# app/modules/tenancy/services/merchant_service.py
"""
Merchant service for managing merchant operations.

This service handles CRUD operations for merchants and merchant-store relationships.
"""

import logging
import secrets
import string

from sqlalchemy import func, select
from sqlalchemy.orm import Session, joinedload

from app.modules.tenancy.exceptions import MerchantNotFoundException, UserNotFoundException
from app.modules.tenancy.models import Merchant
from app.modules.tenancy.models import User
from app.modules.tenancy.schemas.merchant import MerchantCreate, MerchantTransferOwnership, MerchantUpdate

logger = logging.getLogger(__name__)


class MerchantService:
    """Service for managing merchants."""

    def __init__(self):
        """Initialize merchant service."""

    def create_merchant_with_owner(
        self, db: Session, merchant_data: MerchantCreate
    ) -> tuple[Merchant, User, str]:
        """
        Create a new merchant with an owner user account.

        Args:
            db: Database session
            merchant_data: Merchant creation data

        Returns:
            Tuple of (merchant, owner_user, temporary_password)
        """
        # Import AuthManager for password hashing (same pattern as admin_service)
        from middleware.auth import AuthManager

        auth_manager = AuthManager()

        # Check if owner email already exists
        existing_user = db.execute(
            select(User).where(User.email == merchant_data.owner_email)
        ).scalar_one_or_none()

        if existing_user:
            # Use existing user as owner
            owner_user = existing_user
            temp_password = None
            logger.info(f"Using existing user {owner_user.email} as merchant owner")
        else:
            # Generate temporary password for owner
            temp_password = self._generate_temp_password()

            # Create new owner user
            owner_user = User(
                username=merchant_data.owner_email.split("@")[0],
                email=merchant_data.owner_email,
                hashed_password=auth_manager.hash_password(temp_password),
                role="user",
                is_active=True,
                is_email_verified=True,
            )
            db.add(owner_user)
            db.flush()  # Get owner_user.id
            logger.info(f"Created new owner user: {owner_user.email}")

        # Create merchant
        merchant = Merchant(
            name=merchant_data.name,
            description=merchant_data.description,
            owner_user_id=owner_user.id,
            contact_email=merchant_data.contact_email,
            contact_phone=merchant_data.contact_phone,
            website=merchant_data.website,
            business_address=merchant_data.business_address,
            tax_number=merchant_data.tax_number,
            is_active=True,
            is_verified=False,
        )
        db.add(merchant)
        db.flush()
        logger.info(f"Created merchant: {merchant.name} (ID: {merchant.id})")

        return merchant, owner_user, temp_password

    def get_merchant_by_id(self, db: Session, merchant_id: int) -> Merchant:
        """
        Get merchant by ID.

        Args:
            db: Database session
            merchant_id: Merchant ID

        Returns:
            Merchant object

        Raises:
            MerchantNotFoundException: If merchant not found
        """
        merchant = (
            db.execute(
                select(Merchant)
                .where(Merchant.id == merchant_id)
                .options(joinedload(Merchant.stores))
            )
            .unique()
            .scalar_one_or_none()
        )

        if not merchant:
            raise MerchantNotFoundException(merchant_id)

        return merchant

    def get_merchants(
        self,
        db: Session,
        skip: int = 0,
        limit: int = 100,
        search: str | None = None,
        is_active: bool | None = None,
        is_verified: bool | None = None,
    ) -> tuple[list[Merchant], int]:
        """
        Get paginated list of merchants with optional filters.

        Args:
            db: Database session
            skip: Number of records to skip
            limit: Maximum number of records to return
            search: Search term for merchant name
            is_active: Filter by active status
            is_verified: Filter by verified status

        Returns:
            Tuple of (merchants list, total count)
        """
        query = select(Merchant).options(joinedload(Merchant.stores))

        # Apply filters
        if search:
            query = query.where(Merchant.name.ilike(f"%{search}%"))
        if is_active is not None:
            query = query.where(Merchant.is_active == is_active)
        if is_verified is not None:
            query = query.where(Merchant.is_verified == is_verified)

        # Get total count
        count_query = select(func.count()).select_from(query.subquery())
        total = db.execute(count_query).scalar()

        # Apply pagination and order
        query = query.order_by(Merchant.name).offset(skip).limit(limit)

        # Use unique() when using joinedload with collections to avoid duplicate rows
        merchants = list(db.execute(query).scalars().unique().all())

        return merchants, total

    def update_merchant(
        self, db: Session, merchant_id: int, merchant_data: MerchantUpdate
    ) -> Merchant:
        """
        Update merchant information.

