// 分片上传完成合并接口
// 负责将分片文件按顺序合并为完整文件，校验大小，并返回服务器侧可复用的文件路径
// 供前端在第二步调用正式上传接口时复用，避免重复上传大文件
import { NextRequest, NextResponse } from 'next/server'
import { getServerSession } from 'next-auth'
import { authOptions } from '@/lib/auth'
import path from 'path'
import fs from 'fs/promises'
import { createWriteStream, createReadStream } from 'fs'
import { pipeline } from 'stream/promises'
import { getUploadSession, deleteUploadSession } from '@/lib/upload-sessions'
import { sanitizeFileName } from '@/lib/image-processor'

export const runtime = 'nodejs'
export const dynamic = 'force-dynamic'
export const maxDuration = 10800 // 最长3小时

export async function POST(req: NextRequest) {
  try {
    const session = await getServerSession(authOptions)
    if (!session) {
      return NextResponse.json({ error: '请先登录' }, { status: 401 })
    }

    const { uploadId, originalFileName } = await req.json()

    if (!uploadId) {
      return NextResponse.json({ error: '缺少 uploadId' }, { status: 400 })
    }

    const uploadDir = process.env.UPLOAD_DIR || './uploads'
    const tempDir = path.join(uploadDir, 'temp', uploadId)

    // 读取会话
    const uploadSession = await getUploadSession(uploadId)
    if (!uploadSession) {
      return NextResponse.json({ error: '上传会话不存在或已过期' }, { status: 404 })
    }

    // 会话归属校验
    if (uploadSession.userId !== (session.user as any).id) {
      return NextResponse.json({ error: '无权访问此上传会话' }, { status: 403 })
    }

    const totalChunks = uploadSession.totalChunks
    const fileSize = uploadSession.fileSize

    // 收集分片文件
    const chunkFiles = []
    for (let i = 0; i < totalChunks; i++) {
      const chunkPath = path.join(tempDir, `chunk-${i}`)
      chunkFiles.push(chunkPath)
    }

    // 校验分片是否齐全
    for (const chunkPath of chunkFiles) {
      try {
        await fs.access(chunkPath)
      } catch {
        return NextResponse.json({ error: '分片不完整，请重新上传' }, { status: 400 })
      }
    }

    // 合并文件
    await fs.mkdir(tempDir, { recursive: true })
    // 处理文件名：提取纯文件名（去除路径），并清理特殊字符，避免中文路径或特殊字符导致的问题
    const rawFileName = originalFileName || uploadSession.fileName || `upload-${uploadId}`
    const baseFileName = path.basename(rawFileName) // 提取文件名部分，去除路径
    const mergedFileName = sanitizeFileName(baseFileName) || `upload-${uploadId}` // 清理特殊字符
    const mergedPath = path.join(tempDir, `merged-${mergedFileName}`)

    const mergedStream = createWriteStream(mergedPath)
    for (const chunkPath of chunkFiles) {
      const chunkStream = createReadStream(chunkPath)
      await pipeline(chunkStream, mergedStream, { end: false })
    }
    // 手动结束写入并等待关闭
    mergedStream.end()
    await new Promise<void>((resolve, reject) => {
      mergedStream.on('close', () => resolve())
      mergedStream.on('error', (err) => reject(err))
    })

    // 校验大小
    const stat = await fs.stat(mergedPath)
    if (stat.size !== fileSize) {
      return NextResponse.json(
        { error: `合并后的文件大小不匹配，期望 ${fileSize} 实际 ${stat.size}` },
        { status: 400 }
      )
    }

    // 清理分片，保留合并后的文件供后续正式上传使用
    // 使用统一的文件删除工具
    const { deleteFiles } = await import('@/lib/file-cleanup')
    const result = await deleteFiles(chunkFiles)
    if (result.failedCount > 0) {
      console.warn('[UploadComplete] 清理分片失败:', result.errors)
    }

    // 上传完成后，立即删除会话（不再占用Redis内存）
    try {
      const { deleteUploadSession } = await import('@/lib/upload-sessions-redis')
      await deleteUploadSession(uploadId)
      console.log('[UploadComplete] 已删除会话:', uploadId)
    } catch (deleteError) {
      console.warn('[UploadComplete] 删除会话失败（忽略）:', deleteError)
    }

    // 返回合并结果
    return NextResponse.json({
      message: '分片合并完成',
      existingFilePath: mergedPath,
      fileName: mergedFileName,
      fileSize: stat.size,
      uploadId,
    })
  } catch (error) {
    console.error('[UploadComplete] Error:', error)
    return NextResponse.json({ error: '合并分片失败' }, { status: 500 })
  }
}