lbx-invoice/src/utilities/invoice-calc.utilities.ts

Provides functionality around generating invoices.

import { BigNumber, BigNumberUtilities } from './big-number.utilities';
import { BaseInvoice, InvoiceItem, Vat } from '../models';

/**
 * Provides functionality around calculating invoices/prices.
 */
export abstract class InvoiceCalcUtilities {
    /**
     * Gets the total price of an item before tax.
     * @param item - The invoice item to get the price from.
     * @returns The amount of the item times its price.
     */
    static getItemTotalPriceBeforeTax(item: InvoiceItem): BigNumber {
        return BigNumberUtilities.multiply(item.amount, item.price);
    }

    /**
     * Gets the total price of an item after tax.
     * @param item - The invoice item to get the price from.
     * @returns The total price before tax times 1 + tax/100.
     */
    static getItemTotalPriceAfterTax(item: InvoiceItem): BigNumber {
        const itemTotalBeforeTax: BigNumber = InvoiceCalcUtilities.getItemTotalPriceBeforeTax(item);
        const taxMultiplier: BigNumber = BigNumberUtilities.add(1, BigNumberUtilities.divide(item.vat.rate, 100));
        return BigNumberUtilities.multiply(itemTotalBeforeTax, taxMultiplier);
    }

    /**
     * Gets the total tax for the given item.
     * @param item - The item to get the total tax from.
     * @returns The total price before tax times tax/100.
     */
    static getItemTotalTax(item: InvoiceItem): BigNumber {
        const itemTotalBeforeTax: BigNumber = InvoiceCalcUtilities.getItemTotalPriceBeforeTax(item);
        return BigNumberUtilities.multiply(itemTotalBeforeTax, BigNumberUtilities.divide(item.vat.rate, 100));
    }

    /**
     * Gets the total price of an invoice before tax.
     * @param invoice - The invoice to get the price from.
     * @returns The addition of the total price before tax of all items in the invoice. If this would be negative this returns 0.
     */
    static getTotalBeforeTax<Invoice extends BaseInvoice>(invoice: Invoice): BigNumber {
        let res: BigNumber = BigNumberUtilities.new(0);
        for (const item of invoice.items) {
            res = BigNumberUtilities.add(res, InvoiceCalcUtilities.getItemTotalPriceBeforeTax(item));
        }
        return res.lt(0) ? BigNumberUtilities.new(0) : res;
    }

    /**
     * Gets the total price of an invoice after tax.
     * @param invoice - The invoice to get the price from.
     * @returns The addition of the total price before tax and the total tax of the invoice.
     */
    static getTotalAfterTax<Invoice extends BaseInvoice>(invoice: Invoice): BigNumber {
        const totalBeforeTax: BigNumber = InvoiceCalcUtilities.getTotalBeforeTax(invoice);
        const totalTax: BigNumber = InvoiceCalcUtilities.getTotalTax(invoice);
        return BigNumberUtilities.add(totalBeforeTax, totalTax);
    }

    /**
     * Gets the total tax of the invoice.
     * @param invoice - The invoice to get the total tax from.
     * @returns The addition of the tax of all items of the invoice.
     */
    static getTotalTax<Invoice extends BaseInvoice>(invoice: Invoice): BigNumber {
        let res: BigNumber = BigNumberUtilities.new(0);
        for (const item of invoice.items) {
            res = BigNumberUtilities.add(res, InvoiceCalcUtilities.getItemTotalTax(item));
        }
        return res;
    }

    /**
     * Gets the total tax for a specific tax group (eg. 19%).
     * @param invoice - The invoice to get the total tax from.
     * @param group - The tax group for which the total tax should be calculated.
     * @param groupOnlyByRate - Whether or not VAT groups are only determined by rate and not by category code.
     * @returns The addition of the tax of all items that are in the provided tax group.
     */
    static getTotalTaxForTaxGroup<Invoice extends BaseInvoice>(invoice: Invoice, group: Vat, groupOnlyByRate: boolean): BigNumber {
        const itemsInTaxGroup: InvoiceItem[] = this.getItemsForTaxGroup(invoice, group, groupOnlyByRate);
        let res: BigNumber = BigNumberUtilities.new(0);
        for (const item of itemsInTaxGroup) {
            res = BigNumberUtilities.add(res, InvoiceCalcUtilities.getItemTotalTax(item));
        }
        return res;
    }

    /**
     * Gets the total price of an invoice before tax.
     * @param invoice - The invoice to get the price from.
     * @param group - The tax group to get the total before from.
     * @param groupOnlyByRate - Whether or not VAT groups are only determined by rate and not by category code.
     * @returns The addition of the total price before tax of all items in the invoice. If this would be negative this returns 0.
     */
    static getTotalBeforeTaxForTaxGroup<Invoice extends BaseInvoice>(invoice: Invoice, group: Vat, groupOnlyByRate: boolean): BigNumber {
        const itemsInTaxGroup: InvoiceItem[] = this.getItemsForTaxGroup(invoice, group, groupOnlyByRate);
        let res: BigNumber = BigNumberUtilities.new(0);
        for (const item of itemsInTaxGroup) {
            res = BigNumberUtilities.add(res, InvoiceCalcUtilities.getItemTotalPriceBeforeTax(item));
        }
        return res.lt(0) ? BigNumberUtilities.new(0) : res;
    }

    private static getItemsForTaxGroup<Invoice extends BaseInvoice>(invoice: Invoice, group: Vat, groupOnlyByRate: boolean): InvoiceItem[] {
        const itemsInTaxGroup: InvoiceItem[] = invoice.items.filter(item => {
            if (groupOnlyByRate) {
                return item.vat.rate === group.rate;
            }
            return item.vat.categoryCode === group.categoryCode && item.vat.rate === group.rate;
        });
        return itemsInTaxGroup;
    }
}