X/Twitter Scroll Brake

Limit visible posts on X/Twitter and reveal more on demand.
Pregunta tus dudas, ponle nota o notifica una posible infracción de las normas.
Ajuste de línea
// ==UserScript==
// @name         X/Twitter Scroll Brake
// @namespace    https://github.com/local/x-scroll-brake
// @version      1.2.5
// @description  Limit visible posts on X/Twitter and reveal more on demand.
// @license      MIT
// @match        https://x.com/*
// @match        https://twitter.com/*
// @run-at       document-idle
// @grant        none
// ==/UserScript==

(function () {
  "use strict";

  const INITIAL_VISIBLE_POSTS = 10;
  const POSTS_PER_CLICK = 5;

  const BRAKE_ID = "x-scroll-brake";
  const STYLE_ID = "x-scroll-brake-styles";
  const STORAGE_KEY = "x-scroll-brake-posts-per-click";
  const SCAN_DELAY_MS = 75;
  const ROUTE_SETTLE_DELAY_MS = 300;
  const BRAKE_PANEL_HEIGHT = 118;
  const TOP_RESET_SCROLL_Y = 120;
  const TOP_RESET_MIN_DISTANCE = 600;
  const MIN_POSTS_PER_CLICK = 1;
  const MAX_POSTS_PER_CLICK = 100;
  const MAX_SAVED_ROUTE_STATES = 12;

  let visibleItemLimit = getInitialVisiblePostLimit();
  let postsPerClick = readSavedPostsPerClick();
  let currentRouteKey = getRouteKey();
  let scanTimer = null;
  let lastTouchY = null;
  let lastScrollY = window.scrollY;
  let routeSettlesAt = 0;
  let statusRootWasSeen = false;
  let isLocked = false;
  let maxScrollY = null;
  const orderedKeys = [];
  const routeStates = new Map();

  function addStyles() {
    if (document.getElementById(STYLE_ID)) {
      return;
    }

    const style = document.createElement("style");
    style.id = STYLE_ID;
    style.textContent = `
      #${BRAKE_ID} {
        position: fixed;
        left: 50%;
        bottom: 18px;
        z-index: 2147483647;
        box-sizing: border-box;
        width: min(560px, calc(100vw - 32px));
        transform: translateX(-50%);
        padding: 14px 16px;
        border: 1px solid rgb(207, 217, 222);
        border-radius: 16px;
        background: white;
        color: rgb(15, 20, 25);
        box-shadow: 0 12px 36px rgba(15, 20, 25, 0.22);
      }

      #${BRAKE_ID}[hidden] {
        display: none !important;
      }

      #${BRAKE_ID} .x-scroll-brake-controls {
        display: flex;
        align-items: center;
        justify-content: center;
        gap: 10px;
        flex-wrap: wrap;
        font: 15px/1.3 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      }

      #${BRAKE_ID} button {
        border: 0;
        border-radius: 999px;
        padding: 10px 16px;
        background: rgb(29, 155, 240);
        color: white;
        font: 700 15px/1.2 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
        cursor: pointer;
      }

      #${BRAKE_ID} button:hover {
        background: rgb(26, 140, 216);
      }

      #${BRAKE_ID} button:focus-visible,
      #${BRAKE_ID} input:focus-visible {
        outline: 3px solid rgba(29, 155, 240, 0.35);
        outline-offset: 3px;
      }

      #${BRAKE_ID} label {
        display: inline-flex;
        align-items: center;
        gap: 6px;
        font-weight: 600;
      }

      #${BRAKE_ID} input {
        box-sizing: border-box;
        width: 64px;
        border: 1px solid rgb(207, 217, 222);
        border-radius: 8px;
        padding: 8px;
        background: white;
        color: inherit;
        font: 600 15px/1 system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      }

      #${BRAKE_ID} .x-scroll-brake-status {
        width: 100%;
        text-align: center;
        color: rgb(83, 100, 113);
        font-size: 13px;
      }

      @media (prefers-color-scheme: dark) {
        #${BRAKE_ID} {
          border-color: rgb(47, 51, 54);
          background: black;
          color: rgb(231, 233, 234);
          box-shadow: 0 12px 36px rgba(0, 0, 0, 0.5);
        }

        #${BRAKE_ID} input {
          border-color: rgb(83, 100, 113);
          background: black;
        }

