# app/modules/analytics/services/stats_service.py
"""
Statistics service for generating system analytics and metrics.

This is the canonical location for the stats service.

This module provides:
- System-wide statistics (admin)
- Vendor-specific statistics
- Marketplace analytics
- Performance metrics
"""

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

from sqlalchemy import func
from sqlalchemy.orm import Session

from app.exceptions import AdminOperationException, VendorNotFoundException
from app.modules.customers.models.customer import Customer
from app.modules.inventory.models import Inventory
from models.database.marketplace_import_job import MarketplaceImportJob
from models.database.marketplace_product import MarketplaceProduct
from app.modules.orders.models import Order
from models.database.product import Product
from models.database.user import User
from models.database.vendor import Vendor

logger = logging.getLogger(__name__)


class StatsService:
    """Service for statistics operations."""

    # ========================================================================
    # VENDOR-SPECIFIC STATISTICS
    # ========================================================================

    def get_vendor_stats(self, db: Session, vendor_id: int) -> dict[str, Any]:
        """
        Get statistics for a specific vendor.

        Args:
            db: Database session
            vendor_id: Vendor ID

        Returns:
            Dictionary with vendor statistics

        Raises:
            VendorNotFoundException: If vendor doesn't exist
            AdminOperationException: If database query fails
        """
        # Verify vendor exists
        vendor = db.query(Vendor).filter(Vendor.id == vendor_id).first()
        if not vendor:
            raise VendorNotFoundException(str(vendor_id), identifier_type="id")

        try:
            # Catalog statistics
            total_catalog_products = (
                db.query(Product)
                .filter(Product.vendor_id == vendor_id, Product.is_active == True)
                .count()
            )

            featured_products = (
                db.query(Product)
                .filter(
                    Product.vendor_id == vendor_id,
                    Product.is_featured == True,
                    Product.is_active == True,
                )
                .count()
            )

            # Staging statistics
            # TODO: This is fragile - MarketplaceProduct uses vendor_name (string) not vendor_id
            # Should add vendor_id foreign key to MarketplaceProduct for robust querying
            # For now, matching by vendor name which could fail if names don't match exactly
            staging_products = (
                db.query(MarketplaceProduct)
                .filter(MarketplaceProduct.vendor_name == vendor.name)
                .count()
            )

            # Inventory statistics
            total_inventory = (
                db.query(func.sum(Inventory.quantity))
                .filter(Inventory.vendor_id == vendor_id)
                .scalar()
                or 0
            )

            reserved_inventory = (
                db.query(func.sum(Inventory.reserved_quantity))
                .filter(Inventory.vendor_id == vendor_id)
                .scalar()
                or 0
            )

            inventory_locations = (
                db.query(func.count(func.distinct(Inventory.location)))
                .filter(Inventory.vendor_id == vendor_id)
                .scalar()
                or 0
            )

            # Import statistics
            total_imports = (
                db.query(MarketplaceImportJob)
                .filter(MarketplaceImportJob.vendor_id == vendor_id)
                .count()
            )

            successful_imports = (
                db.query(MarketplaceImportJob)
                .filter(
                    MarketplaceImportJob.vendor_id == vendor_id,
                    MarketplaceImportJob.status == "completed",
                )
                .count()
            )

            # Orders
            total_orders = db.query(Order).filter(Order.vendor_id == vendor_id).count()

            # Customers
            total_customers = (
                db.query(Customer).filter(Customer.vendor_id == vendor_id).count()
            )

            # Return flat structure compatible with VendorDashboardStatsResponse schema
            # The endpoint will restructure this into nested format
            return {
                # Product stats
                "total_products": total_catalog_products,
                "active_products": total_catalog_products,
                "featured_products": featured_products,
                # Order stats (TODO: implement when Order model has status field)
                "total_orders": total_orders,
                "pending_orders": 0,  # TODO: filter by status
                "completed_orders": 0,  # TODO: filter by status
                # Customer stats
                "total_customers": total_customers,
                "active_customers": 0,  # TODO: implement active customer logic
                # Revenue stats (TODO: implement when Order model has amount field)
                "total_revenue": 0,
                "revenue_this_month": 0,
                # Import stats
                "total_imports": total_imports,
                "successful_imports": successful_imports,
                "import_success_rate": (
                    (successful_imports / total_imports * 100)
                    if total_imports > 0
                    else 0
                ),
                # Staging stats
                "imported_products": staging_products,
                # Inventory stats
                "total_inventory_quantity": int(total_inventory),
                "reserved_inventory_quantity": int(reserved_inventory),
                "available_inventory_quantity": int(
                    total_inventory - reserved_inventory
                ),
                "inventory_locations_count": inventory_locations,
            }

