Pornolab Preloaded Preview

Preloads and dynamically displays preview images below links, avoiding duplicate previews. Implements fallback to the next image if the first fails to load. Includes debug mode.
Εγκατάσταση αυτού του κώδικα Βοήθεια
Κάντε μια ερώτηση, δημοσιεύστε μια ανασκόπηση, ή αναφέρετε τον κώδικα.
Αναδίπλωση γραμμών
// ==UserScript==
// @name         Pornolab Preloaded Preview
// @version      1.6.5
// @description  Preloads and dynamically displays preview images below links, avoiding duplicate previews. Implements fallback to the next image if the first fails to load. Includes debug mode.
// @author       Ace
// @license      MIT
// @match        *://pornolab.net/forum/tracker*
// @match        *://pornolab.net/forum/viewforum*
// @match        *://pornolab.net/forum/search*
// @icon         https://static.pornolab.net/favicon.ico
// @run-at       document-end
// @grant        none
// @namespace https://greasyfork.org/users/1418199
// ==/UserScript==

(async function () {
    "use strict";

    /* ================= CONFIG ================= */

    const MIN_HEIGHT = 201;
    const MAX_CONCURRENT_FETCHES = 5;
    const PREVIEW_HEIGHT = "17rem";

    /* ================= STYLES ================= */

    const style = document.createElement("style");
    style.textContent = `
    .preview-container {
      height: ${PREVIEW_HEIGHT};
      display: flex;
      justify-content: center;
      align-items: center;
      overflow: hidden;
      margin-top: 0.5rem;

      background: #111;
      border-radius: 6px;
      font-size: 0.9rem;
      color: #888;
    }

    .preview-container img {
      max-width: 100%;
      max-height: 100%;
      object-fit: contain;
      display: block;
    }

    /* Aspect-aware soft constraints */
    .preview-container img.portrait {
      max-width: 70%;
    }

    .preview-container img.landscape {
      max-height: 80%;
    }
  `;
    document.head.appendChild(style);

    /* ================= CACHE ================= */

    // Session-only cache: topic URL -> array of preview URLs
    const previewCache = new Map();

    /* ================= HELPERS ================= */

    function buildUrl(link) {
        // IMPORTANT: preserve /forum/ path
        return new URL(link.getAttribute("href"), location.href).href;
    }

    async function fetchPreviewUrls(url) {
        if (previewCache.has(url)) {
            return previewCache.get(url);
        }

        const res = await fetch(url);
        if (!res.ok) {
            previewCache.set(url, []);
            return [];
        }

        const html = await res.text();
        const doc = new DOMParser().parseFromString(html, "text/html");

        // Forum structure guarantee:
        // <var class="postImg" title="FULL_IMAGE_URL">
        const urls = [...doc.querySelectorAll(".postImg")]
        .map(el => el.getAttribute("title"))
        .filter(Boolean);

        previewCache.set(url, urls);
        return urls;
    }

    function attachFallbackAndAspectLogic(img, urls) {
        let index = 0;

        const tryNext = () => {
            index++;
            if (index < urls.length) {
                img.src = urls[index];
            } else {
                img.replaceWith(createEmptyPlaceholder());
            }
        };

        img.addEventListener("error", tryNext);

        img.addEventListener("load", () => {
            // Reject small images
            if (img.naturalHeight < MIN_HEIGHT) {
                tryNext();
                return;
            }

            // Aspect-aware refinement (cheap, one-time)
            const ratio = img.naturalWidth / img.naturalHeight;
            if (ratio < 0.75) {
                img.classList.add("portrait");
            } else if (ratio > 1.6) {
                img.classList.add("landscape");
            }
        });
    }

    function createEmptyPlaceholder() {
        const div = document.createElement("div");
        div.className = "preview-container";
        div.textContent = "No Eligible preview found";
        return div;
    }

    function insertPreview(link, urls) {
        const container = document.createElement("div");
        container.className = "preview-container";

        if (!urls.length) {
            container.textContent = "No Eligible preview found";
            link.after(container);
            return;
        }

        const img = document.createElement("img");
        img.loading = "lazy";
        img.src = urls[0];

        attachFallbackAndAspectLogic(img, urls);

        container.appendChild(img);
        link.after(container);
    }

    /* ================= PROCESSING ================= */

    const links = [...document.querySelectorAll(".tLink, .tt-text")];
    let index = 0;

    async function worker() {
        while (index < links.length) {
            const link = links[index++];
            if (link.dataset.previewDone) continue;

            link.dataset.previewDone = "1";

            try {
                const urls = await fetchPreviewUrls(buildUrl(link));
                insertPreview(link, urls);
            } catch {
                insertPreview(link, []);
            }
        }
    }

    // Run workers (ordered, balanced)
    await Promise.all(
        Array.from({ length: MAX_CONCURRENT_FETCHES }, worker)
    );

})();