from typing import TYPE_CHECKING
from typing import Callable
from typing import Iterable

from ddtrace.internal.schema.span_attribute_schema import SpanDirection


if TYPE_CHECKING:  # pragma: no cover
    from typing import Any  # noqa:F401
    from typing import Dict  # noqa:F401
    from typing import Mapping  # noqa:F401
    from typing import Optional  # noqa:F401

    from ddtrace import Pin  # noqa:F401
    from ddtrace import Span  # noqa:F401
    from ddtrace import Tracer  # noqa:F401
    from ddtrace.settings import Config  # noqa:F401

from urllib.parse import quote

import wrapt

import ddtrace
from ddtrace import config
from ddtrace.constants import SPAN_KIND
from ddtrace.contrib import trace_utils
from ddtrace.ext import SpanKind
from ddtrace.ext import SpanTypes
from ddtrace.internal import core
from ddtrace.internal._exceptions import BlockingException
from ddtrace.internal.constants import COMPONENT
from ddtrace.internal.logger import get_logger
from ddtrace.internal.schema import schematize_url_operation
from ddtrace.internal.utils import get_blocked
from ddtrace.internal.utils import set_blocked
from ddtrace.propagation._utils import from_wsgi_header
from ddtrace.propagation.http import HTTPPropagator


log = get_logger(__name__)

propagator = HTTPPropagator

config._add(
    "wsgi",
    dict(
        _default_service="wsgi",
        distributed_tracing=True,
    ),
)


def get_version():
    # type: () -> str
    return ""


class _DDWSGIMiddlewareBase(object):
    """Base WSGI middleware class.

    :param application: The WSGI application to apply the middleware to.
    :param tracer: Tracer instance to use the middleware with. Defaults to the global tracer.
    :param int_config: Integration specific configuration object.
    :param pin: Set tracing metadata on a particular traced connection
    :param app_is_iterator: Boolean indicating whether the wrapped app is a Python iterator
    """

    def __init__(self, application, tracer, int_config, pin, app_is_iterator=False):
        # type: (Iterable, Tracer, Config, Pin, bool) -> None
        self.app = application
        self.tracer = tracer
        self._config = int_config
        self._pin = pin
        self.app_is_iterator = app_is_iterator

    @property
    def _request_span_name(self):
        # type: () -> str
        "Returns the name of a request span. Example: `flask.request`"
        raise NotImplementedError

    @property
    def _application_span_name(self):
        # type: () -> str
        "Returns the name of an application span. Example: `flask.application`"
        raise NotImplementedError

    @property
    def _response_span_name(self):
        # type: () -> str
        "Returns the name of a response span. Example: `flask.response`"
        raise NotImplementedError

    def __call__(self, environ: Iterable, start_response: Callable) -> wrapt.ObjectProxy:
        headers = get_request_headers(environ)
        closing_iterable = ()
        not_blocked = True
        with core.context_with_data(
            "wsgi.__call__",
            remote_addr=environ.get("REMOTE_ADDR"),
            headers=headers,
            headers_case_sensitive=True,
            service=trace_utils.int_service(self._pin, self._config),
            span_type=SpanTypes.WEB,
            span_name=(self._request_call_name if hasattr(self, "_request_call_name") else self._request_span_name),
            middleware_config=self._config,
            distributed_headers_config=self._config,
            distributed_headers=environ,
            environ=environ,
            middleware=self,
            call_key="req_span",
        ) as ctx:
            ctx.set_item("wsgi.construct_url", construct_url)

            def blocked_view():
                result = core.dispatch_with_results("wsgi.block.started", (ctx, construct_url)).status_headers_content
                if result:
                    status, headers, content = result.value
                else:
                    status, headers, content = 403, [], ""
                return content, status, headers

            if get_blocked():
                content, status, headers = blocked_view()
                start_response(str(status), headers)
                closing_iterable = [content]
                not_blocked = False

            core.dispatch("wsgi.block_decided", (blocked_view,))
            stop_iteration_exception = None

            if not_blocked:
                core.dispatch("wsgi.request.prepare", (ctx, start_response))
                try:
                    closing_iterable = self.app(environ, ctx.get_item("intercept_start_response"))
                except BlockingException as e:
                    set_blocked(e.args[0])
                    content, status, headers = blocked_view()
                    start_response(str(status), headers)
                    closing_iterable = [content]
                    core.dispatch("wsgi.app.exception", (ctx,))
                except StopIteration as e:
                    """
                    WSGI frameworks emit `StopIteration` when closing connections
                    with Gunicorn as part of their standard workflow.  We don't want to mark
                    these as errors for the UI since they are standard and expected
                    to be caught later.

