import re
import smtplib
from datetime import datetime, timedelta
from email.encoders import encode_base64
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.utils import formatdate
from typing import Optional, Any, Dict, List, Tuple

import vobject

from radicale.hook import BaseHook, HookNotificationItem, HookNotificationItemTypes, DeleteHookNotificationItem
from radicale.log import logger

PLUGIN_CONFIG_SCHEMA = {
    "hook": {
        "smtp_server": {
            "value": "",
            "type": str
        },
        "smtp_port": {
            "value": "",
            "type": str
        },
        "smtp_username": {
            "value": "",
            "type": str
        },
        "smtp_password": {
            "value": "",
            "type": str
        },
        "from_email": {
            "value": "",
            "type": str
        },
        "added_template": {
            "value": """Hello $attendee_name,

You have been added as an attendee to the following calendar event.

    $event_title
    $event_start_time - $event_end_time
    $event_location

This is an automated message. Please do not reply.""",
            "type": str
        },
        "removed_template": {
            "value": """Hello $attendee_name,

You have been removed as an attendee from the following calendar event.

    $event_title
    $event_start_time - $event_end_time
    $event_location

This is an automated message. Please do not reply.""",
            "type": str
        },
        "mass_email": {
            "value": False,
            "type": bool,
        }
    }
}

MESSAGE_TEMPLATE_VARIABLES = [
    "organizer_name",
    "from_email",
    "attendee_name",
    "event_title",
    "event_start_time",
    "event_end_time",
    "event_location",
]


def ics_contents_contains_invited_event(contents: str):
    """
    Check if the ICS contents contain an event (versus a VTODO or VJOURNAL).
    :param contents: The contents of the ICS file.
    :return: True if the ICS file contains an event, False otherwise.
    """
    cal = vobject.readOne(contents)
    return cal.vevent is not None


def extract_email(value: str) -> Optional[str]:
    """Extract email address from a string."""
    if not value:
        return None
    value = value.strip().lower()
    match = re.search(r"mailto:([^;]+)", value)
    if match:
        return match.group(1)
    # Fallback to the whole value if no mailto found
    return value if "@" in value else None


class ContentLine:
    _key: str
    value: Any
    _params: Dict[str, Any]

    def __init__(self, key: str, value: Any, params: Optional[Dict[str, Any]] = None):
        self._key = key
        self.value = value
        self._params = params or {}

    def _get_param(self, name: str) -> List[Optional[Any]]:
        """
        Get a parameter value by name.
        :param name: The name of the parameter to retrieve.
        :return: A list of all matching parameter values, or a single-entry (None) list if the parameter does not exist.
        """
        return self._params.get(name, [None])


class VComponent:
    _vobject_item: vobject.base.Component

    def __init__(self,
                 vobject_item: vobject.base.Component,
                 component_type: str):
        """Initialize a VComponent."""
        if not isinstance(vobject_item, vobject.base.Component):
            raise ValueError("vobject_item must be a vobject.base.Component")
        if vobject_item.name != component_type:
            raise ValueError("Invalid component type: %r, expected %r" %
                             (vobject_item.name, component_type))
        self._vobject_item = vobject_item

    def _get_content_lines(self, name: str) -> List[ContentLine]:
        """Get each matching content line."""
        name = name.lower().strip()
        _content_lines = self._vobject_item.contents.get(name, None)
        if not _content_lines:
            return [ContentLine("", None)]
        if not isinstance(_content_lines, (list, tuple)):
            _content_lines = [_content_lines]
        return [ContentLine(key=name, value=cl.value, params=cl.params)
                for cl in _content_lines if isinstance(cl, vobject.base.ContentLine)] or [ContentLine("", None)]

    def _get_sub_vobjects(self, attribute_name: str, _class: type['VComponent']) -> List['VComponent']:
        """Get sub vobject items of the specified type if they exist."""
        sub_vobjects = getattr(self._vobject_item, attribute_name, None)
        if not sub_vobjects:
            return [None]
        if not isinstance(sub_vobjects, (list, tuple)):
            sub_vobjects = [sub_vobjects]
        return [_class(vobject_item=so) for so in sub_vobjects if isinstance(so, vobject.base.Component)] or [None]


class Attendee(ContentLine):
    def __init__(self, content_line: ContentLine):
        super().__init__(key=content_line._key, value=content_line.value,
                         params=content_line._params)

