feat(代码块): 添加长代码折叠/展开功能

- 超过60行代码自动折叠，预览前30行
- 添加渐变遮罩和展开按钮交互
- 显示总行数和剩余行数信息
- 展开状态下显示收起按钮
- 复制功能始终复制完整代码
- 优化代码区域布局使用 flex 结构

src/components/markdown/CodeBlock.tsx

@@ -1,7 +1,7 @@
 'use client';
 
 import { useEffect, useRef, useState, useMemo } from 'react';
-import { Copy, Check, Eye } from 'lucide-react';
+import { Copy, Check, Eye, ChevronDown, ChevronUp } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import Prism from 'prismjs';
 import { HtmlPreviewModal } from '@/components/ui/HtmlPreviewModal';
@@ -30,6 +30,10 @@ interface CodeBlockProps {
   language?: string;
   showLineNumbers?: boolean;
   className?: string;
+  /** 折叠阈值，超过此行数自动折叠，默认 60 */
+  maxCollapsedLines?: number;
+  /** 折叠时预览的行数，默认 30 */
+  previewLines?: number;
 }
 
 // 语言别名映射
@@ -51,9 +55,12 @@ export function CodeBlock({
   language = 'text',
   showLineNumbers = true,
   className,
+  maxCollapsedLines = 60,
+  previewLines = 30,
 }: CodeBlockProps) {
   const [copied, setCopied] = useState(false);
   const [previewOpen, setPreviewOpen] = useState(false);
+  const [isExpanded, setIsExpanded] = useState(false);
 
   // 规范化语言名称
   const normalizedLanguage = languageAliases[language.toLowerCase()] || language.toLowerCase();
@@ -62,17 +69,33 @@ export function CodeBlock({
   const isHtmlPreviewable = ['html', 'htm', 'markup'].includes(normalizedLanguage) ||
                             ['html', 'htm'].includes(language.toLowerCase());
 
+  const lines = code.split('\n');
+  const totalLines = lines.length;
+  const shouldCollapse = totalLines > maxCollapsedLines;
+  const remainingLines = totalLines - previewLines;
+
+  // 根据折叠状态获取显示的代码
+  const displayCode = useMemo(() => {
+    if (shouldCollapse && !isExpanded) {
+      return lines.slice(0, previewLines).join('\n');
+    }
+    return code;
+  }, [code, lines, shouldCollapse, isExpanded, previewLines]);
+
+  const displayLines = displayCode.split('\n');
+
   // 使用 useMemo 缓存高亮后的 HTML，避免频繁重新高亮
   const highlightedCode = useMemo(() => {
     const grammar = Prism.languages[normalizedLanguage];
     if (grammar) {
-      return Prism.highlight(code, grammar, normalizedLanguage);
+      return Prism.highlight(displayCode, grammar, normalizedLanguage);
     }
-    return code;
+    return displayCode;
-  }, [code, normalizedLanguage]);
+  }, [displayCode, normalizedLanguage]);
 
   const handleCopy = async () => {
     try {
+      // 始终复制完整代码
       await navigator.clipboard.writeText(code);
       setCopied(true);
       setTimeout(() => setCopied(false), 2000);
@@ -81,13 +104,15 @@ export function CodeBlock({
     }
   };
 
-  const lines = code.split('\n');
+  const toggleExpand = () => {
+    setIsExpanded(!isExpanded);
+  };
 
   return (
     <div className={cn('relative group rounded overflow-hidden my-4', className)}
          style={{ boxShadow: 'var(--color-code-shadow)' }}>
       {/* 顶部工具栏 */}
-      <div className="flex items-center justify-between px-4 py-2.5 text-sm"
+      <div className="flex items-center justify-between px-4 py-2.5 text-[0.9em]"
            style={{
              backgroundColor: 'var(--color-code-toolbar-bg)',
              color: 'var(--color-code-toolbar-text)',
@@ -106,6 +131,12 @@ export function CodeBlock({
                   style={{ backgroundColor: '#27c93f', boxShadow: '0 0 0 1px rgba(0, 0, 0, 0.1) inset' }} />
           </div>
           <span className="font-mono text-[13px]">{language || 'code'}</span>
+          {/* 显示总行数 */}
+          {shouldCollapse && (
+            <span className="text-[12px] opacity-60">
+              ({totalLines} 行)
+            </span>
+          )}
         </div>
 
