"""FastAPI dependencies: DB session, Miniapp auth (initData/allowlist), date validation."""

import logging
import re
from typing import Annotated, Generator

from fastapi import Depends, Header, HTTPException, Query, Request
from sqlalchemy.orm import Session

import duty_teller.config as config
from duty_teller.api.telegram_auth import validate_init_data_with_reason
from duty_teller.db.repository import get_duties, get_user_by_telegram_id
from duty_teller.db.schemas import DUTY_EVENT_TYPES, DutyWithUser
from duty_teller.db.session import session_scope
from duty_teller.i18n import t
from duty_teller.i18n.lang import normalize_lang
from duty_teller.utils.dates import DateRangeValidationError, validate_date_range

log = logging.getLogger(__name__)

# Extract primary language code from first Accept-Language tag (e.g. "ru-RU" -> "ru").
_ACCEPT_LANG_CODE_RE = re.compile(r"^([a-zA-Z]{2,3})(?:-|;|,|\s|$)")


def _parse_first_language_code(header: str | None) -> str | None:
    """Extract the first language code from Accept-Language header.

    Args:
        header: Raw Accept-Language value (e.g. "ru-RU,ru;q=0.9,en;q=0.8").

    Returns:
        Two- or three-letter code (e.g. 'ru', 'en') or None if missing/invalid.
    """
    if not header or not header.strip():
        return None
    first = header.strip().split(",")[0].strip()
    m = _ACCEPT_LANG_CODE_RE.match(first)
    return m.group(1).lower() if m else None


def _lang_from_accept_language(header: str | None) -> str:
    """Normalize Accept-Language header to 'ru' or 'en'; fallback to config.DEFAULT_LANGUAGE.

    Args:
        header: Raw Accept-Language header value (e.g. "ru-RU,ru;q=0.9,en;q=0.8").

    Returns:
        'ru' or 'en'.
    """
    code = _parse_first_language_code(header)
    return normalize_lang(code if code is not None else config.DEFAULT_LANGUAGE)


def _auth_error_detail(auth_reason: str, lang: str) -> str:
    """Return translated auth error message."""
    if auth_reason == "hash_mismatch":
        return t(lang, "api.auth_bad_signature")
    return t(lang, "api.auth_invalid")


def _validate_duty_dates(from_date: str, to_date: str, lang: str) -> None:
    """Validate date range; raise HTTPException with translated detail."""
    try:
        validate_date_range(from_date, to_date)
    except DateRangeValidationError as e:
        key = "dates.bad_format" if e.kind == "bad_format" else "dates.from_after_to"
        raise HTTPException(status_code=400, detail=t(lang, key)) from e
    except ValueError as e:
        # Backward compatibility if something else raises ValueError.
        raise HTTPException(status_code=400, detail=t(lang, "dates.bad_format")) from e


def get_validated_dates(
    request: Request,
    from_date: str = Query(..., description="ISO date YYYY-MM-DD", alias="from"),
    to_date: str = Query(..., description="ISO date YYYY-MM-DD", alias="to"),
) -> tuple[str, str]:
    """Validate from/to date query params; use Accept-Language for error messages.

    Args:
        request: FastAPI request (for Accept-Language).
        from_date: Start date YYYY-MM-DD.
        to_date: End date YYYY-MM-DD.

    Returns:
        (from_date, to_date) as strings.

    Raises:
        HTTPException: 400 if format invalid or from_date > to_date.
    """
    lang = _lang_from_accept_language(request.headers.get("Accept-Language"))
    _validate_duty_dates(from_date, to_date, lang)
    return (from_date, to_date)


def get_db_session() -> Generator[Session, None, None]:
    """Yield a DB session for the request; closed automatically by FastAPI."""
    with session_scope(config.DATABASE_URL) as session:
        yield session


def require_miniapp_username(
    request: Request,
    x_telegram_init_data: Annotated[
        str | None, Header(alias="X-Telegram-Init-Data")
    ] = None,
    session: Session = Depends(get_db_session),
) -> str:
    """FastAPI dependency: require valid Miniapp auth; return username/identifier.

