# app/services/subscription_service.py
"""
Subscription service for tier-based access control.

Handles:
- Subscription creation and management
- Tier limit enforcement
- Usage tracking
- Feature gating

Usage:
    from app.services.subscription_service import subscription_service

    # Check if vendor can create an order
    can_create, message = subscription_service.can_create_order(db, vendor_id)

    # Increment order counter after successful order
    subscription_service.increment_order_count(db, vendor_id)
"""

import logging
from datetime import UTC, datetime, timedelta
from typing import Any

from sqlalchemy import func
from sqlalchemy.orm import Session

from models.database.product import Product
from models.database.subscription import (
    SubscriptionStatus,
    SubscriptionTier,
    TIER_LIMITS,
    TierCode,
    VendorSubscription,
)
from models.database.vendor import Vendor, VendorUser
from models.schema.subscription import (
    SubscriptionCreate,
    SubscriptionUpdate,
    SubscriptionUsage,
    TierInfo,
    TierLimits,
    UsageSummary,
)

logger = logging.getLogger(__name__)


class SubscriptionNotFoundException(Exception):
    """Raised when subscription not found."""

    pass


class TierLimitExceededException(Exception):
    """Raised when a tier limit is exceeded."""

    def __init__(self, message: str, limit_type: str, current: int, limit: int):
        super().__init__(message)
        self.limit_type = limit_type
        self.current = current
        self.limit = limit


class FeatureNotAvailableException(Exception):
    """Raised when a feature is not available in current tier."""

    def __init__(self, feature: str, current_tier: str, required_tier: str):
        message = f"Feature '{feature}' requires {required_tier} tier (current: {current_tier})"
        super().__init__(message)
        self.feature = feature
        self.current_tier = current_tier
        self.required_tier = required_tier


class SubscriptionService:
    """Service for subscription and tier limit operations."""

    # =========================================================================
    # Tier Information
    # =========================================================================

    def get_tier_info(self, tier_code: str, db: Session | None = None) -> TierInfo:
        """
        Get full tier information.

        Queries database if db session provided, otherwise falls back to TIER_LIMITS.
        """
        # Try database first if session provided
        if db is not None:
            db_tier = self.get_tier_by_code(db, tier_code)
            if db_tier:
                return TierInfo(
                    code=db_tier.code,
                    name=db_tier.name,
                    price_monthly_cents=db_tier.price_monthly_cents,
                    price_annual_cents=db_tier.price_annual_cents,
                    limits=TierLimits(
                        orders_per_month=db_tier.orders_per_month,
                        products_limit=db_tier.products_limit,
                        team_members=db_tier.team_members,
                        order_history_months=db_tier.order_history_months,
                    ),
                    features=db_tier.features or [],
                )

        # Fallback to hardcoded TIER_LIMITS
        return self._get_tier_from_legacy(tier_code)

    def _get_tier_from_legacy(self, tier_code: str) -> TierInfo:
        """Get tier info from hardcoded TIER_LIMITS (fallback)."""
        try:
            tier = TierCode(tier_code)
        except ValueError:
            tier = TierCode.ESSENTIAL

        limits = TIER_LIMITS[tier]
        return TierInfo(
            code=tier.value,
            name=limits["name"],
            price_monthly_cents=limits["price_monthly_cents"],
            price_annual_cents=limits.get("price_annual_cents"),
            limits=TierLimits(
                orders_per_month=limits.get("orders_per_month"),
                products_limit=limits.get("products_limit"),
                team_members=limits.get("team_members"),
                order_history_months=limits.get("order_history_months"),
            ),
            features=limits.get("features", []),
        )

    def get_all_tiers(self, db: Session | None = None) -> list[TierInfo]:
        """
        Get information for all tiers.

        Queries database if db session provided, otherwise falls back to TIER_LIMITS.
        """
        if db is not None:
            db_tiers = (
                db.query(SubscriptionTier)
                .filter(
                    SubscriptionTier.is_active == True,  # noqa: E712
                    SubscriptionTier.is_public == True,  # noqa: E712
                )
                .order_by(SubscriptionTier.display_order)
                .all()
            )
            if db_tiers:
                return [
                    TierInfo(
                        code=t.code,
                        name=t.name,
                        price_monthly_cents=t.price_monthly_cents,
                        price_annual_cents=t.price_annual_cents,
                        limits=TierLimits(
                            orders_per_month=t.orders_per_month,
                            products_limit=t.products_limit,
                            team_members=t.team_members,
                            order_history_months=t.order_history_months,
                        ),
                        features=t.features or [],
                    )
                    for t in db_tiers
                ]

