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# Subject switch

The tool to check the availability or syntax of domain, IP or URL.

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Provides the extra rules handler based on the "switching" domain behavior of some subjects.

Author: Nissar Chababy, @funilrys, contactTATAfunilrysTODTODcom

Special thanks: https://pyfunceble.github.io/#/special-thanks

Contributors: https://pyfunceble.github.io/#/contributors

Project link: https://github.com/funilrys/PyFunceble

Project documentation: https://docs.pyfunceble.com

Project homepage: https://pyfunceble.github.io/

License: ::

    Copyright 2017, 2018, 2019, 2020, 2022, 2023, 2024 Nissar Chababy

    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

        https://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.

## `SubjectSwitchRulesHandler`

Bases: `ExtraRuleHandlerBase`

Provides our very own "subject switch" handler.

This handler will be used to detects a subject switch behavior from a server. In other words, this handler should be able to detect the following scenario and switch the original subject to :code:`INACTIVE`.

    1. https://www.example.org/hello/world -> https://example.org/hello/world
    2. https://m.example.org/hello/world -> https://example.org/hello/world

Source code in `PyFunceble/checker/availability/extras/subject_switch.py`

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    class SubjectSwitchRulesHandler(ExtraRuleHandlerBase):
        """
        Provides our very own "subject switch" handler.

        This handler will be used to detects a subject switch behavior from a server.
        In other words, this handler should be able to detect the following scenario
        and switch the original subject to :code:`INACTIVE`.

            1. https://www.example.org/hello/world -> https://example.org/hello/world
            2. https://m.example.org/hello/world -> https://example.org/hello/world
        """

        url2netloc: Optional[Url2Netloc] = None

        def __init__(self, status: Optional[AvailabilityCheckerStatus] = None) -> None:
            self.url2netloc = Url2Netloc()
            super().__init__(status)

        def _switch_down_by_history(self) -> "SubjectSwitchRulesHandler":
            """
            Tries to switch the status to :code:`INACTIVE` by following hte history.
            """

            variations = set(
                [
                    self.status.netloc.replace("www.", "", 1),
                    self.status.netloc.replace("m.", "", 1),
                ]
            )

            try:
                # The current netloc should be included in the variations
                variations.remove(self.status.netloc)
            except KeyError:
                pass

            start_path = (
                self.url2netloc.set_data_to_convert(self.req_url)
                .parse_url()
                .parsed_url.path
            )

            for response in self.req.history:
                if (
                    not str(response.status_code).startswith("3")
                    or "location" not in response.headers
                ):
                    continue

                redirect_url = response.headers["location"]

                netloc = self.url2netloc.set_data_to_convert(redirect_url).get_converted()
                local_path = self.url2netloc.parsed_url.path

                if netloc == self.status.idna_subject and netloc not in variations:
                    continue

                if not start_path:
                    if local_path != "/":
                        continue
                elif start_path != local_path:
                    continue

                self.switch_to_down()
                break

            return self

        @ExtraRuleHandlerBase.ensure_status_is_given
        @ExtraRuleHandlerBase.setup_status_before
        @ExtraRuleHandlerBase.setup_status_after
        def start(self) -> "SubjectSwitchRulesHandler":
            """
            Process the check and handling of the current subject.
            """

            PyFunceble.facility.Logger.info(
                "Started to check %r against our subject switcher rules.",
                self.status.idna_subject,
            )

            try:
                if any(self.status.netloc.startswith(x) for x in ("www.", "m.")):
                    self.do_request()

                    if not self.status.status_after_extra_rules:
                        self._switch_down_by_history()
            except PyFunceble.factory.Requester.exceptions.RequestException:
                pass

            PyFunceble.facility.Logger.info(
                "Finished to check %r against our subject switcher rules.",
                self.status.idna_subject,
            )

            return self

### `start()`

Process the check and handling of the current subject.

Source code in `PyFunceble/checker/availability/extras/subject_switch.py`

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    @ExtraRuleHandlerBase.ensure_status_is_given
    @ExtraRuleHandlerBase.setup_status_before
    @ExtraRuleHandlerBase.setup_status_after
    def start(self) -> "SubjectSwitchRulesHandler":
        """
        Process the check and handling of the current subject.
        """

        PyFunceble.facility.Logger.info(
            "Started to check %r against our subject switcher rules.",
            self.status.idna_subject,
        )

        try:
            if any(self.status.netloc.startswith(x) for x in ("www.", "m.")):
                self.do_request()

                if not self.status.status_after_extra_rules:
                    self._switch_down_by_history()
        except PyFunceble.factory.Requester.exceptions.RequestException:
            pass

        PyFunceble.facility.Logger.info(
            "Finished to check %r against our subject switcher rules.",
            self.status.idna_subject,
        )

        return self