    @property
    def email(self) -> Optional[str]:
        """Return the email address of the attendee."""
        return extract_email(self.value)

    @property
    def role(self) -> Optional[str]:
        """Return the role of the attendee."""
        return self._get_param("ROLE")[0]

    @property
    def participation_status(self) -> Optional[str]:
        """Return the participation status of the attendee."""
        return self._get_param("PARTSTAT")[0]

    @property
    def name(self) -> Optional[str]:
        return self._get_param("CN")[0]

    @property
    def delegated_from(self) -> Optional[str]:
        """Return the email address of the attendee who delegated this attendee."""
        delegate = self._get_param("DELEGATED-FROM")[0]
        return extract_email(delegate) if delegate else None


class TimeWithTimezone(ContentLine):
    def __init__(self, content_line: ContentLine):
        """Initialize a time with timezone content line."""
        super().__init__(key=content_line._key, value=content_line.value,
                         params=content_line._params)

    @property
    def timezone_id(self) -> Optional[str]:
        """Return the timezone of the time."""
        return self._get_param("TZID")[0]

    @property
    def time(self) -> Optional[datetime]:
        """Return the time value."""
        return self.value

    def time_string(self, _format: str = "%Y-%m-%d %H:%M:%S") -> Optional[str]:
        """Return the time as a formatted string."""
        if self.time:
            return self.time.strftime(_format)
        return None


class Alarm(VComponent):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a VALARM item."""
        super().__init__(vobject_item, "VALARM")

    @property
    def action(self) -> Optional[str]:
        """Return the action of the alarm."""
        return self._get_content_lines("ACTION")[0].value

    @property
    def description(self) -> Optional[str]:
        """Return the description of the alarm."""
        return self._get_content_lines("DESCRIPTION")[0].value

    @property
    def trigger(self) -> Optional[timedelta]:
        """Return the trigger of the alarm."""
        return self._get_content_lines("TRIGGER")[0].value

    @property
    def repeat(self) -> Optional[int]:
        """Return the repeat interval of the alarm."""
        repeat = self._get_content_lines("REPEAT")[0].value
        return int(repeat) if repeat is not None else None

    @property
    def duration(self) -> Optional[str]:
        """Return the duration of the alarm."""
        return self._get_content_lines("DURATION")[0].value


class SubTimezone(VComponent):
    def __init__(self,
                 vobject_item: vobject.base.Component,
                 component_type: str):
        """Initialize a sub VTIMEZONE item."""
        super().__init__(vobject_item, component_type)

    @property
    def datetime_start(self) -> Optional[datetime]:
        """Return the start datetime of the timezone."""
        return self._get_content_lines("DTSTART")[0].value

    @property
    def timezone_name(self) -> Optional[str]:
        """Return the timezone name."""
        return self._get_content_lines("TZNAME")[0].value

    @property
    def timezone_offset_from(self) -> Optional[str]:
        """Return the timezone offset from."""
        return self._get_content_lines("TZOFFSETFROM")[0].value

    @property
    def timezone_offset_to(self) -> Optional[str]:
        """Return the timezone offset to."""
        return self._get_content_lines("TZOFFSETTO")[0].value


class StandardTimezone(SubTimezone):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a STANDARD item."""
        super().__init__(vobject_item, "STANDARD")


class DaylightTimezone(SubTimezone):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a DAYLIGHT item."""
        super().__init__(vobject_item, "DAYLIGHT")


class Timezone(VComponent):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a VTIMEZONE item."""
        super().__init__(vobject_item, "VTIMEZONE")

    @property
    def timezone_id(self) -> Optional[str]:
        """Return the timezone ID."""
        return self._get_content_lines("TZID")[0].value

    @property
    def standard(self) -> Optional[StandardTimezone]:
        """Return the STANDARD subcomponent if it exists."""
        return self._get_sub_vobjects("standard", StandardTimezone)[0]

    @property
    def daylight(self) -> Optional[DaylightTimezone]:
        """Return the DAYLIGHT subcomponent if it exists."""
        return self._get_sub_vobjects("daylight", DaylightTimezone)[0]


class Event(VComponent):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a VEVENT item."""
        super().__init__(vobject_item, "VEVENT")

    @property
    def datetime_stamp(self) -> Optional[str]:
        """Return the last modification datetime of the event."""
        return self._get_content_lines("DTSTAMP")[0].value

