tingxie.user.js

// ==UserScript==
// @name         tingxie
// @namespace    https://gist.github.com/iron9light/155fb046393b504304b54a1e855715e6
// @version      0.1.21
// @description  Ting Xie
// @author       iron9light
// @match        https://www.youtube.com/watch*
// @grant        none
// @require      https://code.jquery.com/jquery-3.6.0.min.js
// @require      https://cdnjs.cloudflare.com/ajax/libs/immutable/3.8.2/immutable.min.js
// @uploadURL    https://gist.githubusercontent.com/iron9light/155fb046393b504304b54a1e855715e6/raw/
// @downloadURL  https://gist.githubusercontent.com/iron9light/155fb046393b504304b54a1e855715e6/raw/
// ==/UserScript==

(function () {
  "use strict";

  $.when($.ready).then(async function () {
    console.info("try get caption...");
    const caption = await getCaption();
    if (caption === null) {
      console.info("no caption");
      return;
    }

    const videoController = new VideoController($("video"), caption);
    await addDOM(videoController);
  });

  function getVideoId() {
    const searchParams = new URLSearchParams(window.location.search);
    const videoId = searchParams.get("v");
    return videoId;
  }

  async function hasEnCaption(videoId) {
    const url = "https://www.youtube.com/api/timedtext?type=list&v=" + videoId;
    const xml = await $.get(url).promise();
    return $(xml).find("transcript_list > track[lang_code=en]").length > 0;
  }

  async function getCaption() {
    const json =
      ytplayer.config.args.raw_player_response ??
      JSON.parse(ytplayer.config.args.player_response);
    const captionTracks =
      json.captions.playerCaptionsTracklistRenderer.captionTracks;
    const enCaptionTrack = captionTracks.filter(
      (x) =>
        ["en", "en-US", "en-GB"].includes(x.languageCode) && x.kind !== "asr"
    );
    if (enCaptionTrack.length === 0) {
      return null;
    }
    const url = enCaptionTrack[0].baseUrl;
    const captionXml = await $.get(url).promise();
    const caption = $(captionXml)
      .find("transcript > text")
      .toArray()
      .map((x) => $(x))
      .map(
        (x) =>
          new TextLine(
            parseFloat(x.attr("start")),
            parseFloat(x.attr("dur")),
            x.text()
          )
      )
      .filter((x) => !x.isSound);

    if (caption.length === 0) {
      return null;
    }

    return caption;
  }

  const _wordSimilarityCache = {};

  function wordSimilarity(expected, actual) {
    if (actual === "") {
      return 0.0;
    }

    if (expected === actual) {
      return 1.0;
    }

    const key = expected + "|" + actual;
    if (_wordSimilarityCache.hasOwnProperty(key)) {
      return _wordSimilarityCache[key];
    }

    const distance = levenshteinDistance(actual, expected);
    const similarity = 1.0 - (distance * 1.0) / expected.length;
    const value = Math.max(similarity, 0.0);
    _wordSimilarityCache[key] = value;
    return value;
  }

  function _min(d0, d1, d2, bx, ay) {
    return d0 < d1 || d2 < d1
      ? d0 > d2
        ? d2 + 1
        : d0 + 1
      : bx === ay
      ? d1
      : d1 + 1;
  }

  function levenshteinDistance(a, b) {
    if (a === b) {
      return 0;
    }

    if (a.length > b.length) {
      var tmp = a;
      a = b;
      b = tmp;
    }

    var la = a.length;
    var lb = b.length;

    while (la > 0 && a.charCodeAt(la - 1) === b.charCodeAt(lb - 1)) {
      la--;
      lb--;
    }

    var offset = 0;

    while (offset < la && a.charCodeAt(offset) === b.charCodeAt(offset)) {
      offset++;
    }

    la -= offset;
    lb -= offset;

    if (la === 0 || lb < 3) {
      return lb;
    }

    var x = 0;
    var y;
    var d0;
    var d1;
    var d2;
    var d3;
    var dd;
    var dy;
    var ay;
    var bx0;
    var bx1;
    var bx2;
    var bx3;

    var vector = [];

