#!/usr/bin/env python

# under development

import requests
import json
import string
import random
import srp._pysrp as srp
import binascii

safe_unhexlify = lambda x: binascii.unhexlify(x) if (len(x) % 2 == 0) else binascii.unhexlify('0'+x)

# let's have some random name
def id_generator(size=6, chars=string.ascii_uppercase + string.digits):
  return ''.join(random.choice(chars) for x in range(size))

# using globals for a start
server = 'http://localhost:3000/1'
login = id_generator()
password = id_generator() + id_generator()

# print '    username = "' + login + '"'
# print '    password = "' + password + '"'

# log the server communication
def print_and_parse(response):
  # print response.request.method + ': ' + response.url
  # print "    " + json.dumps(response.request.data)
  # print " -> " + response.text
  return json.loads(response.text)

def signup(session):
  salt, vkey = srp.create_salted_verification_key( login, password, srp.SHA256, srp.NG_1024 )
  # print '    salt = "' + binascii.hexlify(salt) + '"'
  # print '    v = "' + binascii.hexlify(vkey) + '"'
  user_params = {
      'user[login]': login,
      'user[password_verifier]': binascii.hexlify(vkey),
      'user[password_salt]': binascii.hexlify(salt)
      }
  return session.post(server + '/users.json', data = user_params)

usr = srp.User( login, password, srp.SHA256, srp.NG_1024 )

def authenticate(session, login):
  uname, A = usr.start_authentication()
  # print '    aa = "' + binascii.hexlify(A) + '"'
  params = {
      'login': uname,
      'A': binascii.hexlify(A)
      }
  init = print_and_parse(session.post(server + '/sessions', data = params))
  # print '    b = "' + init['b'] + '"'
  # print '    bb = "' + init['B'] + '"'
  M = usr.process_challenge( safe_unhexlify(init['salt']), safe_unhexlify(init['B']) )
  # print '    m = "' + binascii.hexlify(M) + '"'
  return session.put(server + '/sessions/' + login, 
      data = {'client_auth': binascii.hexlify(M)})

session = requests.session()
user = print_and_parse(signup(session))

# SRP signup would happen here and calculate M hex
auth = print_and_parse(authenticate(session, user['login']))
if ( 'errors' in auth ):
  print '    u = "%x"' % usr.u
  print '    x = "%x"' % usr.x
  print '    v = "%x"' % usr.v
  print '    S = "%x"' % usr.S
  print '    K = "' + binascii.hexlify(usr.K) + '"'
  print '    M = "%x"' % usr.M
else:
  usr.verify_session( safe_unhexlify(auth["M2"]) )

# At this point the authentication process is complete.
assert usr.authenticated()