import { NextRequest } from 'next/server'
import { createReadStream, statSync } from 'fs'
import { promises as fsp } from 'fs'
import path from 'path'
import mime from 'mime-types'
import { DownloadErrorCode } from '@/lib/download-errors'
import { findBlockedVideoPreviewByUrl, isVideoMediaPath } from '@/lib/video-preview-access'

// Fallback streaming for /uploads/* when NAS/static mapping is not configured.
// Supports Range requests for video playback.
export async function GET(req: NextRequest, context: { params: { path?: string[] } }) {
  const segments = context.params.path || []

  // Health probe: /uploads/health
  if (segments.length === 1 && segments[0] === 'health') {
    return new Response('OK', { status: 200 })
  }

  const uploadsRoot = process.env.UPLOAD_DIR || './uploads'
  // Prevent path traversal
  const safeRel = path.join(...segments)
  const normalizedSafeRel = safeRel.replace(/\\/g, '/')
  const absPath = path.resolve(uploadsRoot, safeRel)
  const rootResolved = path.resolve(uploadsRoot)
  if (!absPath.startsWith(rootResolved)) {
    return new Response('Forbidden', { status: 403 })
  }

  if (isVideoMediaPath(normalizedSafeRel)) {
    const blockedPreview = await findBlockedVideoPreviewByUrl([
      req.url,
      `/uploads/${normalizedSafeRel}`,
      `/api/uploads/${normalizedSafeRel}`,
      normalizedSafeRel,
    ])

    if (blockedPreview) {
      return Response.json(
        {
          error: '视频类素材上传后满 15 天才能预览和下载',
          code: DownloadErrorCode.VIDEO_WAIT_PERIOD,
          details: blockedPreview.message,
        },
        {
          status: 403,
          headers: { 'Cache-Control': 'no-store' },
        },
      )
    }
  }

  try {
    const stat = await fsp.stat(absPath)
    if (!stat.isFile()) {
      return new Response('Not Found', { status: 404 })
    }

    const range = req.headers.get('range')
    const contentType = (mime.contentType(path.extname(absPath)) as string) || 'application/octet-stream'

    if (range) {
      const size = stat.size
      const match = range.match(/bytes=(\d*)-(\d*)/)
      const start = match && match[1] ? parseInt(match[1], 10) : 0
      const end = match && match[2] ? parseInt(match[2], 10) : size - 1
      if (isNaN(start) || isNaN(end) || start > end || end >= size) {
        return new Response('Invalid Range', { status: 416 })
      }
      const chunkSize = end - start + 1
      const stream = createReadStream(absPath, { start, end })
      return new Response(stream as any, {
        status: 206,
        headers: {
          'Content-Range': `bytes ${start}-${end}/${size}`,
          'Accept-Ranges': 'bytes',
          'Content-Length': chunkSize.toString(),
          'Content-Type': contentType,
          'Cache-Control': 'public, max-age=31536000, immutable',
        },
      })
    }

    const stream = createReadStream(absPath)
    return new Response(stream as any, {
      status: 200,
      headers: {
        'Content-Length': stat.size.toString(),
        'Content-Type': contentType,
        'Cache-Control': 'public, max-age=31536000, immutable',
      },
    })
  } catch (err: any) {
    if (err.code === 'ENOENT') {
      return new Response('Not Found', { status: 404 })
    }
    return new Response('Server Error', { status: 500 })
  }
}