    @property
    def datetime_start(self) -> Optional[TimeWithTimezone]:
        """Return the start datetime of the event."""
        _content_line = self._get_content_lines("DTSTART")[0]
        return TimeWithTimezone(_content_line) if _content_line.value else None

    @property
    def datetime_end(self) -> Optional[TimeWithTimezone]:
        """Return the end datetime of the event. Either this or duration will be available, but not both."""
        _content_line = self._get_content_lines("DTEND")[0]
        return TimeWithTimezone(_content_line) if _content_line.value else None

    @property
    def duration(self) -> Optional[int]:
        """Return the duration of the event. Either this or datetime_end will be available, but not both."""
        return self._get_content_lines("DURATION")[0].value

    @property
    def uid(self) -> Optional[str]:
        """Return the UID of the event."""
        return self._get_content_lines("UID")[0].value

    @property
    def status(self) -> Optional[str]:
        """Return the status of the event."""
        return self._get_content_lines("STATUS")[0].value

    @property
    def summary(self) -> Optional[str]:
        """Return the summary of the event."""
        return self._get_content_lines("SUMMARY")[0].value

    @property
    def location(self) -> Optional[str]:
        """Return the location of the event."""
        return self._get_content_lines("LOCATION")[0].value

    @property
    def organizer(self) -> Optional[str]:
        """Return the organizer of the event."""
        return self._get_content_lines("ORGANIZER")[0].value

    @property
    def alarms(self) -> List[Alarm]:
        """Return a list of VALARM items in the event."""
        return self._get_sub_vobjects("valarm", Alarm)  # Can be multiple

    @property
    def attendees(self) -> List[Attendee]:
        """Return a list of ATTENDEE items in the event."""
        _content_lines = self._get_content_lines("ATTENDEE")
        return [Attendee(content_line=attendee) for attendee in _content_lines if attendee.value is not None]


class Calendar(VComponent):
    def __init__(self,
                 vobject_item: vobject.base.Component):
        """Initialize a VCALENDAR item."""
        super().__init__(vobject_item, "VCALENDAR")

    @property
    def version(self) -> Optional[str]:
        """Return the version of the calendar."""
        return self._get_content_lines("VERSION")[0].value

    @property
    def product_id(self) -> Optional[str]:
        """Return the product ID of the calendar."""
        return self._get_content_lines("PRODID")[0].value

    @property
    def event(self) -> Optional[Event]:
        """Return the VEVENT item in the calendar."""
        return self._get_sub_vobjects("vevent", Event)[0]

    # TODO: Add VTODO and VJOURNAL support if needed

    @property
    def timezone(self) -> Optional[Timezone]:
        """Return the VTIMEZONE item in the calendar."""
        return self._get_sub_vobjects("vtimezone", Timezone)[0]


class EmailEvent:
    def __init__(self,
                 event: Event,
                 ics_content: str,
                 ics_file_name: str):
        self.event = event
        self.ics_content = ics_content
        self.file_name = ics_file_name


class ICSEmailAttachment:
    def __init__(self, file_content: str, file_name: str):
        self.file_content = file_content
        self.file_name = file_name

    def prepare_email_part(self) -> MIMEBase:
        # Add file as application/octet-stream
        # Email client can usually download this automatically as attachment
        part = MIMEBase("application", "octet-stream")
        part.set_payload(self.file_content)

        # Encode file in ASCII characters to send by email
        encode_base64(part)

        # Add header as key/value pair to attachment part
        part.add_header(
            "Content-Disposition",
            f"attachment; filename= {self.file_name}",
        )

        return part


class MessageTemplate:
    def __init__(self, subject: str, body: str):
        self.subject = subject
        self.body = body
        if not self._validate_template(template=subject):
            raise ValueError(
                f"Invalid subject template: {subject}. Allowed variables are: {MESSAGE_TEMPLATE_VARIABLES}")
        if not self._validate_template(template=body):
            raise ValueError(f"Invalid body template: {body}. Allowed variables are: {MESSAGE_TEMPLATE_VARIABLES}")

    def __repr__(self):
        return f'MessageTemplate(subject={self.subject}, body={self.body})'

    def __str__(self):
        return f'{self.subject}: {self.body}'

