from __future__ import annotations

import re
from datetime import date

AMOUNT_RE = re.compile(
    r"^\s*(?P<amount>\d+(?:[.,]\d{1,2})?)\s*(?P<note>.*)?$",
    re.UNICODE,
)
NOTE_FIRST_RE = re.compile(
    r"^\s*(?P<note>.+?)\s+(?P<amount>\d+(?:[.,]\d{1,2})?)\s*$",
    re.UNICODE,
)
DATE_RE = re.compile(
    r"^(?P<d>\d{1,2})[./](?P<m>\d{1,2})(?:[./](?P<y>\d{2,4}))?$"
)
# Unambiguous date token: ISO, with year, slash, or zero-padded month (12.09)
DATE_TOKEN_RE = re.compile(
    r"(?P<date>"
    r"\d{4}-\d{2}-\d{2}"
    r"|"
    r"\d{1,2}[./]\d{1,2}[./]\d{2,4}"
    r"|"
    r"\d{1,2}/\d{1,2}"
    r"|"
    r"\d{1,2}\.(?:0[1-9]|1[0-2])"
    r")"
)
ZA_DATE_RE = re.compile(
    r"(?i)(?:^|\s)за\s+(?P<date>"
    r"\d{4}-\d{2}-\d{2}"
    r"|"
    r"\d{1,2}[./]\d{1,2}(?:[./]\d{2,4})?"
    r")"
    r"(?=\s|$)"
)


def parse_amount(value: str) -> float:
    normalized = value.strip().replace(",", ".").replace(" ", "")
    amount = float(normalized)
    if amount <= 0:
        raise ValueError("Сумма должна быть больше нуля")
    return round(amount, 2)


def parse_spent_date(value: str, today: date | None = None) -> date:
    """Parse expense date. Bare DD.MM prefers current/past year (not future)."""
    day = today or date.today()
    raw = value.strip()

    try:
        return date.fromisoformat(raw)
    except ValueError:
        pass

    match = DATE_RE.match(raw)
    if not match:
        raise ValueError("Дата в формате ДД.ММ или ДД.ММ.ГГГГ")

    d = int(match.group("d"))
    m = int(match.group("m"))
    y_raw = match.group("y")
    if y_raw is None:
        try:
            candidate = date(day.year, m, d)
        except ValueError as exc:
            raise ValueError("Некорректная дата") from exc
        if candidate > day:
            try:
                candidate = date(day.year - 1, m, d)
            except ValueError as exc:
                raise ValueError("Некорректная дата") from exc
        return candidate

    y = int(y_raw)
    if y < 100:
        y += 2000
    try:
        return date(y, m, d)
    except ValueError as exc:
        raise ValueError("Некорректная дата") from exc


def parse_end_date(value: str, today: date | None = None) -> date:
    """Parse DD.MM, DD.MM.YYYY, YYYY-MM-DD (for budget end — may roll to next year)."""
    day = today or date.today()
    raw = value.strip()

    try:
        return date.fromisoformat(raw)
    except ValueError:
        pass

    match = DATE_RE.match(raw)
    if not match:
        raise ValueError("Дата в формате ДД.ММ или ДД.ММ.ГГГГ")

    d = int(match.group("d"))
    m = int(match.group("m"))
    y_raw = match.group("y")
    if y_raw is None:
        y = day.year
        candidate = date(y, m, d)
        if candidate < day:
            candidate = date(y + 1, m, d)
        return candidate

    y = int(y_raw)
    if y < 100:
        y += 2000
    return date(y, m, d)


def _parse_amount_and_note(raw: str) -> tuple[float, str | None]:
    text = raw.strip()
    if not text:
        raise ValueError("Не понял трату. Примеры: 250, 250 кофе, кофе 250")

    first_token = text.split()[0]
    if re.fullmatch(r"\d+(?:[.,]\d{1,2})?", first_token):
        match = AMOUNT_RE.match(text)
        if not match:
            raise ValueError("Не понял трату. Примеры: 250, 250 кофе, кофе 250")
        amount = parse_amount(match.group("amount"))
        note = (match.group("note") or "").strip() or None
        return amount, note

    match = NOTE_FIRST_RE.match(text)
    if match:
        amount = parse_amount(match.group("amount"))
        note = match.group("note").strip() or None
        return amount, note

    raise ValueError("Не понял трату. Примеры: 250, 250 кофе, кофе 250")


def parse_expense_message(
    text: str,
    today: date | None = None,
) -> tuple[float, str | None, date | None]:
    """Parse expense text.

    Examples:
    - 250 / 250 кофе / кофе 250
    - за 12.09 250 кофе
    - 250 кофе за 12.09
    - 12.09 250 кофе
    - 250 кофе 12.09
    """
    raw = text.strip()
    if not raw:
        raise ValueError("Пустое сообщение")

    spent_at: date | None = None
    body = raw

    za_match = ZA_DATE_RE.search(raw)
    if za_match:
        spent_at = parse_spent_date(za_match.group("date"), today=today)
        body = (raw[: za_match.start()] + " " + raw[za_match.end() :]).strip()
    else:
        tokens = raw.split()
        if len(tokens) >= 2:
            first = tokens[0].rstrip(":")
            last = tokens[-1]
            if DATE_TOKEN_RE.fullmatch(first):
                spent_at = parse_spent_date(first, today=today)
                body = " ".join(tokens[1:])
            elif DATE_TOKEN_RE.fullmatch(last):
                spent_at = parse_spent_date(last, today=today)
                body = " ".join(tokens[:-1])

    amount, note = _parse_amount_and_note(body)
    return amount, note, spent_at


def format_money(amount: float, currency: str = "₽") -> str:
    sign = "-" if amount < 0 else ""
    return f"{sign}{abs(amount):,.2f} {currency}".replace(",", " ")


def format_date(value: date) -> str:
    return value.strftime("%d.%m.%Y")


def format_status(status) -> str:
    from bot.services.budget import BudgetStatus

    assert isinstance(status, BudgetStatus)
    currency = "₽"
    active = "активен" if status.budget.is_active else "неактивен"
    selected = " · текущий" if status.selected else ""
    lines = [
        f"🏷 {status.budget.name} ({active}{selected})",
        f"📅 До {format_date(status.budget.end_date)} · дней осталось: {status.days_left}",
        f"💰 Бюджет: {format_money(status.budget.total_amount, currency)}",
        f"🧾 Потрачено: {format_money(status.total_spent, currency)}",
        f"🛡 Остаток: {format_money(status.remaining, currency)}",
        "",
        f"📊 Лимит на день: {format_money(status.daily_limit, currency)}",
        f"🛒 Сегодня: {format_money(status.spent_today, currency)}",
        f"✅ Ещё можно сегодня: {format_money(status.remaining_today, currency)}",
    ]

    if status.is_expired:
        lines.append("\n⚠️ Период бюджета закончился. Задай новый: /budget")
    elif status.is_over_budget:
        lines.append("\n🚨 Бюджет уже превышен.")
    elif status.is_over_daily:
        lines.append("\n⚠️ Сегодняшний лимит превышен — завтра лимит пересчитается по остатку.")

    return "\n".join(lines)