@blockcerts/hashlink-verifier/lib/esm/HashlinkVerifier.js

Handling hashlinks in Blockcerts

var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
    return new (P || (P = Promise))(function (resolve, reject) {
        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
        step((generator = generator.apply(thisArg, _arguments || [])).next());
    });
};
import { Hashlink } from './hashlink/Hashlink';
import * as codecs from './hashlink/codecs';
export class HashlinkVerifier {
    constructor() {
        this.hashlinkTable = {}; // keep decoded hashlinks in memory
        this.hl = new Hashlink();
        this.hl.use(new codecs.MultihashSha2256());
        this.hl.use(new codecs.MultihashBlake2b64());
        this.hl.use(new codecs.MultibaseBase58btc());
    }
    /**
     * decode method, abstract wrapper over Hashlink class from digital bazaar hashlink package
     *
     * @param {string} hashlink: the hashlink to be decoded. In this instance it expects a url to be specified.
     * @param {function} onHashlinkUrlDecoded: a callback function called when the source url has been discovered to enable
     * early manipulation (ie: update image in DOM).
     */
    decode(hashlink, onHashlinkUrlDecoded) {
        return __awaiter(this, void 0, void 0, function* () {
            var _a;
            const decodedHashlink = yield this.hl.decode({ hashlink });
            // console.log('hashlink decoded', decodedHashlink);
            if (!decodedHashlink.meta && !((_a = decodedHashlink.meta.url) === null || _a === void 0 ? void 0 : _a.length)) {
                throw new Error('unparseable document, no url provided as meta data');
            }
            this.hashlinkTable[hashlink] = decodedHashlink;
            const sourceUrl = decodedHashlink.meta.url[0];
            onHashlinkUrlDecoded === null || onHashlinkUrlDecoded === void 0 ? void 0 : onHashlinkUrlDecoded(sourceUrl);
            return decodedHashlink;
        });
    }
    verifyHashlinkTable() {
        return __awaiter(this, void 0, void 0, function* () {
            const hashlinks = Object.keys(this.hashlinkTable);
            for (let i = 0; i < hashlinks.length; i++) {
                yield this.verify(hashlinks[i])
                    .catch(error => console.log('caught an hashlink exception', error));
            }
            return true;
        });
    }
    /**
     * verify method, abstract wrapper over Hashlink class from digital bazaar hashlink package
     *
     * @param {string} hashlink: the hashlink to be decoded. It will lookup in the previously decoded hashlinks table.
     * if not found it will decode the hashlink before verification.
     */
    verify(hashlink) {
        return __awaiter(this, void 0, void 0, function* () {
            const sourceUrl = yield this.getSourceUrlFromHashlink(hashlink);
            let imageData;
            yield fetch(sourceUrl)
                .then((response) => __awaiter(this, void 0, void 0, function* () { return yield response.text(); }))
                .then(data => {
                imageData = data;
            });
            const textEncoder = new TextEncoder();
            const verified = yield this.hl.verify({
                data: textEncoder.encode(imageData), // needs an ArrayBuffer
                hashlink
            });
            if (verified) {
                console.log(`hashlink ${hashlink} bound to ${sourceUrl} was successfully verified`);
            }
            else {
                throw new Error(`Hashlink ${hashlink} does not match data from url ${sourceUrl}`);
            }
            return verified;
        });
    }
    hasHashlinksToVerify() {
        return Object.keys(this.hashlinkTable).length > 0;
    }
    getSourceUrlFromHashlink(hashlink) {
        return __awaiter(this, void 0, void 0, function* () {
            let decodedHashlink;
            if (this.hashlinkTable[hashlink]) {
                decodedHashlink = this.hashlinkTable[hashlink];
            }
            else {
                decodedHashlink = yield this.decode(hashlink);
            }
            return this.getMetaUrl(decodedHashlink);
        });
    }
    getMetaUrl(decodedHashlink) {
        return decodedHashlink.meta.url[0];
    }
}