        # Fallback to hardcoded
        return [
            self._get_tier_from_legacy(tier.value)
            for tier in TierCode
        ]

    def get_tier_by_code(self, db: Session, tier_code: str) -> SubscriptionTier | None:
        """Get subscription tier by code."""
        return (
            db.query(SubscriptionTier)
            .filter(SubscriptionTier.code == tier_code)
            .first()
        )

    def get_tier_id(self, db: Session, tier_code: str) -> int | None:
        """Get tier ID from tier code. Returns None if tier not found."""
        tier = self.get_tier_by_code(db, tier_code)
        return tier.id if tier else None

    # =========================================================================
    # Subscription CRUD
    # =========================================================================

    def get_subscription(
        self, db: Session, vendor_id: int
    ) -> VendorSubscription | None:
        """Get vendor subscription."""
        return (
            db.query(VendorSubscription)
            .filter(VendorSubscription.vendor_id == vendor_id)
            .first()
        )

    def get_subscription_or_raise(
        self, db: Session, vendor_id: int
    ) -> VendorSubscription:
        """Get vendor subscription or raise exception."""
        subscription = self.get_subscription(db, vendor_id)
        if not subscription:
            raise SubscriptionNotFoundException(
                f"No subscription found for vendor {vendor_id}"
            )
        return subscription

    def get_current_tier(
        self, db: Session, vendor_id: int
    ) -> TierCode | None:
        """Get vendor's current subscription tier code."""
        subscription = self.get_subscription(db, vendor_id)
        if subscription:
            try:
                return TierCode(subscription.tier)
            except ValueError:
                return None
        return None

    def get_or_create_subscription(
        self,
        db: Session,
        vendor_id: int,
        tier: str = TierCode.ESSENTIAL.value,
        trial_days: int = 14,
    ) -> VendorSubscription:
        """
        Get existing subscription or create a new trial subscription.

        Used when a vendor first accesses the system.
        """
        subscription = self.get_subscription(db, vendor_id)
        if subscription:
            return subscription

        # Create new trial subscription
        now = datetime.now(UTC)
        trial_end = now + timedelta(days=trial_days)

        # Lookup tier_id from tier code
        tier_id = self.get_tier_id(db, tier)

        subscription = VendorSubscription(
            vendor_id=vendor_id,
            tier=tier,
            tier_id=tier_id,
            status=SubscriptionStatus.TRIAL.value,
            period_start=now,
            period_end=trial_end,
            trial_ends_at=trial_end,
            is_annual=False,
        )

        db.add(subscription)
        db.flush()
        db.refresh(subscription)

        logger.info(
            f"Created trial subscription for vendor {vendor_id} "
            f"(tier={tier}, trial_ends={trial_end})"
        )

        return subscription

    def create_subscription(
        self,
        db: Session,
        vendor_id: int,
        data: SubscriptionCreate,
    ) -> VendorSubscription:
        """Create a subscription for a vendor."""
        # Check if subscription exists
        existing = self.get_subscription(db, vendor_id)
        if existing:
            raise ValueError("Vendor already has a subscription")

        now = datetime.now(UTC)

        # Calculate period end based on billing cycle
        if data.is_annual:
            period_end = now + timedelta(days=365)
        else:
            period_end = now + timedelta(days=30)

        # Handle trial
        trial_ends_at = None
        status = SubscriptionStatus.ACTIVE.value
        if data.trial_days > 0:
            trial_ends_at = now + timedelta(days=data.trial_days)
            status = SubscriptionStatus.TRIAL.value
            period_end = trial_ends_at

        # Lookup tier_id from tier code
        tier_id = self.get_tier_id(db, data.tier)

        subscription = VendorSubscription(
            vendor_id=vendor_id,
            tier=data.tier,
            tier_id=tier_id,
            status=status,
            period_start=now,
            period_end=period_end,
            trial_ends_at=trial_ends_at,
            is_annual=data.is_annual,
        )

        db.add(subscription)
        db.flush()
        db.refresh(subscription)

        logger.info(f"Created subscription for vendor {vendor_id}: {data.tier}")
        return subscription

    def update_subscription(
        self,
        db: Session,
        vendor_id: int,
        data: SubscriptionUpdate,
    ) -> VendorSubscription:
        """Update a vendor subscription."""
        subscription = self.get_subscription_or_raise(db, vendor_id)

        update_data = data.model_dump(exclude_unset=True)

        # If tier is being updated, also update tier_id
        if "tier" in update_data:
            tier_id = self.get_tier_id(db, update_data["tier"])
            update_data["tier_id"] = tier_id

        for key, value in update_data.items():
            setattr(subscription, key, value)

        subscription.updated_at = datetime.now(UTC)
        db.flush()
        db.refresh(subscription)

        logger.info(f"Updated subscription for vendor {vendor_id}")
        return subscription

    def upgrade_tier(
        self,
        db: Session,
        vendor_id: int,
        new_tier: str,
    ) -> VendorSubscription:
        """Upgrade vendor to a new tier."""
        subscription = self.get_subscription_or_raise(db, vendor_id)

        old_tier = subscription.tier
        subscription.tier = new_tier
        subscription.tier_id = self.get_tier_id(db, new_tier)
        subscription.updated_at = datetime.now(UTC)

