DinQuant/backend_api_python/app/services/billing_service.py

"""
Billing Service - unified billing service

Responsible for user points balance, function deductions, membership status and package issuance.
The current billing model is:
1. Whether to deduct fees is determined by `BILLING_ENABLED` and the cost configuration of each function.
2. VIP/member status is used to display membership packages and benefits.
3. The `vip_free` logic of community indicators is processed separately in the community purchase process, and no global bypass is done here.

Accounting configuration is stored in the `.env` file and can be configured through the system settings interface.
"""

import os
import time
from datetime import datetime, timedelta, timezone
from decimal import Decimal
from typing import Any, Dict, Optional, Tuple

from app.utils.db import get_db_connection
from app.utils.logger import get_logger

logger = get_logger(__name__)


# Function billing configuration key name
BILLING_CONFIG_PREFIX = "BILLING_"

# Default billing configuration
DEFAULT_BILLING_CONFIG = {
    # global switch
    "enabled": False,  # Whether to enable billing
    # Point consumption for each function (0 means free)
    # ai_analysis unified unit price: real-time analysis / AI filtering / scheduled tasks are all deducted based on this unit price × number of targets
    "cost_ai_analysis": 10,
    "cost_ai_code_gen": 30,
    "cost_polymarket_deep_analysis": 15,
}

# Feature name mapping (for log recording)
FEATURE_NAMES = {
    "ai_analysis": "AI Analysis",
    "ai_code_gen": "AI Code Generation",
    "polymarket_deep_analysis": "Polymarket Deep Analysis",
}


class BillingService:
    """Billing service category"""

    def __init__(self):
        self._config_cache = None
        self._config_cache_time = 0
        self._cache_ttl = 60  # Configure cache for 60 seconds

    def get_billing_config(self) -> Dict[str, Any]:
        """Get billing configuration"""
        now = time.time()
        if self._config_cache and (now - self._config_cache_time) < self._cache_ttl:
            return self._config_cache

        config = {}
        for key, default_value in DEFAULT_BILLING_CONFIG.items():
            env_key = f"{BILLING_CONFIG_PREFIX}{key.upper()}"
            value = os.getenv(env_key)

            if value is None or value == "":
                config[key] = default_value
            elif isinstance(default_value, bool):
                config[key] = str(value).lower() in ("true", "1", "yes")
            elif isinstance(default_value, int):
                try:
                    config[key] = int(value)
                except (ValueError, TypeError):
                    config[key] = default_value
            else:
                config[key] = value

        self._config_cache = config
        self._config_cache_time = now
        return config

    def clear_config_cache(self):
        """Clear configuration cache"""
        self._config_cache = None
        self._config_cache_time = 0

    def is_billing_enabled(self) -> bool:
        """Check if billing is enabled"""
        config = self.get_billing_config()
        return config.get("enabled", False)

    def get_feature_cost(self, feature: str) -> int:
        """Get the points consumption of the specified function, 0 means free"""
        config = self.get_billing_config()
        cost_key = f"cost_{feature}"
        return config.get(cost_key, 0)

    def get_user_credits(self, user_id: int) -> Decimal:
        """Get user points balance"""
        try:
            with get_db_connection() as db:
                cur = db.cursor()
                cur.execute("SELECT credits FROM qd_users WHERE id = ?", (user_id,))
                row = cur.fetchone()
                cur.close()

                if row:
                    return Decimal(str(row.get("credits", 0) or 0))
                return Decimal("0")
        except Exception as e:
            logger.error(f"get_user_credits failed: {e}")
            return Decimal("0")

    def get_user_vip_status(self, user_id: int) -> Tuple[bool, Optional[datetime]]:
        """
        Get user VIP status

        Returns:
            (is_vip, expires_at): whether the VIP is valid, VIP expiration time
        """
        try:
            with get_db_connection() as db:
                cur = db.cursor()
                # Ensure lifetime membership monthly credits are granted (best-effort, silent on failure).
                self._ensure_membership_schema_best_effort(cur)
                self._grant_lifetime_monthly_credits_best_effort(cur, user_id)
                try:
                    db.commit()
                except Exception:
                    pass

                cur.execute("SELECT vip_expires_at FROM qd_users WHERE id = ?", (user_id,))
                row = cur.fetchone()
                cur.close()

                if row and row.get("vip_expires_at"):
                    expires_at = row["vip_expires_at"]
                    # Make sure it is a datetime object
                    if isinstance(expires_at, str):
                        expires_at = datetime.fromisoformat(expires_at.replace("Z", "+00:00"))

