#!/usr/bin/env python
# encoding: utf-8
"""
cli.py

Created by Thomas Mangin on 2014-12-22.
Copyright (c) 2009-2017 Exa Networks. All rights reserved.
License: 3-clause BSD. (See the COPYRIGHT file)
"""

import os
import sys
import time
import select
import signal
import errno

from exabgp.application.bgp import root_folder
from exabgp.application.bgp import named_pipe
from exabgp.application.bgp import get_envfile
from exabgp.application.bgp import get_env
from exabgp.application.control import check_fifo

from exabgp.reactor.network.error import error
from exabgp.reactor.api.response.answer import Answer

from exabgp.vendoring import docopt

errno_block = set((
	errno.EINPROGRESS, errno.EALREADY,
	errno.EAGAIN, errno.EWOULDBLOCK,
	errno.EINTR, errno.EDEADLK,
	errno.EBUSY, errno.ENOBUFS,
	errno.ENOMEM,
))

usage = """\
The BGP swiss army knife of networking

usage: exabgpcli [--root ROOT]
\t\t\t\t\t\t\t\t [--help|<command>...]
\t\t\t\t\t\t\t\t [--env ENV]

positional arguments:
\tcommand               valid exabgpcli command (see below)

optional arguments:
\t--env ENV,   -e ENV   environment configuration file
\t--help,      -h       exabgp manual page
\t--root ROOT, -f ROOT  root folder where etc,bin,sbin are located

commands:
\thelp                  show the commands known by ExaBGP
""".replace('\t','  ')


class AnswerStream:
	done = '\n%s\n' % Answer.done
	error = '\n%s\n' % Answer.error
	shutdown = '\n%s\n' % Answer.error
	buffer_size = Answer.buffer_size + 2

def open_reader (recv):
	def open_timeout(signum, frame):
		sys.stderr.write('could not connect to read response from ExaBGP\n')
		sys.stderr.flush()
		sys.exit(1)

	signal.signal(signal.SIGALRM, open_timeout)
	signal.alarm(5)

	done = False
	while not done:
		try:
			reader = os.open(recv, os.O_RDONLY | os.O_NONBLOCK)
			done = True
		except IOError as exc:
			if exc.args[0] in errno_block:
				signal.signal(signal.SIGALRM, open_timeout)
				signal.alarm(5)
				continue
			sys.stdout.write('could not read answer from ExaBGP')
			sys.stdout.flush()
			sys.exit(1)
	signal.alarm(0)
	return reader

def open_writer (send):
	def write_timeout(signum, frame):
		sys.stderr.write('could not send command to ExaBGP (command timeout)')
		sys.stderr.flush()
		sys.exit(1)

	signal.signal(signal.SIGALRM, write_timeout)
	signal.alarm(5)

	try:
		writer = os.open(send, os.O_WRONLY)
	except OSError as exc:
		if exc.errno == errno.ENXIO:
			sys.stdout.write('ExaBGP is not running / using the configured named pipe')
			sys.stdout.flush()
			sys.exit(1)
		sys.stdout.write('could not communicate with ExaBGP')
		sys.stdout.flush()
		sys.exit(1)
	except IOError as exc:
		sys.stdout.write('could not communicate with ExaBGP')
		sys.stdout.flush()
		sys.exit(1)

	signal.alarm(0)
	return writer

def main ():
	options = docopt.docopt(usage, help=False)
	if options['--env'] is None:
		options['--env'] = ''

	root = root_folder(options,['/bin/exabgpcli','/sbin/exabgpcli','/lib/exabgp/application/cli.py'])
	prefix = '' if root == '/usr' else root
	etc = prefix + '/etc/exabgp'
	envfile = get_envfile(options,etc)
	env = get_env(envfile)
	pipename = env['api']['pipename']

	if options['--help']:
		sys.stdout.write(usage)
		sys.stdout.flush()
		sys.exit(0)

	if not options['<command>']:
		sys.stdout.write(usage)
		sys.stdout.flush()
		sys.exit(0)

	command = ' '.join(options['<command>'])

	pipes = named_pipe(root, pipename)
	if len(pipes) != 1:
		sys.stdout.write('could not find ExaBGP\'s named pipes (%s.in and %s.out) for the cli\n' % (pipename, pipename))
		sys.stdout.write('we scanned the following folders (the number is your PID):\n - ')
		sys.stdout.write('\n - '.join(pipes))
		sys.stdout.flush()
		sys.exit(1)