        #${BRAKE_ID} .x-scroll-brake-status {
          color: rgb(113, 118, 123);
        }
      }
    `;

    document.head.appendChild(style);
  }

  function clampWholeNumber(value, fallback, min, max) {
    const number = Number(value);

    if (!Number.isFinite(number)) {
      return fallback;
    }

    return Math.min(max, Math.max(min, Math.floor(number)));
  }

  function getInitialVisiblePostLimit() {
    return clampWholeNumber(INITIAL_VISIBLE_POSTS, 10, 1, Number.MAX_SAFE_INTEGER);
  }

  function getRouteKey() {
    return `${location.pathname}${location.search}`;
  }

  function readSavedPostsPerClick() {
    let savedValue = null;

    try {
      savedValue = window.localStorage.getItem(STORAGE_KEY);
    } catch (error) {
      savedValue = null;
    }

    return clampWholeNumber(
      savedValue || POSTS_PER_CLICK,
      POSTS_PER_CLICK,
      MIN_POSTS_PER_CLICK,
      MAX_POSTS_PER_CLICK
    );
  }

  function savePostsPerClick() {
    try {
      window.localStorage.setItem(STORAGE_KEY, String(postsPerClick));
    } catch (error) {
      // The visible control still works for this page if storage is unavailable.
    }
  }

  function getMainColumn() {
    return document.querySelector('main[role="main"]');
  }

  function getTimelineRecords() {
    const main = getMainColumn();

    if (!main) {
      return [];
    }

    return getTimelineRecordsFromMain(main);
  }

  function getTimelineRecordsFromMain(main) {
    const seenItems = new Set();
    const records = [];

    Array.from(main.querySelectorAll('article[data-testid="tweet"]')).forEach((article) => {
      if (article.parentElement && article.parentElement.closest('article[data-testid="tweet"]')) {
        return;
      }

      const item = article.closest('[data-testid="cellInnerDiv"]') || article;

      if (seenItems.has(item)) {
        return;
      }

      const key = getPostKey(article);

      if (!key) {
        return;
      }

      seenItems.add(item);
      records.push({ article, item, key });
    });

    return records;
  }

  function normalizePostHref(href) {
    if (!href) {
      return "";
    }

    try {
      const url = new URL(href, location.origin);
      const statusMatch = url.pathname.match(/^\/([^/]+)\/status\/(\d+)/);

      if (statusMatch) {
        return `${statusMatch[1]}/status/${statusMatch[2]}`;
      }

      return url.pathname;
    } catch (error) {
      return href;
    }
  }

  function getPostKey(article) {
    const timestampLink = Array.from(article.querySelectorAll('a[href*="/status/"] time'))
      .map((time) => time.closest('a[href*="/status/"]'))
      .find((link) => link && link.closest('article[data-testid="tweet"]') === article);

    if (timestampLink) {
      return normalizePostHref(timestampLink.getAttribute("href"));
    }

    const statusLink = Array.from(article.querySelectorAll('a[href*="/status/"]'))
      .find((link) => link.closest('article[data-testid="tweet"]') === article);

    return statusLink ? normalizePostHref(statusLink.getAttribute("href")) : "";
  }

  function isStatusPage() {
    return /^\/[^/]+\/status\/\d+/.test(location.pathname);
  }

  function getStatusIdFromPath() {
    const match = location.pathname.match(/^\/[^/]+\/status\/(\d+)/);
    return match ? match[1] : "";
  }

  function getStatusRootIndex(records) {
    const statusId = getStatusIdFromPath();

    if (!statusId) {
      return -1;
    }

    return records.findIndex((record) => record.key.includes(`/status/${statusId}`));
  }

  function getCountableRecords(records) {
    if (!isStatusPage()) {
      return records;
    }

    const rootIndex = getStatusRootIndex(records);

    if (rootIndex !== -1) {
      statusRootWasSeen = true;
      return records.slice(rootIndex + 1);
    }

    return statusRootWasSeen ? records : [];
  }

  function rememberItemOrder(records) {
    records.forEach((record, index) => {
      if (orderedKeys.includes(record.key)) {
        return;
      }

      const previousKnownKey = findNearbyKnownKey(records, index - 1, -1);
      const nextKnownKey = findNearbyKnownKey(records, index + 1, 1);

      if (previousKnownKey) {
        orderedKeys.splice(orderedKeys.indexOf(previousKnownKey) + 1, 0, record.key);
      } else if (nextKnownKey) {
        orderedKeys.splice(orderedKeys.indexOf(nextKnownKey), 0, record.key);
      } else {
        orderedKeys.push(record.key);
      }
    });
  }

  function findNearbyKnownKey(records, startIndex, direction) {
    for (
      let index = startIndex;
      index >= 0 && index < records.length;
      index += direction
    ) {
      if (orderedKeys.includes(records[index].key)) {
        return records[index].key;
      }
    }

