from fastapi import APIRouter, Depends, status
from pydantic import BaseModel
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.api.errors import http_error
from app.api.timeutil import isoformat_utc
from app.auth.dependencies import get_current_user
from app.auth.security import MIN_PASSWORD_LENGTH, create_access_token, hash_password, verify_password
from app.db.models import Round, RoundParticipant, User
from app.db.session import get_session
from app.wallet.balance import compute_pending_balance

router = APIRouter(prefix="/users", tags=["users"])


class MeResponse(BaseModel):
    id: int
    username: str
    address: str
    balance_sats: int
    pending_balance_sats: int
    has_pending: bool
    created_at: str


@router.get("/me", response_model=MeResponse)
async def me(
    user: User = Depends(get_current_user),
    session: AsyncSession = Depends(get_session),
) -> MeResponse:
    pending_balance_sats, has_pending = await compute_pending_balance(session, user)
    return MeResponse(
        id=user.id,
        username=user.username,
        address=user.address,
        balance_sats=user.cached_balance_sats,
        pending_balance_sats=pending_balance_sats,
        has_pending=has_pending,
        created_at=isoformat_utc(user.created_at),
    )


class ChangePasswordRequest(BaseModel):
    current_password: str
    new_password: str


class ChangePasswordResponse(BaseModel):
    access_token: str


@router.post("/me/change-password", response_model=ChangePasswordResponse)
async def change_password(
    body: ChangePasswordRequest,
    user: User = Depends(get_current_user),
    session: AsyncSession = Depends(get_session),
) -> ChangePasswordResponse:
    """Self-service password change — requires the current password, unlike the
    admin-only /admin/users/{id}/reset-password (which is for a user who's
    actually locked out and can't provide it)."""
    if not verify_password(body.current_password, user.password_hash):
        raise http_error(
            status.HTTP_401_UNAUTHORIZED, "current_password_incorrect", "current password is incorrect"
        )
    if len(body.new_password) < MIN_PASSWORD_LENGTH:
        raise http_error(
            status.HTTP_400_BAD_REQUEST,
            "password_too_short",
            f"new password must be at least {MIN_PASSWORD_LENGTH} characters",
            minimum=MIN_PASSWORD_LENGTH,
        )

    user.password_hash = hash_password(body.new_password)
    # B-34: bumping token_version invalidates every token issued before this
    # point — including this very request's own bearer token, and any an
    # attacker who knew the old password might be holding. A fresh token is
    # handed back so *this* session keeps working without forcing a re-login;
    # every other open session (this user's other devices, or an attacker's)
    # gets "session_expired" on its next request.
    user.token_version += 1
    await session.commit()
    return ChangePasswordResponse(access_token=create_access_token(user.id, user.token_version))


class LastRoundResultResponse(BaseModel):
    round_id: int | None = None
    won: bool = False
    amount_sats: int | None = None


@router.get("/me/last-round-result", response_model=LastRoundResultResponse)
async def last_round_result(
    user: User = Depends(get_current_user),
    session: AsyncSession = Depends(get_session),
) -> LastRoundResultResponse:
    """The most recent *closed* round this user participated in, with its outcome.

    Deliberately independent of /rounds/current: that endpoint only exposes
    winner_user_id while the round is "paying_out", and drops it entirely once
    the round flips to "closed" (see rounds/service.get_active_round). A client
    that misses that narrow window (backgrounded tab, missed poll, page loaded
    late) would otherwise never learn the outcome of a round it bet in. This
    endpoint reads the durable DB record instead, so the frontend can always
    catch up regardless of polling timing."""
    row = await session.execute(
        select(Round)
        .join(RoundParticipant, RoundParticipant.round_id == Round.id)
        .where(RoundParticipant.user_id == user.id, Round.status == "closed")
        .order_by(Round.id.desc())
        .limit(1)
    )
    round_ = row.scalar_one_or_none()
    if round_ is None:
        return LastRoundResultResponse()

    won = round_.winner_user_id == user.id
    return LastRoundResultResponse(
        round_id=round_.id,
        won=won,
        amount_sats=round_.winner_amount_sats if won else None,
    )