                    Here we catch the exception and close out the request/app spans through the non-error
                    handling pathways.
                    """
                    stop_iteration_exception = e
                except BaseException:
                    core.dispatch("wsgi.app.exception", (ctx,))
                    raise
                else:
                    if get_blocked():
                        _, _, content = core.dispatch_with_results(
                            "wsgi.block.started", (ctx, construct_url)
                        ).status_headers_content.value or (None, None, "")
                        closing_iterable = [content]
                    core.dispatch("wsgi.app.success", (ctx, closing_iterable))

            result = core.dispatch_with_results(
                "wsgi.request.complete", (ctx, closing_iterable, self.app_is_iterator)
            ).traced_iterable

            if stop_iteration_exception:
                if result.value:
                    # Close the request and app spans
                    result.value._finish_spans()
                    core.dispatch("wsgi.app.success", (ctx, closing_iterable))
                raise stop_iteration_exception
            return result.value if result else []

    def _traced_start_response(self, start_response, request_span, app_span, status, environ, exc_info=None):
        # type: (Callable, Span, Span, str, Dict, Any) -> None
        """sets the status code on a request span when start_response is called"""
        with core.context_with_data(
            "wsgi.response",
            middleware=self,
            request_span=request_span,
            parent_call=app_span,
            status=status,
            environ=environ,
            span_type=SpanTypes.WEB,
            service=trace_utils.int_service(None, self._config),
            start_span=False,
            tags={COMPONENT: self._config.integration_name, SPAN_KIND: SpanKind.SERVER},
            call_key="response_span",
        ):
            return start_response(status, environ, exc_info)

    def _request_span_modifier(self, req_span, environ, parsed_headers=None):
        # type: (Span, Dict, Optional[Dict]) -> None
        """Implement to modify span attributes on the request_span"""

    def _application_span_modifier(self, app_span, environ, result):
        # type: (Span, Dict, Iterable) -> None
        """Implement to modify span attributes on the application_span"""

    def _response_span_modifier(self, resp_span, response):
        # type: (Span, Dict) -> None
        """Implement to modify span attributes on the request_span"""


def construct_url(environ):
    """
    https://www.python.org/dev/peps/pep-3333/#url-reconstruction
    """
    url = environ["wsgi.url_scheme"] + "://"

    if environ.get("HTTP_HOST"):
        url += environ["HTTP_HOST"]
    else:
        url += environ["SERVER_NAME"]

        if environ["wsgi.url_scheme"] == "https":
            if environ["SERVER_PORT"] != "443":
                url += ":" + environ["SERVER_PORT"]
        else:
            if environ["SERVER_PORT"] != "80":
                url += ":" + environ["SERVER_PORT"]

    url += quote(environ.get("SCRIPT_NAME", ""))
    # we need the raw uri here for reporting, not the computed one
    if environ.get("RAW_URI"):
        url += environ["RAW_URI"]
        # on old versions of wsgi, the raw uri does not include the query string
        if environ.get("QUERY_STRING") and "?" not in environ["RAW_URI"]:
            url += "?" + environ["QUERY_STRING"]
    elif environ.get("REQUEST_URI"):
        url += environ["REQUEST_URI"]
        # on old versions of wsgi, the raw uri does not include the query string
        if environ.get("QUERY_STRING") and "?" not in environ["REQUEST_URI"]:
            url += "?" + environ["QUERY_STRING"]
    else:
        url += quote(environ.get("PATH_INFO", ""))
        if environ.get("QUERY_STRING"):
            url += "?" + environ["QUERY_STRING"]

    return url


def get_request_headers(environ):
    # type: (Mapping[str, str]) -> Mapping[str, str]
    """
    Manually grab the request headers from the environ dictionary.
    """
    request_headers = {}  # type: Mapping[str, str]
    for key in environ.keys():
        if key.startswith("HTTP_"):
            name = from_wsgi_header(key)
            if name:
                request_headers[name] = environ[key]
    return request_headers


def default_wsgi_span_modifier(span, environ):
    span.resource = "{} {}".format(environ["REQUEST_METHOD"], environ["PATH_INFO"])


class DDWSGIMiddleware(_DDWSGIMiddlewareBase):
    """WSGI middleware providing tracing around an application.

    :param application: The WSGI application to apply the middleware to.
    :param tracer: Tracer instance to use the middleware with. Defaults to the global tracer.
    :param span_modifier: Span modifier that can add tags to the root span.
                            Defaults to using the request method and url in the resource.
    :param app_is_iterator: Boolean indicating whether the wrapped WSGI app is a Python iterator
    """

    _request_span_name = schematize_url_operation("wsgi.request", protocol="http", direction=SpanDirection.INBOUND)
    _application_span_name = "wsgi.application"
    _response_span_name = "wsgi.response"

    def __init__(self, application, tracer=None, span_modifier=default_wsgi_span_modifier, app_is_iterator=False):
        # type: (Iterable, Optional[Tracer], Callable[[Span, Dict[str, str]], None], bool) -> None
        super(DDWSGIMiddleware, self).__init__(
            application, tracer or ddtrace.tracer, config.wsgi, None, app_is_iterator=app_is_iterator
        )
        self.span_modifier = span_modifier

    def _traced_start_response(self, start_response, request_span, app_span, status, environ, exc_info=None):
        with core.context_with_data(
            "wsgi.response",
            middleware=self,
            request_span=request_span,
            parent_call=app_span,
            status=status,
            environ=environ,
            span_type=SpanTypes.WEB,
            span_name="wsgi.start_response",
            service=trace_utils.int_service(None, self._config),
            start_span=True,
            tags={COMPONENT: self._config.integration_name, SPAN_KIND: SpanKind.SERVER},
            call_key="response_span",
        ) as ctx, ctx.get_item("response_span"):
            return start_response(status, environ, exc_info)

    def _request_span_modifier(self, req_span, environ, parsed_headers=None):
        url = construct_url(environ)
        request_headers = parsed_headers if parsed_headers is not None else get_request_headers(environ)
        core.dispatch("wsgi.request.prepared", (self, req_span, url, request_headers, environ))

    def _response_span_modifier(self, resp_span, response):
        core.dispatch("wsgi.response.prepared", (resp_span, response))
