class TextSearchUI {
    /**
     * @param {object} [options]
     * @param {'light' | 'dark' | 'auto'} [options.theme] - 初始主题
     */
    constructor(options = {}) {
        this.searchBox = null;
        this.currentIndex = 0;
        this.totalMatches = 0;
        // 拖动相关属性
        this.isDragging = false;
        this.dragOffset = { x: 0, y: 0 };
        
        // --- 新增：主题管理 ---
        this.theme = options.theme || 'auto'; // 'light', 'dark', 'auto'
        
        // --- 新增：可搜索的作用域元素（默认 document.body） ---
        this.scopeElement = this._resolveScope(options.scope);

        this.init();
    }

    init() {
        // 添加CSS样式
        this.addStyles();
        
        // 创建搜索UI
        this.createSearchBox();
        
        // 监听Ctrl+F快捷键
        this.addKeyboardShortcut();
        
        // 添加拖动功能
        this.addDragFunctionality();
    }

    /**
     * --- 改进：使用CSS变量重构 ---
     * 所有颜色和主题相关的样式都已提取为CSS变量，
     * 以便通过 data-theme 属性轻松切换。
     */
    addStyles() {
        const style = document.createElement('style');
        style.textContent = `
            /* --- 全局高亮主题变量 --- */
            :root {
                --search-highlight-bg: #ffeb3b;
                --search-highlight-color: #000;
                --search-highlight-current-bg: #ff9800;
                --search-highlight-current-color: #000;
            }

            /* 全局高亮 - 手动暗色 */
            body[data-search-theme="dark"] {
                --search-highlight-bg: #f9a825;
                --search-highlight-color: #000;
                --search-highlight-current-bg: #ff6f00;
                --search-highlight-current-color: #fff;
            }

            /* 全局高亮 - 自动暗色 */
            @media (prefers-color-scheme: dark) {
                body[data-search-theme="auto"] {
                    --search-highlight-bg: #f9a825;
                    --search-highlight-color: #000;
                    --search-highlight-current-bg: #ff6f00;
                    --search-highlight-current-color: #fff;
                }
            }

            /* --- 搜索框容器 --- */
            .text-search-container {
                /* --- 主题变量定义 (浅色为默认) --- */
                --search-bg: #ffffff;
                --search-border: #e0e0e0;
                --search-shadow: 0 4px 12px rgba(0,0,0,0.15);
                --search-color: #333;
                --search-shadow-dragging: 0 8px 24px rgba(0,0,0,0.25);
                --input-bg: #ffffff;
                --input-border: #ddd;
                --input-color: #333;
                --input-placeholder: #999;
                --input-focus-border: #4CAF50;
                --btn-primary-bg: #4CAF50;
                --btn-primary-hover: #45a049;
                --btn-primary-active: #3d8b40;
                --btn-secondary-bg: #2196F3;
                --btn-secondary-hover: #0b7dda;
                --btn-close-bg: #f44336;
                --btn-close-hover: #da190b;
                --info-color: #666;
                --nav-bg: #2196F3;
                --nav-hover: #0b7dda;
                --nav-disabled-bg: #ccc;
                --nav-disabled-color: #fff;

                /* --- 结构样式 --- */
                position: fixed;
                top: 20px;
                right: 20px;
                background: var(--search-bg);
                border: 1px solid var(--search-border);
                border-radius: 8px;
                box-shadow: var(--search-shadow);
                color: var(--search-color);
                padding: 15px;
                z-index: 10000;
                display: none;
                min-width: 320px;
                font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Arial, sans-serif;
                cursor: move;
                user-select: none;
            }

            /* --- 搜索框 - 暗色主题 --- */
            /* 手动暗色 */
            .text-search-container[data-theme="dark"] {
                --search-bg: #2a2a2a;
                --search-border: #404040;
                --search-shadow: 0 4px 12px rgba(0,0,0,0.4);
                --search-color: #e0e0e0;
                --search-shadow-dragging: 0 8px 24px rgba(0,0,0,0.6);
                --input-bg: #3a3a3a;
                --input-border: #555;
                --input-color: #e0e0e0;
                --input-placeholder: #999;
                --input-focus-border: #66BB6A;
                --btn-primary-bg: #66BB6A;
                --btn-primary-hover: #57A75A;
                --btn-primary-active: #4A9A4D;
                --btn-secondary-bg: #42A5F5;
                --btn-secondary-hover: #2196F3;
                --btn-close-bg: #EF5350;
                --btn-close-hover: #E53935;
                --info-color: #aaa;
                --nav-bg: #42A5F5;
                --nav-hover: #2196F3;
                --nav-disabled-bg: #555;
                --nav-disabled-color: #888;
            }

