professor/components/classroom/LessonPane.tsx

'use client';

import ReactMarkdown from 'react-markdown';
import remarkGfm from 'remark-gfm';
import { Prism as SyntaxHighlighter } from 'react-syntax-highlighter';
import { vscDarkPlus } from 'react-syntax-highlighter/dist/esm/styles/prism';
import type { Topic } from '@/types';

interface Props {
  topic: Topic;
  lessonContent: string | null;
  isGenerating: boolean;
  streamingContent: string;
}

export default function LessonPane({ topic, lessonContent, isGenerating, streamingContent }: Props) {
  const content = lessonContent ?? (isGenerating ? streamingContent : null);

  return (
    <div className="flex flex-col h-full bg-zinc-950">
      {/* Header */}
      <div className="flex items-center gap-2 border-b border-zinc-700 bg-zinc-900 px-4 py-2 flex-shrink-0">
        <svg className="h-3.5 w-3.5 text-zinc-400" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth={2}>
          <path d="M2 3h6a4 4 0 0 1 4 4v14a3 3 0 0 0-3-3H2z" />
          <path d="M22 3h-6a4 4 0 0 0-4 4v14a3 3 0 0 1 3-3h7z" />
        </svg>
        <span className="text-sm font-semibold text-zinc-200">{topic.label}</span>
        {isGenerating && (
          <div className="ml-auto flex items-center gap-1.5 text-xs text-zinc-500">
            <div className="h-2 w-2 animate-pulse rounded-full bg-blue-400" />
            Writing lesson…
          </div>
        )}
      </div>

      {/* Content */}
      <div className="flex-1 overflow-y-auto">
        {!content ? (
          <div className="flex h-full items-center justify-center">
            <div className="flex items-center gap-2 text-sm text-zinc-500">
              <div className="h-2 w-2 animate-bounce rounded-full bg-zinc-600 [animation-delay:-0.3s]" />
              <div className="h-2 w-2 animate-bounce rounded-full bg-zinc-600 [animation-delay:-0.15s]" />
              <div className="h-2 w-2 animate-bounce rounded-full bg-zinc-600" />
            </div>
          </div>
        ) : (
          <div className="px-6 py-5 text-sm">
            <ReactMarkdown
              remarkPlugins={[remarkGfm]}
              components={{
                code({ className, children, ...rest }) {
                  const match = /language-(\w+)/.exec(className ?? '');
                  return match ? (
                    <SyntaxHighlighter
                      style={vscDarkPlus as Record<string, React.CSSProperties>}
                      language={match[1]}
                      PreTag="div"
                      customStyle={{ margin: '0.75rem 0', borderRadius: '0.375rem', fontSize: '0.8rem' }}
                    >
                      {String(children).replace(/\n$/, '')}
                    </SyntaxHighlighter>
                  ) : (
                    <code className="rounded bg-zinc-800 px-1 py-0.5 text-xs font-mono text-zinc-300" {...rest}>
                      {children}
                    </code>
                  );
                },
                h1: ({ children }) => <h1 className="mb-4 mt-6 text-xl font-bold text-zinc-100 first:mt-0">{children}</h1>,
                h2: ({ children }) => <h2 className="mb-3 mt-6 text-base font-bold text-zinc-100 border-b border-zinc-800 pb-1">{children}</h2>,
                h3: ({ children }) => <h3 className="mb-2 mt-4 text-sm font-semibold text-zinc-200">{children}</h3>,
                p: ({ children }) => <p className="mb-3 leading-relaxed text-zinc-300">{children}</p>,
                ul: ({ children }) => <ul className="mb-3 list-disc pl-5 space-y-1.5 text-zinc-300">{children}</ul>,
                ol: ({ children }) => <ol className="mb-3 list-decimal pl-5 space-y-1.5 text-zinc-300">{children}</ol>,
                li: ({ children }) => <li className="leading-relaxed">{children}</li>,
                strong: ({ children }) => <strong className="font-semibold text-zinc-100">{children}</strong>,
                blockquote: ({ children }) => (
                  <blockquote className="my-3 border-l-2 border-blue-500 pl-4 italic text-zinc-400">{children}</blockquote>
                ),
                hr: () => <hr className="my-5 border-zinc-800" />,
                table: ({ children }) => (
                  <div className="mb-3 overflow-x-auto">
                    <table className="w-full border-collapse text-xs">{children}</table>
                  </div>
                ),
                th: ({ children }) => <th className="border border-zinc-700 bg-zinc-800 px-3 py-1.5 text-left font-semibold text-zinc-200">{children}</th>,
                td: ({ children }) => <td className="border border-zinc-700 px-3 py-1.5 text-zinc-300">{children}</td>,
              }}
            >
              {content}
            </ReactMarkdown>
          </div>
        )}
      </div>
    </div>
  );
}