    for (y = 0; y < la; y++) {
      vector.push(y + 1);
      vector.push(a.charCodeAt(offset + y));
    }

    var len = vector.length - 1;

    for (; x < lb - 3; ) {
      bx0 = b.charCodeAt(offset + (d0 = x));
      bx1 = b.charCodeAt(offset + (d1 = x + 1));
      bx2 = b.charCodeAt(offset + (d2 = x + 2));
      bx3 = b.charCodeAt(offset + (d3 = x + 3));
      dd = x += 4;
      for (y = 0; y < len; y += 2) {
        dy = vector[y];
        ay = vector[y + 1];
        d0 = _min(dy, d0, d1, bx0, ay);
        d1 = _min(d0, d1, d2, bx1, ay);
        d2 = _min(d1, d2, d3, bx2, ay);
        dd = _min(d2, d3, dd, bx3, ay);
        vector[y] = dd;
        d3 = d2;
        d2 = d1;
        d1 = d0;
        d0 = dy;
      }
    }

    for (; x < lb; ) {
      bx0 = b.charCodeAt(offset + (d0 = x));
      dd = ++x;
      for (y = 0; y < len; y += 2) {
        dy = vector[y];
        vector[y] = dd = _min(dy, d0, dd, bx0, vector[y + 1]);
        d0 = dy;
      }
    }

    return dd;
  }

  function textNormalize(text) {
    const words = text
      .toLowerCase()
      .split(/(\s+|\.\.\.)/)
      .map((x) => x.replace(/[^a-z0-9']/g, ""))
      .filter((x) => x.length > 0);
    return words;
  }

  function originTextNormalize(text) {
    const words = text
      .replaceAll(/\[[^\[\]]+\]/g, "")
      .replaceAll(/\([^\(\)]+\)/g, "")
      .replaceAll(/\<[^\<\>]+\>/g, "")
      .toLowerCase()
      .split(/(\s+|\.\.\.)/)
      .map((x) => x.replace(/[‘’]/u, "'").replace(/[^a-z0-9']/g, ""))
      .filter((x) => x.length > 0);
    return words;
  }

  function compare(expected, actual) {
    return _compare(expected, actual, 0, 0, 0.0, Immutable.List(), -1.0);
  }

  function _compare(
    expected,
    actual,
    expectedIndex,
    actualIndex,
    score,
    result,
    threshold
  ) {
    if (expectedIndex === expected.length) {
      return { score: score, result: result };
    }

    if (actualIndex === actual.length) {
      let newResult = result;
      for (let i = expectedIndex; i < expected.length; ++i) {
        newResult = newResult.push({ score: 0.0, index: -1 });
      }

      return { score: score, result: newResult };
    }

    if (expected[expectedIndex] === actual[actualIndex]) {
      const newResult = result.push({ score: 1.0, index: actualIndex });
      return _compare(
        expected,
        actual,
        expectedIndex + 1,
        actualIndex + 1,
        score + 1.0,
        newResult,
        Math.max(score + 1.0, threshold)
      );
    }

    if (
      score +
        Math.min(
          expected.length - expectedIndex,
          actual.length - actualIndex
        ) <=
      threshold
    ) {
      return { score: -1.0, result: [] };
    }

    let solution;
    {
      const wordScore = wordSimilarity(
        expected[expectedIndex],
        actual[actualIndex]
      );
      const newResult = result.push({ score: wordScore, index: actualIndex });
      solution = _compare(
        expected,
        actual,
        expectedIndex + 1,
        actualIndex + 1,
        score + wordScore,
        newResult,
        Math.max(score + wordScore, threshold)
      );
    }

    threshold = Math.max(solution.score, threshold);
    {
      // skip one expected word
      const newResult = result.push({ score: 0.0, index: -1 });
      const solution1 = _compare(
        expected,
        actual,
        expectedIndex + 1,
        actualIndex,
        score,
        newResult,
        threshold
      );
      if (solution1.score > solution.score) {
        solution = solution1;
        threshold = Math.max(solution.score, threshold);
      }
    }

