This is the JS library for accessing NuMoney Exchange's API

NMXClient.js

// Sign requests using:
// https://tools.ietf.org/html/draft-cavage-http-signatures-09

import hmacSHA256 from 'crypto-js/hmac-sha256';
import sha256 from 'crypto-js/sha256';
import Base64 from 'crypto-js/enc-base64';

// Signed string be MUST be built from headers in this specific order
const SIGNATURE_HEADERS = [
    "(request-target)", "host", "accept", "content-type", "x-original-length",
    "x-timestamp", "digest",
];
const SIGNATURE_HEADERS_VALUE = SIGNATURE_HEADERS.join(" ");

export class NMXClient {
    constructor(config) {
        Object.assign(this, {url: '/'}, config);

        var a = document.createElement('a');
        a.href = this.url;
        this.host = a.host;
        this.requestTarget = "post " + a.pathname + a.search;
        this.textEncoder = new TextEncoder('utf-8');
    }

    query(graphQLParams) {
        // Digest body
        const body = JSON.stringify(graphQLParams);
        const bodyDigest = Base64.stringify(sha256(body));

        // Headers to send with fetch
        var headers = {
            'accept': 'application/json',
            'content-type': 'application/json',
            'x-timestamp': Date.now(),
            'digest': 'SHA-256=' + bodyDigest,
            'x-original-length': this.textEncoder.encode(body).length
        };

        // Extra headers which cannot be set or sent
        var extraHeaders = {
            "(request-target)": this.requestTarget,
            "host": this.host
        };

        // Sign request
        var allHeaders = Object.assign({}, headers, extraHeaders);
        var stringToSignLines = SIGNATURE_HEADERS.map(header => {
            return header + ": " + allHeaders[header]
        });
        var stringToSign = stringToSignLines.join("\n");
        var signature = Base64.stringify(hmacSHA256(stringToSign, this.apiSecret));

        // Build authorization header
        var authHeaderDict = {
            'keyId': this.apiKey,
            'algorithm': 'hmac-sha256',
            'headers': SIGNATURE_HEADERS_VALUE,
            'signature': signature
        };
        var authHeaderParts = [];
        Object.entries(authHeaderDict).forEach(([k, v]) => {
            authHeaderParts.push(k + '="' + v + '"');
        });
        headers['authorization'] = "Signature " + authHeaderParts.join(",");

        // Send request
        return fetch('/', {
            method: 'POST',
            headers: headers,
            body: body
        }).then(response => response.json());
    }
};