// ==UserScript==
// @name         B站视频片段下载器
// @namespace    bilibili-clip-downloader
// @version      1.0
// @description  在B站视频页面选择任意时间段，录制并下载指定片段到自定义文件夹
// @author       WorkBuddy
// @match        https://www.bilibili.com/video/*
// @match        https://www.bilibili.com/watchlater/*
// @match        https://www.bilibili.com/bangumi/play/*
// @grant        none
// @license MIT
// ==/UserScript==

(function() {
    'use strict';

    // ==================== 工具函数 ====================

    /** 解析时间字符串为秒数，支持 "SS" "MM:SS" "HH:MM:SS" */
    function parseTime(str) {
        if (!str) return null;
        var parts = str.trim().split(':');
        for (var i = 0; i < parts.length; i++) {
            if (isNaN(parseInt(parts[i], 10))) return null;
        }
        var nums = parts.map(function(n) { return parseInt(n, 10); });
        if (nums.length === 1) return nums[0];
        if (nums.length === 2) return nums[0] * 60 + nums[1];
        if (nums.length === 3) return nums[0] * 3600 + nums[1] * 60 + nums[2];
        return null;
    }

    /** 秒数格式化为 "MM:SS" 或 "H:MM:SS" */
    function formatTime(seconds) {
        if (isNaN(seconds) || seconds < 0) return '00:00';
        var h = Math.floor(seconds / 3600);
        var m = Math.floor((seconds % 3600) / 60);
        var s = Math.floor(seconds % 60);
        if (h > 0) {
            return h + ':' + String(m).padStart(2, '0') + ':' + String(s).padStart(2, '0');
        }
        return String(m).padStart(2, '0') + ':' + String(s).padStart(2, '0');
    }

    /** 秒数格式化为文件名安全格式 "0m10s" 或 "1h05m30s" */
    function formatTimeForFilename(seconds) {
        var h = Math.floor(seconds / 3600);
        var m = Math.floor((seconds % 3600) / 60);
        var s = Math.floor(seconds % 60);
        if (h > 0) {
            return h + 'h' + String(m).padStart(2, '0') + 'm' + String(s).padStart(2, '0') + 's';
        }
        return m + 'm' + String(s).padStart(2, '0') + 's';
    }

    /** 清理文件名中的非法字符 */
    function sanitizeFilename(name) {
        return name.replace(/[<>:"/\\|?*]/g, '_').trim().substring(0, 60) || 'bilibili_clip';
    }

    /** 获取当前视频标题 */
    function getVideoTitle() {
        var selectors = [
            'h1.video-title .tit',
            'h1.video-title',
            '.video-title .tit',
            '.video-title',
            'h1'
        ];
        for (var i = 0; i < selectors.length; i++) {
            var el = document.querySelector(selectors[i]);
            if (el && el.textContent.trim()) {
                return sanitizeFilename(el.textContent.trim());
            }
        }
        var match = window.location.href.match(/\/video\/(BV\w+)/);
        return match ? match[1] : 'bilibili_clip';
    }

    /** 获取浏览器支持的最佳录制格式 */
    function getSupportedMimeType() {
        var types = [
            'video/mp4;codecs=h264,aac',
            'video/mp4;codecs=avc1',
            'video/mp4',
            'video/webm;codecs=vp9,opus',
            'video/webm;codecs=vp8,opus',
            'video/webm'
        ];
        for (var i = 0; i < types.length; i++) {
            if (MediaRecorder.isTypeSupported(types[i])) return types[i];
        }
        return '';
    }

    /** 根据MIME类型获取文件扩展名 */
    function getExtension(mimeType) {
        if (!mimeType) return 'webm';
        if (mimeType.indexOf('mp4') !== -1) return 'mp4';
        if (mimeType.indexOf('webm') !== -1) return 'webm';
        return 'webm';
    }

    /** 在页面中查找视频元素 */
    function findVideoElement() {
        var selectors = [
            '#bilibili-player video',
            '.bpx-player-video-wrap video',
            '.bilibili-player video',
            'video'
        ];
        for (var i = 0; i < selectors.length; i++) {
            var video = document.querySelector(selectors[i]);
            if (video && video.readyState > 0 && !isNaN(video.duration) && video.duration > 0) {
                return video;
            }
        }
        return null;
    }