        except VendorNotFoundException:
            raise
        except Exception as e:
            logger.error(
                f"Failed to retrieve vendor statistics for vendor {vendor_id}: {str(e)}"
            )
            raise AdminOperationException(
                operation="get_vendor_stats",
                reason=f"Database query failed: {str(e)}",
                target_type="vendor",
                target_id=str(vendor_id),
            )

    def get_vendor_analytics(
        self, db: Session, vendor_id: int, period: str = "30d"
    ) -> dict[str, Any]:
        """
        Get a specific vendor analytics for a time period.

        Args:
            db: Database session
            vendor_id: Vendor ID
            period: Time period (7d, 30d, 90d, 1y)

        Returns:
            Analytics data

        Raises:
            VendorNotFoundException: If vendor doesn't exist
            AdminOperationException: If database query fails
        """
        # Verify vendor exists
        vendor = db.query(Vendor).filter(Vendor.id == vendor_id).first()
        if not vendor:
            raise VendorNotFoundException(str(vendor_id), identifier_type="id")

        try:
            # Parse period
            days = self._parse_period(period)
            start_date = datetime.utcnow() - timedelta(days=days)

            # Import activity
            recent_imports = (
                db.query(MarketplaceImportJob)
                .filter(
                    MarketplaceImportJob.vendor_id == vendor_id,
                    MarketplaceImportJob.created_at >= start_date,
                )
                .count()
            )

            # Products added to catalog
            products_added = (
                db.query(Product)
                .filter(
                    Product.vendor_id == vendor_id, Product.created_at >= start_date
                )
                .count()
            )

            # Inventory changes
            inventory_entries = (
                db.query(Inventory).filter(Inventory.vendor_id == vendor_id).count()
            )

            return {
                "period": period,
                "start_date": start_date.isoformat(),
                "imports": {
                    "count": recent_imports,
                },
                "catalog": {
                    "products_added": products_added,
                },
                "inventory": {
                    "total_locations": inventory_entries,
                },
            }

        except VendorNotFoundException:
            raise
        except Exception as e:
            logger.error(
                f"Failed to retrieve vendor analytics for vendor {vendor_id}: {str(e)}"
            )
            raise AdminOperationException(
                operation="get_vendor_analytics",
                reason=f"Database query failed: {str(e)}",
                target_type="vendor",
                target_id=str(vendor_id),
            )

    def get_vendor_statistics(self, db: Session) -> dict:
        """Get vendor statistics for admin dashboard.

        Returns dict compatible with VendorStatsResponse schema.
        Keys: total, verified, pending, inactive (mapped from internal names)
        """
        try:
            total_vendors = db.query(Vendor).count()
            active_vendors = db.query(Vendor).filter(Vendor.is_active == True).count()
            verified_vendors = (
                db.query(Vendor).filter(Vendor.is_verified == True).count()
            )
            inactive_vendors = total_vendors - active_vendors
            # Pending = active but not yet verified
            pending_vendors = (
                db.query(Vendor)
                .filter(Vendor.is_active == True, Vendor.is_verified == False)
                .count()
            )

            return {
                # Schema-compatible fields (VendorStatsResponse)
                "total": total_vendors,
                "verified": verified_vendors,
                "pending": pending_vendors,
                "inactive": inactive_vendors,
                # Legacy fields for backward compatibility
                "total_vendors": total_vendors,
                "active_vendors": active_vendors,
                "inactive_vendors": inactive_vendors,
                "verified_vendors": verified_vendors,
                "pending_vendors": pending_vendors,
                "verification_rate": (
                    (verified_vendors / total_vendors * 100) if total_vendors > 0 else 0
                ),
            }
        except Exception as e:
            logger.error(f"Failed to get vendor statistics: {str(e)}")
            raise AdminOperationException(
                operation="get_vendor_statistics", reason="Database query failed"
            )

    # ========================================================================
    # SYSTEM-WIDE STATISTICS (ADMIN)
    # ========================================================================

    def get_comprehensive_stats(self, db: Session) -> dict[str, Any]:
        """
        Get comprehensive system statistics for admin dashboard.