                    # Check if expired
                    now = datetime.now(timezone.utc)
                    if expires_at.tzinfo is None:
                        expires_at = expires_at.replace(tzinfo=timezone.utc)

                    is_vip = expires_at > now
                    return is_vip, expires_at

                return False, None
        except Exception as e:
            logger.error(f"get_user_vip_status failed: {e}")
            return False, None

    # ==================== Membership Plans (VIP) ====================

    def get_membership_plans(self) -> Dict[str, Any]:
        """
        Get membership plans from .env (configured via Settings UI).

        Plan keys:
          - monthly: price_usd, credits_once, duration_days
          - yearly: price_usd, credits_once, duration_days
          - lifetime: price_usd, credits_monthly (granted every 30 days)
        """

        def _f(key: str, default: float) -> float:
            try:
                return float(os.getenv(key, str(default)).strip())
            except Exception:
                return float(default)

        def _i(key: str, default: int) -> int:
            try:
                return int(float(os.getenv(key, str(default)).strip()))
            except Exception:
                return int(default)

        return {
            "monthly": {
                "plan": "monthly",
                "price_usd": _f("MEMBERSHIP_MONTHLY_PRICE_USD", 19.9),
                "credits_once": _i("MEMBERSHIP_MONTHLY_CREDITS", 500),
                "duration_days": 30,
            },
            "yearly": {
                "plan": "yearly",
                "price_usd": _f("MEMBERSHIP_YEARLY_PRICE_USD", 199.0),
                "credits_once": _i("MEMBERSHIP_YEARLY_CREDITS", 8000),
                "duration_days": 365,
            },
            "lifetime": {
                "plan": "lifetime",
                "price_usd": _f("MEMBERSHIP_LIFETIME_PRICE_USD", 499.0),
                # Lifetime: monthly credits granted periodically
                "credits_monthly": _i("MEMBERSHIP_LIFETIME_MONTHLY_CREDITS", 800),
            },
        }

    def purchase_membership(self, user_id: int, plan: str) -> Tuple[bool, str, Dict[str, Any]]:
        """
        Purchase membership plan (mock payment: immediately activates).

        NOTE: Real payment gateway can be integrated later; this function is the single activation point.
        """
        plan = (plan or "").strip().lower()
        plans = self.get_membership_plans()
        if plan not in plans:
            return False, "invalid_plan", {}

        try:
            with get_db_connection() as db:
                cur = db.cursor()
                self._ensure_membership_schema_best_effort(cur)
                self._ensure_membership_orders_table_best_effort(cur)

                now = datetime.now(timezone.utc)

                # Read current VIP expiry to support stacking for monthly/yearly.
                cur.execute("SELECT vip_expires_at FROM qd_users WHERE id = ?", (user_id,))
                row = cur.fetchone() or {}
                current_expires = row.get("vip_expires_at")
                if isinstance(current_expires, str) and current_expires:
                    try:
                        current_expires = datetime.fromisoformat(current_expires.replace("Z", "+00:00"))
                    except Exception:
                        current_expires = None
                if current_expires and current_expires.tzinfo is None:
                    current_expires = current_expires.replace(tzinfo=timezone.utc)

                base_time = current_expires if (current_expires and current_expires > now) else now

                vip_expires_at = None
                vip_plan = plan
                vip_is_lifetime = False

                if plan in ("monthly", "yearly"):
                    days = int(plans[plan].get("duration_days") or (30 if plan == "monthly" else 365))
                    vip_expires_at = base_time + timedelta(days=days)
                else:
                    # Lifetime: set very long expiry + mark lifetime flag
                    vip_expires_at = now + timedelta(days=365 * 100)
                    vip_is_lifetime = True