    // ==================== 录制状态 ====================

    var isRecording = false;
    var recordingCancelled = false;

    // ==================== 录制核心逻辑 ====================

    /**
     * 录制视频指定时间段
     * @param {HTMLVideoElement} video - 视频元素
     * @param {number} startTime - 开始时间（秒）
     * @param {number} endTime - 结束时间（秒）
     * @param {function} onProgress - 进度回调 (progress, elapsed, duration)
     * @returns {Promise<Blob>} 录制的视频Blob
     */
    async function recordClip(video, startTime, endTime, onProgress) {
        var duration = endTime - startTime;
        recordingCancelled = false;

        // 保存当前播放状态，录制后恢复
        var savedTime = video.currentTime;
        var wasPaused = video.paused;
        var savedVolume = video.volume;
        var savedMuted = video.muted;
        var savedRate = video.playbackRate;

        // 暂停并跳转到开始时间
        video.pause();
        video.currentTime = startTime;

        // 等待 seek 完成
        await new Promise(function(resolve) {
            var resolved = false;
            var onSeeked = function() {
                if (resolved) return;
                resolved = true;
                video.removeEventListener('seeked', onSeeked);
                resolve();
            };
            video.addEventListener('seeked', onSeeked);
            // 超时保护
            setTimeout(function() {
                if (!resolved) {
                    resolved = true;
                    video.removeEventListener('seeked', onSeeked);
                    resolve();
                }
            }, 5000);
        });

        // 捕获视频流（包含画面和声音）
        var stream;
        if (video.captureStream) {
            stream = video.captureStream();
        } else if (video.mozCaptureStream) {
            stream = video.mozCaptureStream();
        } else {
            throw new Error('浏览器不支持视频流捕获');
        }

        if (!stream) {
            throw new Error('无法创建视频流');
        }

        // 检查视频轨道
        var videoTracks = stream.getVideoTracks();
        if (videoTracks.length === 0) {
            throw new Error('无法捕获视频画面，可能是DRM保护内容');
        }

        // 设置录制器
        var mimeType = getSupportedMimeType();
        var recorderOptions = mimeType ? { mimeType: mimeType } : {};
        var recorder = new MediaRecorder(stream, recorderOptions);
        var chunks = [];

        recorder.ondataavailable = function(e) {
            if (e.data && e.data.size > 0) {
                chunks.push(e.data);
            }
        };

        // 开始录制（每100ms收集一次数据）
        recorder.start(100);

        // 播放视频开始录制
        try {
            await video.play();
        } catch (e) {
            if (recorder.state !== 'inactive') recorder.stop();
            throw new Error('无法播放视频: ' + (e.message || e));
        }

        // 监控录制进度，到达结束时间时停止
        return new Promise(function(resolve, reject) {
            var stopped = false;

            function stop() {
                if (stopped) return;
                stopped = true;
                video.pause();
                if (recorder.state !== 'inactive') {
                    recorder.stop();
                }
            }

            recorder.onstop = function() {
                var blob = new Blob(chunks, { type: mimeType || 'video/webm' });

                // 恢复视频原始状态
                video.currentTime = savedTime;
                video.volume = savedVolume;
                video.muted = savedMuted;
                video.playbackRate = savedRate;

                if (wasPaused) {
                    video.pause();
                } else {
                    video.play().catch(function() {});
                }

                resolve(blob);
            };

            recorder.onerror = function(e) {
                stop();
                reject(e.error || new Error('录制出错'));
            };

            function checkEnd() {
                if (stopped) return;

                // 检查取消
                if (recordingCancelled) {
                    stop();
                    return;
                }

                // 更新进度
                var elapsed = video.currentTime - startTime;
                var progress = Math.min(elapsed / duration, 1);
                onProgress(progress, elapsed, duration);

                // 检查是否到达结束时间
                if (video.currentTime >= endTime || video.ended) {
                    stop();
                } else {
                    requestAnimationFrame(checkEnd);
                }
            }
            requestAnimationFrame(checkEnd);
        });
    }

