"""
Referral rewards (3C.2).

Goals:
- Deterministic, abuse-resistant rewards
- No manual state tracking per referral; we compute from authoritative DB state
- Idempotent updates (can be run via scheduler and on-demand)

Current reward:
- For every N qualified referrals, grant +M bonus watchlist domain slots.

Qualified referral definition:
- referred user has `users.referred_by_user_id = referrer.id`
- referred user is_active AND is_verified
- referred user has an active subscription that is NOT Scout (Trader/Tycoon), and is currently active
"""

from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime, timedelta
from typing import Optional

from sqlalchemy import and_, func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession

from app.config import get_settings
from app.models.subscription import Subscription, SubscriptionStatus, SubscriptionTier
from app.models.telemetry import TelemetryEvent
from app.models.user import User


QUALIFIED_REFERRAL_BATCH_SIZE = 3
BONUS_DOMAINS_PER_BATCH = 5
settings = get_settings()


def compute_bonus_domains(qualified_referrals: int) -> int:
    if qualified_referrals <= 0:
        return 0
    batches = qualified_referrals // QUALIFIED_REFERRAL_BATCH_SIZE
    return int(batches * BONUS_DOMAINS_PER_BATCH)


def compute_badge(qualified_referrals: int) -> Optional[str]:
    if qualified_referrals >= 10:
        return "elite_referrer"
    if qualified_referrals >= 3:
        return "verified_referrer"
    return None


@dataclass(frozen=True)
class ReferralRewardSnapshot:
    referrer_user_id: int
    referred_users_total: int
    qualified_referrals_total: int
    cooldown_days: int
    disqualified_cooldown_total: int
    disqualified_missing_ip_total: int
    disqualified_shared_ip_total: int
    disqualified_duplicate_ip_total: int
    bonus_domains: int
    badge: Optional[str]
    computed_at: datetime


async def get_referral_reward_snapshot(db: AsyncSession, referrer_user_id: int) -> ReferralRewardSnapshot:
    # Total referred users (all-time)
    referred_users_total = int(
        (
            await db.execute(
                select(func.count(User.id)).where(User.referred_by_user_id == referrer_user_id)
            )
        ).scalar()
        or 0
    )

    now = datetime.utcnow()
    cooldown_days = max(0, int(getattr(settings, "referral_rewards_cooldown_days", 7) or 0))
    cooldown_cutoff = now - timedelta(days=cooldown_days) if cooldown_days else None

    # Referrer IP hashes (window) for self-ref/shared-ip checks
    ip_window_days = max(1, int(getattr(settings, "referral_rewards_ip_window_days", 30) or 30))
    ip_window_start = now - timedelta(days=ip_window_days)
    referrer_ip_rows = (
        await db.execute(
            select(TelemetryEvent.ip_hash)
            .where(
                and_(
                    TelemetryEvent.user_id == referrer_user_id,
                    TelemetryEvent.ip_hash.isnot(None),
                    TelemetryEvent.created_at >= ip_window_start,
                    TelemetryEvent.created_at <= now,
                )
            )
            .distinct()
        )
    ).all()
    referrer_ip_hashes = {str(r[0]) for r in referrer_ip_rows if r and r[0]}

    # Referred user's registration IP hash (from telemetry) as subquery
    reg_ip_subq = (
        select(
            TelemetryEvent.user_id.label("user_id"),
            func.max(TelemetryEvent.ip_hash).label("signup_ip_hash"),
        )
        .where(
            and_(
                TelemetryEvent.event_name == "user_registered",
                TelemetryEvent.user_id.isnot(None),
            )
        )
        .group_by(TelemetryEvent.user_id)
        .subquery()
    )