         {/* 右侧：操作按钮 */}
@@ -145,42 +176,95 @@ export function CodeBlock({
       </div>
 
       {/* 代码区域 */}
-      <div className="relative overflow-x-auto"
+      <div style={{ backgroundColor: 'var(--color-code-bg)' }}>
-           style={{ backgroundColor: 'var(--color-code-bg)' }}>
+        {/* 代码内容 - 使用 flex 布局 */}
+        <div className="flex overflow-x-auto">
+          {/* 行号列 */}
           {showLineNumbers && (
-          <div className="absolute left-0 top-0 bottom-0 w-12 select-none"
+            <div
+              className="flex-shrink-0 w-12 select-none py-4 px-2 text-right"
               style={{
                 backgroundColor: 'var(--color-code-bg)',
                 borderRight: '1px solid var(--color-code-line-border)'
-               }}>
+              }}
-            <div className="py-4 px-2 text-right">
+            >
-              {lines.map((_, index) => (
+              {displayLines.map((_, index) => (
                 <div
                   key={index}
-                  className="text-sm font-mono leading-6"
+                  className="font-mono leading-6"
                   style={{ color: 'var(--color-code-line-number)' }}
                 >
                   {index + 1}
                 </div>
               ))}
             </div>
-          </div>
           )}
+          {/* 代码列 */}
           <pre
-          className={cn(
+            className="flex-1 p-4 overflow-x-auto"
-            'p-4 overflow-x-auto',
-            showLineNumbers && 'pl-16'
-          )}
             style={{ margin: 0, background: 'transparent' }}
           >
             <code
-            className={`language-${normalizedLanguage} text-sm leading-6`}
+              className={`language-${normalizedLanguage} leading-6`}
               style={{ color: 'var(--color-code-text)' }}
               dangerouslySetInnerHTML={{ __html: highlightedCode }}
             />
           </pre>
         </div>
 
+        {/* 渐变遮罩和展开按钮（仅在折叠状态下显示） */}
+        {shouldCollapse && !isExpanded && (
+          <>
+            {/* 渐变遮罩 */}
+            <div
+              className="h-16 -mt-16 pointer-events-none relative z-10"
+              style={{
+                background: `linear-gradient(to bottom, transparent, var(--color-code-bg))`
+              }}
+            />
+            {/* 展开按钮 */}
+            <div
+              className="py-3 text-center cursor-pointer transition-colors hover:opacity-80"
+              style={{ backgroundColor: 'var(--color-code-bg)' }}
+              onClick={toggleExpand}
+            >
+              <button
+                className="inline-flex items-center gap-2 px-4 py-2 rounded-lg text-[0.9em] font-medium transition-colors"
+                style={{
+                  color: 'var(--color-primary)',
+                  backgroundColor: 'var(--color-primary-alpha)'
+                }}
+              >
+                <ChevronDown size={16} />
+                <span>展开剩余 {remainingLines} 行代码</span>
+              </button>
+            </div>
+          </>
+        )}
+
+        {/* 收起按钮（仅在展开状态下显示） */}
+        {shouldCollapse && isExpanded && (
+          <div
+            className="py-3 text-center cursor-pointer transition-colors"
+            style={{
+              backgroundColor: 'var(--color-code-bg)',
+              borderTop: '1px solid var(--color-code-line-border)'
+            }}
+            onClick={toggleExpand}
+          >
+            <button
+              className="inline-flex items-center gap-2 px-4 py-2 rounded-lg text-[0.9em] font-medium transition-colors"
+              style={{
+                color: 'var(--color-code-toolbar-text)'
+              }}
+            >
+              <ChevronUp size={16} />
+              <span>收起代码</span>
+            </button>
+          </div>
+        )}
+      </div>
+
       {/* HTML 预览模态框 */}
       {isHtmlPreviewable && (
         <HtmlPreviewModal