Slop-detect/src/content/discovery.ts

import type {
  ImageCandidate,
  PageCandidate,
  PageDisclosureCandidate,
  TextCandidate
} from '../shared/types';
import { discoverHeuristics } from './heuristics';

const IMAGE_ID_ATTRIBUTE = 'data-slopdetect-image-id';
const MAX_TEXT_BLOCKS = 8;
const MIN_TEXT_CHARACTERS = 300;

function isVisible(element: Element): boolean {
  const rect = element.getBoundingClientRect();
  const style = window.getComputedStyle(element);
  return rect.width > 0 && rect.height > 0 && style.visibility !== 'hidden' && style.display !== 'none';
}

function makeImageCandidate(element: Element, url: string, alt = ''): ImageCandidate | undefined {
  if (!url || !isVisible(element)) return undefined;
  const rect = element.getBoundingClientRect();
  if (rect.width < 16 || rect.height < 16) return undefined;
  const existingId = element.getAttribute(IMAGE_ID_ATTRIBUTE);
  const id = existingId || crypto.randomUUID();
  element.setAttribute(IMAGE_ID_ATTRIBUTE, id);
  return {
    id,
    url: new URL(url, document.baseURI).href,
    alt: alt.trim().slice(0, 200),
    width: Math.round(rect.width),
    height: Math.round(rect.height)
  };
}

function discoverImages(): ImageCandidate[] {
  const candidates: ImageCandidate[] = [];
  const seenUrls = new Set<string>();

  for (const image of document.querySelectorAll('img')) {
    const candidate = makeImageCandidate(image, image.currentSrc || image.src, image.alt);
    if (candidate && !seenUrls.has(candidate.url)) {
      candidates.push(candidate);
      seenUrls.add(candidate.url);
    }
  }

  for (const image of document.querySelectorAll('svg image')) {
    const href = image.getAttribute('href') || image.getAttribute('xlink:href') || '';
    const candidate = makeImageCandidate(image, href, image.getAttribute('aria-label') || 'SVG image');
    if (candidate && !seenUrls.has(candidate.url)) {
      candidates.push(candidate);
      seenUrls.add(candidate.url);
    }
  }

  const elements = [...document.querySelectorAll('body *')].slice(0, 2000);
  for (const element of elements) {
    const background = window.getComputedStyle(element).backgroundImage;
    const match = /^url\(["']?(.*?)["']?\)$/.exec(background);
    if (!match?.[1]) continue;
    const candidate = makeImageCandidate(element, match[1], element.getAttribute('aria-label') || 'Background image');
    if (candidate && !seenUrls.has(candidate.url)) {
      candidates.push(candidate);
      seenUrls.add(candidate.url);
    }
  }

  return candidates;
}

export function estimateTokens(text: string): number {
  return text.trim() ? Math.ceil(text.trim().split(/\s+/).length * 1.3) : 0;
}

function discoverText(): TextCandidate[] {
  const selectors = 'article p, main p, [role="main"] p, article li, main li, blockquote';
  const values = [...document.querySelectorAll<HTMLElement>(selectors)]
    .filter(isVisible)
    .map((element) => element.innerText.trim())
    .filter((text) => text.length >= MIN_TEXT_CHARACTERS);

  const unique = [...new Set(values)].sort((left, right) => right.length - left.length).slice(0, MAX_TEXT_BLOCKS);
  if (unique.length === 0) {
    const root = document.querySelector<HTMLElement>('article, main, [role="main"]') || document.body;
    const combined = root?.innerText.trim().slice(0, 24_000) || '';
    if (combined.length >= MIN_TEXT_CHARACTERS) unique.push(combined);
  }

  return unique.map((text) => ({ id: crypto.randomUUID(), text, tokenEstimate: estimateTokens(text) }));
}

function pushDisclosure(
  output: PageDisclosureCandidate[],
  source: string,
  value: string | null | undefined
): void {
  const trimmed = value?.trim();
  if (trimmed) output.push({ source, value: trimmed.slice(0, 2000) });
}

function discoverDisclosures(): PageDisclosureCandidate[] {
  const candidates: PageDisclosureCandidate[] = [];
  const interestingMeta = /ai|artificial|synthetic|provenance|credential|generator|content-origin/i;

  for (const meta of document.querySelectorAll<HTMLMetaElement>('meta[name], meta[property]')) {
    const name = meta.name || meta.getAttribute('property') || '';
    if (interestingMeta.test(name)) {
      pushDisclosure(candidates, `meta:${name}`, meta.content);
    }
  }

  for (const link of document.querySelectorAll<HTMLLinkElement>('link[rel]')) {
    if (/credential|provenance|c2pa|manifest/i.test(link.rel)) {
      pushDisclosure(candidates, `link:${link.rel}`, link.href);
    }
  }

  for (const script of document.querySelectorAll<HTMLScriptElement>('script[type="application/ld+json"]')) {
    if (/"(?:aiGenerated|isAIGenerated|contentOrigin|digitalSourceType)"\s*:\s*(?:true|"[^"]*(?:trainedAlgorithmicMedia|synthetic|AI)[^"]*")/i.test(script.textContent || '')) {
      pushDisclosure(candidates, 'structured-data', script.textContent);
    }
  }

  const labelSelectors = 'figcaption, small, [class*="disclosure" i], [class*="provenance" i], [class*="credit" i], [aria-label*="AI-generated" i]';
  for (const element of document.querySelectorAll<HTMLElement>(labelSelectors)) {
    const value = (element.innerText || element.getAttribute('aria-label') || '').trim();
    if (value.length <= 300 && /\b(?:AI[- ]generated|generated by AI|artificially generated|created with AI|synthetic media)\b/i.test(value)) {
      pushDisclosure(candidates, 'visible-label', value);
    }
  }

  for (const element of document.querySelectorAll<HTMLElement>('[data-ai-generated], [data-content-origin]')) {
    pushDisclosure(
      candidates,
      element.hasAttribute('data-ai-generated') ? 'data-ai-generated' : 'data-content-origin',
      element.getAttribute('data-ai-generated') || element.getAttribute('data-content-origin')
    );
  }

  return candidates;
}

export function discoverPage(): PageCandidate {
  return {
    url: location.href,
    title: document.title,
    images: discoverImages(),
    texts: discoverText(),
    disclosures: discoverDisclosures(),
    heuristics: discoverHeuristics()
  };
}

export { IMAGE_ID_ATTRIBUTE };