import hashlib
import logging
from icalendar import Calendar

logger = logging.getLogger(__name__)


def parse_ics_events(ics_text: str) -> dict[str, str]:
    cal = Calendar.from_ical(ics_text.encode() if isinstance(ics_text, str) else ics_text)
    result = {}
    for component in cal.walk():
        if component.name != "VEVENT":
            continue
        uid = component.get("UID")
        if uid is None:
            logger.warning("Skipping event with no UID")
            continue
        uid_str = str(uid)
        try:
            event_bytes = component.to_ical()
            file_hash = hashlib.sha256(event_bytes).hexdigest()
            result[uid_str] = file_hash
        except Exception as e:
            logger.warning("Failed to process event %s: %s", uid_str, e)
    return result


def compute_diff(ics_uids: dict[str, str], known_uids: dict[str, str]) -> dict:
    to_add = []
    to_update = []
    to_delete = []

    for uid, file_hash in ics_uids.items():
        if uid not in known_uids:
            to_add.append((uid, file_hash))
        elif known_uids[uid] != file_hash:
            to_update.append((uid, file_hash))

    for uid in known_uids:
        if uid not in ics_uids:
            to_delete.append(uid)

    return {
        "to_add": to_add,
        "to_update": to_update,
        "to_delete": to_delete,
    }


def parse_ics_events_with_data(ics_text: str) -> dict[str, bytes]:
    cal = Calendar.from_ical(ics_text.encode() if isinstance(ics_text, str) else ics_text)
    result = {}
    for component in cal.walk():
        if component.name != "VEVENT":
            continue
        uid = component.get("UID")
        if uid is None:
            logger.warning("Skipping event with no UID")
            continue
        uid_str = str(uid)
        try:
            result[uid_str] = component.to_ical()
        except Exception as e:
            logger.warning("Failed to process event %s: %s", uid_str, e)
    return result