    def _validate_template(self, template: str) -> bool:
        """
        Validate the template to ensure it contains only allowed variables.
        :param template: The template string to validate.
        :return: True if the template is valid, False otherwise.
        """
        # Find all variables in the template (starting with $)
        variables = re.findall(r'\$(\w+)', template)
        # Check if all variables are in the allowed list
        for var in variables:
            if var not in MESSAGE_TEMPLATE_VARIABLES:
                logger.error(
                    f"Invalid variable '{var}' found in template. Allowed variables are: {MESSAGE_TEMPLATE_VARIABLES}")
                return False
        return True

    def _populate_template(self, template: str, context: dict) -> str:
        """
        Populate the template with the provided context.
        :param template: The template string to populate.
        :param context: A dictionary containing the context variables.
        :return: The populated template string.
        """
        for key, value in context.items():
            template = template.replace(f"${key}", str(value or ""))
        return template

    def build_message(self, event: EmailEvent, from_email: str, mass_email: bool,
                      attendee: Optional[Attendee] = None) -> str:
        """
        Build the message body using the template.
        :param event: The event to include in the message.
        :param from_email: The email address of the sender.
        :param mass_email: Whether this is a mass email to multiple attendees.
        :param attendee: The specific attendee to include in the message, if not a mass email.
        :return: The formatted message body.
        """
        if mass_email:
            # If this is a mass email, we do not use individual attendee names
            attendee_name = "everyone"
        else:
            assert attendee is not None, "Attendee must be provided for non-mass emails"
            attendee_name = attendee.name if attendee else "Unknown Name"

        context = {
            "attendee_name": attendee_name,
            "from_email": from_email,
            "organizer_name": event.event.organizer or "Unknown Organizer",
            "event_title": event.event.summary or "No Title",
            "event_start_time": event.event.datetime_start.time_string(),
            "event_end_time": event.event.datetime_end.time_string() if event.event.datetime_end else "No End Time",
            "event_location": event.event.location or "No Location Specified",
        }
        return self._populate_template(template=self.body, context=context)

    def build_subject(self, event: EmailEvent, from_email: str, mass_email: bool,
                      attendee: Optional[Attendee] = None) -> str:
        """
        Build the message subject using the template.
        :param attendee: The attendee to include in the subject.
        :param event: The event to include in the subject.
        :param from_email: The email address of the sender.
        :param mass_email: Whether this is a mass email to multiple attendees.
        :param attendee: The specific attendee to include in the message, if not a mass email.
        :return: The formatted message subject.
        """
        if mass_email:
            # If this is a mass email, we do not use individual attendee names
            attendee_name = "everyone"
        else:
            assert attendee is not None, "Attendee must be provided for non-mass emails"
            attendee_name = attendee.name if attendee else "Unknown Name"

        context = {
            "attendee_name": attendee_name,
            "from_email": from_email,
            "organizer_name": event.event.organizer or "Unknown Organizer",
            "event_title": event.event.summary or "No Title",
            "event_start_time": event.event.datetime_start.time_string(),
            "event_end_time": event.event.datetime_end.time_string() if event.event.datetime_end else "No End Time",
            "event_location": event.event.location or "No Location Specified",
        }
        return self._populate_template(template=self.subject, context=context)


class EmailConfig:
    def __init__(self,
                 host: str,
                 port: int,
                 username: str,
                 password: str,
                 from_email: str,
                 send_mass_emails: bool,
                 added_template: MessageTemplate,
                 removed_template: MessageTemplate):
        self.host = host
        self.port = port
        self.username = username
        self.password = password
        self.from_email = from_email
        self.send_mass_emails = send_mass_emails
        self.added_template = added_template
        self.removed_template = removed_template
        self.updated_template = added_template  # Reuse added template for updated events
        self.deleted_template = removed_template  # Reuse removed template for deleted events

    def send_added_email(self, attendees: List[Attendee], event: EmailEvent) -> bool:
        """
        Send a notification for added attendees.
        :param attendees: The attendees to inform.
        :param event: The event the attendee is being added to.
        :return: True if the email was sent successfully, False otherwise.
        """
        ics_attachment = ICSEmailAttachment(file_content=event.ics_content, file_name=f"{event.file_name}")

        return self._prepare_and_send_email(template=self.added_template, attendees=attendees, event=event,
                                            ics_attachment=ics_attachment)

