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from inspect import isawaitable, iscoroutinefunction

from sanic.handlers import ErrorHandler
from sanic.log import logger
from sanic.response import text

from elasticapm.contrib.sanic.sanic_types import ApmHandlerType


class ElasticAPMPatchedErrorHandler(ErrorHandler):
    """
    This is a monkey patchable instance of the Sanic's Error handler infra. Current implementation of Sanic doesn't
    let you chain exception handlers by raising exception chains further down the line. In order to bypass this
    limitation, we monkey patch the current implementation. We invoke the instrumentation function first and then
    chain the exception down to the original handler so that we don't get in the way of standard exception handling.
    """

    def __init__(self, current_handler: ErrorHandler) -> None:
        super(ElasticAPMPatchedErrorHandler, self).__init__()
        self._current_handler = current_handler  # type: ErrorHandler
        self._apm_handler = None  # type: ApmHandlerType

    def add(self, exception, handler, *args, **kwargs) -> None:
        self._current_handler.add(exception, handler, *args, **kwargs)

    def lookup(self, exception, *args, **kwargs):
        return self._current_handler.lookup(exception, *args, **kwargs)

    def setup_apm_handler(self, apm_handler: ApmHandlerType, force: bool = False) -> None:
        if self._apm_handler is None or force:
            self._apm_handler = apm_handler

    async def _patched_response(self, request, exception):
        await self._apm_handler(request, exception)
        handler = self._current_handler.lookup(exception)
        response = None
        try:
            if handler:
                response = handler(request, exception)
            if response is None:
                response = self._current_handler.default(request, exception)
        except Exception:
            try:
                url = repr(request.url)
            except AttributeError:
                url = "unknown"
            response_message = "Exception raised in exception handler " '"%s" for uri: %s'
            logger.exception(response_message, handler.__name__, url)

            if self.debug:
                return text(response_message % (handler.__name__, url), 500)
            else:
                return text("An error occurred while handling an error", 500)
        if iscoroutinefunction(response) or isawaitable(response):
            return await response
        return response

    def response(self, request, exception):
        return self._patched_response(request=request, exception=exception)

    def default(self, request, exception):
        return self._patched_response(request=request, exception=exception)