from functools import partial
from jupyter_client import KernelManager
from jupyter_client.consoleapp import JupyterConsoleApp
from jupyter_client.threaded import ThreadedKernelClient
from jupyter_core.application import JupyterApp

imports = re.compile(
    r'^\s*(from\s+\.*\w+(\.\w+)*\s+import\s+(\w+,\s+)*|import\s+)')
split_pattern = re.compile('[^= \r\n*()@-]')
keyword = re.compile('[A-Za-z0-9_]')

request = '''
try:
    _completions = completion_metadata(get_ipython())
except Exception:
    pass
'''

logger = logging.getLogger(__name__)
error, debug, info, warn = (
    logger.error, logger.debug, logger.info, logger.warn,)
if 'NVIM_IPY_DEBUG_FILE' in os.environ:
    logfile = os.environ['NVIM_IPY_DEBUG_FILE'].strip()
    logger.addHandler(logging.FileHandler(logfile, 'w'))
    logger.level = logging.DEBUG


class RedirectingKernelManager(KernelManager):
    def _launch_kernel(self, cmd, **b):
        # stdout is used to communicate with nvim, redirect it somewhere else
        self._null = open("/dev/null", "wb", 0)
        b['stdout'] = self._null.fileno()
        b['stderr'] = self._null.fileno()
        return super(RedirectingKernelManager, self)._launch_kernel(cmd, **b)


class JupyterVimApp(JupyterApp, JupyterConsoleApp):
    # don't use blocking client; we override call_handlers below
    kernel_client_class = ThreadedKernelClient
    kernel_manager_class = RedirectingKernelManager
    aliases = JupyterConsoleApp.aliases  # this the way?
    flags = JupyterConsoleApp.flags

    def init_kernel_client(self):
        # TODO: cleanup this (by subclassing kernel_clint or something)
        if self.kernel_manager is not None:
            self.kernel_client = self.kernel_manager.client()
        else:
            self.kernel_client = self.kernel_client_class(
                                session=self.session,
                                ip=self.ip,
                                transport=self.transport,
                                shell_port=self.shell_port,
                                iopub_port=self.iopub_port,
                                hb_port=self.hb_port,
                                connection_file=self.connection_file,
                                parent=self,
            )
        self.kernel_client.shell_channel.call_handlers = self.target.on_shell_msg
        self.kernel_client.hb_channel.call_handlers = self.target.on_hb_msg
        self.kernel_client.start_channels()

    def initialize(self, target, argv):
        self.target = target
        super(JupyterVimApp, self).initialize(argv)
        JupyterConsoleApp.initialize(self, argv)


class Async(object):
    """Wrapper that defers all method calls on a plugin object to the event
    loop, given that the object has vim attribute"""

    def __init__(self, wraps):
        self.wraps = wraps

    def __getattr__(self, name):
        return partial(self.wraps.vim.async_call, getattr(self.wraps, name))


@neovim.plugin
@neovim.encoding(True)
class IPythonPlugin(object):

    def __init__(self, vim):
        self.vim = vim
        self.has_connection = False
        self.pending_shell_msgs = {}

    def connect(self, argv):
        self.ip_app = JupyterVimApp.instance()
        self.ip_app.initialize(Async(self), argv)
        self.ip_app.start()
        self.kc = self.ip_app.kernel_client
        self.km = self.ip_app.kernel_manager
        self.has_connection = True

    def handle(self, msg_id, handler):
        self.pending_shell_msgs[msg_id] = handler

    def waitfor(self, msg_id, retval=None):
        # FIXME: add some kind of timeout
        gr = greenlet.getcurrent()
        self.handle(msg_id, gr)
        return gr.parent.switch(retval)

    def ignore(self, msg_id):
        self.handle(msg_id, None)

    @neovim.function("IPyConnect", sync=True)
    def ipy_connect(self, args):
        # 'connect' waits for kernelinfo, and so must be async
        Async(self).connect(args)

    def on_shell_msg(self, m):
        self.last_msg = m
        debug('shell %s: %r', m['msg_type'], m['content'])
        msg_id = m['parent_header']['msg_id']
        try:
            handler = self.pending_shell_msgs.pop(msg_id)
        except KeyError:
            debug('unexpected shell msg: %r', m)
            return
        if isinstance(handler, greenlet.greenlet):
            handler.parent = greenlet.getcurrent()
            handler.switch(m)
        elif handler is not None:
            handler(m)

    # this gets called when heartbeat is lost
    def on_hb_msg(self, time_since):
        raise Exception()


class Source(Base):

    def __init__(self, vim):
        super().__init__(vim)
        self.__plug = IPythonPlugin(vim)
        self.__plug.ipy_connect(['--existing'])
        self.name = 'ipython'
        self.mark = '[IPy]'
        self.filetypes = ['python']
        self.is_volatile = True
        self.input_pattern = '.*'
        self.rank = 2000

    def get_complete_position(self, context):
        line = self.vim.current.line

        # return immediately for imports
        if imports.match(context['input']):
            start = len(context['input'])
            while start and re.match('[._A-Za-z0-9]', line[start - 1]):
                start -= 1
            return start

        # locate the start of the word
        col = self.vim.funcs.col('.')
        start = col - 1
        if start == 0 or (len(line) == start and
                          not split_pattern.match(line[start - 2]) and
                          not (start >= 2 and keyword.match(line[start - 3]))
                          and line[start - 3:start - 1] != '].'):
            start = -1
            return start

        line = self.vim.funcs.getline('.')
        start = self.vim.funcs.strchars(line[:col]) - 1
        bracket_level = 0
        while start > 0 and (
            split_pattern.match(line[start - 1])
                or (line[start - 1] == '.'
                    and start >= 2 and keyword.match(line[start - 2])
                    or (line[start - 1] == '-'
                        and start >= 2 and line[start - 2] == '[')
                    or ''.join(line[start - 2:start]) == '].')):
            if line[start - 1] == '[':
                if (start == 1 or not re.match(
                        '[A-Za-z0-9_\]]', line[start-2])) or bracket_level > 0:
                    break
                bracket_level += 1
            elif line[start-1] == ']':
                bracket_level -= 1
            start -= 1

        return start

    def gather_candidates(self, context):
        plug = self.__plug
        plug.waitfor(plug.kc.complete(context['input'], len(context['input'])))
        reply = plug.waitfor(plug.kc.execute(
            request, silent=True,
            user_expressions={'_completions': '_completions'}))
        metadata = reply['content']['user_expressions']['_completions']
        return ast.literal_eval(metadata['data']['text/plain'])