// ==UserScript==
// @name           bilibili 视频下载
// @version        0.03.02
// @license        MIT
// @description    bilibili 视频下载，支持多种格式（现 b 站已废弃 flv 格式）
// @icon           https://static.hdslb.com/mobile/img/512.png
// @author         fwqaaq
// @namespace      https://github.com/fwqaaq/scripts
// @match          *://www.bilibili.com/video/BV*
// @match          *://m.bilibili.com/video/BV*
// @run-at         document-body
// @grant          GM.addStyle
// @grant          GM_addStyle
// @grant          GM.info
// @grant          GM_info
// @require        https://cdn.jsdelivr.net/npm/js-md5@0.8.3/src/md5.min.js
// @downloadURL https://update.greasyfork.icu/scripts/481459/bilibili%20%E8%A7%86%E9%A2%91%E4%B8%8B%E8%BD%BD.user.js
// @updateURL https://update.greasyfork.icu/scripts/481459/bilibili%20%E8%A7%86%E9%A2%91%E4%B8%8B%E8%BD%BD.meta.js
// ==/UserScript==

/**
 * @typedef {Object} DragState
 * @property {boolean} isDragging
 * @property {{x: number, y: number}} offset
 * 
 * @typedef {Object} DownloadState
 * @property {boolean} isDownloading
 */


const SCRIPT_NAME = GM.info.script.name

const downloadIcon =
  '<svg xmlns="http://www.w3.org/2000/svg" height="32" width="32" viewBox="0 0 512 512"><!--!Font Awesome Free 6.5.1 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free Copyright 2023 Fonticons, Inc.--><path d="M288 32c0-17.7-14.3-32-32-32s-32 14.3-32 32V274.7l-73.4-73.4c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3l128 128c12.5 12.5 32.8 12.5 45.3 0l128-128c12.5-12.5 12.5-32.8 0-45.3s-32.8-12.5-45.3 0L288 274.7V32zM64 352c-35.3 0-64 28.7-64 64v32c0 35.3 28.7 64 64 64H448c35.3 0 64-28.7 64-64V416c0-35.3-28.7-64-64-64H346.5l-45.3 45.3c-25 25-65.5 25-90.5 0L165.5 352H64zm368 56a24 24 0 1 1 0 48 24 24 0 1 1 0-48z"/></svg>'

const mixinKeyEncTab = [
  46, 47, 18, 2, 53, 8, 23, 32, 15, 50, 10, 31, 58, 3, 45, 35, 27, 43, 5, 49,
  33, 9, 42, 19, 29, 28, 14, 39, 12, 38, 41, 13, 37, 48, 7, 16, 24, 55, 40, 61,
  26, 17, 0, 1, 60, 51, 30, 4, 22, 25, 54, 21, 56, 59, 6, 63, 57, 62, 11, 36,
  20, 34, 44, 52,
]

/**
 * @template {new(message?:string) => Error} E - error type
 * @param {Promise<T>} p 
 * @param {E[]} errors
 * @returns {Promise<[undefined, T] | [InstanceType<E>]>}
 */
function catchError(p, errors) {
  return p.then(data => [undefined, data])
    .catch(e => {
      if (e === undefined) return [e]
      if (errors.some(err => e instanceof err)) return [e]
      throw e
    })
}

/**
 * 进度条
 * @param {Response} response 
 * @param {HTMLAnchorElement} a
 * @returns {Response}
 */
const progress = (response, a) => {
  const total = response.headers.get('Content-Length')
  let loaded = 0
  const reader = response.body.getReader()
  const stream = new ReadableStream({
    async start(controller) {
      while (true) {
        const { done, value } = await reader.read()
        if (done) break
        loaded += value.length
        a.innerText = `${((loaded / total) * 100).toFixed(0)}%`
        controller.enqueue(value)
      }
      controller.close()
    },
  })
  return new Response(stream)
}

/**
 * @param {Function} func
 * @param {number} wait
 * @param {boolean} immediate
 * @returns {Function}
 */
const debounce = (func, wait, immediate) => {
  let timer = null
  return (e) => {
    let isImmediate = !timer && immediate
    console.log(`timer: ${timer}, immediate: ${immediate}`)
    if (timer) clearTimeout(timer)
    if (isImmediate) func(e)
    timer = setTimeout(() => {
      func(e)
      timer = null
    }, wait)
  }
}

class NetWorkError extends Error {
  constructor(/**@type {string} */message) {
    super(message)
    this.name = 'NetWorkError'
  }
}

/**
 * @param {string} orig
 * @returns {string}
 */
const getMixinKey = (orig) =>
  mixinKeyEncTab
    .map((n) => orig[n])
    .join('')
    .slice(0, 32)

