hash.js

require('dotenv').config();
const crypto = require('crypto');

const headers = {
    "Access-Control-Allow-Origin": "*",
    "Access-Control-Allow-Headers": "Content-Type"
};

exports.handler = function(event, context, callback) {
    let nonce = event.queryStringParameters.nonce;
    let output;
    if (nonce) {
        output = getJsonOutput("200", "OK", hashWithNonce(nonce));
    } else {
        output = getJsonOutput("400", "Required querystring property is missing.", "");
    }
    if (process.env.DEBUG === "true") {
        output.debug = getDebugInfo(nonce, event, context);
        output.env = process.env;
    }

    callback(null, {
        statusCode: 200,
        headers: headers,
        body: JSON.stringify(output)
    });
}

function hashWithNonce(nonce) {
    return crypto.createHmac("SHA256", process.env.API_SECRET).update(nonce).digest("base64");
}

function getJsonOutput(status, message, hash) {
    return { "status": status, "message": message, "hash": hash };
}

function getDebugInfo(nonce, event, context) {
    return { "apiKey": process.env.API_KEY, "event": event, "context": context };
}