MermsCoreFlask/app/api/services/base_service.py

from app.models import Customer, Account, Transaction
from app.api.enums import TransactionType
from flask import jsonify
from marshmallow import ValidationError
import logging
from app.api.integrations import KafkaIntegration

logger = logging.getLogger(__name__)

class BaseService:
    TRANSACTION_TYPE = None

    @classmethod
    def validate_data(cls, data, schema):
        """
        Validate input data based on the provided schema.
        """
        logger.info(f"Processing {cls.TRANSACTION_TYPE} request")
        return schema.load(data)

    @classmethod
    def get_or_create_customer(cls, validated_data):
        
        """
        Check if a customer exists; if not, create one.
        """

        customer = Customer.query.filter_by(id=validated_data.get("customerId")).first()
        if not customer:
            customer = Customer.create_customer(
                id=validated_data.get("customerId"),
                msisdn=validated_data.get("msisdn"),
                country_code=validated_data.get("countryCode"),
                account_id=validated_data.get("accountId"),
            )
        return customer

    @classmethod
    def validate_account_ownership(cls, account_id, customer_id):
        """
        Check if the provided account belongs to the customer.
        """
        is_valid = Account.is_valid_account(account_id, customer_id)
        return is_valid

    @classmethod
    def log_transaction(cls, validated_data):
        """
        Create a new transaction.
        """
        channel = "USSD" if validated_data.get("channel") is None else validated_data.get("channel")

        return Transaction.create_transaction(
            transaction_id = validated_data.get("transactionId"),
            customer_id =  validated_data.get('customerId', None),
            account_id = validated_data.get("accountId", None),  
            type = cls.TRANSACTION_TYPE,
            channel = channel,
        )
    
    @classmethod
    def async_send_to_kafka(cls, loan_data, request_id, topic):
        KafkaIntegration.send_loan_request(loan_data = loan_data, request_id = request_id, topic = topic)
        KafkaIntegration.flush()


    @classmethod
    def calculate_charges(cls, offer, amount):
        """
        Calculates and returns the charges for the given offer and amount.
        
        Args:
            offer (Offer): The offer object that contains the charges.
            amount (float): The requested loan amount.
        
        Returns:
            dict: A dictionary containing the calculated charges.
        """
        if not offer or not offer.charges:
            logger.error(f"No charges found for offer ID {offer.id}")
            return {"error": "No charges found for the offer"}

        loan_charges = offer.charges
        tenor = offer.schedule # offer.tenor // 30 # Convert to months
        interest =  cls.get_charge_detail(rates = offer.interest_rate, charges = loan_charges, code = "INTEREST", amount = amount)
        management = cls.get_charge_detail(rates = offer.management_rate,  charges = loan_charges, code = "MGTFEE", amount = amount)
        insurance = cls.get_charge_detail(rates = offer.insurance_rate, charges = loan_charges, code = "INSURANCE", amount = amount)
        vat = cls.get_charge_detail(rates = offer.vat_rate, charges = loan_charges, code = "VAT", amount = amount, management_fee = management["fee"])

        # Separate fees into upfront and postpaid
        upfront_fees = [
            fee["fee"]
            for fee in [interest, management, insurance, vat]
            if fee["due_days"] == 0
        ]

        postpaid_fees = [
            fee["fee"]
            for fee in [interest, management, insurance, vat]
            if fee["due_days"] != 0
        ]
        vat_test  = vat["fee"]
        logger.info(f"VAT fee ==  *************** : {vat_test}")

        # Up-front payment: (only those fees due immediately i.e due_days == 0)
        # upfront_payment = sum(upfront_fees)
        if offer.schedule == 1:
            upfront_payment = vat["fee"] + management["fee"] + insurance["fee"] + interest["fee"]
            interest_amount = interest["fee"]
            repayment_amount = amount
        else:
            upfront_payment = vat["fee"] + insurance["fee"]+management["fee"]
            interest_amount = interest["fee"]*offer.schedule
            repayment_amount = amount +  interest_amount


        # Repayment amount: (principal + only those fees not due immediately i.e due_days != 0)
       # repayment_amount = amount + (sum(postpaid_fees) * tenor)

        # Total amount: (upfront_payment + repayment_amount)
        total_amount = upfront_payment + repayment_amount

        # Calculate the installment amount
        installment_amount = repayment_amount / offer.schedule

        return {
            "interest": interest,
            "interest_amount": interest_amount,
            "management": management,
            "insurance": insurance,
            "vat": vat,
            "upfront_payment": round(upfront_payment, 2),
            "repayment_amount": round(repayment_amount, 2),
            "installment_amount": round(installment_amount, 2),
            "total_amount": round(total_amount, 2)
        }

    
    @classmethod
    def get_charge_detail(cls, rates, charges, code, amount, management_fee= 0.0):
        """
        Get details for a specific charge code from a list of loan charges.

        Returns default values if not found.
        """
        fee = 0.0

        if code == "VAT" and management_fee > 0:
            fee = management_fee * rates / 100
        else:
            fee = amount * rates / 100

        return {
            "rate": rates,
            "fee": round(fee, 2),
            "due_days": 30,
            "code": code,
            "description" :  "have no idea how to get this yet"
        }

        # if charge.code == code:
        #     if code == "VAT" and management_fee > 0:
        #         fee = management_fee * rates / 100
        #     else:
        #         fee = amount * rates / 100
        #
        #     return {
        #         "rate": rates,
        #         "fee": round(fee, 2),
        #         "due_days": charge.due
        #     }
            
       # return {"rate": 0, "fee": 0, "due_days": 0}