# ------------------------------------
# Copyright (c) Microsoft Corporation.
# Licensed under the MIT License.
# ------------------------------------
import os
from azure.identity import DefaultAzureCredential
from azure.core.exceptions import HttpResponseError
from azure.digitaltwins.core import DigitalTwinsClient

# Simple example of how to:
# - create a DigitalTwins Service Client using the DigitalTwinsClient constructor
# - query digital twins
#
# Preconditions:
# - Environment variables have to be set
# - DigitalTwins enabled device must exist on the ADT hub
try:
    # DefaultAzureCredential supports different authentication mechanisms and determines
    # the appropriate credential type based of the environment it is executing in.
    # It attempts to use multiple credential types in an order until it finds a working credential.

    # - AZURE_URL: The tenant ID in Azure Active Directory
    url = os.getenv("AZURE_URL")
    if url is None:
        raise ValueError("AZURE_URL environment variable is not set")
    
    # DefaultAzureCredential expects the following three environment variables:
    # - AZURE_TENANT_ID: The tenant ID in Azure Active Directory
    # - AZURE_CLIENT_ID: The application (client) ID registered in the AAD tenant
    # - AZURE_CLIENT_SECRET: The client secret for the registered application
    credential = DefaultAzureCredential()
    service_client = DigitalTwinsClient(url, credential)

    # Query digital twins
    query_expression = 'SELECT * FROM digitaltwins'
    query_result = service_client.query_twins(query_expression)
    print('DigitalTwins:')
    for twin in query_result:
        print(twin)

except HttpResponseError as e:
    print("\nThis sample has caught an error. {0}".format(e.message))