        Args:
            db: Database session

        Returns:
            Dictionary with comprehensive statistics

        Raises:
            AdminOperationException: If database query fails
        """
        try:
            # Vendors
            total_vendors = db.query(Vendor).filter(Vendor.is_active == True).count()

            # Products
            total_catalog_products = db.query(Product).count()
            unique_brands = self._get_unique_brands_count(db)
            unique_categories = self._get_unique_categories_count(db)

            # Marketplaces
            unique_marketplaces = (
                db.query(MarketplaceProduct.marketplace)
                .filter(MarketplaceProduct.marketplace.isnot(None))
                .distinct()
                .count()
            )

            # Inventory
            inventory_stats = self._get_inventory_statistics(db)

            return {
                "total_products": total_catalog_products,
                "unique_brands": unique_brands,
                "unique_categories": unique_categories,
                "unique_marketplaces": unique_marketplaces,
                "unique_vendors": total_vendors,
                "total_inventory_entries": inventory_stats.get("total_entries", 0),
                "total_inventory_quantity": inventory_stats.get("total_quantity", 0),
            }

        except Exception as e:
            logger.error(f"Failed to retrieve comprehensive statistics: {str(e)}")
            raise AdminOperationException(
                operation="get_comprehensive_stats",
                reason=f"Database query failed: {str(e)}",
            )

    def get_marketplace_breakdown_stats(self, db: Session) -> list[dict[str, Any]]:
        """
        Get statistics broken down by marketplace.

        Args:
            db: Database session

        Returns:
            List of marketplace statistics

        Raises:
            AdminOperationException: If database query fails
        """
        try:
            marketplace_stats = (
                db.query(
                    MarketplaceProduct.marketplace,
                    func.count(MarketplaceProduct.id).label("total_products"),
                    func.count(func.distinct(MarketplaceProduct.vendor_name)).label(
                        "unique_vendors"
                    ),
                    func.count(func.distinct(MarketplaceProduct.brand)).label(
                        "unique_brands"
                    ),
                )
                .filter(MarketplaceProduct.marketplace.isnot(None))
                .group_by(MarketplaceProduct.marketplace)
                .all()
            )

            return [
                {
                    "marketplace": stat.marketplace,
                    "total_products": stat.total_products,
                    "unique_vendors": stat.unique_vendors,
                    "unique_brands": stat.unique_brands,
                }
                for stat in marketplace_stats
            ]

        except Exception as e:
            logger.error(
                f"Failed to retrieve marketplace breakdown statistics: {str(e)}"
            )
            raise AdminOperationException(
                operation="get_marketplace_breakdown_stats",
                reason=f"Database query failed: {str(e)}",
            )

    def get_user_statistics(self, db: Session) -> dict[str, Any]:
        """
        Get user statistics for admin dashboard.

        Args:
            db: Database session

        Returns:
            Dictionary with user statistics

        Raises:
            AdminOperationException: If database query fails
        """
        try:
            total_users = db.query(User).count()
            active_users = db.query(User).filter(User.is_active == True).count()
            inactive_users = total_users - active_users
            admin_users = db.query(User).filter(User.role == "admin").count()

            return {
                "total_users": total_users,
                "active_users": active_users,
                "inactive_users": inactive_users,
                "admin_users": admin_users,
                "activation_rate": (
                    (active_users / total_users * 100) if total_users > 0 else 0
                ),
            }
        except Exception as e:
            logger.error(f"Failed to get user statistics: {str(e)}")
            raise AdminOperationException(
                operation="get_user_statistics", reason="Database query failed"
            )

    def get_import_statistics(self, db: Session) -> dict[str, Any]:
        """
        Get import job statistics.