    {
      // skip one actual word
      const solution2 = _compare(
        expected,
        actual,
        expectedIndex,
        actualIndex + 1,
        score,
        result,
        threshold
      );
      if (solution2.score > solution.score) {
        solution = solution2;
      }
    }

    return solution;
  }

  async function getPanelsEle() {
    await new Promise((resolve) => setTimeout(resolve, 3000));
    //const panelsEle = $('#info');
    const panelsEle = $("#panels");
    if (panelsEle.length > 0) {
      return panelsEle;
    }

    //await new Promise(resolve => setTimeout(resolve, 1000));
    return await getPanelsEle();
  }

  async function addDOM(videoController) {
    const panelsEle = await getPanelsEle();
    const txDivEle = $("<div/>")
      .css("color", "var(--yt-spec-text-primary)")
      .css("font-size", "10px");
    const controllerDivEle = $("<div/>");
    const nextButtonEle = $("<button/>")
      .text("Next")
      .on("click", () => videoController.next(true));
    const previousButtonEle = $("<button/>")
      .text("Previous")
      .on("click", () => videoController.previous());
    const resetButtonEle = $("<button/>")
      .text("Reset")
      .on("click", () => videoController.reset());
    const showButtonEle = $("<button/>").text("Show");
    const modeSelectEle = $("<select/>")
      .append(
        $("<option/>").val("repeat").text("repeat").attr("selected", "selected")
      )
      .append($("<option/>").val("stop").text("stop"))
      .append($("<option/>").val("continue").text("continue"))
      .change((ev) => (videoController.mode = ev.target.value));
    const autoNextCheckboxEle = $('<input type="checkbox"/>')
      .attr("id", "autoNext")
      .prop("checked", true);
    const autoNextLabelEle = $("<label/>")
      .text("Auto Next")
      .attr("for", "autoNext");
    controllerDivEle
      .append(previousButtonEle)
      .append(nextButtonEle)
      .append(resetButtonEle)
      .append(showButtonEle)
      .append(modeSelectEle)
      .append(autoNextCheckboxEle)
      .append(autoNextLabelEle);
    const textDivEle = $("<div/>").css("font-size", "18px").hide();
    const scoreDivEle = $("<div/>");
    const inputDivEle = $("<div/>");
    const inputTextarea = $("<textarea/>")
      .css("width", "100%")
      .css("height", "100px");

    let _showMode = 0;
    function doShow() {
      switch (_showMode) {
        case 0:
          scoreDivEle.find(".inputhint").css("visibility", "hidden");
          textDivEle.hide();
          break;
        case 1:
          scoreDivEle.find(".inputhint").css("visibility", "visible");
          break;
        case 2:
          textDivEle.show();
          break;
      }
    }

    showButtonEle.on("click", function () {
      _showMode = (_showMode + 1) % 3;
      doShow();
    });

    let scoreTextEle;
    let _previousIndex = null;
    let _previousInputText = null;
    function dooninputchange() {
      const inputText = inputTextarea.val();
      if (
        videoController.index === _previousIndex &&
        inputText === _previousInputText
      ) {
        return;
      }

      _previousIndex = videoController.index;
      _previousInputText = inputText;
      const normalizedInput = textNormalize(inputText);
      const compareResult = compare(videoController.words, normalizedInput);
      compareResult.result.forEach((x, i) => {
        x.i = i;
        x.word = videoController.words[i];
      });
      compareResult.score /= videoController.words.length;

      if (scoreDivEle.find("span").length === 0) {
        videoController.words.forEach((word) => {
          $("<span/>")
            .text("█".repeat(word.length))
            //.css('margin-right', '3px')
            .addClass("inputhint")
            .appendTo(scoreDivEle);
        });
        $("<span/>").text("█").css("color", "pink").appendTo(scoreDivEle);
        scoreTextEle = $("<span/>").appendTo(scoreDivEle);
        doShow();
      }

      const scoreText = Math.floor(compareResult.score * 100);
      scoreTextEle.text(scoreText);

      compareResult.result.forEach((x) =>
        $(scoreDivEle.find("span")[x.i])
          .css("opacity", x.score)
          .css("color", x.score === 1.0 ? "green" : "yellow")
      );