        # If upgrading from trial, mark as active
        if subscription.status == SubscriptionStatus.TRIAL.value:
            subscription.status = SubscriptionStatus.ACTIVE.value

        db.flush()
        db.refresh(subscription)

        logger.info(f"Upgraded vendor {vendor_id} from {old_tier} to {new_tier}")
        return subscription

    def cancel_subscription(
        self,
        db: Session,
        vendor_id: int,
        reason: str | None = None,
    ) -> VendorSubscription:
        """Cancel a vendor subscription (access until period end)."""
        subscription = self.get_subscription_or_raise(db, vendor_id)

        subscription.status = SubscriptionStatus.CANCELLED.value
        subscription.cancelled_at = datetime.now(UTC)
        subscription.cancellation_reason = reason
        subscription.updated_at = datetime.now(UTC)

        db.flush()
        db.refresh(subscription)

        logger.info(f"Cancelled subscription for vendor {vendor_id}")
        return subscription

    # =========================================================================
    # Usage Tracking
    # =========================================================================

    def get_usage(self, db: Session, vendor_id: int) -> SubscriptionUsage:
        """Get current subscription usage statistics."""
        subscription = self.get_or_create_subscription(db, vendor_id)

        # Get actual counts
        products_count = (
            db.query(func.count(Product.id))
            .filter(Product.vendor_id == vendor_id)
            .scalar()
            or 0
        )

        team_count = (
            db.query(func.count(VendorUser.id))
            .filter(VendorUser.vendor_id == vendor_id, VendorUser.is_active == True)
            .scalar()
            or 0
        )

        # Calculate usage stats
        orders_limit = subscription.orders_limit
        products_limit = subscription.products_limit
        team_limit = subscription.team_members_limit

        def calc_remaining(current: int, limit: int | None) -> int | None:
            if limit is None:
                return None
            return max(0, limit - current)

        def calc_percent(current: int, limit: int | None) -> float | None:
            if limit is None or limit == 0:
                return None
            return min(100.0, (current / limit) * 100)

        return SubscriptionUsage(
            orders_used=subscription.orders_this_period,
            orders_limit=orders_limit,
            orders_remaining=calc_remaining(subscription.orders_this_period, orders_limit),
            orders_percent_used=calc_percent(subscription.orders_this_period, orders_limit),
            products_used=products_count,
            products_limit=products_limit,
            products_remaining=calc_remaining(products_count, products_limit),
            products_percent_used=calc_percent(products_count, products_limit),
            team_members_used=team_count,
            team_members_limit=team_limit,
            team_members_remaining=calc_remaining(team_count, team_limit),
            team_members_percent_used=calc_percent(team_count, team_limit),
        )

    def get_usage_summary(self, db: Session, vendor_id: int) -> UsageSummary:
        """Get usage summary for billing page display."""
        subscription = self.get_or_create_subscription(db, vendor_id)

        # Get actual counts
        products_count = (
            db.query(func.count(Product.id))
            .filter(Product.vendor_id == vendor_id)
            .scalar()
            or 0
        )

        team_count = (
            db.query(func.count(VendorUser.id))
            .filter(VendorUser.vendor_id == vendor_id, VendorUser.is_active == True)
            .scalar()
            or 0
        )

        # Get limits
        orders_limit = subscription.orders_limit
        products_limit = subscription.products_limit
        team_limit = subscription.team_members_limit

        def calc_remaining(current: int, limit: int | None) -> int | None:
            if limit is None:
                return None
            return max(0, limit - current)

        return UsageSummary(
            orders_this_period=subscription.orders_this_period,
            orders_limit=orders_limit,
            orders_remaining=calc_remaining(subscription.orders_this_period, orders_limit),
            products_count=products_count,
            products_limit=products_limit,
            products_remaining=calc_remaining(products_count, products_limit),
            team_count=team_count,
            team_limit=team_limit,
            team_remaining=calc_remaining(team_count, team_limit),
        )

    def increment_order_count(self, db: Session, vendor_id: int) -> None:
        """
        Increment the order counter for the current period.

