from __future__ import annotations

import logging
from datetime import date, timedelta

import httpx

from app.services.platforms.base import PostingStrategy, PostResult

logger = logging.getLogger(__name__)

# Weekday names → int (0=Mon, 6=Sun)
_WEEKDAY_MAP = {
    "monday": 0, "tuesday": 1, "wednesday": 2, "thursday": 3,
    "friday": 4, "saturday": 5, "sunday": 6,
}
# Ordinal names → n
_ORDINAL_MAP = {"first": 1, "second": 2, "third": 3}


def is_nth_weekday(dt: date, weekday: int, n: int) -> bool:
    """True if dt is the nth occurrence of weekday (0=Mon, 6=Sun) in its month."""
    first_of_month = dt.replace(day=1)
    days_until = (weekday - first_of_month.weekday()) % 7
    first_occurrence = first_of_month + timedelta(days=days_until)
    nth_occurrence = first_occurrence + timedelta(weeks=n - 1)
    return dt == nth_occurrence


def parse_occurrence(occurrence: str | None) -> tuple[int, int] | None:
    """Parse an occurrence string into (weekday, n) or None for 'every'.

    Supported: "first_sunday", "second_monday", "third_friday", etc.
    Returns None for "every" or None input.
    Raises ValueError for unrecognised patterns.
    """
    if occurrence is None or occurrence == "every":
        return None
    parts = occurrence.lower().split("_", 1)
    if len(parts) != 2:
        raise ValueError(f"Unrecognised occurrence format: {occurrence!r}")
    ordinal, weekday_name = parts
    if ordinal not in _ORDINAL_MAP or weekday_name not in _WEEKDAY_MAP:
        raise ValueError(f"Unrecognised occurrence: {occurrence!r}")
    return _WEEKDAY_MAP[weekday_name], _ORDINAL_MAP[ordinal]