/**
 * 为请求参数进行 wbi 签名
 * @param {any} params
 * @param {string} img_key
 * @param {string} sub_key
 * @returns {string}
 */
function encWbi(params, img_key, sub_key) {
  const mixin_key = getMixinKey(img_key + sub_key),
    curr_time = Math.round(Date.now() / 1000),
    chr_filter = /[!'()*]/g

  Object.assign(params, { wts: curr_time }) // 添加 wts 字段
  // 按照 key 重排参数
  const query = Object.keys(params)
    .sort()
    .map((key) => {
      // 过滤 value 中的 "!'()*" 字符
      const value = params[key].toString().replace(chr_filter, '')
      return `${encodeURIComponent(key)}=${encodeURIComponent(value)}`
    })
    .join('&')

  const wbi_sign = md5(query + mixin_key) // 计算 w_rid
  return query + '&w_rid=' + wbi_sign
}

/**
 * 获取最新的 img_key 和 sub_key
 * @returns {Promise<{img_key: string, sub_key: string}>}
 */
async function getWbiKeys() {
  const response = await fetch('https://api.bilibili.com/x/web-interface/nav')
  if (!response.ok)
    throw new NetWorkError(`获取 wbi 失败，你的 HTTP 响应状态码是 ${response.status}`)
  const {
    code,
    data: {
      wbi_img: { img_url, sub_url },
    },
  } = await response.json()
  if (code === '-101') console.log('仅能下载 720p 以下的视频')
  return {
    img_key: img_url.slice(
      img_url.lastIndexOf('/') + 1,
      img_url.lastIndexOf('.')
    ),
    sub_key: sub_url.slice(
      sub_url.lastIndexOf('/') + 1,
      sub_url.lastIndexOf('.')
    ),
  }
}

/**
 * 获取 bvid 和 cid
 * @returns {Promise<[string, string]>}
 */
async function getBvidAndCid() {
  const bvid = window.location.pathname
    .split('/')
    .find((item) => item.startsWith('BV'))
  const res = await fetch(
    `https://api.bilibili.com/x/player/pagelist?bvid=${bvid}&jsonp=jsonp`
  )
  const {
    data: [{ cid }],
    code,
  } = await res.json()
  if (!res.ok)
    throw new NetWorkError(
      `获取 cid 失败，HTTP 响应状态码是 ${res.status}. code 码是 ${code}`
    )
  return [bvid, cid]
}

/**
 * 通过 dom 节点设置进度
 * @param {HTMLAnchorElement} a
 * @param {number} [qn=112]
 * @param {number} [fnval=1]
 * @returns
 */
async function getVideo(a, qn = 112, fnval = 1) {
  const [bvidError, __bvid_cid_res] = await catchError(getBvidAndCid(), [NetWorkError])
  if (bvidError) return console.error(bvidError)
  const [bvid, cid] = __bvid_cid_res

  const [keyError, keys] = await catchError(getWbiKeys(), [NetWorkError])
  if (keyError) return console.error(keyError)
  const { img_key, sub_key } = keys

  const params = { bvid, cid, qn, fnval, fnver: 0, fourk: 1 }
  const query = encWbi(params, img_key, sub_key)
  const [urlError, url] = await catchError(getVideoUrl(query), [NetWorkError])
  if (urlError) return console.error(urlError)

  console.log(`INFO:[${SCRIPT_NAME}] 视频下载链接为 ${url}`)
  const __url_res = await fetch(url)
  if (!__url_res.ok) throw new NetWorkError(`视频下载失败，响应状态码为 ${res.status}`)

  const blob = await progress(__url_res, a).blob()

  const video = URL.createObjectURL(blob)
  a.style = Object.assign(a.style, { color: "green", textDecoration: 'underline' })

  // 创建下载链接
  const downloader = document.createElement('a')
  downloader.href = video
  downloader.download = `${bvid}.mp4`
  downloader.click()

  setTimeout(() => {
    URL.revokeObjectURL(video)
    downloader.remove()
    a.remove()
  }, 0)
}

/**
 * @param {string} query
 * @returns {Promise<string>}
 */
async function getVideoUrl(query) {
  const res = await fetch(
    `https://api.bilibili.com/x/player/wbi/playurl?${query}`
  )
  if (!res.ok)
    throw new NetWorkError(`你的视频下载链接获取失败，你的响应状态码是 ${res.status}`)
  const {
    data: {
      durl: [{ url }],
    },
  } = await res.json()
  return url
}

