@leordev-web5/api/src/tech-preview.ts

SDK for accessing the features and capabilities of Web5

import { utils as didUtils } from '@web5/dids';

/**
 * Dynamically selects up to 2 DWN endpoints that are provided
 * by default during the Tech Preview period.
 *
 * @beta
 */
export async function getTechPreviewDwnEndpoints(): Promise<string[]> {
  let response: Response;
  try {
    response = await fetch('https://dwn.tbddev.org/.well-known/did.json');
    if (!response.ok) {
      throw new Error(`HTTP Error: ${response.status} ${response.statusText}`);
    }
  } catch(error: any) {
    console.warn('failed to get tech preview dwn endpoints:', error.message);
    return [];
  }

  const didDocument = await response.json();
  const [ dwnService ] = didUtils.getServices({ didDocument, id: '#dwn', type: 'DecentralizedWebNode' });

  // allocate up to 2 nodes for a user.
  const techPreviewEndpoints = new Set<string>();

  if ('serviceEndpoint' in dwnService
      && !Array.isArray(dwnService.serviceEndpoint)
      && typeof dwnService.serviceEndpoint !== 'string'
      && Array.isArray(dwnService.serviceEndpoint.nodes)) {
    const dwnUrls = dwnService.serviceEndpoint.nodes;

    const numNodesToAllocate = Math.min(dwnUrls.length, 2);

    for (let attempts = 0; attempts < dwnUrls.length && techPreviewEndpoints.size < numNodesToAllocate; attempts += 1) {
      const nodeIdx = getRandomInt(0, dwnUrls.length);
      const dwnUrl = dwnUrls[nodeIdx];

      try {
        const healthCheck = await fetch(`${dwnUrl}/health`);
        if (healthCheck.ok) {
          techPreviewEndpoints.add(dwnUrl);
        }
      } catch(error: unknown) {
        // Ignore healthcheck failures and try the next node.
      }
    }
  }

  return Array.from(techPreviewEndpoints);
}

function getRandomInt(min, max) {
  min = Math.ceil(min);
  max = Math.floor(max);
  return Math.floor(Math.random() * (max - min)) + min;
}