    return "";
  }

  function applyBrake() {
    resetAfterNavigation();

    const settleTimeLeft = routeSettlesAt - Date.now();

    if (settleTimeLeft > 0) {
      scheduleApplyBrake(settleTimeLeft);
      return;
    }

    const main = getMainColumn();

    if (!main) {
      unlockBrake();
      return;
    }

    const records = getTimelineRecordsFromMain(main);
    const countableRecords = getCountableRecords(records);

    rememberItemOrder(countableRecords);

    if (orderedKeys.length < visibleItemLimit) {
      unlockBrake();
      return;
    }

    const anchorRecord = findAnchorRecord(countableRecords);

    if (!anchorRecord) {
      unlockBrake();
      updateBrakeText();
      return;
    }

    lockAtRecord(anchorRecord);
  }

  function findAnchorRecord(records) {
    const anchorKey = orderedKeys[visibleItemLimit - 1];
    const anchorRecord = records.find((record) => record.key === anchorKey);

    if (anchorRecord) {
      return anchorRecord;
    }

    return records.find((record) => orderedKeys.indexOf(record.key) >= visibleItemLimit) || null;
  }

  function lockAtRecord(record) {
    const rect = record.item.getBoundingClientRect();
    const anchorBottom = window.scrollY + rect.bottom;
    const nextMaxScrollY = Math.max(0, anchorBottom - window.innerHeight + BRAKE_PANEL_HEIGHT);

    setMaxScrollY(nextMaxScrollY);
    isLocked = true;
    showBrake();
    updateBrakeText();
    clampScrollToBrake();
    pauseMediaAfterLimit();
  }

  function setMaxScrollY(nextMaxScrollY) {
    if (!isLocked || maxScrollY === null || nextMaxScrollY < maxScrollY) {
      maxScrollY = nextMaxScrollY;
    }
  }

  function unlockBrake() {
    isLocked = false;
    maxScrollY = null;
    hideBrake();
  }

  function ensureBrake() {
    const existingBrake = document.getElementById(BRAKE_ID);

    if (existingBrake) {
      return existingBrake;
    }

    const brake = document.createElement("div");
    brake.id = BRAKE_ID;
    brake.hidden = true;
    brake.innerHTML = `
      <div class="x-scroll-brake-controls">
        <button type="button">Load more posts</button>
        <label>
          <span>Posts</span>
          <input type="number" min="${MIN_POSTS_PER_CLICK}" max="${MAX_POSTS_PER_CLICK}" step="1" inputmode="numeric">
        </label>
        <div class="x-scroll-brake-status" aria-live="polite"></div>
      </div>
    `;

    const input = brake.querySelector("input");
    const button = brake.querySelector("button");

    input.value = String(postsPerClick);
    input.addEventListener("change", syncPostsPerClickFromInput);
    input.addEventListener("blur", syncPostsPerClickFromInput);
    input.addEventListener("input", updateBrakeText);

    button.addEventListener("click", () => {
      resetAfterNavigation();
      clearScheduledScan();
      syncPostsPerClickFromInput();
      visibleItemLimit += postsPerClick;
      unlockBrake();
      scheduleApplyBrake();
    });

    document.body.appendChild(brake);
    return brake;
  }

  function showBrake() {
    ensureBrake().hidden = false;
  }

  function hideBrake() {
    const brake = document.getElementById(BRAKE_ID);

    if (brake) {
      brake.hidden = true;
    }
  }

  function syncPostsPerClickFromInput() {
    const input = document.querySelector(`#${BRAKE_ID} input`);

    if (!input) {
      return;
    }

    postsPerClick = clampWholeNumber(
      input.value,
      postsPerClick,
      MIN_POSTS_PER_CLICK,
      MAX_POSTS_PER_CLICK
    );
    input.value = String(postsPerClick);
    savePostsPerClick();
    updateBrakeText();
  }

  function updateBrakeText() {
    const brake = ensureBrake();
    const input = brake.querySelector("input");
    const button = brake.querySelector("button");
    const status = brake.querySelector(".x-scroll-brake-status");
    const typedCount = input ? input.value : postsPerClick;
    const previewCount = clampWholeNumber(
      typedCount,
      postsPerClick,
      MIN_POSTS_PER_CLICK,
      MAX_POSTS_PER_CLICK
    );
    const itemLabel = isStatusPage() ? "items" : "posts";
    const shownCount = Math.min(visibleItemLimit, orderedKeys.length);
    const buttonText = `Load ${previewCount} more ${itemLabel}`;

