edr-platform/apps/edr-freight-api/src/modules/payment/webhooks/providers/telebirr.service.ts

import { Injectable, } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import * as crypto from "crypto"
import { TelebirrDto } from '../dto/telebirr.dto';
@Injectable()
export class TelebirrWebhookService {
    // private readonly logger = new Logger(TelebirrWebhookService.name);

    constructor(
        private readonly config: ConfigService
    ) { }

    verifyTelebirrNotification(payload: TelebirrDto) {
        // 1. Extract the signature provided by Telebirr
        const { sign, ...bizContent } = payload;

        if (!sign) {
            throw new Error("Missing 'sign' field from Telebirr payload");
        }

        // 2. Sort the remaining keys alphabetically to rebuild the raw string
        const sortedKeys = Object.keys(bizContent).sort();
        const signString = sortedKeys
            .map(key => `${key}=${typeof bizContent[key] === 'object' ? JSON.stringify(bizContent[key]) : bizContent[key]}`)
            .join('&');

        // 3. Convert Telebirr's public key into an object specifying RSA-PSS padding
        const publicKey = {
            key: this.config.get<string>("telebirr.publicKey") ?? "",
            padding: crypto.constants.RSA_PKCS1_PSS_PADDING,
            saltLength: 32 // Telebirr standard salt length
        };

        // 4. Verify the signature against the sorted string
        const isVerified = crypto.verify(
            "sha256",
            Buffer.from(signString),
            publicKey,
            Buffer.from(sign, 'base64')
        );

        return isVerified;
    }

    async handle(payload: TelebirrDto): Promise<void> {
        console.log(payload)
    }

}