            /* 自动暗色 */
            @media (prefers-color-scheme: dark) {
                .text-search-container[data-theme="auto"] {
                    --search-bg: #2a2a2a;
                    --search-border: #404040;
                    --search-shadow: 0 4px 12px rgba(0,0,0,0.4);
                    --search-color: #e0e0e0;
                    --search-shadow-dragging: 0 8px 24px rgba(0,0,0,0.6);
                    --input-bg: #3a3a3a;
                    --input-border: #555;
                    --input-color: #e0e0e0;
                    --input-placeholder: #999;
                    --input-focus-border: #66BB6A;
                    --btn-primary-bg: #66BB6A;
                    --btn-primary-hover: #57A75A;
                    --btn-primary-active: #4A9A4D;
                    --btn-secondary-bg: #42A5F5;
                    --btn-secondary-hover: #2196F3;
                    --btn-close-bg: #EF5350;
                    --btn-close-hover: #E53935;
                    --info-color: #aaa;
                    --nav-bg: #42A5F5;
                    --nav-hover: #2196F3;
                    --nav-disabled-bg: #555;
                    --nav-disabled-color: #888;
                }
            }

            /* --- 剩余组件样式 (已应用CSS变量和作用域) --- */
            .text-search-container.active {
                display: block;
            }

            .text-search-container.dragging {
                box-shadow: var(--search-shadow-dragging);
                opacity: 0.95;
            }

            .text-search-container .search-header {
                display: flex;
                align-items: center;
                gap: 8px;
                margin-bottom: 10px;
            }

            .text-search-container .search-input {
                flex: 1;
                padding: 8px 12px;
                border: 1px solid var(--input-border);
                border-radius: 4px;
                font-size: 14px;
                outline: none;
                cursor: text;
                background: var(--input-bg);
                color: var(--input-color);
            }

            .text-search-container .search-input::placeholder {
                color: var(--input-placeholder);
            }

            .text-search-container .search-input:focus {
                border-color: var(--input-focus-border);
            }

            .text-search-container .search-controls {
                display: flex;
                gap: 8px;
                align-items: center;
            }

            .text-search-container .search-btn {
                padding: 8px 12px;
                background: var(--btn-primary-bg);
                color: white;
                border: none;
                border-radius: 4px;
                cursor: pointer;
                font-size: 14px;
                transition: background 0.2s;
            }

            .text-search-container .search-btn:hover {
                background: var(--btn-primary-hover);
            }

            .text-search-container .search-btn:active {
                background: var(--btn-primary-active);
            }

            .text-search-container .search-btn.secondary {
                background: var(--btn-secondary-bg);
            }

            .text-search-container .search-btn.secondary:hover {
                background: var(--btn-secondary-hover);
            }

            .text-search-container .close-btn {
                background: var(--btn-close-bg);
                width: 32px;
                height: 32px;
                padding: 0;
                font-size: 18px;
                line-height: 1;
                cursor: pointer;
            }

            .text-search-container .close-btn:hover {
                background: var(--btn-close-hover);
            }

            .text-search-container .search-info {
                font-size: 12px;
                color: var(--info-color);
                margin-top: 8px;
                text-align: center;
            }

            .text-search-container .nav-buttons {
                display: flex;
                gap: 5px;
            }

            .text-search-container .nav-btn {
                padding: 6px 10px;
                background: var(--nav-bg);
                color: white;
                border: none;
                border-radius: 4px;
                cursor: pointer;
                font-size: 12px;
            }

            .text-search-container .nav-btn:hover {
                background: var(--nav-hover);
            }

            .text-search-container .nav-btn:disabled {
                background: var(--nav-disabled-bg);
                color: var(--nav-disabled-color);
                cursor: not-allowed;
            }