                # Create order record (mock paid)
                order_plan = plan
                order_price_usd = float(plans[plan].get("price_usd") or 0)
                order_id = None
                try:
                    cur.execute(
                        """
                        INSERT INTO qd_membership_orders
                          (user_id, plan, price_usd, status, created_at, paid_at)
                        VALUES (?, ?, ?, 'paid', NOW(), NOW())
                        RETURNING id
                        """,
                        (user_id, order_plan, order_price_usd),
                    )
                    row2 = cur.fetchone() or {}
                    order_id = row2.get("id")
                except Exception:
                    # Fallback for DB drivers without RETURNING support
                    cur.execute(
                        """
                        INSERT INTO qd_membership_orders
                          (user_id, plan, price_usd, status, created_at, paid_at)
                        VALUES (?, ?, ?, 'paid', NOW(), NOW())
                        """,
                        (user_id, order_plan, order_price_usd),
                    )
                    order_id = getattr(cur, "lastrowid", None)
                order_ref = str(order_id or "")

                # Update user VIP fields
                cur.execute(
                    """
                    UPDATE qd_users
                    SET vip_expires_at = ?,
                        vip_plan = ?,
                        vip_is_lifetime = ?,
                        updated_at = NOW()
                    WHERE id = ?
                    """,
                    (vip_expires_at, vip_plan, 1 if vip_is_lifetime else 0, user_id),
                )

                # Credits grants
                if plan in ("monthly", "yearly"):
                    credits_once = int(plans[plan].get("credits_once") or 0)
                    if credits_once > 0:
                        # Use add_credits to update balance and log
                        # NOTE: add_credits opens its own connection, so we do a direct update here for atomicity.
                        self._add_credits_in_tx(
                            cur,
                            user_id,
                            credits_once,
                            action="membership_bonus",
                            remark=f"Membership bonus ({plan})",
                            reference_id=order_ref,
                        )
                else:
                    # Lifetime: grant first month's credits immediately and set last grant time
                    monthly_credits = int(plans["lifetime"].get("credits_monthly") or 0)
                    if monthly_credits > 0:
                        self._add_credits_in_tx(
                            cur,
                            user_id,
                            monthly_credits,
                            action="membership_monthly",
                            remark="Lifetime membership monthly credits",
                            reference_id=order_ref,
                        )
                    try:
                        cur.execute(
                            "UPDATE qd_users SET vip_monthly_credits_last_grant = ?, updated_at = NOW() WHERE id = ?",
                            (now, user_id),
                        )
                    except Exception:
                        # Column may not exist; ignore
                        pass

                # VIP log entry (for audit)
                cur.execute(
                    """
                    INSERT INTO qd_credits_log
                      (user_id, action, amount, balance_after, remark, operator_id, reference_id, created_at)
                    VALUES (?, 'membership_purchase', 0,
                            (SELECT credits FROM qd_users WHERE id = ?),
                            ?, NULL, ?, NOW())
                    """,
                    (user_id, user_id, f"Membership purchased: {plan}", order_ref),
                )

                db.commit()
                cur.close()

            return (
                True,
                "success",
                {
                    "order_id": order_id,
                    "plan": plan,
                    "vip_expires_at": vip_expires_at.isoformat() if vip_expires_at else None,
                },
            )
        except Exception as e:
            logger.error(f"purchase_membership failed: {e}", exc_info=True)
            return False, f"error:{str(e)}", {}

    def _ensure_membership_schema_best_effort(self, cur):
        """Best-effort schema upgrade for membership fields on qd_users."""
        try:
            # vip_plan / vip_is_lifetime / vip_monthly_credits_last_grant
            cur.execute("ALTER TABLE qd_users ADD COLUMN IF NOT EXISTS vip_plan VARCHAR(20) DEFAULT ''")
            cur.execute("ALTER TABLE qd_users ADD COLUMN IF NOT EXISTS vip_is_lifetime BOOLEAN DEFAULT FALSE")
            cur.execute("ALTER TABLE qd_users ADD COLUMN IF NOT EXISTS vip_monthly_credits_last_grant TIMESTAMP")
        except Exception:
            # Ignore schema upgrade failures (e.g., insufficient privileges)
            pass

    def _ensure_membership_orders_table_best_effort(self, cur):
        """Best-effort create membership orders table (mock payment)."""
        try:
            cur.execute(
                """
                CREATE TABLE IF NOT EXISTS qd_membership_orders (
                  id SERIAL PRIMARY KEY,
                  user_id INTEGER NOT NULL,
                  plan VARCHAR(20) NOT NULL,
                  price_usd DECIMAL(10,2) DEFAULT 0,
                  status VARCHAR(20) DEFAULT 'paid',
                  created_at TIMESTAMP DEFAULT NOW(),
                  paid_at TIMESTAMP
                )
                """
            )
        except Exception:
            pass