    def send_removed_email(self, attendees: List[Attendee], event: EmailEvent) -> bool:
        """
        Send a notification for removed attendees.
        :param attendees: The attendees to inform.
        :param event: The event the attendee is being removed from.
        :return: True if the email was sent successfully, False otherwise.
        """
        return self._prepare_and_send_email(template=self.removed_template, attendees=attendees, event=event,
                                            ics_attachment=None)

    def send_updated_email(self, attendees: List[Attendee], event: EmailEvent) -> bool:
        """
        Send a notification for updated events.
        :param attendees: The attendees to inform.
        :param event: The event being updated.
        :return: True if the email was sent successfully, False otherwise.
        """
        ics_attachment = ICSEmailAttachment(file_content=event.ics_content, file_name=f"{event.file_name}")

        return self._prepare_and_send_email(template=self.updated_template, attendees=attendees, event=event,
                                            ics_attachment=ics_attachment)

    def send_deleted_email(self, attendees: List[Attendee], event: EmailEvent) -> bool:
        """
        Send a notification for deleted events.
        :param attendees: The attendees to inform.
        :param event: The event being deleted.
        :return: True if the email was sent successfully, False otherwise.
        """
        return self._prepare_and_send_email(template=self.deleted_template, attendees=attendees, event=event,
                                            ics_attachment=None)

    def _prepare_and_send_email(self, template: MessageTemplate, attendees: List[Attendee],
                                event: EmailEvent, ics_attachment: Optional[ICSEmailAttachment] = None) -> bool:
        """
        Prepare the email message(s) and send them to the attendees.
        :param template: The message template to use for the email.
        :param attendees: The list of attendees to notify.
        :param event: The event to include in the email.
        :param ics_attachment: An optional ICS attachment to include in the email.
        :return: True if the email(s) were sent successfully, False otherwise.
        """
        if self.send_mass_emails:
            # If mass emails are enabled, we send one email to all attendees
            body = template.build_message(event=event, from_email=self.from_email,
                                          mass_email=self.send_mass_emails, attendee=None)
            subject = template.build_subject(event=event, from_email=self.from_email,
                                             mass_email=self.send_mass_emails, attendee=None)

            return self._send_email(subject=subject, body=body, attendees=attendees, ics_attachment=ics_attachment)
        else:
            failure_encountered = False
            for attendee in attendees:
                # For individual emails, we send one email per attendee
                body = template.build_message(event=event, from_email=self.from_email,
                                              mass_email=self.send_mass_emails, attendee=attendee)
                subject = template.build_subject(event=event, from_email=self.from_email,
                                                 mass_email=self.send_mass_emails, attendee=attendee)

                if not self._send_email(subject=subject, body=body, attendees=[attendee],
                                        ics_attachment=ics_attachment):
                    failure_encountered = True

            return not failure_encountered  # Return True if all emails were sent successfully

    def _send_email(self,
                    subject: str,
                    body: str,
                    attendees: Attendee,
                    ics_attachment: Optional[ICSEmailAttachment] = None) -> bool:
        """
        Send the notification using the email service.
        :param subject: The subject of the notification.
        :param body: The body of the notification.
        :param attendees: The attendees to notify.
        :param ics_attachment: An optional ICS attachment to include in the email.
        :return: True if the email was sent successfully, False otherwise.
        """
        to_addresses = [attendee.email for attendee in attendees if attendee.email]
        if not to_addresses:
            logger.warning("No valid email addresses found in attendees. Cannot send email.")
            return False

        # Add headers
        message = MIMEMultipart("mixed")
        message["From"] = self.from_email
        message["Reply-To"] = self.from_email
        message["Subject"] = subject
        message["Date"] = formatdate(localtime=True)

        # Add body text
        message.attach(MIMEText(body, "plain"))

        # Add ICS attachment if provided
        if ics_attachment:
            ical_attachment = ics_attachment.prepare_email_part()
            message.attach(ical_attachment)

