// ==UserScript==
// @name         Archive Links for Images (Throttled, Non-duplicating)
// @namespace    https://perplexity.ai
// @version      1.0.0
// @description  Adds archive/wayback links under valid images in posting areas, throttled and deduplicated.
// @author       Perplexity QA AI
// @include      */threads/*
// @grant        none
// @run-at       document-end
// ==/UserScript==

(function() {
  'use strict';

  // ---- Configurable: posting area selector ----
  const POSTING_AREA_SELECTOR = 'body'; // Change e.g. '.message-body' as needed

  // ---- Exclusion logic, per spec ----
  function isExcluded(src) {
    if (!src) return true;
    return (
      src.includes('https://static.cdninstagram.com') ||
      src.includes('/data/avatars/') ||
      src.includes('twimg.com/profile_images') ||
      src.includes('twitter.com/profile_images') ||
      src.startsWith('https://www.thecoli.com/styles/') ||
      src.startsWith('data:image/') ||
      src.startsWith('https://cdn.jsdelivr.net') ||
      src.toLowerCase().includes('unicode') ||
      src.toLowerCase().includes('favicon')
    );
  }

  // ---- Marking processed images for deduplication ----
  const ARCHIVE_MARK = 'data-archive-links';

  // ---- Archive Link Generation ----
  function createArchiveLinks(url) {
    const archiveUrl = 'https://web.archive.org/save/' + encodeURIComponent(url);
    const archiveIsUrl = 'https://archive.is/?run=1&url=' + encodeURIComponent(url);
    const viewArchiveUrl = 'https://web.archive.org/web/*/' + encodeURIComponent(url);

    // Container
    const div = document.createElement('div');
    div.style.textAlign = 'center';
    div.style.fontSize = '12px';
    div.style.marginTop = '2px';

    // Archive (Wayback Save) link
    const aArchive = document.createElement('a');
    aArchive.href = archiveUrl;
    aArchive.textContent = 'archive';
    aArchive.target = '_blank';
    aArchive.rel = 'noopener noreferrer';
    aArchive.style.textDecoration = 'underline';

    // Archive.is link
    const aArchiveIs = document.createElement('a');
    aArchiveIs.href = archiveIsUrl;
    aArchiveIs.textContent = 'archive.is';
    aArchiveIs.target = '_blank';
    aArchiveIs.rel = 'noopener noreferrer';
    aArchiveIs.style.textDecoration = 'underline';
    aArchiveIs.style.margin = '0 5px';

    // View archive (Wayback Index)
    const aView = document.createElement('a');
    aView.href = viewArchiveUrl;
    aView.textContent = 'view archive';
    aView.target = '_blank';
    aView.rel = 'noopener noreferrer';
    aView.style.textDecoration = 'underline';

    div.appendChild(aArchive);
    div.appendChild(document.createTextNode(' | '));
    div.appendChild(aArchiveIs);
    div.appendChild(document.createTextNode(' | '));
    div.appendChild(aView);

    return div;
  }

  // ---- Main processing logic ----
  function processImages() {
    const area = document.querySelector(POSTING_AREA_SELECTOR);
    if (!area) return;

    area.querySelectorAll('img').forEach(img => {
      if (img.hasAttribute(ARCHIVE_MARK)) return; // Already processed
      const src = img.getAttribute('src') || '';
      if (isExcluded(src)) return;
      img.setAttribute(ARCHIVE_MARK, '1');
      const links = createArchiveLinks(src);
      // Insert after image, in DOM order
      if (img.nextSibling) {
        img.parentNode.insertBefore(links, img.nextSibling);
      } else {
        img.parentNode.appendChild(links);
      }
    });
  }

  // ---- Throttled mutation observer logic ----
  let throttleTimeout = null;
  function throttledProcess() {
    if (throttleTimeout) return;
    throttleTimeout = setTimeout(() => {
      throttleTimeout = null;
      processImages();
    }, 300); // 300ms throttle; adjust if needed
  }

  // Observe entire posting area for changes
  const observer = new MutationObserver(throttledProcess);
  observer.observe(document.querySelector(POSTING_AREA_SELECTOR), {
    childList: true,
    subtree: true
  });

  // Process initially on DOM ready
  processImages();

  // Self-check mechanism to prevent excessive CPU usage on complex pages
  let cycleCount = 0;
  const MAX_CYCLES = 10;
  const cycleMonitor = setInterval(() => {
    if (++cycleCount > MAX_CYCLES) {
      // If we're still active after many cycles, reduce observation sensitivity
      observer.disconnect();

      // Reconnect with more conservative settings
      observer.observe(document.querySelector(POSTING_AREA_SELECTOR), {
        childList: true,
        subtree: true,
        attributes: false,
        characterData: false
      });

      clearInterval(cycleMonitor);
    }
  }, 5000);

  // Cleanup function - explicit disconnect when page unloads
  window.addEventListener('beforeunload', () => {
    observer.disconnect();
    clearInterval(cycleMonitor);
    if (throttleTimeout) {
      clearTimeout(throttleTimeout);
      throttleTimeout = null;
    }
  }, { once: true });

  // Handle potential errors to prevent script failure
  window.addEventListener('error', (e) => {
    if (e.error && e.error.message && e.error.message.includes('observer')) {
      console.error('Image Archive Links: Observer error detected, reconnecting');
      try {
        observer.disconnect();
        setTimeout(() => {
          observer.observe(document.querySelector(POSTING_AREA_SELECTOR), {
            childList: true,
            subtree: true
          });
        }, 1000);
      } catch (err) {
        console.error('Image Archive Links: Recovery failed');
      }
    }
  });
})();