# Copyright The OpenTelemetry Authors
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Usage
-----

.. code-block:: python

    from opentelemetry.instrumentation.starlette import StarletteInstrumentor
    from starlette import applications
    from starlette.responses import PlainTextResponse
    from starlette.routing import Route

    def home(request):
        return PlainTextResponse("hi")

    app = applications.Starlette(
        routes=[Route("/foobar", home)]
    )
    StarletteInstrumentor.instrument_app(app)

Configuration
-------------

Exclude lists
*************
To exclude certain URLs from tracking, set the environment variable ``OTEL_PYTHON_STARLETTE_EXCLUDED_URLS``
(or ``OTEL_PYTHON_EXCLUDED_URLS`` to cover all instrumentations) to a string of comma delimited regexes that match the
URLs.

For example,

::

    export OTEL_PYTHON_STARLETTE_EXCLUDED_URLS="client/.*/info,healthcheck"

will exclude requests such as ``https://site/client/123/info`` and ``https://site/xyz/healthcheck``.

Request/Response hooks
**********************

This instrumentation supports request and response hooks. These are functions that get called
right after a span is created for a request and right before the span is finished for the response.

- The server request hook is passed a server span and ASGI scope object for every incoming request.
- The client request hook is called with the internal span and an ASGI scope when the method ``receive`` is called.
- The client response hook is called with the internal span and an ASGI event when the method ``send`` is called.

For example,

.. code-block:: python

    def server_request_hook(span: Span, scope: dict):
        if span and span.is_recording():
            span.set_attribute("custom_user_attribute_from_request_hook", "some-value")
    def client_request_hook(span: Span, scope: dict):
        if span and span.is_recording():
            span.set_attribute("custom_user_attribute_from_client_request_hook", "some-value")
    def client_response_hook(span: Span, message: dict):
        if span and span.is_recording():
            span.set_attribute("custom_user_attribute_from_response_hook", "some-value")

   StarletteInstrumentor().instrument(server_request_hook=server_request_hook, client_request_hook=client_request_hook, client_response_hook=client_response_hook)

Capture HTTP request and response headers
*****************************************
You can configure the agent to capture specified HTTP headers as span attributes, according to the
`semantic convention <https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#http-request-and-response-headers>`_.

Request headers
***************
To capture HTTP request headers as span attributes, set the environment variable
``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST`` to a comma delimited list of HTTP header names.

For example,
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="content-type,custom_request_header"

will extract ``content-type`` and ``custom_request_header`` from the request headers and add them as span attributes.

Request header names in Starlette are case-insensitive. So, giving the header name as ``CUStom-Header`` in the
environment variable will capture the header named ``custom-header``.

Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="Accept.*,X-.*"

Would match all request headers that start with ``Accept`` and ``X-``.

Additionally, the special keyword ``all`` can be used to capture all request headers.
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_REQUEST="all"

The name of the added span attribute will follow the format ``http.request.header.<header_name>`` where ``<header_name>``
is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
single item list containing all the header values.

For example:
``http.request.header.custom_request_header = ["<value1>,<value2>"]``

Response headers
****************
To capture HTTP response headers as span attributes, set the environment variable
``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE`` to a comma delimited list of HTTP header names.

For example,
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="content-type,custom_response_header"

will extract ``content-type`` and ``custom_response_header`` from the response headers and add them as span attributes.

Response header names in Starlette are case-insensitive. So, giving the header name as ``CUStom-Header`` in the
environment variable will capture the header named ``custom-header``.

Regular expressions may also be used to match multiple headers that correspond to the given pattern.  For example:
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="Content.*,X-.*"

Would match all response headers that start with ``Content`` and ``X-``.

Additionally, the special keyword ``all`` can be used to capture all response headers.
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SERVER_RESPONSE="all"

The name of the added span attribute will follow the format ``http.response.header.<header_name>`` where ``<header_name>``
is the normalized HTTP header name (lowercase, with ``-`` replaced by ``_``). The value of the attribute will be a
single item list containing all the header values.

For example:
``http.response.header.custom_response_header = ["<value1>,<value2>"]``

Sanitizing headers
******************
In order to prevent storing sensitive data such as personally identifiable information (PII), session keys, passwords,
etc, set the environment variable ``OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS``
to a comma delimited list of HTTP header names to be sanitized.  Regexes may be used, and all header names will be
matched in a case-insensitive manner.

For example,
::

    export OTEL_INSTRUMENTATION_HTTP_CAPTURE_HEADERS_SANITIZE_FIELDS=".*session.*,set-cookie"

will replace the value of headers such as ``session-id`` and ``set-cookie`` with ``[REDACTED]`` in the span.

Note:
    The environment variable names used to capture HTTP headers are still experimental, and thus are subject to change.