    Raises:
        HTTPException: 403 if initData missing/invalid or user not in allowlist.
    """
    return get_authenticated_username(request, x_telegram_init_data, session)


def _is_private_client(client_host: str | None) -> bool:
    """Return True if client_host is localhost or RFC 1918 private IPv4.

    Used to allow /api/duties without initData when opened from local/private
    network (e.g. dev). IPv4 only; IPv6 only 127/::1 checked.

    Args:
        client_host: Client IP or hostname from request.

    Returns:
        True if loopback or 10.x, 172.16–31.x, 192.168.x.x.
    """
    if not client_host:
        return False
    if client_host in ("127.0.0.1", "::1"):
        return True
    # RFC 1918 private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
    parts = client_host.split(".")
    if len(parts) == 4:
        try:
            a, b, c, d = (int(x) for x in parts)
            if (a == 10) or (a == 172 and 16 <= b <= 31) or (a == 192 and b == 168):
                return True
        except (ValueError, IndexError):
            pass
    return False


def get_authenticated_username(
    request: Request,
    x_telegram_init_data: str | None,
    session: Session,
) -> str:
    """Return identifier for miniapp auth (username or full_name or id:...); empty if skip-auth.

    Args:
        request: FastAPI request (client host for private-IP bypass).
        x_telegram_init_data: Raw X-Telegram-Init-Data header value.
        session: DB session (for phone allowlist lookup).

    Returns:
        Username, full_name, or "id:<telegram_id>"; empty string if MINI_APP_SKIP_AUTH
        or private IP and no initData.

    Raises:
        HTTPException: 403 if initData missing/invalid or user not in allowlist.
    """
    if config.MINI_APP_SKIP_AUTH:
        log.warning("allowing without any auth check (MINI_APP_SKIP_AUTH is set)")
        return ""
    init_data = (x_telegram_init_data or "").strip()
    if not init_data:
        client_host = request.client.host if request.client else None
        if _is_private_client(client_host):
            return ""
        log.warning("no X-Telegram-Init-Data header (client=%s)", client_host)
        lang = _lang_from_accept_language(request.headers.get("Accept-Language"))
        raise HTTPException(status_code=403, detail=t(lang, "api.open_from_telegram"))
    max_age = config.INIT_DATA_MAX_AGE_SECONDS or None
    telegram_user_id, username, auth_reason, lang = validate_init_data_with_reason(
        init_data, config.BOT_TOKEN, max_age_seconds=max_age
    )
    if auth_reason != "ok":
        log.warning("initData validation failed: %s", auth_reason)
        raise HTTPException(
            status_code=403, detail=_auth_error_detail(auth_reason, lang)
        )
    if username and config.can_access_miniapp(username):
        return username
    failed_phone: str | None = None
    if telegram_user_id is not None:
        user = get_user_by_telegram_id(session, telegram_user_id)
        if user and user.phone and config.can_access_miniapp_by_phone(user.phone):
            return username or (user.full_name or "") or f"id:{telegram_user_id}"
        if user and user.phone:
            failed_phone = config.normalize_phone(user.phone)
    log.warning(
        "username/phone not in allowlist (username=%s, telegram_id=%s, phone=%s)",
        username,
        telegram_user_id,
        failed_phone if failed_phone else "—",
    )
    raise HTTPException(status_code=403, detail=t(lang, "api.access_denied"))


def fetch_duties_response(
    session: Session, from_date: str, to_date: str
) -> list[DutyWithUser]:
    """Load duties in range and return as DutyWithUser list for API response.

    Args:
        session: DB session.
        from_date: Start date YYYY-MM-DD.
        to_date: End date YYYY-MM-DD.

    Returns:
        List of DutyWithUser (id, user_id, start_at, end_at, full_name, event_type).
    """
    rows = get_duties(session, from_date=from_date, to_date=to_date)
    return [
        DutyWithUser(
            id=duty.id,
            user_id=duty.user_id,
            start_at=duty.start_at,
            end_at=duty.end_at,
            full_name=full_name,
            event_type=(
                duty.event_type if duty.event_type in DUTY_EVENT_TYPES else "duty"
            ),
        )
        for duty, full_name in rows
    ]