    // ==================== 文件保存 ====================

    /**
     * 保存Blob到文件
     * 优先使用 File System Access API 让用户选择文件夹
     * 不支持时回退到普通下载
     */
    async function saveBlob(blob, filename) {
        // 优先使用 File System Access API
        if (window.showDirectoryPicker) {
            try {
                var dirHandle = await window.showDirectoryPicker({
                    mode: 'readwrite',
                    id: 'bilibili-clips',
                    startIn: 'downloads'
                });
                var fileHandle = await dirHandle.getFileHandle(filename, { create: true });
                var writable = await fileHandle.createWritable();
                await writable.write(blob);
                await writable.close();
                return { method: 'folder', dirName: dirHandle.name };
            } catch (e) {
                if (e.name === 'AbortError') return null; // 用户取消
                // 其他错误，回退到普通下载
                console.warn('File System Access API failed, falling back', e);
            }
        }

        // 后备方案：触发浏览器下载
        var url = URL.createObjectURL(blob);
        var a = document.createElement('a');
        a.href = url;
        a.download = filename;
        document.body.appendChild(a);
        a.click();
        document.body.removeChild(a);
        setTimeout(function() { URL.revokeObjectURL(url); }, 10000);
        return { method: 'download' };
    }

    // ==================== UI 样式 ====================

    function createStyles() {
        var style = document.createElement('style');
        style.id = 'bili-clip-styles';
        style.textContent = [
            '#bili-clip-panel {',
            '    position: fixed; top: 80px; right: 20px; z-index: 99999;',
            '    width: 290px; background: #fff; border-radius: 12px;',
            '    box-shadow: 0 4px 20px rgba(0,0,0,0.15);',
            '    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;',
            '    font-size: 13px; overflow: hidden;',
            '}',
            '#bili-clip-panel .clip-header {',
            '    display: flex; justify-content: space-between; align-items: center;',
            '    padding: 10px 14px; background: #fb7299; color: #fff;',
            '    font-weight: bold; font-size: 14px; cursor: move; user-select: none;',
            '}',
            '#bili-clip-panel .clip-header span { pointer-events: none; }',
            '#bili-clip-panel .clip-toggle {',
            '    background: none; border: none; color: #fff; font-size: 18px;',
            '    cursor: pointer; padding: 0 4px; line-height: 1;',
            '}',
            '#bili-clip-panel .clip-toggle:hover { opacity: 0.8; }',
            '#bili-clip-panel .clip-body { padding: 12px 14px; }',
            '#bili-clip-panel .clip-body.collapsed { display: none; }',
            '#bili-clip-panel .clip-row {',
            '    display: flex; align-items: center; gap: 6px; margin-bottom: 8px;',
            '}',
            '#bili-clip-panel .clip-row label {',
            '    width: 34px; color: #666; flex-shrink: 0;',
            '}',
            '#bili-clip-panel .clip-row input {',
            '    flex: 1; padding: 6px 8px; border: 1px solid #ddd;',
            '    border-radius: 6px; font-size: 13px; outline: none;',
            '    transition: border-color 0.2s; min-width: 0;',
            '}',
            '#bili-clip-panel .clip-row input:focus { border-color: #fb7299; }',
            '#bili-clip-panel .clip-now-btn {',
            '    background: #f0f0f0; border: none; border-radius: 6px;',
            '    padding: 6px 8px; cursor: pointer; font-size: 14px;',
            '    flex-shrink: 0; transition: background 0.2s;',
            '}',
            '#bili-clip-panel .clip-now-btn:hover { background: #e0e0e0; }',
            '#bili-clip-panel .clip-info {',
            '    font-size: 12px; color: #999; margin: 8px 0; min-height: 16px;',
            '}',
            '#bili-clip-panel .clip-progress-wrap { margin: 8px 0; display: none; }',
            '#bili-clip-panel .clip-progress-wrap.active { display: block; }',
            '#bili-clip-panel .clip-progress-bar-bg {',
            '    height: 6px; background: #eee; border-radius: 3px; overflow: hidden;',
            '}',
            '#bili-clip-panel .clip-progress-bar {',
            '    height: 100%; background: #fb7299; width: 0%;',
            '    border-radius: 3px; transition: width 0.2s;',
            '}',
            '#bili-clip-panel .clip-progress-text {',
            '    font-size: 12px; color: #666; margin-top: 4px;',
            '}',
            '#bili-clip-panel .clip-download-btn {',
            '    width: 100%; padding: 10px; background: #fb7299; color: #fff;',
            '    border: none; border-radius: 8px; font-size: 14px; font-weight: bold;',
            '    cursor: pointer; transition: background 0.2s;',
            '}',
            '#bili-clip-panel .clip-download-btn:hover:not(:disabled) { background: #f0567f; }',
            '#bili-clip-panel .clip-download-btn:disabled { background: #ccc; cursor: not-allowed; }',
            '#bili-clip-panel .clip-cancel-btn {',
            '    width: 100%; padding: 8px; background: #fff; color: #ff5757;',
            '    border: 1px solid #ff5757; border-radius: 8px; font-size: 13px;',
            '    cursor: pointer; margin-top: 6px; display: none;',
            '}',
            '#bili-clip-panel .clip-cancel-btn.active { display: block; }',
            '#bili-clip-panel .clip-cancel-btn:hover { background: #fff5f5; }',
            '#bili-clip-panel .clip-tip {',
            '    font-size: 11px; color: #bbb; margin-top: 8px; line-height: 1.4;',
            '}'
        ].join('\n');
        return style;
    }