    if (button && button.textContent !== buttonText) {
      button.textContent = buttonText;
    }

    if (button) {
      button.disabled = false;
    }

    if (input && document.activeElement !== input) {
      input.value = String(postsPerClick);
    }

    if (status && status.textContent !== `Showing ${shownCount} ${itemLabel}`) {
      status.textContent = `Showing ${shownCount} ${itemLabel}`;
    }
  }

  function pauseMediaAfterLimit() {
    const records = getCountableRecords(getTimelineRecords());

    records.forEach((record) => {
      const keyIndex = orderedKeys.indexOf(record.key);

      if (keyIndex >= visibleItemLimit) {
        pauseMediaInElement(record.item);
      }
    });
  }

  function pauseMediaInElement(element) {
    element.querySelectorAll("audio, video").forEach((media) => {
      media.pause();
      media.autoplay = false;
      media.removeAttribute("autoplay");
    });
  }

  function scheduleApplyBrake(delay) {
    const routeChanged = resetAfterNavigation();

    if (scanTimer !== null) {
      return;
    }

    const wait = routeChanged
      ? ROUTE_SETTLE_DELAY_MS
      : clampWholeNumber(delay, SCAN_DELAY_MS, 0, ROUTE_SETTLE_DELAY_MS);

    scanTimer = window.setTimeout(() => {
      scanTimer = null;
      applyBrake();
    }, wait);
  }

  function clearScheduledScan() {
    if (scanTimer === null) {
      return;
    }

    window.clearTimeout(scanTimer);
    scanTimer = null;
  }

  function resetAfterNavigation() {
    const nextRouteKey = getRouteKey();

    if (nextRouteKey === currentRouteKey) {
      return false;
    }

    saveCurrentRouteState();
    currentRouteKey = nextRouteKey;

    if (!restoreRouteState(nextRouteKey)) {
      resetCurrentTimelineProgress();
    }

    return true;
  }

  function saveCurrentRouteState() {
    routeStates.delete(currentRouteKey);
    routeStates.set(currentRouteKey, {
      visibleItemLimit,
      statusRootWasSeen,
      orderedKeys: orderedKeys.slice(),
    });

    while (routeStates.size > MAX_SAVED_ROUTE_STATES) {
      const oldestKey = routeStates.keys().next().value;
      routeStates.delete(oldestKey);
    }
  }

  function restoreRouteState(routeKey) {
    const state = routeStates.get(routeKey);

    if (!state) {
      return false;
    }

    visibleItemLimit = clampWholeNumber(
      state.visibleItemLimit,
      getInitialVisiblePostLimit(),
      1,
      Number.MAX_SAFE_INTEGER
    );
    statusRootWasSeen = Boolean(state.statusRootWasSeen);
    orderedKeys.length = 0;
    state.orderedKeys.forEach((key) => {
      if (key && !orderedKeys.includes(key)) {
        orderedKeys.push(key);
      }
    });
    routeSettlesAt = Date.now() + ROUTE_SETTLE_DELAY_MS;
    clearScheduledScan();
    unlockBrake();
    return true;
  }

  function resetCurrentTimelineProgress() {
    routeStates.delete(currentRouteKey);
    visibleItemLimit = getInitialVisiblePostLimit();
    routeSettlesAt = Date.now() + ROUTE_SETTLE_DELAY_MS;
    statusRootWasSeen = false;
    orderedKeys.length = 0;
    clearScheduledScan();
    unlockBrake();
  }

  function clampScrollToBrake() {
    const currentScrollY = window.scrollY;

    if (resetAfterNavigation()) {
      lastScrollY = currentScrollY;
      scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
      return;
    }

    if (shouldResetAfterTopJump(currentScrollY)) {
      resetCurrentTimelineProgress();
      lastScrollY = currentScrollY;
      scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
      return;
    }

    if (!isLocked || maxScrollY === null || window.scrollY <= maxScrollY) {
      lastScrollY = window.scrollY;
      return;
    }

    window.scrollTo({
      top: maxScrollY,
      left: window.scrollX,
      behavior: "auto",
    });
    lastScrollY = maxScrollY;
  }

  function shouldResetAfterTopJump(currentScrollY) {
    return (
      isLocked &&
      maxScrollY !== null &&
      currentScrollY <= TOP_RESET_SCROLL_Y &&
      (maxScrollY >= TOP_RESET_MIN_DISTANCE ||
        lastScrollY - currentScrollY >= TOP_RESET_MIN_DISTANCE)
    );
  }

  function preventScrollPastBrake(event) {
    if (resetAfterNavigation()) {
      scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
      return;
    }

