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[] = [];
  protected 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);
  }

  /**
   * Escapes special XML characters
   * @protected
   * @param str - String to escape
   * @returns Escaped string
   */
  protected escapeXml(str: string): string {
    return str
      .replace(/&/g, '&amp;')
      .replace(/</g, '&lt;')
      .replace(/>/g, '&gt;')
      .replace(/"/g, '&quot;')
      .replace(/'/g, '&apos;');
  }

  /**
   * Formats a Date object to RFC 822 format for RSS 2.0
   * @private
   * @param date - Date to format
   * @returns RFC 822 formatted date string
   */
  private formatRfc822Date(date: Date): string {
    return date.toUTCString();
  }

  /**
   * Formats a Date object to ISO 8601 format for Atom/JSON
   * @private
   * @param date - Date to format
   * @returns ISO 8601 formatted date string
   */
  private formatIso8601Date(date: Date): string {
    return date.toISOString();
  }

  /**
   * Generates RSS 2.0 feed
   * @private
   * @returns RSS 2.0 XML string
   */
  private generateRss2(): string {
    let rss = '<?xml version="1.0" encoding="utf-8"?>\n';
    rss += '<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">\n';
    rss += '<channel>\n';

    // Channel metadata
    rss += `<title>${this.escapeXml(this.options.title)}</title>\n`;
    rss += `<link>https://${this.options.domain}</link>\n`;
    rss += `<description>${this.escapeXml(this.options.description)}</description>\n`;
    rss += `<language>en</language>\n`;
    rss += `<copyright>All rights reserved, ${this.escapeXml(this.options.company)}</copyright>\n`;
    rss += `<generator>@push.rocks/smartfeed</generator>\n`;
    rss += `<lastBuildDate>${this.formatRfc822Date(new Date())}</lastBuildDate>\n`;
    rss += `<category>${this.escapeXml(this.options.category)}</category>\n`;

    // Atom self link
    rss += `<atom:link href="https://${this.options.domain}/feed.xml" rel="self" type="application/rss+xml" />\n`;

    // Items
    for (const item of this.items) {
      rss += '<item>\n';
      rss += `<title>${this.escapeXml(item.title)}</title>\n`;
      rss += `<link>${item.url}</link>\n`;
      rss += `<guid isPermaLink="true">${item.id || item.url}</guid>\n`;
      rss += `<pubDate>${this.formatRfc822Date(new Date(item.timestamp))}</pubDate>\n`;
      rss += `<description>${this.escapeXml(item.content)}</description>\n`;
      rss += `<author>${this.options.companyEmail} (${this.escapeXml(item.authorName)})</author>\n`;
      rss += `<enclosure url="${item.imageUrl}" type="image/jpeg" length="0" />\n`;
      rss += '</item>\n';
    }

    rss += '</channel>\n';
    rss += '</rss>';

    return rss;
  }

  /**
   * Generates Atom 1.0 feed
   * @private
   * @returns Atom 1.0 XML string
   */
  private generateAtom1(): string {
    let atom = '<?xml version="1.0" encoding="utf-8"?>\n';
    atom += '<feed xmlns="http://www.w3.org/2005/Atom">\n';

    // Feed metadata
    atom += `<id>https://${this.options.domain}</id>\n`;
    atom += `<title>${this.escapeXml(this.options.title)}</title>\n`;
    atom += `<subtitle>${this.escapeXml(this.options.description)}</subtitle>\n`;
    atom += `<link href="https://${this.options.domain}" />\n`;
    atom += `<link href="https://${this.options.domain}/feed.xml" rel="self" />\n`;
    atom += `<updated>${this.formatIso8601Date(new Date())}</updated>\n`;
    atom += `<generator>@push.rocks/smartfeed</generator>\n`;
    atom += '<author>\n';
    atom += `<name>${this.escapeXml(this.options.company)}</name>\n`;
    atom += `<email>${this.options.companyEmail}</email>\n`;
    atom += `<uri>${this.options.companyDomain}</uri>\n`;
    atom += '</author>\n';
    atom += '<category>\n';
    atom += `<term>${this.escapeXml(this.options.category)}</term>\n`;
    atom += '</category>\n';

    // Entries
    for (const item of this.items) {
      atom += '<entry>\n';
      atom += `<id>${item.id || item.url}</id>\n`;
      atom += `<title>${this.escapeXml(item.title)}</title>\n`;
      atom += `<link href="${item.url}" />\n`;
      atom += `<updated>${this.formatIso8601Date(new Date(item.timestamp))}</updated>\n`;
      atom += '<author>\n';
      atom += `<name>${this.escapeXml(item.authorName)}</name>\n`;
      atom += '</author>\n';
      atom += '<content type="html">\n';
      atom += this.escapeXml(item.content);
      atom += '\n</content>\n';
      atom += `<link rel="enclosure" href="${item.imageUrl}" type="image/jpeg" />\n`;
      atom += '</entry>\n';
    }

    atom += '</feed>';

    return atom;
  }

  /**
   * Generates JSON Feed 1.0
   * @private
   * @returns JSON Feed 1.0 string
   */
  private generateJsonFeed(): string {
    const jsonFeed = {
      version: 'https://jsonfeed.org/version/1',
      title: this.options.title,
      home_page_url: `https://${this.options.domain}`,
      feed_url: `https://${this.options.domain}/feed.json`,
      description: this.options.description,
      icon: '',
      favicon: '',
      author: {
        name: this.options.company,
        url: this.options.companyDomain,
      },
      items: this.items.map(item => ({
        id: item.id || item.url,
        url: item.url,
        title: item.title,
        content_html: item.content,
        image: item.imageUrl,
        date_published: this.formatIso8601Date(new Date(item.timestamp)),
        author: {
          name: item.authorName,
        },
      })),
    };

    return JSON.stringify(jsonFeed, null, 2);
  }

  /**
   * 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.generateRss2();
  }

  /**
   * 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.generateAtom1();
  }

  /**
   * 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.generateJsonFeed();
  }
}