        Args:
            db: Database session
            merchant_id: Merchant ID
            merchant_data: Updated merchant data

        Returns:
            Updated merchant

        Raises:
            MerchantNotFoundException: If merchant not found
        """
        merchant = self.get_merchant_by_id(db, merchant_id)

        # Update only provided fields
        update_data = merchant_data.model_dump(exclude_unset=True)
        for field, value in update_data.items():
            setattr(merchant, field, value)

        db.flush()
        logger.info(f"Updated merchant ID {merchant_id}")

        return merchant

    def delete_merchant(self, db: Session, merchant_id: int) -> None:
        """
        Delete a merchant and all associated stores.

        Args:
            db: Database session
            merchant_id: Merchant ID

        Raises:
            MerchantNotFoundException: If merchant not found
        """
        merchant = self.get_merchant_by_id(db, merchant_id)

        # Due to cascade="all, delete-orphan", associated stores will be deleted
        db.delete(merchant)
        db.flush()
        logger.info(f"Deleted merchant ID {merchant_id} and associated stores")

    def toggle_verification(
        self, db: Session, merchant_id: int, is_verified: bool
    ) -> Merchant:
        """
        Toggle merchant verification status.

        Args:
            db: Database session
            merchant_id: Merchant ID
            is_verified: New verification status

        Returns:
            Updated merchant

        Raises:
            MerchantNotFoundException: If merchant not found
        """
        merchant = self.get_merchant_by_id(db, merchant_id)
        merchant.is_verified = is_verified
        db.flush()
        logger.info(f"Merchant ID {merchant_id} verification set to {is_verified}")

        return merchant

    def toggle_active(self, db: Session, merchant_id: int, is_active: bool) -> Merchant:
        """
        Toggle merchant active status.

        Args:
            db: Database session
            merchant_id: Merchant ID
            is_active: New active status

        Returns:
            Updated merchant

        Raises:
            MerchantNotFoundException: If merchant not found
        """
        merchant = self.get_merchant_by_id(db, merchant_id)
        merchant.is_active = is_active
        db.flush()
        logger.info(f"Merchant ID {merchant_id} active status set to {is_active}")

        return merchant

    def transfer_ownership(
        self,
        db: Session,
        merchant_id: int,
        transfer_data: MerchantTransferOwnership,
    ) -> tuple[Merchant, User, User]:
        """
        Transfer merchant ownership to another user.

        This is a critical operation that:
        - Changes the merchant's owner_user_id
        - All stores under the merchant automatically inherit the new owner
        - Logs the transfer for audit purposes

        Args:
            db: Database session
            merchant_id: Merchant ID
            transfer_data: Transfer ownership data

        Returns:
            Tuple of (merchant, old_owner, new_owner)

        Raises:
            MerchantNotFoundException: If merchant not found
            UserNotFoundException: If new owner user not found
            ValueError: If trying to transfer to current owner
        """
        # Get merchant
        merchant = self.get_merchant_by_id(db, merchant_id)
        old_owner_id = merchant.owner_user_id

        # Get old owner
        old_owner = db.execute(
            select(User).where(User.id == old_owner_id)
        ).scalar_one_or_none()
        if not old_owner:
            raise UserNotFoundException(str(old_owner_id))

        # Get new owner
        new_owner = db.execute(
            select(User).where(User.id == transfer_data.new_owner_user_id)
        ).scalar_one_or_none()
        if not new_owner:
            raise UserNotFoundException(str(transfer_data.new_owner_user_id))

        # Prevent transferring to same owner
        if old_owner_id == transfer_data.new_owner_user_id:
            raise ValueError("Cannot transfer ownership to the current owner")

        # Update merchant owner (stores inherit ownership via merchant relationship)
        merchant.owner_user_id = new_owner.id

        db.flush()

        logger.info(
            f"Merchant {merchant.id} ({merchant.name}) ownership transferred "
            f"from user {old_owner.id} ({old_owner.email}) "
            f"to user {new_owner.id} ({new_owner.email}). "
            f"Reason: {transfer_data.transfer_reason or 'Not specified'}"
        )

        return merchant, old_owner, new_owner

    def _generate_temp_password(self, length: int = 12) -> str:
        """Generate secure temporary password."""
        alphabet = string.ascii_letters + string.digits + "!@#$%^&*"
        return "".join(secrets.choice(alphabet) for _ in range(length))


# Create service instance following the same pattern as other services
merchant_service = MerchantService()