from ws4py.client.threadedclient import WebSocketClient
import threading
import json
import os
import time
import ssl
import re
import config
import logging
import arvados

_logger = logging.getLogger('arvados.events')

class EventClient(WebSocketClient):
    def __init__(self, url, filters, on_event):
        ssl_options = None
        if re.match(r'(?i)^(true|1|yes)$',
                    config.get('ARVADOS_API_HOST_INSECURE', 'no')):
            ssl_options={'cert_reqs': ssl.CERT_NONE}
        else:
            ssl_options={'cert_reqs': ssl.CERT_REQUIRED}
        super(EventClient, self).__init__(url, ssl_options=ssl_options)
        self.filters = filters
        self.on_event = on_event

    def opened(self):
        self.subscribe(self.filters)

    def received_message(self, m):
        self.on_event(json.loads(str(m)))

    def close_connection(self):
        try:
            self.sock.shutdown(socket.SHUT_RDWR)
            self.sock.close()
        except:
            pass

    def subscribe(self, filters, last_log_id=None):
        m = {"method": "subscribe", "filters": filters}
        if last_log_id is not None:
            m["last_log_id"] = last_log_id
        self.send(json.dumps(m))

    def unsubscribe(self, filters):
        self.send(json.dumps({"method": "unsubscribe", "filters": filters}))

class PollClient(threading.Thread):
    def __init__(self, api, filters, on_event, poll_time):
        super(PollClient, self).__init__()
        self.api = api
        if filters:
            self.filters = [filters]
        else:
            self.filters = [[]]
        self.on_event = on_event
        self.poll_time = poll_time
        self.stop = threading.Event()

    def run(self):
        self.id = 0
        for f in self.filters:
            items = self.api.logs().list(limit=1, order="id desc", filters=f).execute()['items']
            if items:
                if items[0]['id'] > self.id:
                    self.id = items[0]['id']

        self.on_event({'status': 200})

        while not self.stop.isSet():
            max_id = self.id
            for f in self.filters:
                items = self.api.logs().list(order="id asc", filters=f+[["id", ">", str(self.id)]]).execute()['items']
                for i in items:
                    if i['id'] > max_id:
                        max_id = i['id']
                    self.on_event(i)
            self.id = max_id
            self.stop.wait(self.poll_time)

    def close(self):
        self.stop.set()
        self.join()

    def subscribe(self, filters):
        self.on_event({'status': 200})
        self.filters.append(filters)

    def unsubscribe(self, filters):
        del self.filters[self.filters.index(filters)]


def subscribe(api, filters, on_event, poll_fallback=15):
    '''
    api: Must be a newly created from arvados.api(cache=False), not shared with the caller, as it may be used by a background thread.
    filters: Initial subscription filters.
    on_event: The callback when a message is received
    poll_fallback: If websockets are not available, fall back to polling every N seconds.  If poll_fallback=False, this will return None if websockets are not available.
    '''
    ws = None
    if 'websocketUrl' in api._rootDesc:
        try:
            url = "{}?api_token={}".format(api._rootDesc['websocketUrl'], api.api_token)
            ws = EventClient(url, filters, on_event)
            ws.connect()
            return ws
        except Exception as e:
            _logger.warn("Got exception %s trying to connect to websockets at %s" % (e, api._rootDesc['websocketUrl']))
            if ws:
                ws.close_connection()
    if poll_fallback:
        _logger.warn("Websockets not available, falling back to log table polling")
        p = PollClient(api, filters, on_event, poll_fallback)
        p.start()
        return p
    else:
        _logger.error("Websockets not available")
        return None