import type * as interfaces from './interfaces/index.js';
import { XmlRenderer } from './smartsitemap.classes.xmlrenderer.js';
import { UrlsetBuilder } from './smartsitemap.classes.urlsetbuilder.js';

/**
 * Builder for sitemap index files (<sitemapindex>).
 * Used when you have multiple sitemaps that need to be referenced from a single index.
 * Every mutating method returns `this` for fluent chaining.
 */
export class SitemapIndexBuilder {
  private entries: interfaces.ISitemapIndexEntry[] = [];
  private options: interfaces.ISitemapOptions;

  constructor(options?: interfaces.ISitemapOptions) {
    this.options = options ?? {};
  }

  /** Add a sitemap index entry */
  add(entry: interfaces.ISitemapIndexEntry): this {
    this.entries.push(entry);
    return this;
  }

  /** Add a sitemap by URL, optionally with lastmod */
  addSitemap(loc: string, lastmod?: Date | string | number): this {
    const entry: interfaces.ISitemapIndexEntry = { loc };
    if (lastmod != null) {
      entry.lastmod = lastmod;
    }
    this.entries.push(entry);
    return this;
  }

  /** Add multiple sitemap entries */
  addSitemaps(entries: interfaces.ISitemapIndexEntry[]): this {
    this.entries.push(...entries);
    return this;
  }

  /**
   * Build an index and individual sitemaps from a UrlsetBuilder that needs splitting.
   * The builder's URLs are divided into chunks of maxUrlsPerSitemap.
   */
  static fromBuilder(
    builder: UrlsetBuilder,
    baseUrl: string,
  ): { index: SitemapIndexBuilder; sitemaps: UrlsetBuilder[] } {
    const urls = builder.getUrls();
    const options = builder.getOptions();
    const maxUrls = Math.min(options.maxUrlsPerSitemap ?? 50000, 50000);

    const index = new SitemapIndexBuilder(options);
    const sitemaps: UrlsetBuilder[] = [];

    for (let i = 0; i < urls.length; i += maxUrls) {
      const chunk = urls.slice(i, i + maxUrls);
      const chunkBuilder = new UrlsetBuilder(options);
      chunkBuilder.addUrls(chunk);
      sitemaps.push(chunkBuilder);

      const filename = `sitemap-${sitemaps.length}.xml`;
      index.addSitemap(`${baseUrl.replace(/\/$/, '')}/${filename}`);
    }

    return { index, sitemaps };
  }

  /** Export as sitemap index XML string */
  toXml(): string {
    return XmlRenderer.renderIndex(this.entries, this.options);
  }

  /** Get all entries */
  getEntries(): interfaces.ISitemapIndexEntry[] {
    return [...this.entries];
  }

  /** Get the number of sitemaps in this index */
  get count(): number {
    return this.entries.length;
  }
}