#!/usr/bin/python3
"""Watch https://osmcal.org/ for another Paris OSM hack weekend."""

import email.message
import email.utils
from urllib.parse import urlparse
import smtplib
import sys

import typing
import requests
import simplejson.errors

MAIL_FROM = "edward@4angle.com"
MAIL_TO = "edward@4angle.com"
SMTP_HOST = "4angle.com"

URL = "https://osmcal.org/api/v2/events/?in=France"

SEEN_EVENT_IDS = {4064, 4606, 4641}


def get_event_id(event: dict[str, typing.Any]) -> int | None:
    """Extract the numeric event ID from API data."""
    if "id" in event:
        return typing.cast(int, event["id"])

    path_parts = [part for part in urlparse(event["url"]).path.split("/") if part]
    if len(path_parts) >= 2 and path_parts[-2] == "event":
        try:
            return int(path_parts[-1])
        except ValueError:
            return None

    return None


def get_detailed_location(event: dict[str, typing.Any]) -> str:
    """Return an event's detailed location, or an empty string if absent."""
    location = event.get("location")
    if not isinstance(location, dict):
        return ""

    detailed = location.get("detailed")
    return detailed if isinstance(detailed, str) else ""


def send_mail(subject: str, body: str) -> None:
    """Send an e-mail."""
    msg = email.message.EmailMessage()

    msg["Subject"] = subject
    msg["To"] = f"Edward Betts <{MAIL_TO}>"
    msg["From"] = f"OSM Calendar alert <{MAIL_FROM}>"
    msg["Date"] = email.utils.formatdate()
    msg["Message-ID"] = email.utils.make_msgid()

    msg.set_content(body)

    s = smtplib.SMTP(SMTP_HOST)
    s.sendmail(MAIL_FROM, [MAIL_TO], msg.as_string())
    s.quit()


def check_for_paris_events() -> None:
    """Check for upcoming OSM events in Paris and send an email if found."""
    r = requests.get(URL)
    try:
        events = r.json()
    except simplejson.errors.JSONDecodeError:
        print(r.text)
        raise

    all_paris_events = [
        event
        for event in events
        if "paris" in get_detailed_location(event).lower()
    ]
    seen_paris_events = [
        event for event in all_paris_events if get_event_id(event) in SEEN_EVENT_IDS
    ]
    paris_events = [
        event for event in all_paris_events if get_event_id(event) not in SEEN_EVENT_IDS
    ]

    if not paris_events:
        if sys.stdin.isatty():
            total_events = len(events)
            seen_count = len(seen_paris_events)
            paris_label = "Paris event" if seen_count == 1 else "Paris events"
            print(
                f"{total_events} events found in France; "
                + f"{seen_count} {paris_label} already seen; "
                + "no new Paris events."
            )
        return

    subject = "Upcoming Paris OSM Hack Weekend Found!"
    count = len(paris_events)
    body = f"Found {count} {'event' if count == 1 else 'events'} in Paris:\n\n"
    for event in paris_events:
        body += (
            f"{event['name']} - {event['url']}\n"
            + f"Date: {event['date']['human']}\n"
            + f"Location: {get_detailed_location(event)}\n\n"
        )
    send_mail(subject, body)


if __name__ == "__main__":
    check_for_paris_events()