# SPDX-FileCopyrightText: 2026 Dennis Fink <me+coding@dennisfink.me>
#
# SPDX-License-Identifier: BSD-3-Clause

from urllib.parse import urlsplit

from flask import current_app
from wtforms import Field, ValidationError
from wtforms.form import BaseForm

from ..url_security import AddressResolutionError, is_public_url


class NotEqualTo:
    """
    Validate that a field does not equal another field.

    :param fieldname: Name of the field to compare against.
    :param message: Optional validation error message.
    """

    def __init__(self, fieldname: str, message: str | None = None) -> None:
        """
        Initialize the validator.

        :param fieldname: Name of the field to compare against.
        :param message: Optional validation error message.
        """
        self.fieldname = fieldname
        self.message = message

    def __call__(self, form: BaseForm, field: Field) -> None:
        """
        Validate that two fields do not contain equal values.

        :param form: Form containing the fields to compare.
        :param field: Field being validated.
        :raises ValidationError: If the comparison field does not exist or both
            fields contain equal values.
        """
        try:
            other = form[self.fieldname]
        except KeyError as exc:
            raise ValidationError(
                field.gettext("Invalid field name '%s'.") % self.fieldname
            ) from exc

        if field.data != other.data:
            return

        d = {
            "other_label": hasattr(other, "label")
            and other.label.text
            or self.fieldname,
            "other_name": self.fieldname,
        }
        message = self.message or field.gettext(
            "Field must not be equal to %(other_name)s."
        )
        raise ValidationError(message % d)


class AllowedHostname:
    """
    Validate that a URL uses an allowed hostname.

    :param message: Optional validation error message.
    """

    def __init__(self, message: str | None = None) -> None:
        """
        Initialize the validator.

        :param message: Optional validation error message.
        """
        self.message = message

    def __call__(self, form: BaseForm, field: Field) -> None:
        """
        Validate that a URL uses an allowed hostname.

        :param form: Form containing the field.
        :param field: Field containing the URL to validate.
        :raises ValidationError: If the URL hostname is not configured as allowed.
        """
        if (
            urlsplit(field.data).hostname
            in current_app.config["WEBMENTIONS_SSG_ALLOWED_HOSTNAMES"]
        ):
            return
        raise ValidationError(self.message or field.gettext("Invalid input."))


class PublicURL:
    """
    Validate that a URL resolves exclusively to public IP addresses.

    :param message: Optional validation error message.
    """

    def __init__(self, message: str | None = None) -> None:
        """
        Initialize the validator.

        :param message: Optional validation error message.
        """
        self.message = message

    def __call__(self, form: BaseForm, field: Field) -> None:
        """
        Validate that a URL resolves exclusively to public IP addresses.

        :param form: Form containing the field.
        :param field: Field containing the URL to validate.
        :raises ValidationError: If the URL cannot be resolved, has no hostname, or
            resolves to a non-public address.
        """
        message = self.message

        if message is None:
            message = field.gettext("URL must resolve to a public address.")

        try:
            if not is_public_url(field.data):
                raise ValidationError(message)
        except (AddressResolutionError, ValueError) as exc:
            raise ValidationError(message) from exc