"""
Razorpay Payment Service - Modular, plug-and-play payment integration.

This module provides a complete Razorpay integration that can be easily
moved to another project with minimal changes.

Features:
- Create Razorpay orders for credit purchases
- Verify payment signatures (HMAC SHA256)
- Process webhook events
- Configurable credit packages

Usage:
    from services.razorpay_service import RazorpayService, CREDIT_PACKAGES
    
    # Initialize
    service = RazorpayService()  # Uses environment variables
    
    # Or with explicit credentials
    service = RazorpayService(
        key_id="rzp_test_xxx",
        key_secret="secret",
        webhook_secret="webhook_secret"
    )
    
    # Create order
    order = service.create_order(
        amount_paise=9900,
        transaction_id="txn_abc123",
        notes={"user_id": "user123"}
    )
    
    # Verify payment
    is_valid = service.verify_payment_signature(
        order_id="order_xxx",
        payment_id="pay_xxx",
        signature="signature"
    )

Environment Variables:
    RAZORPAY_KEY_ID: Your Razorpay Key ID
    RAZORPAY_KEY_SECRET: Your Razorpay Key Secret
    RAZORPAY_WEBHOOK_SECRET: Webhook secret for signature verification
"""

import os
import hmac
import hashlib
import logging
from typing import Optional, Dict, Any, List
from dataclasses import dataclass
from enum import Enum

import razorpay

logger = logging.getLogger(__name__)


# =============================================================================
# Credit Packages Configuration
# =============================================================================

@dataclass
class CreditPackage:
    """Represents a purchasable credit package."""
    id: str
    name: str
    credits: int
    amount_paise: int  # Amount in paise (INR × 100)
    currency: str = "INR"
    
    @property
    def amount_rupees(self) -> float:
        """Get amount in rupees."""
        return self.amount_paise / 100
    
    def to_dict(self) -> Dict[str, Any]:
        """Convert to dictionary for API responses."""
        return {
            "id": self.id,
            "name": self.name,
            "credits": self.credits,
            "amount_paise": self.amount_paise,
            "amount_rupees": self.amount_rupees,
            "currency": self.currency
        }


# Available credit packages
CREDIT_PACKAGES: Dict[str, CreditPackage] = {
    "starter": CreditPackage(
        id="starter",
        name="Starter Pack",
        credits=100,
        amount_paise=9900  # ₹99
    ),
    "standard": CreditPackage(
        id="standard",
        name="Standard Pack",
        credits=500,
        amount_paise=44900  # ₹449
    ),
    "pro": CreditPackage(
        id="pro",
        name="Pro Pack",
        credits=1000,
        amount_paise=79900  # ₹799
    )
}


def get_package(package_id: str) -> Optional[CreditPackage]:
    """Get a credit package by ID."""
    return CREDIT_PACKAGES.get(package_id.lower())


def list_packages() -> List[Dict[str, Any]]:
    """List all available credit packages."""
    return [pkg.to_dict() for pkg in CREDIT_PACKAGES.values()]


# =============================================================================
# Payment Status Enum
# =============================================================================

class PaymentStatus(str, Enum):
    """Payment transaction statuses."""
    CREATED = "created"
    AUTHORIZED = "authorized"
    CAPTURED = "captured"
    PAID = "paid"
    FAILED = "failed"
    REFUNDED = "refunded"


# =============================================================================
# Razorpay Service
# =============================================================================

class RazorpayServiceError(Exception):
    """Base exception for Razorpay service errors."""
    pass


class RazorpayConfigError(RazorpayServiceError):
    """Raised when Razorpay is not properly configured."""
    pass


class RazorpayOrderError(RazorpayServiceError):
    """Raised when order creation fails."""
    pass


class RazorpayVerificationError(RazorpayServiceError):
    """Raised when payment verification fails."""
    pass


class RazorpayService:
    """
    Modular Razorpay payment service.
    
    This service handles all Razorpay interactions including:
    - Order creation
    - Payment signature verification
    - Webhook signature verification
    
    The service can be initialized with explicit credentials or will
    automatically use environment variables.
    """
    
    def __init__(
        self,
        key_id: Optional[str] = None,
        key_secret: Optional[str] = None,
        webhook_secret: Optional[str] = None
    ):
        """
        Initialize Razorpay service.
        
        Args:
            key_id: Razorpay Key ID (or RAZORPAY_KEY_ID env var)
            key_secret: Razorpay Key Secret (or RAZORPAY_KEY_SECRET env var)
            webhook_secret: Webhook secret (or RAZORPAY_WEBHOOK_SECRET env var)
        """
        self.key_id = key_id or os.getenv("RAZORPAY_KEY_ID")
        self.key_secret = key_secret or os.getenv("RAZORPAY_KEY_SECRET")
        self.webhook_secret = webhook_secret or os.getenv("RAZORPAY_WEBHOOK_SECRET")
        
        if not self.key_id or not self.key_secret:
            raise RazorpayConfigError(
                "Razorpay credentials not configured. "
                "Set RAZORPAY_KEY_ID and RAZORPAY_KEY_SECRET environment variables."
            )
        
        # Initialize Razorpay client
        self._client = razorpay.Client(auth=(self.key_id, self.key_secret))
        logger.info("Razorpay service initialized")
    
    @property
    def is_configured(self) -> bool:
        """Check if the service is properly configured."""
        return bool(self.key_id and self.key_secret)
    
    def create_order(
        self,
        amount_paise: int,
        transaction_id: str,
        currency: str = "INR",
        notes: Optional[Dict[str, str]] = None
    ) -> Dict[str, Any]:
        """
        Create a Razorpay order for payment.
        