    // ==================== UI 面板 ====================

    function createPanel() {
        var panel = document.createElement('div');
        panel.id = 'bili-clip-panel';
        panel.innerHTML = [
            '<div class="clip-header">',
            '    <span>🎬 视频片段下载器</span>',
            '    <button class="clip-toggle">−</button>',
            '</div>',
            '<div class="clip-body">',
            '    <div class="clip-row">',
            '        <label>开始</label>',
            '        <input type="text" id="bili-clip-start" placeholder="00:00" value="00:00">',
            '        <button class="clip-now-btn" data-target="start" title="使用当前播放时间">📍</button>',
            '    </div>',
            '    <div class="clip-row">',
            '        <label>结束</label>',
            '        <input type="text" id="bili-clip-end" placeholder="00:00" value="00:00">',
            '        <button class="clip-now-btn" data-target="end" title="使用当前播放时间">📍</button>',
            '    </div>',
            '    <div class="clip-info" id="bili-clip-info"></div>',
            '    <div class="clip-progress-wrap" id="bili-clip-progress-wrap">',
            '        <div class="clip-progress-bar-bg">',
            '            <div class="clip-progress-bar" id="bili-clip-progress-bar"></div>',
            '        </div>',
            '        <div class="clip-progress-text" id="bili-clip-progress-text"></div>',
            '    </div>',
            '    <button class="clip-download-btn" id="bili-clip-download">🎬 下载片段</button>',
            '    <button class="clip-cancel-btn" id="bili-clip-cancel">⏹ 取消录制</button>',
            '    <div class="clip-tip">提示：录制时视频将实时播放，请先将播放器画质调至所需清晰度</div>',
            '</div>'
        ].join('');
        return panel;
    }

    // ==================== 拖拽功能 ====================

    function makeDraggable(panel) {
        var header = panel.querySelector('.clip-header');
        var isDragging = false;
        var startX, startY, startLeft, startTop;

        header.addEventListener('mousedown', function(e) {
            if (e.target.classList.contains('clip-toggle')) return;
            isDragging = true;
            var rect = panel.getBoundingClientRect();
            startX = e.clientX;
            startY = e.clientY;
            startLeft = rect.left;
            startTop = rect.top;
            panel.style.transition = 'none';
            e.preventDefault();
        });

        document.addEventListener('mousemove', function(e) {
            if (!isDragging) return;
            var dx = e.clientX - startX;
            var dy = e.clientY - startY;
            panel.style.left = (startLeft + dx) + 'px';
            panel.style.top = (startTop + dy) + 'px';
            panel.style.right = 'auto';
        });

        document.addEventListener('mouseup', function() {
            if (isDragging) {
                isDragging = false;
                panel.style.transition = '';
            }
        });
    }