            /* 高亮样式 (使用全局变量) */
            mark.search-highlight {
                background-color: var(--search-highlight-bg);
                color: var(--search-highlight-color);
                padding: 2px 0;
            }

            mark.search-highlight.current {
                background-color: var(--search-highlight-current-bg);
                color: var(--search-highlight-current-color)!important;
                font-weight: bold;
            }
        `;
        document.head.appendChild(style);
    }

    createSearchBox() {
        const container = document.createElement('div');
        container.className = 'text-search-container';
        container.innerHTML = `
            <div class="search-header">
                <input type="text" class="search-input" placeholder="查找文本..." />
                <button class="search-btn close-btn" title="关闭">×</button>
            </div>
            <div class="search-controls">
                <div class="nav-buttons">
                    <button class="nav-btn" data-action="prev">↑ 上一个</button>
                    <button class="nav-btn" data-action="next">↓ 下一个</button>
                </div>
                <button class="search-btn" data-action="search">查找</button>
                <button class="search-btn secondary" data-action="clear">清除</button>
            </div>
            <div class="search-info"></div>
        `;

        document.body.appendChild(container);
        this.searchBox = container;

        // --- 新增：应用初始主题 ---
        this.updateTheme();

        // 绑定事件
        this.bindEvents();
    }

    bindEvents() {
        const input = this.searchBox.querySelector('.search-input');
        const closeBtn = this.searchBox.querySelector('.close-btn');
        const searchBtn = this.searchBox.querySelector('[data-action="search"]');
        const clearBtn = this.searchBox.querySelector('[data-action="clear"]');
        const prevBtn = this.searchBox.querySelector('[data-action="prev"]');
        const nextBtn = this.searchBox.querySelector('[data-action="next"]');

        // 关闭按钮
        closeBtn.addEventListener('click', (e) => {
            e.stopPropagation();
            this.hide();
        });

        // 查找按钮
        searchBtn.addEventListener('click', (e) => {
            e.stopPropagation();
            const searchTerm = input.value.trim();
            if (searchTerm) {
                this.search(searchTerm);
            }
        });

        // 清除按钮
        clearBtn.addEventListener('click', (e) => {
            e.stopPropagation();
            this.clear();
        });

        // 上一个/下一个
        prevBtn.addEventListener('click', (e) => {
            e.stopPropagation();
            this.findPrevious();
        });
        
        nextBtn.addEventListener('click', (e) => {
            e.stopPropagation();
            this.findNext();
        });

        // 输入框防止拖动
        input.addEventListener('mousedown', (e) => {
            e.stopPropagation();
        });

        // 回车键搜索
        input.addEventListener('keydown', (e) => {
            if (e.key === 'Enter') {
                e.preventDefault();
                if (e.shiftKey) {
                    this.findPrevious();
                } else {
                    const searchTerm = input.value.trim();
                    if (searchTerm) {
                        if (this.totalMatches > 0) {
                            this.findNext();
                        } else {
                            this.search(searchTerm);
                        }
                    }
                }
            } else if (e.key === 'Escape') {
                this.hide();
            }
        });

        // 实时搜索（可选）
        input.addEventListener('input', (e) => {
            const searchTerm = e.target.value.trim();
            if (searchTerm.length >= 2) {
                this.search(searchTerm);
            } else if (searchTerm.length === 0) {
                this.clear();
            }
        });
    }

    addDragFunctionality() {
        const container = this.searchBox;

        // 鼠标按下开始拖动
        const startDrag = (e) => {
            // 如果点击的是输入框、按钮等交互元素，不触发拖动
            if (e.target.tagName === 'INPUT' || 
                e.target.tagName === 'BUTTON' ||
                e.target.closest('button')) {
                return;
            }

            this.isDragging = true;
            container.classList.add('dragging');

            // 计算鼠标相对于容器的偏移量
            const rect = container.getBoundingClientRect();
            this.dragOffset.x = e.clientX - rect.left;
            this.dragOffset.y = e.clientY - rect.top;

            e.preventDefault();
        };

        // 鼠标移动时更新位置
        const drag = (e) => {
            if (!this.isDragging) return;

            e.preventDefault();

            // 计算新位置
            let newX = e.clientX - this.dragOffset.x;
            let newY = e.clientY - this.dragOffset.y;

