Crunchyroll subtitle unfucker userscript

crsubfix.user.js

// ==UserScript==
// @name         CR Subtitle Unfucker
// @description  crunchyroll changed from aegisub to OOONA and made it everybodys problem
// @version      0.0.1
// @namespace    rip.shi.crsubfix
// @author       shi
// @match        https://www.crunchyroll.com/watch/*
// @match        https://static.crunchyroll.com/*
// @run-at       document-start
// @grant        none
// @updateURL    https://gist.github.com/shinmai/35edc1522a966088c40d69f83287a285/raw/crsubfix.user.js
// @downloadURL  https://gist.github.com/shinmai/35edc1522a966088c40d69f83287a285/raw/crsubfix.user.js
// ==/UserScript==
(() => {
  'use strict';

  const SUB_URL = /crunchyrollcdn\.com\/static\/.*\/closed-caption-.*\.vtt/,
  RULES = [
    [/\{break\}/g, '\n'],
    [/\\N/g, '\n'],
    [/\\n/g, '\n'],
    [/\n{2,}/g, '\n'],
  ],
  isAllCapsLine = s => {
    const letters = s.replace(/<[^>]+>/g, '')
    return /[A-Z]/.test(letters) && !/[a-z]/.test(letters)
  },
  sentenceCase = text => text.replace(/([^<>]+)(?=<|$)/g, seg => seg.toLowerCase().replace(/(^|[.!?]\s+|\n)([a-z])/g, (m, p, c) => p + c.toUpperCase()).replace(/\bi\b/g, 'I')),
  fixCueText = text => {
    let out = text
    for(const [re, rep] of RULES) out = out.replace(re, rep)
    if(isAllCapsLine(out)) out = sentenceCase(out)
    return out
  },
  processVtt = vtt => {
    const lines = vtt.split('\n')
    let inCue = false
    for(let i = 0; i < lines.length; i++) {
      if(lines[i].includes('-->')) { inCue = true; continue }
      if(inCue) {
        if(lines[i].trim() === '') { inCue = false; continue }
        lines[i] = fixCueText(lines[i])
      }
    }
    return lines.join('\n')
  },
  transformBody = body => {
    try {
      let text = body
      let wasB64 = false
      if(!text.trimStart().startsWith('WEBVTT')) {
        try {
          const dec = atob(text.trim())
          if(!dec.trimStart().startsWith('WEBVTT')) return null
          text = dec
          wasB64 = true
        } catch { return null }
      }
      let fixed = processVtt(text)
      if(wasB64) fixed = btoa(unescape(encodeURIComponent(fixed)))
      return fixed
    } catch { return null }
  },
  XHR = XMLHttpRequest.prototype,
  origOpen = XHR.open,
  protoResponseText = Object.getOwnPropertyDescriptor(XHR, 'responseText').get,
  protoResponse = Object.getOwnPropertyDescriptor(XHR, 'response').get

  XHR.open = function (method, url, ...rest) {
    if (SUB_URL.test(String(url))) {
      const xhr = this
      let cached, cachedFor = null
      const getFixed = raw => {
        if(raw !== cachedFor) {
          cachedFor = raw
          const t = transformBody(raw)
          cached = t === null?raw:t
        }
        return cached
      }
      Object.defineProperty(xhr, 'responseText', {
        get() {
          const raw = protoResponseText.call(xhr)
          if (xhr.readyState !== 4) return raw
          return getFixed(raw)
        }
      })
      Object.defineProperty(xhr, 'response', {
        get() {
          if (xhr.responseType && xhr.responseType !== 'text') { return protoResponse.call(xhr) }
          const raw = protoResponse.call(xhr)
          if (xhr.readyState !== 4) return raw
          return getFixed(raw)
        }
      })
    }
    return origOpen.call(this, method, url, ...rest)
  }
})()