    if (!isLocked || maxScrollY === null || isEditableTarget(event.target)) {
      return;
    }

    const deltaY = getScrollDeltaY(event);

    if (deltaY <= 0 || window.scrollY + deltaY <= maxScrollY) {
      return;
    }

    event.preventDefault();

    if (window.scrollY < maxScrollY) {
      window.scrollTo({
        top: maxScrollY,
        left: window.scrollX,
        behavior: "auto",
      });
    }
  }

  function isEditableTarget(target) {
    if (!(target instanceof Element)) {
      return false;
    }

    return Boolean(target.closest('input, textarea, select, [contenteditable="true"]'));
  }

  function getScrollDeltaY(event) {
    if (event.type === "wheel") {
      if (event.deltaMode === WheelEvent.DOM_DELTA_LINE) {
        return event.deltaY * 16;
      }

      if (event.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
        return event.deltaY * window.innerHeight;
      }

      return event.deltaY;
    }

    if (event.type === "touchmove") {
      const touch = event.touches[0];

      if (!touch || lastTouchY === null) {
        return 0;
      }

      return lastTouchY - touch.clientY;
    }

    if (event.type !== "keydown") {
      return 0;
    }

    const keyDeltas = {
      ArrowDown: 40,
      PageDown: window.innerHeight * 0.85,
      End: Number.MAX_SAFE_INTEGER,
      " ": window.innerHeight * 0.85,
    };

    return keyDeltas[event.key] || 0;
  }

  function rememberTouchPosition(event) {
    const touch = event.touches[0];
    lastTouchY = touch ? touch.clientY : null;
  }

  function forgetTouchPosition() {
    lastTouchY = null;
  }

  function handleProgressResetClick(event) {
    if (!shouldResetProgressForClick(event.target)) {
      return;
    }

    resetCurrentTimelineProgress();
    scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
  }

  function shouldResetProgressForClick(target) {
    if (!(target instanceof Element)) {
      return false;
    }

    if (target.closest('a[href="/home"], a[href$="/home"]')) {
      return true;
    }

    const control = target.closest('button, [role="button"], a');

    if (!control) {
      return false;
    }

    const label = `${control.getAttribute("aria-label") || ""} ${control.textContent || ""}`;

    return /\b(back|scroll)\s+to\s+top\b|\bshow\s+\d+\s+(new\s+)?posts?\b/i.test(label);
  }

  function handleTopResetShortcut(event) {
    if (isEditableTarget(event.target)) {
      return;
    }

    if (event.key !== "Home" && !((event.metaKey || event.ctrlKey) && event.key === "ArrowUp")) {
      return;
    }

    resetCurrentTimelineProgress();
    scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
  }

  function installNavigationHooks() {
    const notifyNavigation = () => {
      if (resetAfterNavigation()) {
        scheduleApplyBrake(ROUTE_SETTLE_DELAY_MS);
      }
    };

    ["pushState", "replaceState"].forEach((methodName) => {
      const originalMethod = history[methodName];

      if (typeof originalMethod !== "function") {
        return;
      }

      history[methodName] = function () {
        const result = originalMethod.apply(this, arguments);
        window.setTimeout(notifyNavigation, 0);
        return result;
      };
    });

    window.addEventListener("popstate", notifyNavigation);
  }

  function boot() {
    addStyles();
    ensureBrake();
    installNavigationHooks();
    applyBrake();

    const observer = new MutationObserver(() => {
      scheduleApplyBrake();
    });
    observer.observe(document.body, {
      childList: true,
      subtree: true,
    });

    window.addEventListener("scroll", clampScrollToBrake, { passive: true });
    window.addEventListener("click", handleProgressResetClick, {
      capture: true,
      passive: true,
    });
    window.addEventListener("wheel", preventScrollPastBrake, {
      capture: true,
      passive: false,
    });
    window.addEventListener("keydown", handleTopResetShortcut, {
      capture: true,
    });
    window.addEventListener("keydown", preventScrollPastBrake, {
      capture: true,
    });
    window.addEventListener("touchstart", rememberTouchPosition, {
      capture: true,
      passive: true,
    });
    window.addEventListener("touchmove", preventScrollPastBrake, {
      capture: true,
      passive: false,
    });
    window.addEventListener("touchmove", rememberTouchPosition, {
      capture: true,
      passive: true,
    });
    window.addEventListener("touchend", forgetTouchPosition, {
      capture: true,
      passive: true,
    });
  }

  if (document.readyState === "loading") {
    document.addEventListener("DOMContentLoaded", boot, { once: true });
  } else {
    boot();
  }
})();