        Args:
            db: Database session

        Returns:
            Dictionary with import statistics

        Raises:
            AdminOperationException: If database query fails
        """
        try:
            total = db.query(MarketplaceImportJob).count()
            pending = (
                db.query(MarketplaceImportJob)
                .filter(MarketplaceImportJob.status == "pending")
                .count()
            )
            processing = (
                db.query(MarketplaceImportJob)
                .filter(MarketplaceImportJob.status == "processing")
                .count()
            )
            completed = (
                db.query(MarketplaceImportJob)
                .filter(
                    MarketplaceImportJob.status.in_(
                        ["completed", "completed_with_errors"]
                    )
                )
                .count()
            )
            failed = (
                db.query(MarketplaceImportJob)
                .filter(MarketplaceImportJob.status == "failed")
                .count()
            )

            return {
                # Frontend-expected fields
                "total": total,
                "pending": pending,
                "processing": processing,
                "completed": completed,
                "failed": failed,
                # Legacy fields for backward compatibility
                "total_imports": total,
                "completed_imports": completed,
                "failed_imports": failed,
                "success_rate": (completed / total * 100) if total > 0 else 0,
            }
        except Exception as e:
            logger.error(f"Failed to get import statistics: {str(e)}")
            return {
                "total": 0,
                "pending": 0,
                "processing": 0,
                "completed": 0,
                "failed": 0,
                "total_imports": 0,
                "completed_imports": 0,
                "failed_imports": 0,
                "success_rate": 0,
            }

    def get_order_statistics(self, db: Session) -> dict[str, Any]:
        """
        Get order statistics.

        Args:
            db: Database session

        Returns:
            Dictionary with order statistics

        Note:
            TODO: Implement when Order model is fully available
        """
        return {"total_orders": 0, "pending_orders": 0, "completed_orders": 0}

    def get_product_statistics(self, db: Session) -> dict[str, Any]:
        """
        Get product statistics.

        Args:
            db: Database session

        Returns:
            Dictionary with product statistics

        Note:
            TODO: Implement when Product model is fully available
        """
        return {"total_products": 0, "active_products": 0, "out_of_stock": 0}

    # ========================================================================
    # PRIVATE HELPER METHODS
    # ========================================================================

    def _parse_period(self, period: str) -> int:
        """
        Parse period string to days.

        Args:
            period: Period string (7d, 30d, 90d, 1y)

        Returns:
            Number of days
        """
        period_map = {
            "7d": 7,
            "30d": 30,
            "90d": 90,
            "1y": 365,
        }
        return period_map.get(period, 30)

    def _get_unique_brands_count(self, db: Session) -> int:
        """
        Get count of unique brands.

        Args:
            db: Database session

        Returns:
            Count of unique brands
        """
        return (
            db.query(MarketplaceProduct.brand)
            .filter(
                MarketplaceProduct.brand.isnot(None), MarketplaceProduct.brand != ""
            )
            .distinct()
            .count()
        )

    def _get_unique_categories_count(self, db: Session) -> int:
        """
        Get count of unique categories.

        Args:
            db: Database session

        Returns:
            Count of unique categories
        """
        return (
            db.query(MarketplaceProduct.google_product_category)
            .filter(
                MarketplaceProduct.google_product_category.isnot(None),
                MarketplaceProduct.google_product_category != "",
            )
            .distinct()
            .count()
        )

    def _get_inventory_statistics(self, db: Session) -> dict[str, int]:
        """
        Get inventory-related statistics.

        Args:
            db: Database session

        Returns:
            Dictionary with inventory statistics
        """
        total_entries = db.query(Inventory).count()
        total_quantity = db.query(func.sum(Inventory.quantity)).scalar() or 0
        total_reserved = db.query(func.sum(Inventory.reserved_quantity)).scalar() or 0

        return {
            "total_entries": total_entries,
            "total_quantity": int(total_quantity),
            "total_reserved": int(total_reserved),
            "total_available": int(total_quantity - total_reserved),
        }


# Create service instance
stats_service = StatsService()

__all__ = ["stats_service", "StatsService"]