"""Server-authoritative login session activity for the admin account list."""

from __future__ import annotations

import uuid
from dataclasses import dataclass
from datetime import datetime, timedelta, timezone
from typing import Any, Iterable

from sqlalchemy import select, update
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import settings
from app.models.user_login_session import UserLoginSession


@dataclass(frozen=True)
class UserLoginSummary:
    status: str = "OFFLINE"
    last_login_at: datetime | None = None
    last_seen_at: datetime | None = None
    client_type: str | None = None
    active_session_count: int = 0


def _now() -> datetime:
    return datetime.now(timezone.utc)


def _as_utc(value: datetime) -> datetime:
    return value.replace(tzinfo=timezone.utc) if value.tzinfo is None else value.astimezone(timezone.utc)


def _text_header(headers: Any, name: str, limit: int) -> str | None:
    value = (headers.get(name) or "").strip()
    return value[:limit] or None


def session_id_from_payload(payload: dict[str, Any]) -> uuid.UUID:
    raw_session_id = payload.get("sid")
    try:
        return uuid.UUID(str(raw_session_id))
    except (TypeError, ValueError):
        # Tokens issued before session tracking are mapped to a deterministic
        # legacy session without persisting the token or a token-derived value.
        legacy_key = ":".join(
            [
                str(payload.get("sub") or ""),
                str(payload.get("orig_iat") or payload.get("iat") or ""),
                str(payload.get("client_type") or "web"),
            ]
        )
        return uuid.uuid5(uuid.NAMESPACE_URL, f"ctms:legacy-session:{legacy_key}")


def session_client_type(payload: dict[str, Any], headers: Any) -> str:
    from_payload = (payload.get("client_type") or "").strip().lower()
    from_header = (headers.get("x-ctms-client-type") or "").strip().lower()
    return "desktop" if "desktop" in {from_payload, from_header} else "web"


async def create_login_session(
    db: AsyncSession,
    *,
    session_id: uuid.UUID,
    user_id: uuid.UUID,
    request: Any,
    login_at: datetime | None = None,
) -> UserLoginSession:
    occurred_at = login_at or _now()
    session = UserLoginSession(
        id=session_id,
        user_id=user_id,
        client_type=session_client_type({}, request.headers),
        client_platform=_text_header(request.headers, "x-ctms-client-platform", 32),
        client_version=_text_header(request.headers, "x-ctms-client-version", 64),
        client_source=_text_header(request.headers, "x-ctms-client-source", 32),
        login_at=occurred_at,
        last_seen_at=occurred_at,
    )
    db.add(session)
    await db.commit()
    await db.refresh(session)
    return session


async def touch_login_session(
    db: AsyncSession,
    *,
    user_id: uuid.UUID,
    payload: dict[str, Any],
    request: Any,
) -> UserLoginSession | None:
    session_id = session_id_from_payload(payload)
    session = await db.get(UserLoginSession, session_id)
    now = _now()
    if session is None:
        session = UserLoginSession(
            id=session_id,
            user_id=user_id,
            client_type=session_client_type(payload, request.headers),
            client_platform=_text_header(request.headers, "x-ctms-client-platform", 32),
            client_version=_text_header(request.headers, "x-ctms-client-version", 64),
            client_source=_text_header(request.headers, "x-ctms-client-source", 32),
            login_at=now,
            last_seen_at=now,
        )
        db.add(session)
    elif session.user_id != user_id or session.ended_at is not None:
        return None
    else:
        session.last_seen_at = now
        session.client_platform = _text_header(request.headers, "x-ctms-client-platform", 32) or session.client_platform
        session.client_version = _text_header(request.headers, "x-ctms-client-version", 64) or session.client_version
    await db.commit()
    await db.refresh(session)
    return session


async def end_login_session(
    db: AsyncSession,
    *,
    user_id: uuid.UUID,
    payload: dict[str, Any],
    reason: str = "logout",
) -> bool:
    session_id = session_id_from_payload(payload)
    result = await db.execute(
        update(UserLoginSession)
        .where(
            UserLoginSession.id == session_id,
            UserLoginSession.user_id == user_id,
            UserLoginSession.ended_at.is_(None),
        )
        .values(ended_at=_now(), end_reason=reason, last_seen_at=_now())
    )
    await db.commit()
    return bool(result.rowcount)


async def get_login_summaries(
    db: AsyncSession,
    user_ids: Iterable[uuid.UUID],
) -> dict[uuid.UUID, UserLoginSummary]:
    ids = list(user_ids)
    if not ids:
        return {}
    rows = (
        await db.execute(
            select(UserLoginSession)
            .where(UserLoginSession.user_id.in_(ids))
            .order_by(UserLoginSession.user_id, UserLoginSession.login_at.desc())
        )
    ).scalars().all()
    cutoff = _now() - timedelta(seconds=settings.USER_SESSION_ONLINE_SECONDS)
    summaries: dict[uuid.UUID, UserLoginSummary] = {}
    mutable: dict[uuid.UUID, dict[str, Any]] = {}
    for row in rows:
        current = mutable.setdefault(
            row.user_id,
            {
                "last_login_at": row.login_at,
                "last_seen_at": row.last_seen_at,
                "client_type": row.client_type,
                "active_session_count": 0,
            },
        )
        row_last_seen_at = _as_utc(row.last_seen_at)
        if row_last_seen_at and (
            current["last_seen_at"] is None or row_last_seen_at > _as_utc(current["last_seen_at"])
        ):
            current["last_seen_at"] = row_last_seen_at
        if row.ended_at is None and row_last_seen_at >= cutoff:
            current["active_session_count"] += 1
    for user_id, item in mutable.items():
        summaries[user_id] = UserLoginSummary(
            status="ONLINE" if item["active_session_count"] else "OFFLINE",
            last_login_at=item["last_login_at"],
            last_seen_at=item["last_seen_at"],
            client_type=item["client_type"],
            active_session_count=item["active_session_count"],
        )
    return summaries


async def list_login_activities(
    db: AsyncSession,
    *,
    user_id: uuid.UUID,
    limit: int,
) -> list[UserLoginSession]:
    result = await db.execute(
        select(UserLoginSession)
        .where(UserLoginSession.user_id == user_id)
        .order_by(UserLoginSession.login_at.desc())
        .limit(limit)
    )
    return list(result.scalars().all())