"""Reading the moment a Federal Reserve document became public.

Every modern FOMC release states its own embargo: *For release at 2:00 p.m.
EDT*. That line is the fact, and it is read out of the document rather than
assumed -- a statement is at 2:00 p.m., the minutes three weeks later are at
2:00 p.m. too, and a longer-run strategy revision might be at 11:00 a.m.
Assuming one of them would be right most of the time, which is the worst kind
of wrong.

Where a document states no time -- the minutes pages carry none, only the
calendar's release date -- nothing is invented. The instant becomes the end of
that day in Washington and `knowledge_time_precision` says `date`. That is late
by up to a day and never early, which is the only direction a knowledge
timestamp is allowed to be wrong in.
"""

from __future__ import annotations

import re
from datetime import UTC, date, datetime, time

from .config import EASTERN

MONTHS = {
    "january": 1, "february": 2, "march": 3, "april": 4, "may": 5, "june": 6,
    "july": 7, "august": 8, "september": 9, "october": 10, "november": 11, "december": 12,
    "jan": 1, "feb": 2, "mar": 3, "apr": 4, "jun": 6, "jul": 7, "aug": 8,
    "sept": 9, "sep": 9, "oct": 10, "nov": 11, "dec": 12,
}

MONTH_NAMES = "|".join(sorted(MONTHS, key=len, reverse=True))
DATE = re.compile(rf"\b({MONTH_NAMES})\.?\s+(\d{{1,2}})\s*,?\s+((?:19|20)\d{{2}})", re.IGNORECASE)
# "For release at 2:00 p.m. EDT" and "For release at 2:00 p.m., EDT, June 17, 2026"
RELEASE_TIME = re.compile(
    r"for\s+release\s+at\s+(\d{1,2}):(\d{2})\s*(a|p)\.?\s?m\.?", re.IGNORECASE
)
# The end of the day in Washington: late, and never early.
END_OF_DAY = time(23, 59, 59)


def parse_date(text: str) -> date | None:
    match = DATE.search(text or "")
    if not match:
        return None
    month = MONTHS.get(match.group(1).lower().rstrip("."))
    if month is None:
        return None
    try:
        return date(int(match.group(3)), month, int(match.group(2)))
    except ValueError:
        return None


def release_instant(text: str, *, on: date | None = None, window: int = 6000) -> tuple:
    """The document's own embargo instant, or the end of its release day.

    Returns `(instant, precision)`. `on` is the release date where it is known
    from elsewhere -- the calendar states when minutes came out, and the minutes
    themselves do not.
    """

    head = (text or "")[:window]
    match = RELEASE_TIME.search(head)
    day = on
    if day is None:
        day = parse_date(head)
    if day is None:
        return None, "unknown"
    if match is None:
        return _at(day, END_OF_DAY), "date"
    hour = int(match.group(1)) % 12 + (12 if match.group(3).lower() == "p" else 0)
    return _at(day, time(hour, int(match.group(2)))), "exact"


def _at(day: date, moment: time) -> datetime:
    return datetime(
        day.year, day.month, day.day, moment.hour, moment.minute, moment.second, tzinfo=EASTERN
    ).astimezone(UTC)


def end_of_day(day: date) -> datetime:
    return _at(day, END_OF_DAY)


__all__ = ["END_OF_DAY", "MONTHS", "end_of_day", "parse_date", "release_instant"]