/**
 * @returns {[HTMLDivElement, HTMLDivElement]}
 */
function createDownloaderElement() {
  const downloader = document.createElement('div')
  downloader.classList.add('downloader-icon')
  const nav = document.createElement('nav')
  nav.classList.add('downloader-nav')
  nav.innerHTML = `<div data-id="16" class="a-flag">360P 流畅</div>
                 <div data-id="32" class="a-flag">480P 清晰</div>
                 <div data-id="64" class="a-flag">720P 高清</div>
                 <div data-id="74" class="a-flag">720P60 高帧率（登陆）</div>
                 <div data-id="80" class="a-flag">1080P 高清（登陆）</div>
                 <div data-id="112" class="a-flag">1080P+ 高码率（大会员）</div>
                 <div data-id="116" class="a-flag">1080P60 高帧率（大会员）</div>
                 <div data-id="120" class="a-flag">4K 超清（大会员）</div>
                 <div class="a-flag"><a target="_blank" href="https://github.com/fwqaaq/scripts">有问题请点击该链接🔗</a></div>`

  downloader.innerHTML = `
        <div style="display: flex;justify-content: center;margin: 0 auto;align-items: center;height: inherit;">
        ${downloadIcon}
        </div>`
  const container = document.createElement('div')
  container.classList.add("downloader-container")
  container.appendChild(downloader)
  container.appendChild(nav)
  document.body.appendChild(container)
  return [downloader, nav]
}

function addStyles() {
  const styles = `
      :root{
        --init-left: 48px;
        --icon-width: 48px;
        --icon-height: 48px;
        --nav-width: 200px;
        --nav-height: 260px;
      }
      .downloader-container {
        position: fixed;
        left: var(--init-left);
        top: 74px;
        z-index: 9999;
      }
      .downloader-icon {
        width: var(--icon-width);
        height: var(--icon-height);
        background: rgb(255,117,152);
        cursor: pointer;
        border-radius: 50%;
      }
      .a-flag {
        display: flex;
        cursor: pointer;
        justify-content: space-between;
        padding: 4px 8px;
        border: rgb(242,110,137) solid 1px;
      }
      .a-flag:hover {
        color: blue;
      }
      .downloader-nav {
        display: flex;
        flex-direction: column;
        width: var(--nav-width);
        background: rgba(255,117,152, 0.8);
        max-height: 0;
        transform: translateX(calc(-50% + var(--icon-width) / 2));
        overflow: hidden;
        transition: max-height 0.5s;
      }
      .downloader-container:hover  .downloader-nav {
        height: auto;
        max-height: var(--nav-height);
      }
    `
  GM.addStyle(styles)
}

const createDragState = () => ({ isDragging: false, offset: { x: 0, y: 0 } })

/**
 * @param {DragState} state
 * @param {HTMLDivElement} nav
 * @returns 
 */
const handleDragStart = (state, nav) => (/**@type {MouseEvent}*/e) => {
  if (e.target.matches('a')) return
  state.isDragging = true
  nav.hidden = true
  const rect = e.currentTarget.getBoundingClientRect()
  state.offset = { x: e.clientX - rect.left, y: e.clientY - rect.top }
  e.preventDefault()
}

/**
 * @param {DragState} state
 * @param {HTMLDivElement} nav
 * @returns 
 */
const handleDragMove = (state, nav) => (/**@type {MouseEvent}*/e) => {
  if (!state.isDragging || e.target.matches('a')) return
  // 拖动的时候，也隐藏 nav
  if (!nav.hidden) nav.hidden = !nav.hidden
  const /**@type {HTMLDivElement} */ container = e.currentTarget.parentElement
  container.style.left = e.clientX - state.offset.x + 'px'
  container.style.top = e.clientY - state.offset.y + 'px'
}

/**
 * @param {DragState} state
 * @param {HTMLDivElement} nav
 * @returns 
 */
const handleDragEnd = (state, nav) => () => {
  if (!state.isDragging) return

  state.isDragging = false
  nav.hidden = false
}

// 下载状态管理
const createDownloadState = () => ({ isDownloading: false })

/**
 * @param {DownloadState} state
 */
const handleDownloadClick = (state, callback) => async (/**@type {MouseEvent}*/e) => {
  if (state.isDownloading) return
  const /**@type {HTMLDivElement}*/target = e.target
  if (target.matches('a') || !target.dataset.id) return
  state.isDownloading = true
  const a = document.createElement('a')
  target.appendChild(a)

  const [error, _] = await catchError(callback(a, parseInt(target.dataset.id)), [NetWorkError])
  if (error) alert(error)
  state.isDownloading = false
}

/**
 * @param {HTMLDivElement} downloader 
 * @param {HTMLDivElement} nav 
 * @param {function(): Promise<T>} callback 
 */
function setupEventListener(downloader, nav, callback) {
  const dragState = createDragState()
  const downloadState = createDownloadState()

  downloader.addEventListener('mousedown', handleDragStart(dragState, nav))
  downloader.addEventListener('mousemove', handleDragMove(dragState, nav))
  downloader.addEventListener('mouseup', handleDragEnd(dragState, nav))
  nav.addEventListener('click', debounce(handleDownloadClick(downloadState, callback), 10000, true))
}

function init() {
  const [downloader, nav] = createDownloaderElement()
  addStyles()
  setupEventListener(downloader, nav, getVideo)
}

init()