from __future__ import annotations

import asyncio
import dataclasses
import datetime as dt
import inspect
import json
import logging
import threading

from contextlib import contextmanager
from functools import partial, wraps
from typing import (
    Callable, Iterator, List, Optional,
)

from bokeh.application.application import SessionContext
from bokeh.document.document import Document
from bokeh.document.events import (
    ColumnDataChangedEvent, ColumnsPatchedEvent, ColumnsStreamedEvent,
    DocumentChangedEvent, ModelChangedEvent,
)
from bokeh.models import CustomJS

from ..config import config
from ..util import param_watchers
from .loading import LOADING_INDICATOR_CSS_CLASS
from .model import monkeypatch_events
from .state import curdoc_locked, state

logger = logging.getLogger(__name__)

#---------------------------------------------------------------------
# Private API
#---------------------------------------------------------------------

DISPATCH_EVENTS = (
    ColumnDataChangedEvent, ColumnsPatchedEvent, ColumnsStreamedEvent,
    ModelChangedEvent
)

@dataclasses.dataclass
class Request:
    headers : dict
    cookies : dict
    arguments : dict


class MockSessionContext(SessionContext):

    def __init__(self, *args, document=None, **kwargs):
        self._document = document
        super().__init__(*args, server_context=None, session_id=None, **kwargs)

    def with_locked_document(self, *args):
        return

    @property
    def destroyed(self) -> bool:
        return False

    @property
    def request(self):
        return Request(headers={}, cookies={}, arguments={})


def _dispatch_events(doc: Document, events: List[DocumentChangedEvent]) -> None:
    """
    Handles dispatch of events which could not be processed in
    unlocked decorator.
    """
    for event in events:
        doc.callbacks.trigger_on_change(event)

def _cleanup_doc(doc, destroy=True):
    for callback in doc.session_destroyed_callbacks:
        try:
            callback(None)
        except Exception:
            pass
    if hasattr(doc.callbacks, '_change_callbacks'):
        doc.callbacks._change_callbacks[None] = {}

    # Remove views
    from ..viewable import Viewable
    views = {}
    for ref, (pane, root, vdoc, comm) in list(state._views.items()):
        if vdoc is doc:
            pane._cleanup(root)
            if isinstance(pane, Viewable):
                pane._hooks = []
                for p in pane.select():
                    p._hooks = []
                    param_watchers(p, {})
                    p._documents = {}
                    p._internal_callbacks = {}
            param_watchers(pane, {})
            pane._documents = {}
            pane._internal_callbacks = {}
        else:
            views[ref] = (pane, root, doc, comm)
    state._views = views

    # When reusing sessions we must clean up the Panel state but we
    # must **not** destroy the template or the document
    if not destroy:
        return

    # Clean up templates
    if doc in state._templates:
        tmpl = state._templates[doc]
        tmpl._documents = {}
        del state._templates[doc]

    # Destroy document
    doc.destroy(None)

#---------------------------------------------------------------------
# Public API
#---------------------------------------------------------------------

def create_doc_if_none_exists(doc: Optional[Document]) -> Document:
    curdoc = doc or curdoc_locked()
    if curdoc is None:
        curdoc = Document()
    elif not isinstance(curdoc, Document):
        curdoc = curdoc._doc
    return curdoc

def init_doc(doc: Optional[Document]) -> Document:
    curdoc = create_doc_if_none_exists(doc)
    if not curdoc.session_context:
        return curdoc

    thread = threading.current_thread()
    if thread:
        state._thread_id_[curdoc] = thread.ident

    if config.global_loading_spinner:
        curdoc.js_on_event(
            'document_ready', CustomJS(code=f"""
            const body = document.getElementsByTagName('body')[0]
            body.classList.remove({LOADING_INDICATOR_CSS_CLASS!r}, {config.loading_spinner!r})
            """)
        )

    session_id = curdoc.session_context.id
    sessions = state.session_info['sessions']
    if session_id not in sessions:
        return curdoc

    sessions[session_id].update({
        'started': dt.datetime.now().timestamp()
    })
    curdoc.on_event('document_ready', state._init_session)
    return curdoc

def with_lock(func: Callable) -> Callable:
    """
    Wrap a callback function to execute with a lock allowing the
    function to modify bokeh models directly.