        Call this after successfully creating/importing an order.
        """
        subscription = self.get_or_create_subscription(db, vendor_id)
        subscription.increment_order_count()
        db.flush()

    def reset_period_counters(self, db: Session, vendor_id: int) -> None:
        """Reset counters for a new billing period."""
        subscription = self.get_subscription_or_raise(db, vendor_id)
        subscription.reset_period_counters()
        db.flush()
        logger.info(f"Reset period counters for vendor {vendor_id}")

    # =========================================================================
    # Limit Checks
    # =========================================================================

    def can_create_order(
        self, db: Session, vendor_id: int
    ) -> tuple[bool, str | None]:
        """
        Check if vendor can create/import another order.

        Returns: (allowed, error_message)
        """
        subscription = self.get_or_create_subscription(db, vendor_id)
        return subscription.can_create_order()

    def check_order_limit(self, db: Session, vendor_id: int) -> None:
        """
        Check order limit and raise exception if exceeded.

        Use this in order creation flows.
        """
        can_create, message = self.can_create_order(db, vendor_id)
        if not can_create:
            subscription = self.get_subscription(db, vendor_id)
            raise TierLimitExceededException(
                message=message or "Order limit exceeded",
                limit_type="orders",
                current=subscription.orders_this_period if subscription else 0,
                limit=subscription.orders_limit if subscription else 0,
            )

    def can_add_product(
        self, db: Session, vendor_id: int
    ) -> tuple[bool, str | None]:
        """
        Check if vendor can add another product.

        Returns: (allowed, error_message)
        """
        subscription = self.get_or_create_subscription(db, vendor_id)

        products_count = (
            db.query(func.count(Product.id))
            .filter(Product.vendor_id == vendor_id)
            .scalar()
            or 0
        )

        return subscription.can_add_product(products_count)

    def check_product_limit(self, db: Session, vendor_id: int) -> None:
        """
        Check product limit and raise exception if exceeded.

        Use this in product creation flows.
        """
        can_add, message = self.can_add_product(db, vendor_id)
        if not can_add:
            subscription = self.get_subscription(db, vendor_id)
            products_count = (
                db.query(func.count(Product.id))
                .filter(Product.vendor_id == vendor_id)
                .scalar()
                or 0
            )
            raise TierLimitExceededException(
                message=message or "Product limit exceeded",
                limit_type="products",
                current=products_count,
                limit=subscription.products_limit if subscription else 0,
            )

    def can_add_team_member(
        self, db: Session, vendor_id: int
    ) -> tuple[bool, str | None]:
        """
        Check if vendor can add another team member.

        Returns: (allowed, error_message)
        """
        subscription = self.get_or_create_subscription(db, vendor_id)

        team_count = (
            db.query(func.count(VendorUser.id))
            .filter(VendorUser.vendor_id == vendor_id, VendorUser.is_active == True)
            .scalar()
            or 0
        )

        return subscription.can_add_team_member(team_count)

    def check_team_limit(self, db: Session, vendor_id: int) -> None:
        """
        Check team member limit and raise exception if exceeded.

        Use this in team member invitation flows.
        """
        can_add, message = self.can_add_team_member(db, vendor_id)
        if not can_add:
            subscription = self.get_subscription(db, vendor_id)
            team_count = (
                db.query(func.count(VendorUser.id))
                .filter(VendorUser.vendor_id == vendor_id, VendorUser.is_active == True)
                .scalar()
                or 0
            )
            raise TierLimitExceededException(
                message=message or "Team member limit exceeded",
                limit_type="team_members",
                current=team_count,
                limit=subscription.team_members_limit if subscription else 0,
            )

    # =========================================================================
    # Feature Gating
    # =========================================================================

    def has_feature(self, db: Session, vendor_id: int, feature: str) -> bool:
        """Check if vendor has access to a feature."""
        subscription = self.get_or_create_subscription(db, vendor_id)
        return subscription.has_feature(feature)

    def check_feature(self, db: Session, vendor_id: int, feature: str) -> None:
        """
        Check feature access and raise exception if not available.

        Use this to gate premium features.
        """
        if not self.has_feature(db, vendor_id, feature):
            subscription = self.get_or_create_subscription(db, vendor_id)

            # Find which tier has this feature
            required_tier = None
            for tier_code, limits in TIER_LIMITS.items():
                if feature in limits.get("features", []):
                    required_tier = limits["name"]
                    break

            raise FeatureNotAvailableException(
                feature=feature,
                current_tier=subscription.tier,
                required_tier=required_tier or "higher",
            )

    def get_feature_tier(self, feature: str) -> str | None:
        """Get the minimum tier required for a feature."""
        for tier_code in [
            TierCode.ESSENTIAL,
            TierCode.PROFESSIONAL,
            TierCode.BUSINESS,
            TierCode.ENTERPRISE,
        ]:
            if feature in TIER_LIMITS[tier_code].get("features", []):
                return tier_code.value
        return None


# Singleton instance
subscription_service = SubscriptionService()