API
---
"""
import typing
from typing import Collection

from starlette import applications
from starlette.routing import Match

from opentelemetry.instrumentation.asgi import OpenTelemetryMiddleware
from opentelemetry.instrumentation.asgi.package import _instruments
from opentelemetry.instrumentation.instrumentor import BaseInstrumentor
from opentelemetry.instrumentation.starlette.version import __version__
from opentelemetry.metrics import get_meter
from opentelemetry.semconv.trace import SpanAttributes
from opentelemetry.trace import Span
from opentelemetry.util.http import get_excluded_urls

_excluded_urls = get_excluded_urls("STARLETTE")

_ServerRequestHookT = typing.Optional[typing.Callable[[Span, dict], None]]
_ClientRequestHookT = typing.Optional[typing.Callable[[Span, dict], None]]
_ClientResponseHookT = typing.Optional[typing.Callable[[Span, dict], None]]


class StarletteInstrumentor(BaseInstrumentor):
    """An instrumentor for starlette

    See `BaseInstrumentor`
    """

    _original_starlette = None

    @staticmethod
    def instrument_app(
        app: applications.Starlette,
        server_request_hook: _ServerRequestHookT = None,
        client_request_hook: _ClientRequestHookT = None,
        client_response_hook: _ClientResponseHookT = None,
        meter_provider=None,
        tracer_provider=None,
    ):
        """Instrument an uninstrumented Starlette application."""
        meter = get_meter(__name__, __version__, meter_provider)
        if not getattr(app, "is_instrumented_by_opentelemetry", False):
            app.add_middleware(
                OpenTelemetryMiddleware,
                excluded_urls=_excluded_urls,
                default_span_details=_get_route_details,
                server_request_hook=server_request_hook,
                client_request_hook=client_request_hook,
                client_response_hook=client_response_hook,
                tracer_provider=tracer_provider,
                meter=meter,
            )
            app.is_instrumented_by_opentelemetry = True

            # adding apps to set for uninstrumenting
            if app not in _InstrumentedStarlette._instrumented_starlette_apps:
                _InstrumentedStarlette._instrumented_starlette_apps.add(app)

    @staticmethod
    def uninstrument_app(app: applications.Starlette):
        app.user_middleware = [
            x
            for x in app.user_middleware
            if x.cls is not OpenTelemetryMiddleware
        ]
        app.middleware_stack = app.build_middleware_stack()
        app._is_instrumented_by_opentelemetry = False

    def instrumentation_dependencies(self) -> Collection[str]:
        return _instruments

    def _instrument(self, **kwargs):
        self._original_starlette = applications.Starlette
        _InstrumentedStarlette._tracer_provider = kwargs.get("tracer_provider")
        _InstrumentedStarlette._server_request_hook = kwargs.get(
            "server_request_hook"
        )
        _InstrumentedStarlette._client_request_hook = kwargs.get(
            "client_request_hook"
        )
        _InstrumentedStarlette._client_response_hook = kwargs.get(
            "client_response_hook"
        )
        _InstrumentedStarlette._meter_provider = kwargs.get("_meter_provider")

        applications.Starlette = _InstrumentedStarlette

    def _uninstrument(self, **kwargs):

        """uninstrumenting all created apps by user"""
        for instance in _InstrumentedStarlette._instrumented_starlette_apps:
            self.uninstrument_app(instance)
        _InstrumentedStarlette._instrumented_starlette_apps.clear()
        applications.Starlette = self._original_starlette


class _InstrumentedStarlette(applications.Starlette):
    _tracer_provider = None
    _meter_provider = None
    _server_request_hook: _ServerRequestHookT = None
    _client_request_hook: _ClientRequestHookT = None
    _client_response_hook: _ClientResponseHookT = None
    _instrumented_starlette_apps = set()

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        meter = get_meter(
            __name__, __version__, _InstrumentedStarlette._meter_provider
        )
        self.add_middleware(
            OpenTelemetryMiddleware,
            excluded_urls=_excluded_urls,
            default_span_details=_get_route_details,
            server_request_hook=_InstrumentedStarlette._server_request_hook,
            client_request_hook=_InstrumentedStarlette._client_request_hook,
            client_response_hook=_InstrumentedStarlette._client_response_hook,
            tracer_provider=_InstrumentedStarlette._tracer_provider,
            meter=meter,
        )
        self._is_instrumented_by_opentelemetry = True
        # adding apps to set for uninstrumenting
        _InstrumentedStarlette._instrumented_starlette_apps.add(self)

    def __del__(self):
        _InstrumentedStarlette._instrumented_starlette_apps.remove(self)


def _get_route_details(scope):
    """Callback to retrieve the starlette route being served.

    TODO: there is currently no way to retrieve http.route from
    a starlette application from scope.

    See: https://github.com/encode/starlette/pull/804
    """
    app = scope["app"]
    route = None
    for starlette_route in app.routes:
        match, _ = starlette_route.matches(scope)
        if match == Match.FULL:
            route = starlette_route.path
            break
        if match == Match.PARTIAL:
            route = starlette_route.path
    # method only exists for http, if websocket
    # leave it blank.
    span_name = route or scope.get("method", "")
    attributes = {}
    if route:
        attributes[SpanAttributes.HTTP_ROUTE] = route
    return span_name, attributes
