Substack Newsletter Provider (providers/substack.ts)

Implements NewsletterProviderInterface for Substack, generating embed URLs and indicating iframe‑only integration.

// Source: https://github.com/mperkins0155/llms-txt-hub | License: MIT | Copyright 2025 David Dias
// Provided via justclaw.it.com; keep this notice with the code.
import type {
  NewsletterProviderInterface,
  NewsletterSubscriber,
  SubscribeRequest,
  SubscribeResponse,
  SubstackConfig
} from '../types'

export class SubstackProvider implements NewsletterProviderInterface {
  private config: SubstackConfig

  constructor(config: SubstackConfig) {
    this.config = config

    if (!config.publicationUrl) {
      throw new Error('Substack publication URL is required')
    }
  }

  async subscribe(_data: SubscribeRequest): Promise<SubscribeResponse> {
    // Substack doesn't have an API - it uses an embedded iframe
    // This provider is mainly for configuration and generating the embed 

... (truncated -- full source via MCP)