#!/usr/bin/env python

# --------------------------------------------------------------------------------------------
# Copyright (c) Microsoft Corporation. All rights reserved.
# Licensed under the MIT License. See License.txt in the project root for license information.
# --------------------------------------------------------------------------------------------

"""
Example to demonstrate utilizing SAS (Shared Access Signature) tokens to authenticate with Event Hubs
"""

import asyncio
import os
import time
import hmac
import hashlib
import base64
try:
    from urllib.parse import quote as url_parse_quote
except ImportError:
    from urllib import pathname2url as url_parse_quote

from azure.core.credentials import AccessToken
from azure.eventhub.aio import EventHubProducerClient
from azure.eventhub import EventData


def generate_sas_token(uri, sas_name, sas_value, token_ttl):
    """Performs the signing and encoding needed to generate a sas token from a sas key."""
    sas = sas_value.encode('utf-8')
    expiry = str(int(time.time() + token_ttl))
    string_to_sign = (uri + '\n' + expiry).encode('utf-8')
    signed_hmac_sha256 = hmac.HMAC(sas, string_to_sign, hashlib.sha256)
    signature = url_parse_quote(base64.b64encode(signed_hmac_sha256.digest()))
    return 'SharedAccessSignature sr={}&sig={}&se={}&skn={}'.format(uri, signature, expiry, sas_name)


class CustomizedSASCredential(object):
    def __init__(self, token, expiry):
        """
        :param str token: The token string
        :param float expiry: The epoch timestamp

        """
        self.token = token
        self.expiry = expiry
        self.token_type = b"servicebus.windows.net:sastoken"

    async def get_token(self, *scopes, **kwargs):
        """
        This method is automatically called when token is about to expire.
        """
        return AccessToken(self.token, self.expiry)


# Target namespace and hub must also be specified.  Consumer group is set to default unless required otherwise.
FULLY_QUALIFIED_NAMESPACE = os.environ['EVENT_HUB_HOSTNAME']
EVENTHUB_NAME = os.environ['EVENT_HUB_NAME']

# The following part creates a SAS token. Users can use any way to create a SAS token.
SAS_POLICY = os.environ['EVENT_HUB_SAS_POLICY']
SAS_KEY = os.environ['EVENT_HUB_SAS_KEY']


async def create_with_sas_token():
    uri = "sb://{}/{}".format(FULLY_QUALIFIED_NAMESPACE, EVENTHUB_NAME)
    token_ttl = 3000  # seconds
    sas_token = generate_sas_token(uri, SAS_POLICY, SAS_KEY, token_ttl)
    # end of creating a SAS token

    producer_client = EventHubProducerClient(
        fully_qualified_namespace=FULLY_QUALIFIED_NAMESPACE,
        eventhub_name=EVENTHUB_NAME,
        credential=CustomizedSASCredential(sas_token, time.time() + token_ttl),
        logging_enable=True
    )

    async with producer_client:
        event_data_batch = await producer_client.create_batch()
        event_data_batch.add(EventData('Single message'))
        await producer_client.send_batch(event_data_batch)


start_time = time.time()
asyncio.run(create_with_sas_token())
print("Send messages in {} seconds.".format(time.time() - start_time))