    // ==================== 事件处理 ====================

    function getCurrentVideoTime() {
        var video = findVideoElement();
        return video ? video.currentTime : 0;
    }

    function updateInfo() {
        var video = findVideoElement();
        var info = document.getElementById('bili-clip-info');
        if (!info) return;

        var startInput = document.getElementById('bili-clip-start');
        var endInput = document.getElementById('bili-clip-end');
        if (!startInput || !endInput) return;

        var startTime = parseTime(startInput.value);
        var endTime = parseTime(endInput.value);

        if (startTime === null || endTime === null) {
            info.textContent = '⚠️ 时间格式错误，请输入 MM:SS 或 HH:MM:SS';
            info.style.color = '#ff5757';
            return;
        }

        if (startTime >= endTime) {
            info.textContent = '⚠️ 开始时间必须小于结束时间';
            info.style.color = '#ff5757';
            return;
        }

        var clipDuration = endTime - startTime;
        var videoDuration = video ? video.duration : 0;

        var infoText = '片段时长: ' + formatTime(clipDuration);
        if (videoDuration > 0 && !isNaN(videoDuration) && isFinite(videoDuration)) {
            infoText += ' | 视频: ' + formatTime(videoDuration);
            if (endTime > videoDuration) {
                infoText += ' ⚠️ 超出视频长度';
                info.style.color = '#ff5757';
            } else {
                info.style.color = '#999';
            }
        } else {
            info.style.color = '#999';
        }
        info.textContent = infoText;
    }

    function setProgress(active, percent, text) {
        var wrap = document.getElementById('bili-clip-progress-wrap');
        var bar = document.getElementById('bili-clip-progress-bar');
        var textEl = document.getElementById('bili-clip-progress-text');
        var cancelBtn = document.getElementById('bili-clip-cancel');

        if (!wrap || !bar || !textEl || !cancelBtn) return;

        if (active) {
            wrap.classList.add('active');
            cancelBtn.classList.add('active');
        } else {
            wrap.classList.remove('active');
            cancelBtn.classList.remove('active');
        }

        if (percent !== undefined) {
            bar.style.width = Math.round(percent * 100) + '%';
        }
        if (text !== undefined) {
            textEl.textContent = text;
        }
    }

    function showInfoMessage(message, color) {
        var info = document.getElementById('bili-clip-info');
        if (!info) return;
        var originalText = info.textContent;
        var originalColor = info.style.color;
        info.textContent = message;
        info.style.color = color || '#4caf50';
        setTimeout(function() {
            info.textContent = originalText;
            info.style.color = originalColor;
        }, 5000);
    }

    async function downloadClip() {
        if (isRecording) return;

        var downloadBtn = document.getElementById('bili-clip-download');
        var startInput = document.getElementById('bili-clip-start');
        var endInput = document.getElementById('bili-clip-end');

        var startTime = parseTime(startInput.value);
        var endTime = parseTime(endInput.value);

        // 验证输入
        if (startTime === null || endTime === null) {
            alert('时间格式错误！\n请输入 MM:SS 或 HH:MM:SS 格式\n例如：00:10 或 1:23:45');
            return;
        }
        if (startTime >= endTime) {
            alert('开始时间必须小于结束时间！');
            return;
        }

        // 查找视频元素
        var video = findVideoElement();
        if (!video) {
            alert('未找到视频元素！\n请确保视频已加载并开始播放过');
            return;
        }

        // 检查浏览器API支持
        if (!video.captureStream && !video.mozCaptureStream) {
            alert('当前浏览器不支持视频流捕获！\n请使用 Chrome 86+ 或 Edge 浏览器');
            return;
        }
        if (typeof MediaRecorder === 'undefined') {
            alert('当前浏览器不支持 MediaRecorder API！\n请使用 Chrome 或 Edge 浏览器');
            return;
        }

        // 限制结束时间不超过视频时长
        var actualEndTime = endTime;
        if (video.duration && isFinite(video.duration) && endTime > video.duration) {
            actualEndTime = video.duration;
        }

        // 如果未选择文件夹，先让用户选择
        var dirHandle = null;
        if (window.showDirectoryPicker) {
            try {
                dirHandle = await window.showDirectoryPicker({
                    mode: 'readwrite',
                    id: 'bilibili-clips',
                    startIn: 'downloads'
                });
            } catch (e) {
                if (e.name === 'AbortError') {
                    return; // 用户取消选择文件夹
                }
                // 忽略错误，稍后回退到普通下载
            }
        }

