"""Generate iCalendar feeds for conferences."""

import hashlib
from datetime import datetime, timedelta, timezone

import agenda
import agenda.utils
from agenda import ical
from agenda.types import StrDict


def _conference_uid(conf: StrDict) -> str:
    """Generate deterministic UID for conference events."""
    start = agenda.utils.as_date(conf["start"])
    raw = f"conference|{start.isoformat()}|{conf.get('name','unknown')}"
    digest = hashlib.sha1(raw.encode("utf-8")).hexdigest()
    return f"conference-{digest}@agenda-codex"


def _conference_location(conf: StrDict) -> str | None:
    """Build conference location string."""
    parts: list[str] = []
    venue = conf.get("venue")
    location = conf.get("location")
    if isinstance(venue, str) and venue.strip():
        parts.append(venue.strip())
    if isinstance(location, str) and location.strip():
        parts.append(location.strip())
    if country_code := conf.get("country"):
        country = agenda.get_country(country_code)
        if country:
            parts.append(country.name)
    return ", ".join(parts) if parts else None


def _conference_description(conf: StrDict) -> str:
    """Build textual description for conferences."""
    lines: list[str] = []
    if topic := conf.get("topic"):
        lines.append(f"Topic: {topic}")
    if venue := conf.get("venue"):
        lines.append(f"Venue: {venue}")
    if address := conf.get("address"):
        lines.append(f"Address: {address}")
    if url := conf.get("url"):
        lines.append(f"URL: {url}")
    status_bits: list[str] = []
    if conf.get("going"):
        status_bits.append("attending")
    if conf.get("speaking"):
        status_bits.append("speaking")
    if status_bits:
        lines.append(f"Status: {', '.join(status_bits)}")
    return "\n".join(lines) if lines else "Conference"


def build_conference_ical(items: list[StrDict]) -> bytes:
    """Build iCalendar feed for all conferences."""
    lines = [
        "BEGIN:VCALENDAR",
        "VERSION:2.0",
        "PRODID:-//Agenda Codex//Conferences//EN",
        "CALSCALE:GREGORIAN",
        "METHOD:PUBLISH",
        "X-WR-CALNAME:Conferences",
    ]
    generated = datetime.now(tz=timezone.utc)

    for conf in items:
        if not conf["has_exact_dates"]:
            continue
        start_date = agenda.utils.as_date(conf["start"])
        end_date = agenda.utils.as_date(conf["end"])
        end_exclusive = end_date + timedelta(days=1)

        lines.append("BEGIN:VEVENT")
        ical.append_property(lines, "UID", _conference_uid(conf))
        ical.append_property(lines, "DTSTAMP", ical.format_datetime_utc(generated))
        ical.append_property(lines, "DTSTART;VALUE=DATE", ical.format_date(start_date))
        ical.append_property(lines, "DTEND;VALUE=DATE", ical.format_date(end_exclusive))
        ical.append_property(lines, "SUMMARY", ical.escape_text(conf["name"]))
        description = ical.escape_text(_conference_description(conf))
        ical.append_property(lines, "DESCRIPTION", description)
        if location := _conference_location(conf):
            ical.append_property(lines, "LOCATION", ical.escape_text(location))
        lines.append("END:VEVENT")

    lines.append("END:VCALENDAR")
    ical_text = "\r\n".join(lines) + "\r\n"
    return ical_text.encode("utf-8")