# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you 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
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# KIND, either express or implied.  See the License for the
# specific language governing permissions and limitations
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from __future__ import annotations

from typing import TYPE_CHECKING, Iterable
from urllib.parse import urlsplit

from werkzeug.middleware.dispatcher import DispatcherMiddleware
from werkzeug.middleware.proxy_fix import ProxyFix

from airflow.configuration import conf
from airflow.exceptions import AirflowConfigException

if TYPE_CHECKING:
    from _typeshed.wsgi import StartResponse, WSGIEnvironment
    from flask import Flask


def _root_app(env: WSGIEnvironment, resp: StartResponse) -> Iterable[bytes]:
    resp("404 Not Found", [("Content-Type", "text/plain")])
    return [b"Apache Airflow is not at this location"]


def init_wsgi_middleware(flask_app: Flask) -> None:
    """Handle X-Forwarded-* headers and base_url support."""
    webserver_base_url = conf.get_mandatory_value("webserver", "BASE_URL", fallback="")
    if webserver_base_url.endswith("/"):
        raise AirflowConfigException("webserver.base_url conf cannot have a trailing slash.")
    # Apply DispatcherMiddleware
    base_url = urlsplit(webserver_base_url)[2]
    if not base_url or base_url == "/":
        base_url = ""
    if base_url:
        wsgi_app = DispatcherMiddleware(_root_app, mounts={base_url: flask_app.wsgi_app})
        flask_app.wsgi_app = wsgi_app  # type: ignore[assignment]

    # Apply ProxyFix middleware
    if conf.getboolean("webserver", "ENABLE_PROXY_FIX"):
        flask_app.wsgi_app = ProxyFix(  # type: ignore
            flask_app.wsgi_app,
            x_for=conf.getint("webserver", "PROXY_FIX_X_FOR", fallback=1),
            x_proto=conf.getint("webserver", "PROXY_FIX_X_PROTO", fallback=1),
            x_host=conf.getint("webserver", "PROXY_FIX_X_HOST", fallback=1),
            x_port=conf.getint("webserver", "PROXY_FIX_X_PORT", fallback=1),
            x_prefix=conf.getint("webserver", "PROXY_FIX_X_PREFIX", fallback=1),
        )