    def _add_credits_in_tx(self, cur, user_id: int, amount: int, action: str, remark: str, reference_id: str = ""):
        """Add credits within an existing DB transaction and write qd_credits_log."""
        try:
            cur.execute("SELECT credits FROM qd_users WHERE id = ?", (user_id,))
            row = cur.fetchone() or {}
            credits = Decimal(str(row.get("credits", 0) or 0))
            new_balance = credits + Decimal(str(amount))

            cur.execute(
                "UPDATE qd_users SET credits = ?, updated_at = NOW() WHERE id = ?", (float(new_balance), user_id)
            )
            cur.execute(
                """
                INSERT INTO qd_credits_log
                  (user_id, action, amount, balance_after, remark, operator_id, reference_id, created_at)
                VALUES (?, ?, ?, ?, ?, NULL, ?, NOW())
                """,
                (user_id, action, amount, float(new_balance), remark, reference_id),
            )
        except Exception as e:
            logger.debug(f"_add_credits_in_tx failed: {e}", exc_info=True)

    def _grant_lifetime_monthly_credits_best_effort(self, cur, user_id: int):
        """Grant lifetime monthly credits if due (best-effort)."""
        try:
            plans = self.get_membership_plans()
            monthly_credits = int(plans.get("lifetime", {}).get("credits_monthly") or 0)
            if monthly_credits <= 0:
                return

            cur.execute(
                "SELECT vip_is_lifetime, vip_expires_at, vip_monthly_credits_last_grant FROM qd_users WHERE id = ?",
                (user_id,),
            )
            row = cur.fetchone() or {}
            if not row.get("vip_is_lifetime"):
                return

            expires_at = row.get("vip_expires_at")
            if isinstance(expires_at, str) and expires_at:
                try:
                    expires_at = datetime.fromisoformat(expires_at.replace("Z", "+00:00"))
                except Exception:
                    expires_at = None
            if expires_at and expires_at.tzinfo is None:
                expires_at = expires_at.replace(tzinfo=timezone.utc)
            now = datetime.now(timezone.utc)
            if expires_at and expires_at <= now:
                return

            last = row.get("vip_monthly_credits_last_grant")
            if isinstance(last, str) and last:
                try:
                    last = datetime.fromisoformat(last.replace("Z", "+00:00"))
                except Exception:
                    last = None
            if last and last.tzinfo is None:
                last = last.replace(tzinfo=timezone.utc)

            # First time: do nothing (purchase flow already grants), but set last to now if missing
            if not last:
                cur.execute(
                    "UPDATE qd_users SET vip_monthly_credits_last_grant = ?, updated_at = NOW() WHERE id = ?",
                    (now, user_id),
                )
                return

            # Use 30-day periods. Catch up up to 6 periods max to avoid abuse.
            delta_days = int((now - last).total_seconds() // 86400)
            periods = delta_days // 30
            if periods <= 0:
                return
            if periods > 6:
                periods = 6

            total = monthly_credits * periods
            self._add_credits_in_tx(
                cur,
                user_id,
                total,
                action="membership_monthly",
                remark=f"Lifetime membership monthly credits x{periods}",
                reference_id="",
            )
            cur.execute(
                "UPDATE qd_users SET vip_monthly_credits_last_grant = ?, updated_at = NOW() WHERE id = ?",
                (now, user_id),
            )
        except Exception:
            # Best-effort; never break caller
            pass

    def check_and_consume(self, user_id: int, feature: str, reference_id: str = "") -> Tuple[bool, str]:
        """
        Check and spend points

        Args:
            user_id: user ID
            feature: function name (ai_analysis / polymarket_deep_analysis)
            reference_id: association ID (optional)

        Returns:
            (success, message): Whether it is successful, prompt message
        """
        # Check if billing is enabled
        if not self.is_billing_enabled():
            return True, "billing_disabled"

        config = self.get_billing_config()  # noqa
        cost = self.get_feature_cost(feature)

        # free features
        if cost <= 0:
            return True, "free_feature"

        # Note: There is no longer a global point deduction bypass based on VIP.
        # VIP/membership is reserved only for package, expiry time and community vip_free metric benefits.

