softseti-sale-calculator-library/src/core/refund-calculator.js

Sales calculation engine by Softseti

// src/refund-calculator.js
const {
  validateRefund,
  calculatePreviousRefundsTotal,
  calculateMaxRefundableAmount,
  findProductInSale
} = require('../utils/helpers');

class RefundCalculator {
  static calculateRefund(sale, returnItems, options, currentMemoId) {
    const existingCreditMemo = options.credit_memo || null;

    // Validate the refund request
    const validationError = validateRefund(sale, returnItems, options, currentMemoId);
    if (validationError) {
      const errorResponse = {
        valid: false,
        message: validationError,
        total_refund: existingCreditMemo?.total_refund || 0,
        return_items: existingCreditMemo?.return_items || [],
        remaining_sale_total: sale.total - calculatePreviousRefundsTotal(sale, currentMemoId),
        previous_refunds_total: calculatePreviousRefundsTotal(sale, currentMemoId),
        input_type: options.input_type
      };

      // Merge additional fields from existing credit memo
      if (existingCreditMemo) {
        Object.keys(existingCreditMemo).forEach(key => {
          if (!errorResponse.hasOwnProperty(key)) {
            errorResponse[key] = existingCreditMemo[key];
          }
        });
        // Ensure validity reflects current error state
        errorResponse.valid = false;
      }

      return errorResponse;
    }

    const previousRefundsTotal = calculatePreviousRefundsTotal(sale, options, currentMemoId);
    const maxRefundable = calculateMaxRefundableAmount(sale, currentMemoId);

    let totalRefund = 0;
    let calculatedItems = [];

    // Use existing items if available, otherwise calculate new ones
    if (existingCreditMemo?.return_items) {
      totalRefund = existingCreditMemo.return_items.reduce((sum, item) => sum + (item.refund_amount || 0), 0);
    }
    // Calculate refund based on input type
    switch (options.input_type) {
      case 'amount_only':
        calculatedItems = RefundCalculator.calculateAmountOnlyRefund(
          sale,
          options.requested_refund_amount || 0,
          maxRefundable,
          options
        );
        break;

      case 'items_with_custom_amount':
        calculatedItems = RefundCalculator.calculateCustomAmountRefund(
          sale,
          returnItems,
          options
        );
        break;

      case 'items_full_refund':
      default:
        calculatedItems = RefundCalculator.calculateFullItemRefund(
          sale,
          returnItems,
          options
        );
    }
    totalRefund = calculatedItems.reduce((sum, item) => sum + (item.refund_amount || 0), 0);

    // Scale down if exceeds max refundable amount (only for new calculations)
    if (!existingCreditMemo && totalRefund > maxRefundable) {
      const scaleFactor = maxRefundable / totalRefund;
      calculatedItems.forEach(item => {
        item.refund_amount = parseFloat((item.refund_amount * scaleFactor).toFixed(options.decimal_precision));
      });
      totalRefund = calculatedItems.reduce((sum, item) => sum + item.refund_amount, 0);
    }

    let remaining = 0
    if (existingCreditMemo?.remaining_sale_total) {
      remaining = sale.total  - previousRefundsTotal - totalRefund;

    } else {
      remaining = sale.total - previousRefundsTotal - totalRefund;

    }

    // Build result with calculated values
    const result = {
      ...sale,
      valid: true,
      total_refund: parseFloat(totalRefund.toFixed(options.decimal_precision)),
      return_items: calculatedItems,
      remaining_sale_total: parseFloat(remaining.toFixed(options.decimal_precision)),
      previous_refunds_total: previousRefundsTotal,
      input_type: options.input_type
    };

    // Preserve all existing credit memo fields not in our result
    if (existingCreditMemo) {
      Object.keys(existingCreditMemo).forEach(key => {
        if (!result.hasOwnProperty(key) && key !== 'return_items') {
          result[key] = existingCreditMemo[key];
        }
      });
    }

    return result;
  }

  static calculateAmountOnlyRefund(sale, requestedAmount, maxRefundable, options) {
    const refundAmount = Math.min(requestedAmount, maxRefundable);
    const totalSaleValue = sale.return_items.reduce(
      (sum, item) => sum + (item.price * item.sale_product_quantity), 0
    );

    return sale.return_items.map(saleItem => {
      const itemValue = saleItem.price * saleItem.sale_product_quantity;
      const proportion = totalSaleValue > 0 ? itemValue / totalSaleValue : 0;
      const itemRefund = parseFloat((refundAmount * proportion).toFixed(options.decimal_precision));
      const proportionalQuantity = saleItem.sale_product_quantity * proportion;

      // Preserve all existing item properties
      return {
        ...saleItem,  // Keep all existing properties
        quantity: parseFloat(proportionalQuantity.toFixed(options.decimal_precision)),
        refund_amount: itemRefund
      };
    });
  }

  static calculateCustomAmountRefund(sale, returnItems, options) {
    return returnItems.map(returnItem => {
      const saleItem = findProductInSale(sale, returnItem.product_id);
      if (!saleItem) return null;

      const refundAmount = returnItem.refund_amount || 0;
      const proportionalQuantity = saleItem.price !== 0
        ? parseFloat((refundAmount / saleItem.price).toFixed(options.decimal_precision))
        : 0;

      // Preserve all existing item properties
      return {
        ...saleItem,  // Keep all existing properties
        ...returnItem, // Merge with input properties
        quantity: proportionalQuantity,
        refund_amount: refundAmount
      };
    }).filter(item => item !== null);
  }

  static calculateFullItemRefund(sale, returnItems, options) {
    return returnItems.map(returnItem => {
      const saleItem = findProductInSale(sale, returnItem.product_id);
      if (!saleItem) return null;

      const quantity = returnItem.quantity ?? 0;
      const refundAmount = saleItem.price * quantity;

      // Preserve all existing item properties
      return {
        ...saleItem,  // Keep all existing properties
        ...returnItem, // Merge with input properties
        quantity: quantity,
        refund_amount: parseFloat(refundAmount.toFixed(options.decimal_precision))
      };
    }).filter(item => item !== null);
  }
}

module.exports = RefundCalculator;