    Arguments
    ---------
    func: callable
      The callable to wrap

    Returns
    -------
    wrapper: callable
      Function wrapped to execute without a Document lock.
    """
    if inspect.iscoroutinefunction(func):
        @wraps(func)
        async def wrapper(*args, **kw):
            return await func(*args, **kw)
    else:
        @wraps(func)
        def wrapper(*args, **kw):
            return func(*args, **kw)
    wrapper.lock = True # type: ignore
    return wrapper

def dispatch_tornado(conn, events):
    from tornado.websocket import WebSocketHandler
    socket = conn._socket
    ws_conn = getattr(socket, 'ws_connection', False)
    if not ws_conn or ws_conn.is_closing(): # type: ignore
        return []
    msg = conn.protocol.create('PATCH-DOC', events)
    futures = [
        WebSocketHandler.write_message(socket, msg.header_json),
        WebSocketHandler.write_message(socket, msg.metadata_json),
        WebSocketHandler.write_message(socket, msg.content_json)
    ]
    for buffer in msg._buffers:
        header = json.dumps(buffer.ref)
        payload = buffer.to_bytes()
        futures.extend([
            WebSocketHandler.write_message(socket, header),
            WebSocketHandler.write_message(socket, payload, binary=True)
        ])
    return futures

def dispatch_django(conn, events):
    socket = conn._socket
    msg = conn.protocol.create('PATCH-DOC', events)
    futures = [
        socket.send(text_data=msg.header_json),
        socket.send(text_data=msg.metadata_json),
        socket.send(text_data=msg.content_json)
    ]
    for buffer in msg._buffers:
        header = json.dumps(buffer.ref)
        payload = buffer.to_bytes()
        futures.extend([
            socket.send(text_data=header),
            socket.send(binary_data=payload)
        ])
    return futures

@contextmanager
def unlocked() -> Iterator:
    """
    Context manager which unlocks a Document and dispatches
    ModelChangedEvents triggered in the context body to all sockets
    on current sessions.
    """
    curdoc = state.curdoc
    session_context = getattr(curdoc, 'session_context', None)
    session = getattr(session_context, 'session', None)
    if curdoc is None or session_context is None or session is None or state._jupyter_kernel_context:
        yield
        return
    elif curdoc.callbacks.hold_value:
        yield
        monkeypatch_events(curdoc.callbacks._held_events)
        return

    from tornado.websocket import WebSocketClosedError, WebSocketHandler
    connections = session._subscribed_connections

    curdoc.hold()
    try:
        yield

        locked = False
        for conn in connections:
            socket = conn._socket
            if hasattr(socket, 'write_lock') and socket.write_lock._block._value == 0:
                locked = True
                break

        events = curdoc.callbacks._held_events
        monkeypatch_events(events)
        remaining_events, dispatch_events = [], []
        for event in events:
            if isinstance(event, DISPATCH_EVENTS) and not locked:
                dispatch_events.append(event)
            else:
                remaining_events.append(event)

        futures = []
        for conn in connections:
            if not dispatch_events:
                continue
            elif isinstance(conn._socket, WebSocketHandler):
                futures += dispatch_tornado(conn, dispatch_events)
            else:
                futures += dispatch_django(conn, dispatch_events)

        # Ensure that all write_message calls are awaited and handled
        async def handle_write_errors():
            for future in futures:
                try:
                    await future
                except WebSocketClosedError:
                    logger.warning("Failed sending message as connection was closed")
                except Exception as e:
                    logger.warning(f"Failed sending message due to following error: {e}")

        if futures:
            if state._unblocked(curdoc):
                try:
                    asyncio.ensure_future(handle_write_errors())
                except RuntimeError:
                    curdoc.add_next_tick_callback(handle_write_errors)
            else:
                curdoc.add_next_tick_callback(handle_write_errors)

        curdoc.callbacks._held_events = remaining_events
    finally:
        try:
            curdoc.unhold()
        except RuntimeError:
            if remaining_events:
                curdoc.add_next_tick_callback(partial(_dispatch_events, curdoc, remaining_events))
