nestjs-khalti/src/khalti.service.ts

This is simple wrapper for Khalti Payment extended from @dallotech/nestjs-khalti. It supports ePayment Gateway(NEW) and transaction verification, but later more will be added. Just ping us or open pull request and contribute :)

import {BadRequestException, Inject, Injectable, InternalServerErrorException} from '@nestjs/common';
import {HttpService} from '@nestjs/axios';
import {firstValueFrom} from 'rxjs';
import {
    KHALTI_CONFIG_OPTIONS,
    KHALTI_LOOKUP_TEST_URL,
    KHALTI_LOOKUP_URL,
    KHALTI_PAYMENT_TEST_URL,
    KHALTI_PAYMENT_URL,
    KHALTI_VERIFY_URL,
    KhaltiDto, KhaltiInitResponse,
    KhaltiOptions,
    KhaltiRequestDto, KhaltiResponseDto,
    PaymentMode
} from "./khalti.interface";

@Injectable()
export class KhaltiService {
    private readonly paymentMode = null;
    private readonly secretKey = null;
    private readonly initiateUrl = null;
    private readonly initiateUrlForTest = null;
    private readonly lookupUrl = null;
    private readonly lookupUrlForTest = null;
    private readonly verifyUrl = null;

    constructor(@Inject(KHALTI_CONFIG_OPTIONS) private readonly options: KhaltiOptions, private readonly httpService: HttpService) {
        if (!options.secretKey) {
            throw new InternalServerErrorException("Secret Key for khalti payment is missing")
        }
        this.paymentMode = options.paymentMode || PaymentMode.TEST;
        this.secretKey = options.secretKey;
        this.initiateUrl = options.initiateUrl || KHALTI_PAYMENT_URL;
        this.initiateUrlForTest = options.initiateUrlForTest || KHALTI_PAYMENT_TEST_URL;
        this.lookupUrl = options.lookupUrl || KHALTI_LOOKUP_URL;
        this.lookupUrlForTest = options.lookupUrl || KHALTI_LOOKUP_TEST_URL;
        this.verifyUrl = KHALTI_VERIFY_URL;
    }


    async init(khaltiRequestDto: KhaltiRequestDto):Promise<KhaltiInitResponse> {
        const {
            returnUrl,
            websiteUrl,
            amount,
            purchaseOrderId,
            purchaseOrderName,
            customerInfo,
            amountBreakdown,
            productDetails
        } = khaltiRequestDto;
        if (!returnUrl || !websiteUrl || !amount || !purchaseOrderId || !purchaseOrderName) {
            throw new BadRequestException("Data missing for initiating Khalti payment");
        }
        const khaltiDto: KhaltiDto = {
            return_url: returnUrl,
            website_url: websiteUrl,
            amount: amount,
            purchase_order_id: purchaseOrderId,
            purchase_order_name: purchaseOrderName,
            customer_info: customerInfo,
            amount_breakdown: amountBreakdown,
            product_details: productDetails
        }

        const response =  await firstValueFrom(this.httpService
            .post(
                this.paymentMode.localeCompare(PaymentMode.TEST) == 0 ? this.initiateUrlForTest : this.initiateUrl,
                khaltiDto, {
                    headers: {
                        Authorization: this.secretKey,
                    },
                }));
        if(response && response?.status == 200 && response?.data){
            const {pidx,payment_url,expires_in,expires_at} = response?.data;
            return{
                pidx: pidx,
                paymentUrl: payment_url,
                expiresIn: expires_in,
                expiresAt: expires_at,
            }
        }
    }

    async lookUp(data: any):Promise<KhaltiResponseDto> {
        try{
            const {pidx} = data;
            if (!pidx) {
                throw new BadRequestException("pidx missing for validating khalti payment");
            }
            const response = await firstValueFrom(this.httpService
                .post(
                    this.paymentMode.localeCompare(PaymentMode.TEST) == 0 ? this.lookupUrlForTest : this.lookupUrl,
                    {pidx},
                    {
                        headers: {
                            Authorization: this.secretKey,
                        },
                    },
                ));

            if(response && response?.status == 200 && response?.data){
                const {pidx,total_amount,status,transaction_id,fee,refunded} = response?.data;
                return{
                    pidx,
                    totalAmount:total_amount,
                    status,
                    transactionId:transaction_id,
                    fee,
                    refunded
                }
            }
            throw new InternalServerErrorException('Unexpected response from Khalti lookup endpoint');
        }catch (error:any) {
            throw new InternalServerErrorException(`Error in payment verification \n ${error?.message}`);
        }
    }

}