            // 获取容器尺寸和视口尺寸
            const rect = container.getBoundingClientRect();
            const maxX = window.innerWidth - rect.width;
            const maxY = window.innerHeight - rect.height;

            // 限制在视口范围内
            newX = Math.max(0, Math.min(newX, maxX));
            newY = Math.max(0, Math.min(newY, maxY));

            // 设置新位置
            container.style.left = newX + 'px';
            container.style.top = newY + 'px';
            container.style.right = 'auto'; // 清除right定位
        };

        // 鼠标释放停止拖动
        const stopDrag = () => {
            if (this.isDragging) {
                this.isDragging = false;
                container.classList.remove('dragging');
            }
        };

        // 绑定事件
        container.addEventListener('mousedown', startDrag);
        document.addEventListener('mousemove', drag);
        document.addEventListener('mouseup', stopDrag);

        // 触摸设备支持
        container.addEventListener('touchstart', (e) => {
            // 如果点击的是交互元素，不触发拖动
            if (e.target.tagName === 'INPUT' || 
                e.target.tagName === 'BUTTON' ||
                e.target.closest('button')) {
                return;
            }

            const touch = e.touches[0];
            const mouseEvent = new MouseEvent('mousedown', {
                clientX: touch.clientX,
                clientY: touch.clientY
            });
            mouseEvent.target = e.target;
            startDrag(mouseEvent);
        });

        document.addEventListener('touchmove', (e) => {
            if (!this.isDragging) return;
            const touch = e.touches[0];
            const mouseEvent = new MouseEvent('mousemove', {
                clientX: touch.clientX,
                clientY: touch.clientY
            });
            drag(mouseEvent);
        });

        document.addEventListener('touchend', stopDrag);
    }

    addKeyboardShortcut() {
        document.addEventListener('keydown', (e) => {
            // Ctrl+F 或 Cmd+F
            if ((e.ctrlKey || e.metaKey) && e.key === 'f') {
                e.preventDefault();
                this.show();
            }
        });
    }

    show() {
        this.searchBox.classList.add('active');
        const input = this.searchBox.querySelector('.search-input');
        input.focus();
        input.select();
    }

    hide() {
        this.searchBox.classList.remove('active');
        this.clear();
    }

    search(searchTerm) {
        // 清除之前的搜索
        this.clearHighlights();
        
        if (!searchTerm) {
            this.updateInfo('请输入搜索内容');
            return;
        }

        // 使用window.find进行搜索并高亮
        this.highlightMatches(searchTerm);
    }

    highlightMatches(searchTerm) {
        const bodyText = this.scopeElement.innerText || this.scopeElement.textContent;
        const searchRegex = new RegExp(searchTerm, 'gi');
        const matches = bodyText.match(searchRegex);
        
        if (!matches || matches.length === 0) {
            this.totalMatches = 0;
            this.updateInfo('未找到匹配项');
            return;
        }

        this.totalMatches = matches.length;
        this.currentIndex = 0;

        // 高亮所有匹配项
        this.highlightText(searchTerm);
        
        // 跳转到第一个匹配项
        this.scrollToCurrent();
        this.updateInfo(`找到 ${this.totalMatches} 个匹配项 (${this.currentIndex + 1}/${this.totalMatches})`);
    }

    highlightText(searchTerm) {
        const walker = document.createTreeWalker(
            this.scopeElement,
            NodeFilter.SHOW_TEXT,
            {
                acceptNode: (node) => {
                    // 跳过脚本、样式和搜索框本身
                    if (node.parentElement.closest('script, style, .text-search-container')) {
                        return NodeFilter.FILTER_REJECT;
                    }
                    if (node.textContent.toLowerCase().includes(searchTerm.toLowerCase())) {
                        return NodeFilter.FILTER_ACCEPT;
                    }
                    return NodeFilter.FILTER_REJECT;
                }
            }
        );

        const nodesToReplace = [];
        let node;
        while (node = walker.nextNode()) {
            nodesToReplace.push(node);
        }

        nodesToReplace.forEach((textNode, index) => {
            const parent = textNode.parentNode;
            const text = textNode.textContent;
            const regex = new RegExp(`(${this.escapeRegex(searchTerm)})`, 'gi');
            
            const fragment = document.createDocumentFragment();
            let lastIndex = 0;
            let match;
            let matchIndex = 0;

            const tempRegex = new RegExp(this.escapeRegex(searchTerm), 'gi');
            while (match = tempRegex.exec(text)) {
                // 添加匹配前的文本
                if (match.index > lastIndex) {
                    fragment.appendChild(document.createTextNode(text.slice(lastIndex, match.index)));
                }

