import { NextRequest, NextResponse } from 'next/server'
import { requireAuth } from '@/lib/auth'
import { getUploadSession, markChunkUploaded, generatePresignedUrl } from '@/lib/upload'
import { writeFile, mkdir } from 'fs/promises'
import { join } from 'path'

export async function POST(
  request: NextRequest,
  { params }: { params: Promise<{ uploadId: string; chunkIndex: string }> }
) {
  try {
    const user = await requireAuth()
    const { uploadId, chunkIndex: chunkIndexStr } = await params
    const chunkIndex = parseInt(chunkIndexStr)

    if (isNaN(chunkIndex)) {
      return NextResponse.json(
        { error: 'Invalid chunk index' },
        { status: 400 }
      )
    }

    // Get upload session
    const uploadSession = await getUploadSession(uploadId, user.id)
    if (!uploadSession) {
      return NextResponse.json(
        { error: 'Upload session not found or expired' },
        { status: 404 }
      )
    }

    if (uploadSession.status === 'completed') {
      return NextResponse.json(
        { error: 'Upload already completed' },
        { status: 400 }
      )
    }

    if (chunkIndex < 0 || chunkIndex >= uploadSession.totalChunks) {
      return NextResponse.json(
        { error: 'Invalid chunk index' },
        { status: 400 }
      )
    }

    // Get the chunk data from the request
    const chunkData = await request.arrayBuffer()
    const expectedSize = Math.min(uploadSession.chunkSize, uploadSession.fileSize - chunkIndex * uploadSession.chunkSize)

    if (chunkData.byteLength !== expectedSize) {
      return NextResponse.json(
        { error: `Invalid chunk size. Expected ${expectedSize}, got ${chunkData.byteLength}` },
        { status: 400 }
      )
    }

    // In a real implementation, you would:
    // 1. Upload to S3/CloudStorage using the presigned URL
    // 2. Or store temporarily on disk/cloud storage
    // For now, we'll simulate by storing in a temporary directory

    const tempDir = join(process.cwd(), 'temp', 'uploads', uploadId)
    await mkdir(tempDir, { recursive: true })

    const chunkPath = join(tempDir, `chunk-${chunkIndex}`)
    await writeFile(chunkPath, Buffer.from(chunkData))

    // Mark chunk as uploaded
    const updatedSession = await markChunkUploaded(uploadId, chunkIndex)

    // Generate presigned URL for next chunk if not complete
    let nextPresignedUrl = null
    if (updatedSession.status !== 'completed' && chunkIndex + 1 < uploadSession.totalChunks) {
      const { url } = await generatePresignedUrl(
        `chunk-${chunkIndex + 1}-${uploadSession.fileName}`,
        uploadSession.mimeType
      )
      nextPresignedUrl = url
    }

    return NextResponse.json(
      {
        success: true,
        chunkIndex,
        uploadedChunks: updatedSession.uploadedChunks,
        totalChunks: updatedSession.totalChunks,
        status: updatedSession.status,
        nextPresignedUrl,
      },
      { status: 200 }
    )
  } catch (error) {
    console.error('Chunk upload error:', error)
    if (error instanceof Error && error.message === 'Unauthorized') {
      return NextResponse.json(
        { error: 'Unauthorized' },
        { status: 401 }
      )
    }
    return NextResponse.json(
      { error: 'Failed to upload chunk' },
      { status: 500 }
    )
  }
}