import { Page } from '@playwright/test';
import { SEOResult, MetaTagResult, HeadingResult, LinkResult, ImageResult } from '../../types';

export class SEOValidator {
  constructor(private page: Page) {}

  async validateSEO(): Promise<SEOResult> {
    const metaTags = await this.validateMetaTags();
    const headings = await this.validateHeadings();
    const links = await this.validateLinks();
    const images = await this.validateImages();

    const score = this.calculateScore(metaTags, headings, links, images);

    return {
      score,
      metaTags,
      headings,
      links,
      images
    };
  }

  async validateMetaTags(): Promise<MetaTagResult> {
    const title = await this.page.title();
    const description = await this.page.getAttribute('meta[name="description"]', 'content');
    const keywords = await this.page.getAttribute('meta[name="keywords"]', 'content');
    const ogTitle = await this.page.getAttribute('meta[property="og:title"]', 'content');
    const ogDescription = await this.page.getAttribute('meta[property="og:description"]', 'content');
    const canonical = await this.page.getAttribute('link[rel="canonical"]', 'href');

    return {
      title: !!title && title.length >= 10 && title.length <= 60,
      description: !!description && description.length >= 50 && description.length <= 160,
      keywords: !!keywords,
      ogTitle: !!ogTitle,
      ogDescription: !!ogDescription,
      canonical: !!canonical
    };
  }

  async validateHeadings(): Promise<HeadingResult> {
    const h1Count = await this.page.locator('h1').count();
    const hasH1 = h1Count > 0;
    const multipleH1 = h1Count > 1;

    const headings = await this.page.evaluate(() => {
      const elements = document.querySelectorAll('h1, h2, h3, h4, h5, h6');
      return Array.from(elements).map(el => el.tagName);
    });

    let headingStructure = true;
    let previousLevel = 0;
    for (const heading of headings) {
      const level = parseInt(heading.charAt(1));
      if (level > previousLevel + 1) {
        headingStructure = false;
        break;
      }
      previousLevel = level;
    }

    return {
      hasH1,
      headingStructure,
      multipleH1
    };
  }

  async validateLinks(): Promise<LinkResult> {
    const links = await this.page.locator('a').all();
    let internal = 0;
    let external = 0;
    let broken = 0;

    for (const link of links) {
      const href = await link.getAttribute('href');
      if (!href) continue;

      if (href.startsWith('http')) {
        external++;
      } else {
        internal++;
      }
    }

    return {
      total: links.length,
      broken,
      internal,
      external
    };
  }

  async validateImages(): Promise<ImageResult> {
    const images = await this.page.locator('img').all();
    let withAlt = 0;
    let withoutAlt = 0;

    for (const image of images) {
      const alt = await image.getAttribute('alt');
      if (alt && alt.trim() !== '') {
        withAlt++;
      } else {
        withoutAlt++;
      }
    }

    return {
      total: images.length,
      withAlt,
      withoutAlt
    };
  }

  private calculateScore(metaTags: MetaTagResult, headings: HeadingResult, _links: LinkResult, images: ImageResult): number {
    let score = 0;
    let total = 0;

    const metaTagValues = Object.values(metaTags);
    score += metaTagValues.filter(v => v).length;
    total += metaTagValues.length;

    if (headings.hasH1) score++;
    if (headings.headingStructure) score++;
    if (!headings.multipleH1) score++;
    total += 3;

    if (images.withoutAlt === 0) score++;
    total++;

    return Math.round((score / total) * 100);
  }
}