Kez/nodejs/packages/kez-channels/src/bluesky.ts

// Bluesky channel: queries the public AppView's getAuthorFeed (no auth)
// and scans post text for KEZ proofs.

import type { Identity } from "@kez/core";
import { ChannelError, type Channel, type ChannelHit, parseAndVerifyFor } from "./index.js";

const DEFAULT_APPVIEW = "https://public.api.bsky.app";
const USER_AGENT = "kez-channels-node/0.1 (+https://example.invalid/kez)";

export interface BlueskyChannelOptions {
  appviewBase?: string;
  fetch?: typeof fetch;
}

export class BlueskyChannel implements Channel {
  readonly system = "bluesky";
  private readonly base: string;
  private readonly fetch: typeof fetch;

  constructor(opts: BlueskyChannelOptions = {}) {
    this.base = opts.appviewBase ?? DEFAULT_APPVIEW;
    this.fetch = opts.fetch ?? globalThis.fetch;
  }

  async fetchAndVerify(identity: Identity): Promise<ChannelHit> {
    const actor = identity.id;
    if (!actor) throw ChannelError.other("bluesky identity has empty handle");

    const url = authorFeedUrl(this.base, actor);
    let resp: Response;
    try {
      resp = await this.fetch(url, { headers: { "User-Agent": USER_AGENT } });
    } catch (e) {
      throw ChannelError.unreachable(`GET ${url}: ${(e as Error).message}`, e);
    }
    if (!resp.ok) throw ChannelError.unreachable(`GET ${url}: ${resp.status}`);
    const body = (await resp.json()) as unknown;
    const candidates = extractPostTexts(body);

    let lastError: ChannelError | undefined;
    for (const text of candidates) {
      try {
        return parseAndVerifyFor(text, identity);
      } catch (e) {
        lastError = e instanceof ChannelError ? e : ChannelError.invalid((e as Error).message, e);
      }
    }
    throw lastError ?? ChannelError.notFound(identity);
  }
}

export function authorFeedUrl(base: string, actor: string): string {
  return `${base}/xrpc/app.bsky.feed.getAuthorFeed?actor=${encodeURIComponent(actor)}&limit=100`;
}

export function extractPostTexts(body: unknown): string[] {
  if (typeof body !== "object" || body === null) return [];
  const feed = (body as Record<string, unknown>).feed;
  if (!Array.isArray(feed)) return [];
  const out: string[] = [];
  for (const item of feed) {
    const text = (((item as Record<string, unknown>)?.post as Record<string, unknown>)
      ?.record as Record<string, unknown>)?.text;
    if (typeof text === "string" && text.trim().length > 0) out.push(text);
  }
  return out;
}