import boto3
import os
import binascii
import requests
import json

class CustomResource():

  # Usage:
  # from cfncustomresource import CustomResource
  #
  # cr = None
  #
  # def oncreate():
  #   cr.success(response={'Key': 'Value'})

  # def handler(event, context):
  #   global cr
  #   cr = CustomResource()
  #   cr.add_hook('create', oncreate)
  #   cr.load_event(event)

  def __init__(self, event = None):
    self.oncreate = None
    self.ondelete = None
    self.onupdate = None
    self.Payload = {}

    if event != None:
      self.load_event(event)

  def success(self, response):
    self.Payload['Status'] = 'SUCCESS'
    self.set_response(response)

  def fail(self, response):
    self.Payload['Status'] = 'FAILED'
    self.set_response(response)

  def send_response(self):
    self.Payload['StackId'] = self.StackId
    self.Payload['RequestId'] = self.RequestId
    self.Payload['LogicalResourceId'] = self.LogicalResourceId
    self.Payload['PhysicalResourceId'] =  binascii.b2a_hex(os.urandom(15))
    requests.put(self.url, data=json.dumps(self.Payload))

  def set_response(self, response):
    self.Payload['Data'] = response
    self.send_response()

  def load_event(self, event):
    self.event = event
    self.StackId = event['StackId']
    self.RequestId = event['RequestId']
    self.LogicalResourceId = event['LogicalResourceId']
    self.EventType = event['RequestType']
    self.url = event['ResponseURL']
    self.ResourceProperties = event['ResourceProperties']
    self.exec_hook()

  def add_hook(self, action, func):
    if action.lower() == 'create':
      self.oncreate = func
    if action.lower() == 'delete':
      self.ondelete = func
    if action.lower() == 'update':
      self.onupdate = func

  def exec_hook(self):
    if self.EventType.lower() == 'create':
       if self.oncreate != None:
         self.oncreate()
       else:
         self.success(response = {})
    elif self.EventType.lower() == 'delete':
      if self.ondelete != None:
        self.ondelete()
      else:
        self.success(response = {})
    elif self.EventType.lower() == 'update':
      if self.onupdate != None:
        self.onupdate()
      else:
        self.success(response = {})