import re
from datetime import datetime, time
from typing import cast

import pytz
from icalendar import Calendar, Event

from core.enums import AlertType, Continent
from data.alert import Alert
from providers.alert.http_alert_provider import HTTPAlertProvider


class RSGBICALAlertProvider(HTTPAlertProvider):
    """Generic alert provider for RSGB contest ICAL calendars."""

    def __init__(self, name, provider_config, url, poll_interval):
        super().__init__(name, provider_config, url, poll_interval)

    FREQ_PATTERN = re.compile(r"([\d.]+(?:MHz|GHz))|SHF")

    def _http_response_to_alerts(self, http_response):
        new_alerts = []
        cal = Calendar.from_ical(http_response.content)

        # Iterate through events
        for component in cal.walk():
            if component.name != "VEVENT":
                continue

            event = cast(Event, component)
            summary = str(event.get("summary", "")).strip()

            # Ensure summaries start with "RSGB" to avoid any confusion
            if not summary.startswith("RSGB "):
                summary = "RSGB " + summary

            # Extract freq from summary
            freqs_modes = ""

            # HF contests don't give frequencies, all VHF ones do
            match = self.FREQ_PATTERN.search(summary)
            if match:
                freqs_modes = match.group()
            else:
                freqs_modes = "HF bands"
            freqs_modes = freqs_modes + ", "

            # Extract mode from summary
            if "FMAC" in summary:
                freqs_modes = freqs_modes + "FM"
            elif "CW" in summary:
                freqs_modes = freqs_modes + "CW"
            elif "SSB" in summary:
                freqs_modes = freqs_modes + "SSB"
            elif "FT8" in summary:
                freqs_modes = freqs_modes + "FT8"
            elif "FT4" in summary:
                freqs_modes = freqs_modes + "FT4"
            elif "DATA" in summary:
                freqs_modes = freqs_modes + "Data modes"
            else:
                freqs_modes = freqs_modes + "All modes"

            dtstart = event.get("dtstart")
            dtend = event.get("dtend")
            start_timestamp = self._to_utc_timestamp(dtstart.dt)
            end_timestamp = self._to_utc_timestamp(dtend.dt) - 1 if dtend is not None else start_timestamp

            # Convert to our alert format
            alert = Alert(
                source=self.name,
                dx_calls=[],
                dx_country="United Kingdom",
                dx_dxcc_id=235,
                dx_continent=Continent.EU,
                dx_cq_zone=14,
                dx_itu_zone=27,
                dx_flag="🇬🇧",
                freqs_modes=freqs_modes,
                comment=summary,
                start_time=start_timestamp,
                end_time=end_timestamp,
                alert_type=AlertType.CONTEST,
            )

            # Add to our list.
            new_alerts.append(alert)
        return new_alerts

    @staticmethod
    def _to_utc_timestamp(value):
        """Convert a date or datetime value from an iCal field into a UTC UNIX timestamp."""

        # Datetime object so we can treat it as-is, check if it has a non-UTC tz and convert it if necessary
        if isinstance(value, datetime):
            if value.tzinfo is None:
                value = pytz.UTC.localize(value)
            return value.astimezone(pytz.UTC).timestamp()

        # Date object so this is an all day event
        return pytz.UTC.localize(datetime.combine(value, time.min)).timestamp()