import { NextRequest, NextResponse } from 'next/server';
import { mkdir, writeFile, appendFile } from 'fs/promises';
import path from 'path';
import crypto from 'crypto';

export async function POST(request: NextRequest) {
  try {
    const formData = await request.formData();
    
    const chunk = formData.get('chunk') as File;
    const filename = formData.get('filename') as string;
    const chunkIndex = parseInt(formData.get('chunkIndex') as string);
    const totalChunks = parseInt(formData.get('totalChunks') as string);
    const fileId = formData.get('fileId') as string;
    
    if (!chunk || !filename || isNaN(chunkIndex) || isNaN(totalChunks) || !fileId) {
      return NextResponse.json({ success: false, error: '필수 매개변수가 누락되었습니다' }, { status: 400 });
    }
    
    // 임시 디렉토리 생성
    const tempDir = path.join(process.cwd(), 'temp', fileId);
    await mkdir(tempDir, { recursive: true });
    
    // 청크 파일 저장
    const chunkPath = path.join(tempDir, `chunk-${chunkIndex}`);
    const buffer = Buffer.from(await chunk.arrayBuffer());
    await writeFile(chunkPath, buffer);
    
    // 마지막 청크인 경우 모든 청크를 합쳐 최종 파일 생성
    if (chunkIndex === totalChunks - 1) {
      const uploadDir = path.join(process.cwd(), "public", "basicContract", "template");
      await mkdir(uploadDir, { recursive: true });
      
      // 파일명 생성
      const timestamp = Date.now();
      const randomHash = crypto.createHash('md5')
        .update(`${filename}-${timestamp}`)
        .digest('hex')
        .substring(0, 8);
      const hashedFileName = `${timestamp}-${randomHash}${path.extname(filename)}`;
      const finalPath = path.join(uploadDir, hashedFileName);
      
      // 모든 청크 병합
      await writeFile(finalPath, Buffer.alloc(0)); // 빈 파일 생성
      for (let i = 0; i < totalChunks; i++) {
        const chunkData = await require('fs/promises').readFile(path.join(tempDir, `chunk-${i}`));
        await appendFile(finalPath, chunkData);
      }
      
      // 임시 파일 정리 (비동기로 처리)
      require('fs/promises').rm(tempDir, { recursive: true, force: true })
      .catch((e: unknown) => console.error('청크 정리 오류:', e));
      
      return NextResponse.json({ 
        success: true, 
        fileName: filename,
        filePath: `/basicContract/template/${hashedFileName}` 
      });
    }
    
    return NextResponse.json({ 
      success: true, 
      chunkIndex, 
      message: `청크 ${chunkIndex + 1}/${totalChunks} 업로드 완료` 
    });
    
  } catch (error) {
    console.error('청크 업로드 오류:', error);
    return NextResponse.json({ success: false, error: '서버 오류' }, { status: 500 });
  }
}