        # Convert message to text
        text = message.as_string()

        try:
            server = smtplib.SMTP(host=self.host, port=self.port)
            server.ehlo()  # Identify self to server
            server.starttls()  # Start TLS connection
            server.ehlo()  # Identify again after starting TLS
            server.login(user=self.username, password=self.password)
            errors: Dict[str, Tuple[int, str]] = server.sendmail(from_addr=self.from_email, to_addrs=to_addresses,
                                                                 msg=text)
            server.quit()
        except smtplib.SMTPException as e:
            logger.error(f"SMTP error occurred: {e}")
            return False

        if errors:
            for email, (code, error) in errors.items():
                logger.error(f"Failed to send email to {email}: {error} (Code: {code})")
            return False

        return True

    def __repr__(self):
        return f'EmailConfig(host={self.host}, port={self.port}, from_email={self.from_email})'

    def __str__(self):
        return f'{self.from_email} ({self.host}:{self.port})'


def _read_event(vobject_data: str) -> EmailEvent:
    """
    Read the vobject item from the provided string and create an EmailEvent.
    """
    v_cal: vobject.base.Component = vobject.readOne(vobject_data)
    cal: Calendar = Calendar(vobject_item=v_cal)
    event: Event = cal.event

    return EmailEvent(
        event=event,
        ics_content=vobject_data,
        ics_file_name="event.ics"
    )


class Hook(BaseHook):
    def __init__(self, configuration):
        super().__init__(configuration)
        self.email_config = EmailConfig(
            host=self.configuration.get("hook", "smtp_server"),
            port=self.configuration.get("hook", "smtp_port"),
            username=self.configuration.get("hook", "smtp_username"),
            password=self.configuration.get("hook", "smtp_password"),
            from_email=self.configuration.get("hook", "from_email"),
            send_mass_emails=self.configuration.get("hook", "mass_email"),
            added_template=MessageTemplate(
                subject="You have been added to an event",
                body=self.configuration.get("hook", "added_template")
            ),
            removed_template=MessageTemplate(
                subject="You have been removed from an event",
                body=self.configuration.get("hook", "removed_template")
            ),
        )

    def notify(self, notification_item) -> None:
        """
        Entrypoint for processing a single notification item.
        Overrides default notify method from BaseHook.
        Triggered by Radicale when a notifiable event occurs (e.g. item added, updated or deleted)
        """
        if isinstance(notification_item, HookNotificationItem):
            self._process_event_and_notify(notification_item)

    def _process_event_and_notify(self, notification_item: HookNotificationItem) -> None:
        """
        Process the event and send an email notification.
        :param notification_item: The single item to process.
        :type notification_item: HookNotificationItem
        :return: None
        """
        logger.debug("Received notification item: %s", notification_item)
        try:
            notification_type = HookNotificationItemTypes(value=notification_item.type)
        except ValueError:
            logger.warning("Unknown notification item type: %s", notification_item.type)
            return

        if notification_type == HookNotificationItemTypes.CPATCH:
            # Ignore cpatch notifications (PROPPATCH requests for WebDAV metadata updates)
            return

        elif notification_type == HookNotificationItemTypes.UPSERT:
            # Handle upsert notifications (POST request for new item and PUT for updating existing item)

            # We don't have access to the original content for a PUT request, just the incoming data

            item_str: str = notification_item.content  # A serialized vobject.base.Component
            file_path: str = notification_item.point  # The path to the item, e.g. "calendars/user/calendar.ics"

            if not ics_contents_contains_invited_event(contents=item_str):
                # If the ICS file does not contain an event, we do not send any notifications.
                logger.debug("No event found in the ICS file, skipping notification.")
                return

            email_event: EmailEvent = _read_event(vobject_data=item_str, file_path=file_path)

            email_success: bool = self.email_config.send_updated_email(
                attendees=email_event.event.attendees,
                event=email_event
            )
            if not email_success:
                logger.error("Failed to send some or all email notifications for event: %s", email_event.event.uid)

            return

        elif notification_type == HookNotificationItemTypes.DELETE:
            # Handle delete notifications (DELETE requests)

            # Ensure it's a delete notification, as we need the old content
            if not isinstance(notification_item, DeleteHookNotificationItem):
                return

            item_hash: str = notification_item.content  # The hash of the item
            item_str: str = notification_item.old_content  # A serialized vobject.base.Component
            file_path: str = notification_item.point  # The path to the item, e.g. "calendars/user/calendar.ics"

            if not ics_contents_contains_invited_event(contents=item_str):
                # If the ICS file does not contain an event, we do not send any notifications.
                logger.debug("No event found in the ICS file, skipping notification.")
                return

            email_event: EmailEvent = _read_event(vobject_data=item_str, file_path=file_path)

            email_success: bool = self.email_config.send_deleted_email(
                attendees=email_event.event.attendees,
                event=email_event
            )
            if not email_success:
                logger.error("Failed to send some or all email notifications for event: %s", email_event.event.uid)

            return

        return