"""
Banking/payment services. transaction_initiate is called by checkout (and others)
to start a payment flow. Replace the stub with real gateway integration (e.g. Razorpay).
"""
from decimal import Decimal
from django.contrib.auth import get_user_model
from banking_operations.models import PaymentTransaction, PaymentGateway

User = get_user_model()


def transaction_initiate(
    request,
    user,
    amount,
    currency="INR",
    reference_type="checkout",
    reference_id=None,
    bookings=None,
    extra_data=None,
):
    """
    Initiate a payment transaction (e.g. create Razorpay order and return payment URL).

    Args:
        request: Django request (for building URLs, gateway config, etc.).
        user: User instance (customer).
        amount: Total amount in payment currency (Decimal or float).
        currency: Currency code, e.g. "INR".
        reference_type: Application reference type, e.g. "checkout".
        reference_id: Application reference id (e.g. booking_ids or order id).
        bookings: Optional list of Booking instances or IDs linked to this transaction.
        extra_data: Optional dict for gateway-specific data.

    Returns:
        dict: On success: {"success": True, "transaction_id": "...", "payment_url": "...", "message": "..."}
              On failure: {"success": False, "message": "..."}
    """
    # Stub: replace with real gateway call when banking_operations payment flow is implemented.
    return {
        "success": True,
        "message": "Transaction initiation stub",
        "transaction_id": None,
        "payment_url": None,
    }


def create_payment_transaction(
    payment_type,
    payment_sub_type,
    payment_gateway,
    transaction_amount,
    currency="INR",
    notes=None,
    raw_data=None,
    user=None,
):
    """
    Create a PaymentTransaction with pending status.

    Args:
        payment_type: Payment type - 'credit', 'debit', 'transfer', or 'other'
        payment_sub_type: Payment sub type - 'online', 'offline', or 'other'
        payment_gateway: PaymentGateway instance or payment_gateway_id (str)
        transaction_amount: Transaction amount (Decimal, float, or string)
        currency: Currency code, e.g. "INR" (default: "INR")
        notes: Optional transaction notes (str)
        raw_data: Optional raw data dict to store in payment_transaction_raw_data (dict)
        user: Optional User instance for last_updated_by

    Returns:
        tuple: (success: bool, transaction: PaymentTransaction or None, error_message: str or None)
    """
    try:
        # Validate payment_type
        valid_payment_types = ['credit', 'debit', 'transfer', 'other']
        if payment_type not in valid_payment_types:
            return False, None, f"Invalid payment_type. Must be one of: {', '.join(valid_payment_types)}"

        # Validate payment_sub_type
        valid_payment_sub_types = ['online', 'offline', 'other']
        if payment_sub_type not in valid_payment_sub_types:
            return False, None, f"Invalid payment_sub_type. Must be one of: {', '.join(valid_payment_sub_types)}"

        # Get PaymentGateway instance
        if isinstance(payment_gateway, PaymentGateway):
            gateway = payment_gateway
        elif isinstance(payment_gateway, str):
            try:
                gateway = PaymentGateway.objects.get(payment_gateway_id=payment_gateway)
            except PaymentGateway.DoesNotExist:
                return False, None, f"PaymentGateway with id '{payment_gateway}' not found."
        else:
            return False, None, "payment_gateway must be a PaymentGateway instance or payment_gateway_id string."

        # Validate transaction_amount
        try:
            amount = Decimal(str(transaction_amount))
            if amount <= 0:
                return False, None, "transaction_amount must be greater than zero."
        except (ValueError, TypeError):
            return False, None, "transaction_amount must be a valid number."

        # Validate currency
        if not currency or len(currency) > 10:
            return False, None, "currency must be a valid currency code (max 10 characters)."

        # Create PaymentTransaction
        transaction = PaymentTransaction.objects.create(
            payment_type=payment_type,
            payment_sub_type=payment_sub_type,
            payment_gateway=gateway,
            payment_transaction_amount=amount,
            payment_transaction_currency=currency,
            payment_transaction_status='pending',  # Initial state as requested
            payment_transaction_notes=notes,
            payment_transaction_raw_data=raw_data,
            last_updated_by=user if isinstance(user, User) else None,
        )

        return True, transaction.payment_transaction_id, None

    except Exception as e:
        return False, None, str(e)

def update_payment_transaction(
    payment_transaction_id,
    payment_transaction_status,
    payment_transaction_notes=None,
    payment_transaction_raw_data=None,
    payment_transaction_response=None,
    payment_transaction_error=None,
    user=None,
):
    """
    Update a PaymentTransaction with the given status and notes.
    Args:
        payment_transaction_id: PaymentTransaction id (str)
        payment_transaction_status: PaymentTransaction status - 'pending', 'completed', 'failed', 'refunded', 'cancelled'
        payment_transaction_notes: Optional transaction notes (str)
        payment_transaction_raw_data: Optional raw data dict to store in payment_transaction_raw_data (dict)
        payment_transaction_response: Optional response dict to store in payment_transaction_response (dict)
        payment_transaction_error: Optional error dict to store in payment_transaction_error (dict)
        user: Optional User instance for last_updated_by
    """ 
    try:
        # Get PaymentTransaction instance
        if isinstance(payment_transaction_id, PaymentTransaction):
            transaction = payment_transaction_id
        elif isinstance(payment_transaction_id, str):
            try:
                transaction = PaymentTransaction.objects.get(payment_transaction_id=payment_transaction_id)
            except PaymentTransaction.DoesNotExist:
                return False, None, f"PaymentTransaction with id '{payment_transaction_id}' not found."
        else:
            return False, None, "payment_transaction_id must be a PaymentTransaction instance or payment_transaction_id string."

        # Update PaymentTransaction
        transaction.payment_transaction_status = payment_transaction_status
        transaction.payment_transaction_notes = payment_transaction_notes
        transaction.payment_transaction_raw_data = payment_transaction_raw_data
        transaction.payment_transaction_response = payment_transaction_response
        transaction.payment_transaction_error = payment_transaction_error
        transaction.last_updated_by = user if isinstance(user, User) else None
        transaction.save()

        return True, transaction.payment_transaction_id, None

    except Exception as e:
        return False, None, str(e)