import React from 'react';

function parseInlineMarkdown(text: string): React.ReactNode {
  const parts: React.ReactNode[] = [];
  let remaining = text;
  let keyIndex = 0;

  while (remaining.length > 0) {
    // Inline code
    const codeMatch = remaining.match(/^`([^`]+)`/);
    if (codeMatch) {
      parts.push(
        <code key={keyIndex++} className="bg-zinc-800 px-1.5 py-0.5 rounded text-[#697565] text-sm font-mono">
          {codeMatch[1]}
        </code>
      );
      remaining = remaining.slice(codeMatch[0].length);
      continue;
    }

    // Bold
    const boldMatch = remaining.match(/^\*\*([^*]+)\*\*/);
    if (boldMatch) {
      parts.push(<strong key={keyIndex++} className="font-semibold text-white">{boldMatch[1]}</strong>);
      remaining = remaining.slice(boldMatch[0].length);
      continue;
    }

    // Italic
    const italicMatch = remaining.match(/^\*([^*]+)\*/);
    if (italicMatch) {
      parts.push(<em key={keyIndex++} className="italic">{italicMatch[1]}</em>);
      remaining = remaining.slice(italicMatch[0].length);
      continue;
    }

    // Links
    const linkMatch = remaining.match(/^\[([^\]]+)\]\(([^)]+)\)/);
    if (linkMatch) {
      parts.push(
        <a key={keyIndex++} href={linkMatch[2]} className="text-[#697565] hover:text-[#8a9a7e] underline" target="_blank" rel="noopener noreferrer">
          {linkMatch[1]}
        </a>
      );
      remaining = remaining.slice(linkMatch[0].length);
      continue;
    }

    // Regular character
    const nextSpecial = remaining.search(/[`*\[]/);
    if (nextSpecial === -1) {
      parts.push(remaining);
      break;
    } else if (nextSpecial === 0) {
      parts.push(remaining[0]);
      remaining = remaining.slice(1);
    } else {
      parts.push(remaining.slice(0, nextSpecial));
      remaining = remaining.slice(nextSpecial);
    }
  }

  return parts.length === 1 ? parts[0] : <>{parts}</>;
}

export function renderMarkdown(content: string): React.ReactNode {
  const lines = content.split('\n');
  const elements: React.ReactNode[] = [];
  let i = 0;
  let listItems: { type: 'ul' | 'ol'; items: React.ReactNode[] } | null = null;
  let codeBlock: { language: string; lines: string[] } | null = null;
  let tableRows: string[][] | null = null;

  const flushList = () => {
    if (listItems) {
      if (listItems.type === 'ul') {
        elements.push(
          <ul key={`ul-${elements.length}`} className="list-disc list-inside space-y-2 my-4 text-zinc-300">
            {listItems.items}
          </ul>
        );
      } else {
        elements.push(
          <ol key={`ol-${elements.length}`} className="list-decimal list-inside space-y-2 my-4 text-zinc-300">
            {listItems.items}
          </ol>
        );
      }
      listItems = null;
    }
  };

  const flushTable = () => {
    if (tableRows && tableRows.length > 0) {
      const header = tableRows[0];
      const body = tableRows.slice(2); // Skip header separator row
      elements.push(
        <div key={`table-${elements.length}`} className="overflow-x-auto my-6">
          <table className="min-w-full border-collapse">
            <thead>
              <tr className="border-b border-zinc-700">
                {header.map((cell, idx) => (
                  <th key={idx} className="px-4 py-2 text-left text-zinc-200 font-semibold">
                    {cell.trim()}
                  </th>
                ))}
              </tr>
            </thead>
            <tbody>
              {body.map((row, rowIdx) => (
                <tr key={rowIdx} className="border-b border-zinc-800">
                  {row.map((cell, cellIdx) => (
                    <td key={cellIdx} className="px-4 py-2 text-zinc-300">
                      {cell.trim()}
                    </td>
                  ))}
                </tr>
              ))}
            </tbody>
          </table>
        </div>
      );
      tableRows = null;
    }
  };

  while (i < lines.length) {
    const line = lines[i];

    // Code block start/end
    if (line.startsWith('```')) {
      if (codeBlock) {
        // End code block
        elements.push(
          <pre key={`code-${elements.length}`} className="bg-zinc-900 border border-zinc-800 rounded-lg p-4 overflow-x-auto my-6">
            <code className="text-sm font-mono text-zinc-300">
              {codeBlock.lines.join('\n')}
            </code>
          </pre>
        );
        codeBlock = null;
      } else {
        // Start code block
        flushList();
        flushTable();
        const language = line.slice(3).trim();
        codeBlock = { language, lines: [] };
      }
      i++;
      continue;
    }

