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"""
Connects to the first FIDO device found which supports the PRF extension,
creates a new credential for it with the extension enabled, and uses it to
derive two separate secrets.
"""

import os

from exampleutils import get_client

from fido2.server import Fido2Server
from fido2.utils import websafe_encode

# Locate a suitable FIDO authenticator
client, _ = get_client(lambda info: "hmac-secret" in info.extensions)

uv = "discouraged"

server = Fido2Server({"id": "example.com", "name": "Example RP"}, attestation="none")
user = {"id": b"user_id", "name": "A. User"}

# Prepare parameters for makeCredential
create_options, state = server.register_begin(
    user,
    resident_key_requirement="discouraged",
    user_verification=uv,
    authenticator_attachment="cross-platform",
)

# Generate salts for PRF:
salt = websafe_encode(os.urandom(32))
salt2 = websafe_encode(os.urandom(32))

# Create a credential
result = client.make_credential(
    {
        **create_options["publicKey"],
        "extensions": {"prf": {"eval": {"first": salt, "second": salt2}}},
    }
)

# Complete registration
auth_data = server.register_complete(state, result)
credential = auth_data.credential_data

# PRF result:
if result.client_extension_results.get("prf", {}).get("enabled"):
    print("New credential created, with PRF")
else:
    # This fails on Windows, but we might still be able to use prf even if
    # the credential wasn't made with it, so keep going
    print("Failed to create credential with PRF, it might not work")

# If created with UV, keep using UV
if auth_data.is_user_verified():
    uv = "required"

print("First salt:", salt)

# Prepare parameters for getAssertion
credentials = [credential]
request_options, state = server.authenticate_begin(credentials, user_verification=uv)

prf_results = result.client_extension_results.get("prf", {}).get("results")
if prf_results:
    output1 = prf_results["first"]
    print("Credential created, with salt. Secret:", output1)
else:
    # Authenticate the credential
    result = client.get_assertion(
        {
            **request_options["publicKey"],
            "extensions": {"prf": {"eval": {"first": salt}}},
        }
    )

    # Only one cred in allowCredentials, only one response.
    response = result.get_response(0)

    output1 = response.client_extension_results["prf"]["results"]["first"]
    print("Authenticated, with salt. Secret:", output1)

# Authenticate again, using two salts to generate two secrets.

# This time we will use evalByCredential, which can be used if there are multiple
# credentials which use different salts. Here it is not needed, but provided for
# completeness of the example.

print("Authenticate with second salt:", salt2)
# The first salt is reused, which should result in the same secret.

result = client.get_assertion(
    {
        **request_options["publicKey"],
        "extensions": {
            "prf": {
                "evalByCredential": {
                    websafe_encode(credential.credential_id): {
                        "first": salt,
                        "second": salt2,
                    }
                }
            }
        },
    }
)

# Only one cred in allowCredentials, only one response.
response = result.get_response(0)

output = response.client_extension_results["prf"]["results"]
print("Old secret:", output["first"])
print("New secret:", output["second"])
