from urllib.parse import urlsplit

from flask import current_app
from wtforms import ValidationError

from ..url_security import (
    AddressResolutionError,
    NonPublicAddressError,
    ensure_public_url,
)


class NotEqualTo:
    """
    Compares the values of two fields.

    :param fieldname:
        The name of the other field to compare to.
    :param message:
        Error message to raise in case of a validation error. Can be
        interpolated with `%(other_label)s` and `%(other_name)s` to provide a
        more helpful error.
    """

    def __init__(self, fieldname, message=None):
        self.fieldname = fieldname
        self.message = message

    def __call__(self, form, field):
        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
        if message is None:
            message = field.gettext("Field must not be equal to %(other_name)s.")

        raise ValidationError(message % d)


class AllowedHostname:
    def __init__(self, message=None):
        self.message = message

    def __call__(self, form, field):
        if (
            urlsplit(field.data).hostname
            in current_app.config["WEBMENTIONS_SSG_ALLOWED_HOSTNAMES"]
        ):
            return

        message = self.message
        if self.message is None:
            message = field.gettext("Invalid input.")

        raise ValidationError(message)


class PublicURL:
    def __init__(self, message=None):
        self.message = message

    def __call__(self, form, field):
        try:
            ensure_public_url(field.data)
        except (
            AddressResolutionError,
            NonPublicAddressError,
        ) as exc:
            message = self.message

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

            raise ValidationError(message) from exc