                // 添加高亮的匹配文本
                const mark = document.createElement('mark');
                mark.className = 'search-highlight';
                mark.textContent = match[0];
                mark.dataset.searchIndex = matchIndex++;
                fragment.appendChild(mark);

                lastIndex = match.index + match[0].length;
            }

            // 添加剩余文本
            if (lastIndex < text.length) {
                fragment.appendChild(document.createTextNode(text.slice(lastIndex)));
            }

            parent.replaceChild(fragment, textNode);
        });
    }

    escapeRegex(string) {
        return string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
    }

    clearHighlights() {
        // 仅清除当前作用域内的高亮
        this.scopeElement.querySelectorAll('mark.search-highlight').forEach(mark => {
            const parent = mark.parentNode;
            parent.replaceChild(document.createTextNode(mark.textContent), mark);
            parent.normalize(); // 合并相邻的文本节点
        });
    }

    scrollToCurrent() {
        const highlights = this.scopeElement.querySelectorAll('mark.search-highlight');
        if (highlights.length === 0) return;

        // 移除所有current类
        highlights.forEach(h => h.classList.remove('current'));

        // 添加当前高亮
        const current = highlights[this.currentIndex];
        if (current) {
            current.classList.add('current');
            current.scrollIntoView({ behavior: 'smooth', block: 'center' });
        }
    }

    findNext() {
        if (this.totalMatches === 0) return;
        
        this.currentIndex = (this.currentIndex + 1) % this.totalMatches;
        this.scrollToCurrent();
        this.updateInfo(`匹配项 ${this.currentIndex + 1}/${this.totalMatches}`);
    }

    findPrevious() {
        if (this.totalMatches === 0) return;
        
        this.currentIndex = (this.currentIndex - 1 + this.totalMatches) % this.totalMatches;
        this.scrollToCurrent();
        this.updateInfo(`匹配项 ${this.currentIndex + 1}/${this.totalMatches}`);
    }

    clear() {
        this.clearHighlights();
        this.totalMatches = 0;
        this.currentIndex = 0;
        this.updateInfo('');
        const input = this.searchBox.querySelector('.search-input');
        input.value = '';
    }

    updateInfo(message) {
        const info = this.searchBox.querySelector('.search-info');
        info.textContent = message;
    }

    // --- 新增：公共方法 - 设置主题 ---
    /**
     * 设置搜索框的主题
     * @param {'light' | 'dark' | 'auto'} theme
     */
    setTheme(theme) {
        if (['light', 'dark', 'auto'].includes(theme)) {
            this.theme = theme;
            this.updateTheme();
        } else {
            console.warn(`Invalid theme: ${theme}. Must be 'light', 'dark', or 'auto'.`);
        }
    }

    // --- 新增：私有方法 - 更新DOM主题 ---
    /**
     * 更新DOM上的主题属性
     * @private
     */
    updateTheme() {
        // 更新容器的主题
        if (this.searchBox) {
            this.searchBox.dataset.theme = this.theme;
        }
        // 更新body上的主题 (用于全局高亮)
        // 使用 data-search-theme 避免与页面其他主题设置冲突
        document.body.dataset.searchTheme = this.theme;
    }

    // --- 新增：设置/解析搜索作用域 ---
    /**
     * 设置搜索作用域。参数可以是：
     * - CSS 选择器字符串（取第一个匹配元素）
     * - DOM Element
     * - null/undefined（恢复到 document.body）
     * @param {string|Element|null} scope
     */
    setScope(scope) {
        this.scopeElement = this._resolveScope(scope);
    }

    _resolveScope(scope) {
        if (!scope) return document.body;
        if (typeof scope === 'string') {
            const el = document.querySelector(scope);
            return el || document.body;
        }
        if (scope instanceof Element) return scope;
        return document.body;
    }
}