        # Check points balance
        credits = self.get_user_credits(user_id)
        if credits < cost:
            return False, f"insufficient_credits:{credits}:{cost}"

        # Points deducted
        try:
            new_balance = credits - Decimal(str(cost))

            with get_db_connection() as db:
                cur = db.cursor()

                # Update user points
                cur.execute(
                    "UPDATE qd_users SET credits = ?, updated_at = NOW() WHERE id = ?", (float(new_balance), user_id)
                )

                # Logging - Use UTC time to ensure correct display across time zones
                feature_name = FEATURE_NAMES.get(feature, feature)
                created_at_utc = datetime.now(timezone.utc)
                cur.execute(
                    """
                    INSERT INTO qd_credits_log
                    (user_id, action, amount, balance_after, feature, reference_id, remark, created_at)
                    VALUES (?, 'consume', ?, ?, ?, ?, ?, ?)
                    """,
                    (
                        user_id,
                        -cost,
                        float(new_balance),
                        feature,
                        reference_id,
                        f"Consume: {feature_name}",
                        created_at_utc,
                    ),
                )

                db.commit()
                cur.close()

            logger.info(f"User {user_id} consumed {cost} credits for {feature}, balance: {new_balance}")
            return True, "consumed"

        except Exception as e:
            logger.error(f"check_and_consume failed: {e}")
            return False, f"error:{str(e)}"

    def add_credits(
        self,
        user_id: int,
        amount: int,
        action: str = "recharge",
        remark: str = "",
        operator_id: int = None,
        reference_id: str = "",
    ) -> Tuple[bool, str]:
        """
        Increase user points

        Args:
            user_id: user ID
            amount: increase the amount (positive number)
            action: action type (recharge/admin_adjust/refund/referral_bonus/register_bonus)
            remark: remark
            operator_id: operator ID (when the administrator operates)
            reference_id: association ID (such as invited user ID, order number, etc.)

        Returns:
            (success, message)
        """
        if amount <= 0:
            return False, "amount_must_be_positive"

        try:
            credits = self.get_user_credits(user_id)
            new_balance = credits + Decimal(str(amount))

            with get_db_connection() as db:
                cur = db.cursor()

                # Update user points
                cur.execute(
                    "UPDATE qd_users SET credits = ?, updated_at = NOW() WHERE id = ?", (float(new_balance), user_id)
                )

                # Logging (contains reference_id)
                cur.execute(
                    """
                    INSERT INTO qd_credits_log
                    (user_id, action, amount, balance_after, remark, operator_id, reference_id, created_at)
                    VALUES (?, ?, ?, ?, ?, ?, ?, NOW())
                    """,
                    (user_id, action, amount, float(new_balance), remark, operator_id, reference_id),
                )

                db.commit()
                cur.close()

            logger.info(f"User {user_id} added {amount} credits ({action}), balance: {new_balance}")
            return True, str(new_balance)

        except Exception as e:
            logger.error(f"add_credits failed: {e}")
            return False, str(e)

    def set_credits(self, user_id: int, amount: int, remark: str = "", operator_id: int = None) -> Tuple[bool, str]:
        """
        Set user points (set directly by the administrator)

        Args:
            user_id: user ID
            amount: the set amount
            remark: remark
            operator_id: operator ID

        Returns:
            (success, message)
        """
        if amount < 0:
            return False, "amount_cannot_be_negative"

        try:
            old_credits = self.get_user_credits(user_id)
            diff = Decimal(str(amount)) - old_credits

            with get_db_connection() as db:
                cur = db.cursor()

                # Update user points
                cur.execute("UPDATE qd_users SET credits = ?, updated_at = NOW() WHERE id = ?", (amount, user_id))

                # logging
                cur.execute(
                    """
                    INSERT INTO qd_credits_log
                    (user_id, action, amount, balance_after, remark, operator_id, created_at)
                    VALUES (?, 'admin_adjust', ?, ?, ?, ?, NOW())
                    """,
                    (user_id, float(diff), amount, remark or f"Admin adjust: {old_credits} -> {amount}", operator_id),
                )

                db.commit()
                cur.close()

            logger.info(f"User {user_id} credits set to {amount} by admin {operator_id}")
            return True, str(amount)

        except Exception as e:
            logger.error(f"set_credits failed: {e}")
            return False, str(e)

    def set_vip(
        self, user_id: int, expires_at: Optional[datetime], remark: str = "", operator_id: int = None
    ) -> Tuple[bool, str]:
        """
        Set user VIP status