        Args:
            amount_paise: Amount in paise (₹1 = 100 paise)
            transaction_id: Your internal transaction/receipt ID
            currency: Currency code (default: INR)
            notes: Optional notes to attach to the order
            
        Returns:
            Razorpay order response containing order_id
            
        Raises:
            RazorpayOrderError: If order creation fails
        """
        try:
            order_data = {
                "amount": amount_paise,
                "currency": currency,
                "receipt": transaction_id,
                "notes": notes or {}
            }
            
            order = self._client.order.create(data=order_data)
            
            logger.info(
                f"Created Razorpay order: {order['id']} "
                f"for amount: {amount_paise} paise, "
                f"receipt: {transaction_id}"
            )
            
            return order
            
        except razorpay.errors.BadRequestError as e:
            logger.error(f"Razorpay order creation failed (bad request): {e}")
            raise RazorpayOrderError(f"Invalid order data: {e}")
        except razorpay.errors.ServerError as e:
            logger.error(f"Razorpay server error: {e}")
            raise RazorpayOrderError(f"Razorpay server error: {e}")
        except Exception as e:
            logger.error(f"Unexpected error creating Razorpay order: {e}")
            raise RazorpayOrderError(f"Failed to create order: {e}")
    
    def verify_payment_signature(
        self,
        order_id: str,
        payment_id: str,
        signature: str
    ) -> bool:
        """
        Verify Razorpay payment signature.
        
        This MUST be called after receiving payment confirmation from the
        client to ensure the payment is authentic.
        
        Args:
            order_id: Razorpay order ID
            payment_id: Razorpay payment ID
            signature: Razorpay signature from checkout response
            
        Returns:
            True if signature is valid
            
        Raises:
            RazorpayVerificationError: If signature verification fails
        """
        try:
            # Generate expected signature
            message = f"{order_id}|{payment_id}"
            expected_signature = hmac.new(
                self.key_secret.encode('utf-8'),
                message.encode('utf-8'),
                hashlib.sha256
            ).hexdigest()
            
            # Constant-time comparison to prevent timing attacks
            is_valid = hmac.compare_digest(expected_signature, signature)
            
            if is_valid:
                logger.info(f"Payment signature verified: order={order_id}, payment={payment_id}")
            else:
                logger.warning(f"Invalid payment signature: order={order_id}, payment={payment_id}")
            
            return is_valid
            
        except Exception as e:
            logger.error(f"Error verifying payment signature: {e}")
            raise RazorpayVerificationError(f"Signature verification failed: {e}")
    
    def verify_webhook_signature(
        self,
        body: bytes,
        signature: str
    ) -> bool:
        """
        Verify Razorpay webhook signature.
        
        Use this to authenticate incoming webhook requests.
        
        Args:
            body: Raw request body bytes
            signature: X-Razorpay-Signature header value
            
        Returns:
            True if webhook signature is valid
        """
        if not self.webhook_secret:
            logger.warning("Webhook secret not configured, skipping verification")
            return False
        
        try:
            expected_signature = hmac.new(
                self.webhook_secret.encode('utf-8'),
                body,
                hashlib.sha256
            ).hexdigest()
            
            is_valid = hmac.compare_digest(expected_signature, signature)
            
            if not is_valid:
                logger.warning("Invalid webhook signature received")
            
            return is_valid
            
        except Exception as e:
            logger.error(f"Error verifying webhook signature: {e}")
            return False
    
    def fetch_payment(self, payment_id: str) -> Dict[str, Any]:
        """
        Fetch payment details from Razorpay.
        
        Args:
            payment_id: Razorpay payment ID
            
        Returns:
            Payment details from Razorpay
        """
        try:
            payment = self._client.payment.fetch(payment_id)
            return payment
        except Exception as e:
            logger.error(f"Error fetching payment {payment_id}: {e}")
            raise RazorpayServiceError(f"Failed to fetch payment: {e}")
    
    def fetch_order(self, order_id: str) -> Dict[str, Any]:
        """
        Fetch order details from Razorpay.
        
        Args:
            order_id: Razorpay order ID
            
        Returns:
            Order details from Razorpay
        """
        try:
            order = self._client.order.fetch(order_id)
            return order
        except Exception as e:
            logger.error(f"Error fetching order {order_id}: {e}")
            raise RazorpayServiceError(f"Failed to fetch order: {e}")


# =============================================================================
# Module-level convenience functions
# =============================================================================

_service_instance: Optional[RazorpayService] = None


def get_razorpay_service() -> RazorpayService:
    """
    Get or create a singleton Razorpay service instance.
    
    Returns:
        RazorpayService instance
        
    Raises:
        RazorpayConfigError: If Razorpay is not configured
    """
    global _service_instance
    
    if _service_instance is None:
        _service_instance = RazorpayService()
    
    return _service_instance


def is_razorpay_configured() -> bool:
    """Check if Razorpay credentials are configured in environment."""
    return bool(
        os.getenv("RAZORPAY_KEY_ID") and 
        os.getenv("RAZORPAY_KEY_SECRET")
    )