	send = pipes[0] + pipename + '.in'
	recv = pipes[0] + pipename + '.out'

	if not check_fifo(send):
		sys.stdout.write('could not find write named pipe to connect to ExaBGP')
		sys.stdout.flush()
		sys.exit(1)

	if not check_fifo(recv):
		sys.stdout.write('could not find read named pipe to connect to ExaBGP')
		sys.stdout.flush()
		sys.exit(1)

	reader = open_reader(recv)

	rbuffer = ''
	start = time.time()
	while True:
		try:
			while select.select([reader], [], [], 0) != ([], [], []):
				rbuffer += os.read(reader,4096)
				rbuffer = rbuffer[-AnswerStream.buffer_size:]
		except IOError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not clear named pipe from potential previous command data (%s)' % str(exc))
			sys.stdout.flush()
			sys.exit(1)
		except OSError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not clear named pipe from potential previous command data (%s)' % str(exc))
			sys.stdout.write(exc)
			sys.stdout.flush()
			sys.exit(1)

		# we read nothing, nothing to do
		if not rbuffer:
			break
		# we read some data but it is not ending by a new line (ie: not a command completion)
		if rbuffer[-1] != '\n':
			continue
		if AnswerStream.done.endswith(rbuffer[-len(AnswerStream.done):]):
			break
		if AnswerStream.error.endswith(rbuffer[-len(AnswerStream.error):]):
			break
		if AnswerStream.shutdown.endswith(rbuffer[-len(AnswerStream.shutdown):]):
			break
		# we are not ack'ing the command and probably have read all there is
		if time.time() > start + 1.5:
			break


	writer = open_writer(send)
	try:
		os.write(writer, command.encode('utf-8') + b'\n')
		os.close(writer)
	except IOError as exc:
		sys.stdout.write('could not send command to ExaBGP (%s)' % str(exc))
		sys.stdout.flush()
		sys.exit(1)
	except OSError as exc:
		sys.stdout.write('could not send command to ExaBGP (%s)' % str(exc))
		sys.stdout.flush()
		sys.exit(1)

	if command == 'reset':
		sys.exit(0)

	waited = 0.0
	buf = b''
	done = False
	while not done:
		try:
			r, _, _ = select.select([reader], [], [], 0.01)
		except OSError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not get answer from ExaBGP (%s)' % str(exc))
			sys.stdout.flush()
			sys.exit(1)
		except IOError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not get answer from ExaBGP (%s)' % str(exc))
			sys.stdout.flush()
			sys.exit(1)

		if waited > 5.0:
			sys.stderr.write('\n')
			sys.stderr.write('warning: no end of command message received\n')
			sys.stderr.write('warning: normal if exabgp.api.ack is set to false otherwise some data may get stuck on the pipe\n')
			sys.stderr.write('warning: otherwise it may cause exabgp reactor to block\n')
			sys.exit(0)
		elif not r:
			waited += 0.01
			continue
		else:
			waited = 0.0

		try:
			raw = os.read(reader, 4096)
		except OSError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not read answer from ExaBGP (%s)' % str(exc))
			sys.stdout.flush()
			sys.exit(1)
		except IOError as exc:
			if exc.errno in error.block:
				continue
			sys.stdout.write('could not read answer from ExaBGP (%s)' % str(exc))
			sys.stdout.flush()
			sys.exit(1)

		buf += raw
		while b'\n' in buf:
			line,buf = buf.split(b'\n',1)
			string = line.decode()
			if string == Answer.done:
				done = True
				break
			if string == Answer.shutdown:
				sys.stderr.write('ExaBGP is shutting down, command aborted\n')
				sys.stderr.flush()
				done = True
				break
			if string == Answer.error:
				done = True
				sys.stderr.write('ExaBGP returns an error (see ExaBGP\'s logs for more information)\n')
				sys.stderr.write('use help for a list of available commands\n')
				sys.stderr.flush()
				break
			sys.stdout.write('%s\n' % string)
			sys.stdout.flush()

	try:
		os.close(reader)
	except Exception:
		pass

	sys.exit(0)


if __name__ == '__main__':
	try:
		main()
	except KeyboardInterrupt:
		pass