        // 禁用按钮，开始录制
        isRecording = true;
        downloadBtn.disabled = true;
        downloadBtn.textContent = '⏳ 录制中...';
        setProgress(true, 0, '准备中...');

        try {
            // 生成文件名
            var title = getVideoTitle();
            var mimeType = getSupportedMimeType();
            var ext = getExtension(mimeType);
            var filename = title + '_' + formatTimeForFilename(startTime) + '-' + formatTimeForFilename(actualEndTime) + '.' + ext;

            // 录制片段
            var blob = await recordClip(video, startTime, actualEndTime, function(progress, elapsed, duration) {
                setProgress(true, progress, '录制中 ' + formatTime(elapsed) + ' / ' + formatTime(duration));
            });

            setProgress(true, 1, '录制完成，正在保存...');

            // 保存文件
            var sizeMB = (blob.size / 1024 / 1024).toFixed(1);
            var saveResult;

            if (dirHandle) {
                // 使用已选择的文件夹
                try {
                    var fileHandle = await dirHandle.getFileHandle(filename, { create: true });
                    var writable = await fileHandle.createWritable();
                    await writable.write(blob);
                    await writable.close();
                    saveResult = { method: 'folder', dirName: dirHandle.name };
                } catch (e) {
                    // 文件夹保存失败，回退到普通下载
                    saveResult = await saveBlob(blob, filename);
                }
            } else {
                // 没有文件夹API，使用普通下载
                saveResult = await saveBlob(blob, filename);
            }

            // 恢复UI状态
            setProgress(false, 0, '');
            downloadBtn.disabled = false;
            downloadBtn.textContent = '🎬 下载片段';
            isRecording = false;

            if (saveResult === null) {
                showInfoMessage('已取消', '#999');
                return;
            }

            if (saveResult.method === 'folder') {
                showInfoMessage('✅ 已保存到「' + saveResult.dirName + '」(' + sizeMB + 'MB, ' + ext.toUpperCase() + ')');
            } else {
                showInfoMessage('✅ 已下载到下载文件夹 (' + sizeMB + 'MB, ' + ext.toUpperCase() + ')');
            }

        } catch (e) {
            console.error('录制失败:', e);
            setProgress(false, 0, '');
            downloadBtn.disabled = false;
            downloadBtn.textContent = '🎬 下载片段';
            isRecording = false;
            alert('录制失败: ' + (e.message || e));
        }
    }

    // ==================== 初始化 ====================

    function init() {
        if (document.getElementById('bili-clip-panel')) return;
        if (!document.querySelector('video')) return;

        // 添加样式
        if (!document.getElementById('bili-clip-styles')) {
            document.head.appendChild(createStyles());
        }

        // 创建面板
        var panel = createPanel();
        document.body.appendChild(panel);

        // 拖拽
        makeDraggable(panel);

        // 折叠/展开
        var toggle = panel.querySelector('.clip-toggle');
        var body = panel.querySelector('.clip-body');
        toggle.addEventListener('click', function() {
            body.classList.toggle('collapsed');
            toggle.textContent = body.classList.contains('collapsed') ? '+' : '−';
        });

        // "使用当前时间"按钮
        var nowBtns = panel.querySelectorAll('.clip-now-btn');
        for (var i = 0; i < nowBtns.length; i++) {
            nowBtns[i].addEventListener('click', function() {
                var target = this.dataset.target;
                var input = document.getElementById('bili-clip-' + target);
                var currentTime = getCurrentVideoTime();
                input.value = formatTime(currentTime);
                updateInfo();
            });
        }

        // 输入变化时更新信息
        document.getElementById('bili-clip-start').addEventListener('input', updateInfo);
        document.getElementById('bili-clip-end').addEventListener('input', updateInfo);

        // 下载按钮
        document.getElementById('bili-clip-download').addEventListener('click', downloadClip);

        // 取消录制按钮
        document.getElementById('bili-clip-cancel').addEventListener('click', function() {
            recordingCancelled = true;
        });

        // 延迟更新信息（等待视频加载）
        setTimeout(updateInfo, 500);

        // 定期更新信息（应对视频加载延迟）
        var infoInterval = setInterval(updateInfo, 2000);
        panel.dataset.infoInterval = infoInterval;
    }

    // ==================== 启动 ====================

    setInterval(function() {
        if (!document.getElementById('bili-clip-panel') && document.querySelector('video')) {
            init();
        }
    }, 1000);

})();