Copy LeetCode Title

Adds a native-looking button to copy the LeetCode problem title
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// ==UserScript==
// @name         Copy LeetCode Title
// @namespace    http://tampermonkey.net/
// @version      2026.03.14
// @description  Adds a native-looking button to copy the LeetCode problem title
// @author       Holden Hu
// @match        https://leetcode.cn/problems/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=leetcode.cn
// @grant        none
// @license      MIT
// ==/UserScript==

(function() {
    'use strict';

    function copyToClipboard(text) {
        navigator.clipboard.writeText(text).then(function() {
            console.log('标题已成功复制: ' + text);
        }, function(err) {
            console.error('无法复制: ', err);
        });
    }

    function addButton() {
        if (document.getElementById('custom-copy-btn')) return;

        const titleElement = document.querySelector('.text-title-large');
        if (!titleElement) return;

        const copyButton = document.createElement('button');
        copyButton.id = 'custom-copy-btn';
        copyButton.textContent = '复制标题';

        // 这种样式写法能保证在 LeetCode 的不同主题下都有很好的融合度
        Object.assign(copyButton.style, {
            marginLeft: '12px',
            padding: '2px 10px',
            fontSize: '12px',
            borderRadius: '12px',
            border: 'none',
            cursor: 'pointer',
            backgroundColor: 'rgba(128, 128, 128, 0.15)', // 半透明灰色，适配深浅色背景
            color: 'inherit',
            transition: 'background-color 0.2s',
            verticalAlign: 'middle'
        });

        // 悬停效果
        copyButton.onmouseover = () => copyButton.style.backgroundColor = 'rgba(128, 128, 128, 0.25)';
        copyButton.onmouseout = () => copyButton.style.backgroundColor = 'rgba(128, 128, 128, 0.15)';

        copyButton.addEventListener('click', function() {
            // 点击时动态获取最新的标题
            const currentTitle = document.querySelector('.text-title-large')?.textContent.trim();
            if (currentTitle) {
                copyToClipboard(currentTitle);
                const originalText = copyButton.textContent;
                copyButton.textContent = '已复制!';
                setTimeout(() => { copyButton.textContent = originalText; }, 1500);
            }
        });

        titleElement.parentElement.appendChild(copyButton);
    }

    // 观察者，解决 SPA 页面不刷新的问题
    const observer = new MutationObserver(() => addButton());
    observer.observe(document.body, { childList: true, subtree: true });

    addButton();
})();