// ==UserScript==
// @name         b站视频音量调节触控板翻转
// @namespace    http://zhangmaimai.com/
// @version      1.0
// @description  优化b站视频音量调节在触控板上的体验，触控板上的上下滑动是与鼠标滚轮翻转的，使用此脚本后当你在b站视频全屏时向下滑动将减少音量（默认为增大）
// @author       maxchang3
// @match        https://www.bilibili.com/video/*
// @match        https://www.bilibili.com/bangumi/play/*
// @icon         https://www.bilibili.com/favicon.ico
// @grant        none
// @license      https://github.com/996icu/996.ICU/blob/master/LICENSE
// @downloadURL none
// ==/UserScript==

(function () {
    'use strict';
    let hintTimer = undefined

    const initHint = () => {
        const hintCode = `<div class="bpx-player-volume-hint" style="opacity: 0; display: none;"><span class="bpx-player-volume-hint-icon"><span class="bpx-common-svg-icon" style=""><svg viewBox="0 0 22 22"><use xlink:href="#bpx-svg-sprite-volume"></use></svg></span><span class="bpx-common-svg-icon" style="display: none;"><svg viewBox="0 0 22 22"><use xlink:href="#bpx-svg-sprite-volume-off"></use></svg></span></span><span class="bpx-player-volume-hint-text">20%</span></div>`
        if (document.querySelector('.bpx-player-volume-hint')) return
        document.querySelector('.bpx-player-video-area').insertAdjacentHTML('beforeend', hintCode)
    }

    const showHint = (volume) => {
        window.clearTimeout(hintTimer)
        const volHint = document.querySelector('.bpx-player-volume-hint')
        const volText = volHint.querySelector('.bpx-player-volume-hint-text')
        const volIconArea = volHint.querySelector('.bpx-player-volume-hint-icon')
        const volIcons = volIconArea.querySelectorAll('.bpx-common-svg-icon')
        if (volume == 0) {
            volText.innerText = '静音'
            volIcons[0].style.display = 'none'
            volIcons[1].style.display = 'inline-flex'
        } else {
            volIcons[0].style.display = 'inline-flex'
            volIcons[1].style.display = 'none'
            volText.innerText = `${Math.ceil(volume * 100)}%`
        }
        volHint.style.display = ''
        volHint.style.opacity = 1
        hintTimer = window.setTimeout((function () {
            const animation = volHint.animate({ opacity: 0 }, 300);
            animation.onfinish = function () {
                animation.cancel()
                volHint.style.display = 'none'
                volHint.style.opacity = 0
            }
        }), 1e3)
    }

    const isFullScreen = () => {
        return !!(
            document.fullscreen ||
            document.mozFullScreen ||
            document.webkitIsFullScreen ||
            document.webkitFullScreen ||
            document.msFullScreen
        );
    }

    const handler = (e) => {
        // 同时接管触控板与鼠标滚轮出发下的提醒，从而避免提醒重复显示的情况，因此对于鼠标触发的值需要额外放大魔数以计算增长音量与wheelDeltaY的关系。
        // 触控板下wheelDeltaY更为精准因此明显小于鼠标，这里以100为阈值。经过测试（罗技MX Anywhere2s下）鼠标最低约在240或360左右，这里为了防止硬件差异选择100。
        // 灵感来自：https://stackoverflow.com/questions/10744645/detect-touchpad-vs-mouse-in-javascript 在这里不需要过于精准的判断，基本够用。
        let isTrackpad = (e.wheelDeltaY && Math.abs(e.wheelDeltaY) < 100);
        let isFullscreen = (Array.from(document.querySelector('body').classList)).includes("player-fullscreen-fix") || isFullScreen();
        if (!(isFullscreen)) return false //非全屏下不接管事件
        //阻止默认事件
        e.stopImmediatePropagation();
        e.stopPropagation();
        let flag = -1 // Trackpad 值转为 1 与 -1 ，在触控板与鼠标情况下进行加减的逆转。
        let MAGIC_NUMBER = 36000
        if (isTrackpad && isFullscreen) { flag = 1; MAGIC_NUMBER /= 72; }
        let newVolume = window.player.getVolume() - flag * e.wheelDeltaY / MAGIC_NUMBER;
        newVolume = (newVolume < 1) ? Math.max(newVolume, 0) : 1 // 小于0取0，大于1取1
        window.player.setVolume(newVolume)
        showHint(window.player.getVolume())
    }

    const init = () => {
        initHint()
        document.addEventListener("DOMMouseScroll", handler, false);
        document.addEventListener("wheel", handler, false);
    }

    window.onload = init
})();