#
# Copyright (C) 2020-2021 Soleta Networks <info@soleta.eu>
#
# This program is free software: you can redistribute it and/or modify it under
# the terms of the GNU Affero General Public License as published by the
# Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.

import errno
import select
import socket
import time
import email
import logging
from io import StringIO

from src.restRequest import *
from src.ogRest import *
from enum import Enum

class State(Enum):
	CONNECTING = 0
	RECEIVING = 1
	FORCE_DISCONNECTED = 2

class ogClient:
	OG_PATH = '/opt/opengnsys/'

	def __init__(self, config):
		self.CONFIG = config

		self.mode = self.CONFIG['opengnsys']['mode']
		if self.mode not in {'virtual', 'live', 'linux', 'windows'}:
			logging.critical('Invalid ogClient mode')
			raise ValueError('Mode not supported.')
		if self.mode in {'linux', 'windows', 'live'}:
			self.event_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
			self.event_sock.setblocking(0)
			self.event_sock.bind(('127.0.0.1', 55885))
		else:
			self.event_sock = None

		if self.CONFIG['samba']['activate']:
			assert('user' in self.CONFIG['samba'])
			assert('pass' in self.CONFIG['samba'])

		self.ip = self.CONFIG['opengnsys']['ip']
		self.port = self.CONFIG['opengnsys']['port']
		self.ogrest = ogRest(self.CONFIG)
		self.seq = None

	def get_socket(self):
		return self.sock

	def get_event_socket(self):
		return self.event_sock

	def get_state(self):
		return self.state

	def send_event_hint(self, message):
		try:
			event, action, user = message.split(" ")
			logging.debug('Sending event: %s, %s, %s', event, action, user)
		except:
			logging.warning('Error parsing session datagram')
			return

		if (event != "session" or
		    action not in ['start', 'stop'] or
		    not user):
			logging.warning('Invalid value in session datagram: %s', message)

		payload = jsonBody({'event': event, 'action': action, 'user': user})
		response = restResponse(ogResponses.EARLY_HINTS, payload)
		self.send(response.get())
		logging.debug('Sending event OK')

	def cleanup(self):
		self.data = ""
		self.content_len = 0
		self.header_len = 0
		self.trailer = False

	def connect(self):
		logging.debug('Connecting...')
		self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
		self.sock.setblocking(0)
		self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
		self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, 60)
		self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, 30)
		self.sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, 4)

		self.state = State.CONNECTING
		self.cleanup()

		try:
			self.sock.connect((self.ip, self.port))
		except socket.error as err:
			if err.errno == errno.EINPROGRESS:
				return
			elif err.errno == errno.ECONNREFUSED:
				return

	def send(self, msg):
		self.sock.send(bytes(msg, 'utf-8'))
		return len(msg)

	def connect2(self):
		try:
			self.sock.connect((self.ip, self.port))
		except socket.error as err:
			if err.errno == errno.EISCONN:
				logging.debug('Connected')
				self.state = State.RECEIVING
			else:
				time.sleep(1)
				logging.warning('Connection refused, retrying...')
				self.state = State.CONNECTING
				self.sock.close()
				self.connect()

	def receive(self):
		try:
			data = self.sock.recv(1024).decode('utf-8')
		except socket.error as err:
			data = ''
			logging.warning('Receive failed: %s', str(err))

		if len(data) == 0:
			self.sock.close()
			self.ogrest.kill_process()
			self.connect()
			return

		self.data = self.data + data
		request = restRequest()

		if not self.trailer:
			header_len = self.data.find("\r\n\r\n")
			if header_len > 0:
				# https://stackoverflow.com/questions/4685217/parse-raw-http-headers
				request_line, headers_alone = self.data.split('\n', 1)
				headers = email.message_from_file(StringIO(headers_alone))

				if 'Content-Length' in headers.keys():
					self.content_len = int(headers['Content-Length'])
				if 'X-Sequence' in headers.keys():
					self.seq = int(headers['X-Sequence'])

				self.trailer = True
				# Add 4 because self.data.find("\r\n\r\n") does not count
				# "\r\n\r\n" for the length
				self.header_len = header_len + 4

		if self.trailer and (len(self.data) >= self.content_len + self.header_len):
			request.parser(self.data)
			self.ogrest.process_request(request, self)
			self.cleanup()

	def disconnect(self):
		self.state = State.FORCE_DISCONNECTED
		self.sock.shutdown(socket.SHUT_RDWR)
		self.sock.close()

	def run(self):
		while 1:
			sock = self.get_socket()
			event_sock = self.get_event_socket()
			state = self.get_state()

			if state == State.CONNECTING:
				readset = [ sock ]
				writeset = [ sock ]
				exceptset = [ sock ]
			elif state == State.FORCE_DISCONNECTED:
				return 0
			else:
				readset = [ sock, event_sock ] if event_sock else [ sock ]
				writeset = [ ]
				exceptset = [ ]

			readable, writable, exception = select.select(readset, writeset, exceptset)
			if state == State.CONNECTING and sock in writable:
				self.connect2()
			elif state == State.RECEIVING and sock in readable:
				self.receive()
			elif state == State.CONNECTING and sock in exception:
				self.connect2()
			elif state == State.RECEIVING and event_sock in readable:
				message = event_sock.recv(4096).decode('utf-8').rstrip()
				self.send_event_hint(message)
			else:
				logging.critical('Invalid state: %s', str(state))