        Args:
            user_id: user ID
            expires_at: VIP expiration time (None means canceling VIP)
            remark: remark
            operator_id: operator ID

        Returns:
            (success, message)
        """
        try:
            with get_db_connection() as db:
                cur = db.cursor()

                # Update VIP expiration time
                cur.execute(
                    "UPDATE qd_users SET vip_expires_at = ?, updated_at = NOW() WHERE id = ?", (expires_at, user_id)
                )

                # logging
                action = "vip_grant" if expires_at else "vip_revoke"
                log_remark = remark or (f"VIP granted until {expires_at}" if expires_at else "VIP revoked")
                cur.execute(
                    """
                    INSERT INTO qd_credits_log
                    (user_id, action, amount, balance_after, remark, operator_id, created_at)
                    VALUES (?, ?, 0, (SELECT credits FROM qd_users WHERE id = ?), ?, ?, NOW())
                    """,
                    (user_id, action, user_id, log_remark, operator_id),
                )

                db.commit()
                cur.close()

            logger.info(f"User {user_id} VIP set to {expires_at} by admin {operator_id}")
            return True, "success"

        except Exception as e:
            logger.error(f"set_vip failed: {e}")
            return False, str(e)

    def get_credits_log(self, user_id: int, page: int = 1, page_size: int = 20) -> Dict[str, Any]:
        """Get user points change log"""
        offset = (page - 1) * page_size

        try:
            with get_db_connection() as db:
                cur = db.cursor()

                # Get total
                cur.execute("SELECT COUNT(*) as count FROM qd_credits_log WHERE user_id = ?", (user_id,))
                total = cur.fetchone()["count"]

                # Get log
                cur.execute(
                    """
                    SELECT id, action, amount, balance_after, feature, reference_id, remark, created_at
                    FROM qd_credits_log
                    WHERE user_id = ?
                    ORDER BY created_at DESC
                    LIMIT ? OFFSET ?
                    """,
                    (user_id, page_size, offset),
                )
                rows = cur.fetchall() or []
                cur.close()

                # Format created_at as ISO 8601 with Z (UTC) for correct frontend display
                logs = []
                for r in rows:
                    d = dict(r)
                    if d.get("created_at"):
                        dt = d["created_at"]
                        if hasattr(dt, "isoformat"):
                            if getattr(dt, "tzinfo", None) is not None:
                                d["created_at"] = dt.astimezone(timezone.utc).strftime("%Y-%m-%dT%H:%M:%S") + "Z"
                            else:
                                # No time zone: New records are written in UTC, and old records may be in the local time of the server. They are returned in UTC to facilitate correct conversion by the front end.
                                d["created_at"] = dt.strftime("%Y-%m-%dT%H:%M:%S") + "Z"
                    logs.append(d)

                return {
                    "items": logs,
                    "total": total,
                    "page": page,
                    "page_size": page_size,
                    "total_pages": (total + page_size - 1) // page_size,
                }
        except Exception as e:
            logger.error(f"get_credits_log failed: {e}")
            return {"items": [], "total": 0, "page": 1, "page_size": page_size, "total_pages": 0}

    def get_user_billing_info(self, user_id: int) -> Dict[str, Any]:
        """Get a snapshot of user billing and membership information (for front-end display)"""
        credits = self.get_user_credits(user_id)
        is_vip, vip_expires_at = self.get_user_vip_status(user_id)
        config = self.get_billing_config()

        return {
            "credits": float(credits),
            "is_vip": is_vip,
            "vip_expires_at": vip_expires_at.isoformat() if vip_expires_at else None,
            "billing_enabled": config.get("enabled", False),
            "feature_costs": {
                "ai_analysis": config.get("cost_ai_analysis", 0),
                "ai_code_gen": config.get("cost_ai_code_gen", 0),
                "polymarket_deep_analysis": config.get("cost_polymarket_deep_analysis", 0),
            },
        }


# Global singleton
_billing_service = None


def get_billing_service() -> BillingService:
    """Get billing service singleton instance"""
    global _billing_service
    if _billing_service is None:
        _billing_service = BillingService()
    return _billing_service