    # Candidate referred users (paid + verified + active)
    rows = (
        await db.execute(
            select(
                User.id,
                User.created_at,
                Subscription.started_at,
                reg_ip_subq.c.signup_ip_hash,
            )
            .select_from(User)
            .join(Subscription, Subscription.user_id == User.id)
            .outerjoin(reg_ip_subq, reg_ip_subq.c.user_id == User.id)
            .where(
                and_(
                    User.referred_by_user_id == referrer_user_id,
                    User.is_active == True,
                    User.is_verified == True,
                    Subscription.tier.in_([SubscriptionTier.TRADER, SubscriptionTier.TYCOON]),
                    Subscription.status.in_([SubscriptionStatus.ACTIVE, SubscriptionStatus.PAST_DUE]),
                    or_(Subscription.expires_at.is_(None), Subscription.expires_at >= now),
                )
            )
        )
    ).all()

    require_ip = bool(getattr(settings, "referral_rewards_require_ip_hash", True))

    disqualified_cooldown_total = 0
    disqualified_missing_ip_total = 0
    disqualified_shared_ip_total = 0
    disqualified_duplicate_ip_total = 0

    qualified_ip_hashes: set[str] = set()
    qualified_referrals_total = 0

    for _user_id, user_created_at, sub_started_at, signup_ip_hash in rows:
        # Cooldown: user account age AND subscription age must pass cooldown
        if cooldown_cutoff is not None:
            if (user_created_at and user_created_at > cooldown_cutoff) or (
                sub_started_at and sub_started_at > cooldown_cutoff
            ):
                disqualified_cooldown_total += 1
                continue

        ip_hash = str(signup_ip_hash) if signup_ip_hash else None
        if require_ip and not ip_hash:
            disqualified_missing_ip_total += 1
            continue

        if ip_hash and referrer_ip_hashes and ip_hash in referrer_ip_hashes:
            disqualified_shared_ip_total += 1
            continue

        if ip_hash and ip_hash in qualified_ip_hashes:
            disqualified_duplicate_ip_total += 1
            continue

        if ip_hash:
            qualified_ip_hashes.add(ip_hash)
        qualified_referrals_total += 1

    bonus_domains = compute_bonus_domains(qualified_referrals_total)
    badge = compute_badge(qualified_referrals_total)
    return ReferralRewardSnapshot(
        referrer_user_id=referrer_user_id,
        referred_users_total=referred_users_total,
        qualified_referrals_total=qualified_referrals_total,
        cooldown_days=cooldown_days,
        disqualified_cooldown_total=disqualified_cooldown_total,
        disqualified_missing_ip_total=disqualified_missing_ip_total,
        disqualified_shared_ip_total=disqualified_shared_ip_total,
        disqualified_duplicate_ip_total=disqualified_duplicate_ip_total,
        bonus_domains=bonus_domains,
        badge=badge,
        computed_at=datetime.utcnow(),
    )


async def apply_referral_rewards_for_user(db: AsyncSession, referrer_user_id: int) -> ReferralRewardSnapshot:
    """
    Apply rewards to the referrer's subscription row, based on current qualified referrals.

    This is idempotent: it sets the bonus to the computed value.
    """
    snapshot = await get_referral_reward_snapshot(db, referrer_user_id)

    sub_res = await db.execute(select(Subscription).where(Subscription.user_id == referrer_user_id))
    sub = sub_res.scalar_one_or_none()
    if not sub:
        # Create default subscription so bonus can be stored
        sub = Subscription(user_id=referrer_user_id, tier=SubscriptionTier.SCOUT, max_domains=5)
        db.add(sub)
        await db.flush()

    desired = int(snapshot.bonus_domains)
    current = int(getattr(sub, "referral_bonus_domains", 0) or 0)
    if current != desired:
        sub.referral_bonus_domains = desired
        await db.flush()

    return snapshot


async def apply_referral_rewards_all(db: AsyncSession) -> dict[str, int]:
    """
    Apply rewards for all users that have an invite_code.
    """
    res = await db.execute(select(User.id).where(User.invite_code.isnot(None)))
    user_ids = [int(r[0]) for r in res.all()]

    updated = 0
    processed = 0
    for user_id in user_ids:
        processed += 1
        snap = await get_referral_reward_snapshot(db, user_id)
        sub_res = await db.execute(select(Subscription).where(Subscription.user_id == user_id))
        sub = sub_res.scalar_one_or_none()
        if not sub:
            sub = Subscription(user_id=user_id, tier=SubscriptionTier.SCOUT, max_domains=5)
            db.add(sub)
            await db.flush()
        desired = int(snap.bonus_domains)
        current = int(getattr(sub, "referral_bonus_domains", 0) or 0)
        if current != desired:
            sub.referral_bonus_domains = desired
            updated += 1
    return {"processed": processed, "updated": updated}