    // Inside code block
    if (codeBlock) {
      codeBlock.lines.push(line);
      i++;
      continue;
    }

    // Table row
    if (line.startsWith('|') && line.endsWith('|')) {
      flushList();
      const cells = line.slice(1, -1).split('|');
      if (!tableRows) {
        tableRows = [];
      }
      tableRows.push(cells);
      i++;
      continue;
    } else if (tableRows) {
      flushTable();
    }

    // Headers
    if (line.startsWith('#### ')) {
      flushList();
      elements.push(
        <h4 key={`h4-${elements.length}`} className="text-lg font-semibold text-white mt-5 mb-2">
          {parseInlineMarkdown(line.slice(5))}
        </h4>
      );
      i++;
      continue;
    }

    if (line.startsWith('### ')) {
      flushList();
      elements.push(
        <h3 key={`h3-${elements.length}`} className="text-xl font-semibold text-white mt-6 mb-3">
          {parseInlineMarkdown(line.slice(4))}
        </h3>
      );
      i++;
      continue;
    }

    if (line.startsWith('## ')) {
      flushList();
      elements.push(
        <h2 key={`h2-${elements.length}`} className="text-2xl font-bold text-white mt-8 mb-4">
          {parseInlineMarkdown(line.slice(3))}
        </h2>
      );
      i++;
      continue;
    }

    if (line.startsWith('# ')) {
      flushList();
      elements.push(
        <h1 key={`h1-${elements.length}`} className="text-3xl font-bold text-white mt-8 mb-4">
          {parseInlineMarkdown(line.slice(2))}
        </h1>
      );
      i++;
      continue;
    }

    // Unordered list items
    if (line.match(/^[-*]\s/)) {
      if (!listItems || listItems.type !== 'ul') {
        flushList();
        listItems = { type: 'ul', items: [] };
      }
      listItems.items.push(
        <li key={`li-${listItems.items.length}`}>
          {parseInlineMarkdown(line.replace(/^[-*]\s/, ''))}
        </li>
      );
      i++;
      continue;
    }

    // Ordered list items
    if (line.match(/^\d+\.\s/)) {
      if (!listItems || listItems.type !== 'ol') {
        flushList();
        listItems = { type: 'ol', items: [] };
      }
      listItems.items.push(
        <li key={`li-${listItems.items.length}`}>
          {parseInlineMarkdown(line.replace(/^\d+\.\s/, ''))}
        </li>
      );
      i++;
      continue;
    }

    // Checkbox list items
    if (line.match(/^[-*]\s\[[ x]\]/i)) {
      if (!listItems || listItems.type !== 'ul') {
        flushList();
        listItems = { type: 'ul', items: [] };
      }
      const checked = line.match(/^[-*]\s\[x\]/i);
      const itemContent = line.replace(/^[-*]\s\[[ x]\]\s?/i, '');
      listItems.items.push(
        <li key={`li-${listItems.items.length}`} className="flex items-center gap-2">
          <span className={checked ? 'text-green-500' : 'text-zinc-500'}>
            {checked ? '✓' : '○'}
          </span>
          {parseInlineMarkdown(itemContent)}
        </li>
      );
      i++;
      continue;
    }

    // Horizontal rule
    if (line.match(/^[-*_]{3,}$/)) {
      flushList();
      elements.push(<hr key={`hr-${elements.length}`} className="border-zinc-700 my-8" />);
      i++;
      continue;
    }

    // Blockquote
    if (line.startsWith('> ')) {
      flushList();
      elements.push(
        <blockquote key={`quote-${elements.length}`} className="border-l-4 border-[#697565] pl-4 my-4 text-zinc-400 italic">
          {parseInlineMarkdown(line.slice(2))}
        </blockquote>
      );
      i++;
      continue;
    }

    // Empty line
    if (!line.trim()) {
      flushList();
      i++;
      continue;
    }

    // Regular paragraph
    flushList();
    elements.push(
      <p key={`p-${elements.length}`} className="text-zinc-300 mb-4 leading-relaxed">
        {parseInlineMarkdown(line)}
      </p>
    );
    i++;
  }

  // Flush any remaining items
  flushList();
  flushTable();

  return <div className="prose prose-invert prose-zinc max-w-none">{elements}</div>;
}
