import { DocumentAST, DocumentBlock } from '../types/block';
import { cleanHeadingContent } from './autoNumber';

/**
 * blockASTToMarkdown: 将 Block AST 树无损还原为整洁的标准 Markdown 文本
 */
export function blockASTToMarkdown(ast: DocumentAST): string {
  const chunks: string[] = [];

  function serializeBlock(block: DocumentBlock) {
    switch (block.type) {
      case 'heading': {
        const level = Math.max(1, Math.min(6, block.level || 1));
        const prefix = '#'.repeat(level);
        const titleText = cleanHeadingContent(block.content);
        const numPrefix = block.numbering ? `${block.numbering} ` : '';
        chunks.push(`${prefix} ${numPrefix}${titleText}\n`);
        break;
      }
      case 'paragraph': {
        if (block.content) {
          chunks.push(`${block.content}\n`);
        }
        break;
      }
      case 'list': {
        const isOrdered = block.properties?.isOrdered ?? true;
        const items =
          block.properties?.listItems ||
          block.content
            .split('\n')
            .map((line) => line.replace(/^\s*(\d+\.|[-*+])\s+/, '').trim())
            .filter(Boolean);
        const start = block.properties?.startNumber || 1;

        items.forEach((item, idx) => {
          const clean = item.trim();
          if (!clean) return;
          if (isOrdered) {
            chunks.push(`${start + idx}. ${clean}\n`);
          } else {
            chunks.push(`- ${clean}\n`);
          }
        });
        chunks.push('\n');
        break;
      }
      case 'divider': {
        chunks.push('---\n');
        break;
      }
      case 'callout': {
        const typeTag = block.properties?.calloutType === 'regulatory' ? '合规依据' : '提示';
        chunks.push(`> **[${typeTag}]** ${block.content}\n`);
        break;
      }
      case 'mermaid': {
        chunks.push('```mermaid\n' + block.content.trim() + '\n```\n');
        break;
      }
      case 'math': {
        chunks.push('$$\n' + block.content.trim() + '\n$$\n');
        break;
      }
      case 'table': {
        const data = block.properties?.tableData;
        if (data && data.length > 0) {
          const colCount = Math.max(...data.map((r) => r.length));
          const lines: string[] = [];

          // 表头行
          const header = data[0];
          const headerCells = Array.from({ length: colCount }, (_, idx) => header[idx] || '');
          lines.push('| ' + headerCells.join(' | ') + ' |');

          // 分隔线
          const sep = Array.from({ length: colCount }, () => '---');
          lines.push('| ' + sep.join(' | ') + ' |');

          // 数据行
          for (let r = 1; r < data.length; r++) {
            const row = data[r];
            const rowCells = Array.from({ length: colCount }, (_, idx) => row[idx] || '');
            lines.push('| ' + rowCells.join(' | ') + ' |');
          }

          chunks.push(lines.join('\n') + '\n');
        }
        break;
      }
      case 'document': {
        if (block.children) {
          for (const child of block.children) {
            serializeBlock(child);
          }
        }
        break;
      }
      default: {
        if (block.content) {
          chunks.push(`${block.content}\n`);
        }
        break;
      }
    }
  }

  serializeBlock(ast.rootBlock);
  return chunks.join('\n').trim() + '\n';
}