      if (compareResult.score === 1.0 && autoNextCheckboxEle.is(":checked")) {
        videoController.next(false);
      }
    }
    function oninputchange() {
      setTimeout(dooninputchange, 1000);
    }
    inputTextarea.on("input", oninputchange);
    videoController.onReset = () => {
      _showMode = 0;
      doShow();
      textDivEle.text(videoController.decodedText);
      scoreDivEle.find("span").remove();
      inputTextarea.val("");
      oninputchange();
    };
    inputDivEle.append(inputTextarea);
    txDivEle
      .append(controllerDivEle)
      .append(inputDivEle)
      .append(textDivEle)
      .append(scoreDivEle);
    //panelsEle.before(txDivEle);
    panelsEle.append(txDivEle);
    videoController.newTextLine();
    oninputchange();
  }

  class TextLine {
    constructor(start, duration, text) {
      this.start = start;
      this.duration = duration;
      this.end = start + duration;
      this.text = text;
      const textArea = document.createElement("textarea");
      textArea.innerHTML = this.text;
      this.decodedText = textArea.value;
      this.words = originTextNormalize(this.decodedText);
    }

    isIn(time) {
      return time >= this.start && time < this.end;
    }

    isBefore(time) {
      return time < this.start;
    }

    isAfter(time) {
      return time >= this.end;
    }

    get isSound() {
      return this.words.length === 0;
    }
  }

  class VideoController {
    constructor(video, caption) {
      this.video = $(video);
      this.caption = caption;
      this.index = 0;
      this.mode = "repeat";

      const self = this;
      this.video.on("timeupdate", () => self.ontimeupdate());
      this.onReset = null;
    }

    get currentTextLine() {
      return this.caption[this.index];
    }

    ontimeupdate() {
      switch (this.mode) {
        case "repeat":
          this._ontimeupdateRepeatMode();
          break;
        case "stop":
          this._ontimeupdateStopMode();
          break;
        case "continue":
          this._ontimeupdateContinueMode();
          break;
        default:
          throw "unsupported mode: " + this.mode;
      }
    }

    _ontimeupdateRepeatMode() {
      const time = this.video[0].currentTime;
      const textLine = this.currentTextLine;
      if (textLine.isAfter(time)) {
        this._setVideoTime(textLine.start);
      }
    }

    _ontimeupdateStopMode() {
      const time = this.video[0].currentTime;
      const textLine = this.currentTextLine;
      if (textLine.isAfter(time)) {
        this.video[0].pause();
      }
    }

    _ontimeupdateContinueMode() {
      const time = this.video[0].currentTime;
      let i = this.index;
      while (true) {
        const textLine = this.caption[i];
        if (textLine.isIn(time)) {
          break;
        }

        if (textLine.isBefore(time)) {
          if (i === 0 || this.caption[i - 1].isAfter(time)) {
            break;
          } else {
            --i;
            continue;
          }
        } else {
          if (i < this.caption.length) {
            ++i;
            continue;
          } else {
            break;
          }
        }
      }

      this._search(i);
    }

    _search(i) {
      if (this.index === i) {
        return;
      }

      if (i < 0 || i >= this.caption.length) {
        throw "index out of range: " + i;
      }

      this.index = i;
      this.newTextLine();
    }

    next(force) {
      if (this.index < this.caption.length - 1) {
        this.index++;
        if (force) {
          this._setVideoTime(this.currentTextLine.start);
        }

        if (this.mode === "stop") {
          this.video[0].play();
        }

        this.newTextLine();
      }
    }

    previous() {
      if (this.index > 0) {
        this.index--;
        this._setVideoTime(this.currentTextLine.start);
        this.newTextLine();
      }
    }

    reset() {
      const textLine = this.currentTextLine;
      this._setVideoTime(textLine.start);
      this.video[0].play();
    }

    newTextLine() {
      this.decodedText = this.currentTextLine.decodedText;
      this.words = this.currentTextLine.words;
      if (this.onReset !== null) {
        this.onReset();
      }
    }

    _setVideoTime(time) {
      this.video[0].currentTime = Math.max(time - 0.5, 0);
    }
  }
})();

What exactly does this script do?