@bsv/sdk/dist/esm/src/storage/StorageDownloader.js

BSV Blockchain Software Development Kit

import { LookupResolver } from '../overlay-tools/index.js';
import { StorageUtils } from './index.js';
import PushDrop from '../script/templates/PushDrop.js';
import Transaction from '../transaction/Transaction.js';
import { Hash, Utils } from '../primitives/index.js';
export class StorageDownloader {
    networkPreset = 'mainnet';
    lookupResolver;
    constructor(config) {
        this.networkPreset = config?.networkPreset ?? 'mainnet';
        this.lookupResolver = new LookupResolver({ networkPreset: this.networkPreset });
    }
    /**
     * Resolves the UHRP URL to a list of HTTP URLs where content can be downloaded.
     * @param uhrpUrl The UHRP URL to resolve.
     * @returns A promise that resolves to an array of HTTP URLs.
     */
    async resolve(uhrpUrl) {
        // Use UHRP lookup service
        const response = await this.lookupResolver.query({ service: 'ls_uhrp', query: { uhrpUrl } });
        if (response.type !== 'output-list') {
            throw new Error('Lookup answer must be an output list');
        }
        const decodedResults = [];
        const currentTime = Math.floor(Date.now() / 1000);
        for (let i = 0; i < response.outputs.length; i++) {
            const tx = Transaction.fromBEEF(response.outputs[i].beef);
            const { fields } = PushDrop.decode(tx.outputs[response.outputs[i].outputIndex].lockingScript);
            const expiryTime = new Utils.Reader(fields[3]).readVarIntNum();
            if (expiryTime < currentTime) {
                continue;
            }
            decodedResults.push(Utils.toUTF8(fields[2]));
        }
        return decodedResults;
    }
    /**
     * Downloads the content from the UHRP URL after validating the hash for integrity.
     * @param uhrpUrl The UHRP URL to download.
     * @returns A promise that resolves to the downloaded content.
     */
    async download(uhrpUrl) {
        if (!StorageUtils.isValidURL(uhrpUrl)) {
            throw new Error('Invalid parameter UHRP url');
        }
        const hash = StorageUtils.getHashFromURL(uhrpUrl);
        const expected = Utils.toHex(hash);
        const downloadURLs = await this.resolve(uhrpUrl);
        if (!Array.isArray(downloadURLs) || downloadURLs.length === 0) {
            throw new Error('No one currently hosts this file!');
        }
        for (let i = 0; i < downloadURLs.length; i++) {
            try {
                // The url is fetched
                const result = await fetch(downloadURLs[i], { method: 'GET' });
                // If the request fails, continue to the next url
                if (!result.ok || result.status >= 400 || result.body == null) {
                    continue;
                }
                const reader = result.body.getReader();
                const hashStream = new Hash.SHA256();
                const chunks = [];
                let totalLength = 0;
                while (true) {
                    const { done, value } = await reader.read();
                    if (done)
                        break;
                    hashStream.update(Array.from(value));
                    chunks.push(value);
                    totalLength += value.length;
                }
                const digest = Utils.toHex(hashStream.digest());
                if (digest !== expected) {
                    throw new Error('Data integrity error: value of content does not match hash of the url given');
                }
                const data = new Uint8Array(totalLength);
                let offset = 0;
                for (const chunk of chunks) {
                    data.set(chunk, offset);
                    offset += chunk.length;
                }
                return {
                    data,
                    mimeType: result.headers.get('Content-Type')
                };
            }
            catch (error) {
                continue;
            }
        }
        throw new Error(`Unable to download content from ${uhrpUrl}`);
    }
}
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