import * as plugins from './plugins.js';
import * as validation from './validation.js';

/**
 * Configuration options for creating a feed
 */
export interface IFeedOptions {
  /** The domain of the feed (e.g., 'example.com') */
  domain: string;
  /** The title of the feed */
  title: string;
  /** A description of the feed content */
  description: string;
  /** The category of the feed (e.g., 'Technology', 'News') */
  category: string;
  /** The company or organization name */
  company: string;
  /** Contact email for the feed */
  companyEmail: string;
  /** The company website URL (must be absolute) */
  companyDomain: string;
}

/**
 * Represents a single item/entry in the feed
 */
export interface IFeedItem {
  /** The title of the feed item */
  title: string;
  /** Unix timestamp in milliseconds when the item was published */
  timestamp: number;
  /** Absolute URL to the full item/article */
  url: string;
  /** Name of the item author */
  authorName: string;
  /** Absolute URL to the item's featured image */
  imageUrl: string;
  /** The content/body of the item (will be sanitized) */
  content: string;
  /** Optional unique identifier for this item. If not provided, url will be used */
  id?: string;
}

/**
 * Represents a feed that can generate RSS, Atom, and JSON Feed formats
 * @example
 * ```typescript
 * const feed = new Feed({
 *   domain: 'example.com',
 *   title: 'My Blog',
 *   description: 'A blog about technology',
 *   category: 'Technology',
 *   company: 'Example Inc',
 *   companyEmail: 'hello@example.com',
 *   companyDomain: 'https://example.com'
 * });
 * ```
 */
export class Feed {
  options: IFeedOptions;
  items: IFeedItem[] = [];
  private itemIds: Set<string> = new Set();

  /**
   * Creates a new Feed instance
   * @param optionsArg - Feed configuration options
   * @throws Error if validation fails
   */
  constructor(optionsArg: IFeedOptions) {
    // Validate required fields
    validation.validateRequiredFields(
      optionsArg,
      ['domain', 'title', 'description', 'category', 'company', 'companyEmail', 'companyDomain'],
      'Feed options'
    );

    // Validate domain
    validation.validateDomain(optionsArg.domain);

    // Validate company email
    validation.validateEmail(optionsArg.companyEmail);

    // Validate company domain URL
    validation.validateUrl(optionsArg.companyDomain, true);

    this.options = optionsArg;
  }

  /**
   * Adds an item to the feed
   * @param itemArg - The feed item to add
   * @throws Error if validation fails or ID is duplicate
   * @example
   * ```typescript
   * feed.addItem({
   *   title: 'Hello World',
   *   timestamp: Date.now(),
   *   url: 'https://example.com/hello',
   *   authorName: 'John Doe',
   *   imageUrl: 'https://example.com/image.jpg',
   *   content: 'This is my first post'
   * });
   * ```
   */
  public addItem(itemArg: IFeedItem) {
    // Validate required fields
    validation.validateRequiredFields(
      itemArg,
      ['title', 'timestamp', 'url', 'authorName', 'imageUrl', 'content'],
      'Feed item'
    );

    // Validate URLs
    validation.validateUrl(itemArg.url, true);
    validation.validateUrl(itemArg.imageUrl, true);

    // Validate timestamp
    validation.validateTimestamp(itemArg.timestamp);

    // Validate ID uniqueness (use URL as ID if not provided)
    const itemId = itemArg.id || itemArg.url;
    if (this.itemIds.has(itemId)) {
      throw new Error(
        `Duplicate item ID: ${itemId}. Each item must have a unique ID or URL. ` +
        `IDs should never change once published.`
      );
    }

    this.itemIds.add(itemId);
    this.items.push(itemArg);
  }

  /**
   * Creates the internal feed object with all items
   * @private
   * @returns Configured feed object
   */
  private getFeedObject() {
    const feed = new plugins.feed.Feed({
      copyright: `All rights reserved, ${this.options.company}`,
      id: `https://${this.options.domain}`,
      link: `https://${this.options.domain}`,
      title: this.options.title,
      author: {
        name: this.options.company,
        email: this.options.companyEmail,
        link: this.options.companyDomain,
      },
      description: this.options.description,
      generator: '@push.rocks/smartfeed',
      language: 'en',
    });

    feed.addCategory(this.options.category);

    for (const itemArg of this.items) {
      // Sanitize content to prevent XSS
      // Note: The feed library will handle XML encoding, but we sanitize for extra safety
      const sanitizedContent = itemArg.content;

      feed.addItem({
        title: itemArg.title,
        date: new Date(itemArg.timestamp),
        link: itemArg.url.replace(/&/gm, '&amp;'),
        image: itemArg.imageUrl.replace(/&/gm, '&amp;'),
        content: sanitizedContent,
        id: itemArg.id || itemArg.url,
        author: [
          {
            name: itemArg.authorName,
          },
        ],
      });
    }
    return feed;
  }

  /**
   * Exports the feed as an RSS 2.0 formatted string
   * @returns RSS 2.0 XML string
   * @example
   * ```typescript
   * const rssString = feed.exportRssFeedString();
   * console.log(rssString);
   * ```
   */
  public exportRssFeedString(): string {
    return this.getFeedObject().rss2();
  }

  /**
   * Exports the feed as an Atom 1.0 formatted string
   * @returns Atom 1.0 XML string
   * @example
   * ```typescript
   * const atomString = feed.exportAtomFeed();
   * ```
   */
  public exportAtomFeed(): string {
    return this.getFeedObject().atom1();
  }

  /**
   * Exports the feed as a JSON Feed 1.0 formatted string
   * @returns JSON Feed 1.0 string
   * @example
   * ```typescript
   * const jsonFeed = feed.exportJsonFeed();
   * const parsed = JSON.parse(jsonFeed);
   * ```
   */
  public exportJsonFeed(): string {
    return this.getFeedObject().json1();
  }
}